- #951
- 2,444
- 429
Nice 4 link from what I can see
Automotive Race car suspension Class
- Thread starter Ranger Mike
- Start date
-
- Tags
- Car Class Race Suspension
AI Thread Summary
The discussion emphasizes the importance of understanding race car suspension dynamics to improve handling and performance. Key issues include the car's tendency to push while entering corners and being loose upon exit, which can be addressed by adjusting downforce and the third link location. The roll center and instant center are critical factors in suspension design, affecting tire loading and grip during cornering. The conversation also highlights the significance of software tools like Suspension Analyzer for optimizing suspension geometry. Overall, proper suspension setup is essential for maximizing tire contact and achieving competitive performance on the track.
- #952
Outfront2
- 1
- 0
First time poster, long time reader... Lol.
Thanks Mike for this forum, it is very helpful.
What are your thoughts on this new style top link or 3rd link, or lift/pull arm... I work on template late models of cra, southern super series straight rail aphsalt cars
Thanks Mike for this forum, it is very helpful.
What are your thoughts on this new style top link or 3rd link, or lift/pull arm... I work on template late models of cra, southern super series straight rail aphsalt cars
Attachments
- #953
drobbie
- 36
- 2
In the Northeast this is referred to as a Torque arm. They have been used on primarily on asphalt modifieds. I have seen them mounted to both the left and right sides of the rear ends and used successfully. You show a solid link at the front, many guys around here use a rubber biscuit and control the amount of bite" by how much play is in the biscuit.
I know when I look at it, I see a three link suspension with different mounting point. I would be curious to hear what others opinions and experiences are with this setup is as well.
I know when I look at it, I see a three link suspension with different mounting point. I would be curious to hear what others opinions and experiences are with this setup is as well.
- #954
- 2,444
- 429
Thanks Drobbie
Welcome Out front, nice to hear from you.
Your inquiry tells me you have the car handling going in and turning in the middle ok. Now its time to hook it up on exit. Or I would say it is a safe assumption.
If the competition is handling going in and coming out as good as you are, Congratulations. You are now in the drag race phase and the first one to come off the corner with the best hook up wins. The new concept has definite merit.
Lets review the old 3 link and what's happening.
The 3 Link set up has evolved from the old truck rear end set up with long training arms and two upper links. The 4 link evolved as well and took off in the dirt track world with the bird cage and many tuning variations. This long Traction Arm is a variation for the 3 Link set up. The geometry of the 3 link linkages are such that Acceleration caused by the engine translates into rotational force via the differential. We have Tires contacting the track in one direction, axle wrap in the opposite direction.
Various linkages ( 3 or 4 link) react to the forces by lifting and pushing. It just so happens that if we draw a line from these links to the front of the car we construct an Instant Center (IC)where they meet. From this IC we have a Torque Arm ( lever) and this all results in the application of force during acceleration. This force will compress the springs and cause Anti-squat.
Anti-squat causes the rear end housing to apply more force to the chassis and down loads the tire for more traction. We get 100% anti squat and we do a wheelie! Not good in round track racing!
The longer the Instant Center the less the IC will move around during rear chassis roll, wheel and suspension links moving up and down and will provide the driver with a more stable feeling under acceleration. I think we ran a pull bar from the traditional mount on the Quick Change all the way to the transmission chassis hoop one time.
The whole point of this is try to maximize the control of the rear ends rotational torque for optimum tuning. The big draw back to anti-squat is that it will have an equal and opposite reaction under Braking. You could suffer wheel hop and a light rear end under braking conditions.
Bottom line is – Any time you can have an Instant Center closer to the front of the race car, it will have less movement during chassis roll. You will have a longer lever to counter rear end axlel wrap. This will make for a more stable car under acceleration and braking.
One note for the readers who are trying to understand the forces we are dealing with. Think Drag Racing.
Anyone who was around in the 1960s ( I was) will remember the Detroit Iron Muscle cars were the rage and just about every Camaro and Mustang had traction bars sticking out in from of the rear tires. No one bothered to tune them but the looked mean as help and did manage to hook up half way good. Of course the Chrysler boys engineered the proper set up and had a pinion snubber working with Hemi leaf springs but that is another matter.
There are three points to ponder here. Traction Bars use rear end rotation to slap the traction bar to the chassis and hook up the tires under acceleration. The Suspension links still formed an IC. Traction bars were mounted only at one end. Again, Anti-squat causes the rear end housing to apply more force to the chassis and down load the tires for more traction. We get 100% anti squat and we do a wheelie! Not good in round track racing!
Welcome Out front, nice to hear from you.
Your inquiry tells me you have the car handling going in and turning in the middle ok. Now its time to hook it up on exit. Or I would say it is a safe assumption.
If the competition is handling going in and coming out as good as you are, Congratulations. You are now in the drag race phase and the first one to come off the corner with the best hook up wins. The new concept has definite merit.
Lets review the old 3 link and what's happening.
The 3 Link set up has evolved from the old truck rear end set up with long training arms and two upper links. The 4 link evolved as well and took off in the dirt track world with the bird cage and many tuning variations. This long Traction Arm is a variation for the 3 Link set up. The geometry of the 3 link linkages are such that Acceleration caused by the engine translates into rotational force via the differential. We have Tires contacting the track in one direction, axle wrap in the opposite direction.
Various linkages ( 3 or 4 link) react to the forces by lifting and pushing. It just so happens that if we draw a line from these links to the front of the car we construct an Instant Center (IC)where they meet. From this IC we have a Torque Arm ( lever) and this all results in the application of force during acceleration. This force will compress the springs and cause Anti-squat.
Anti-squat causes the rear end housing to apply more force to the chassis and down loads the tire for more traction. We get 100% anti squat and we do a wheelie! Not good in round track racing!
The longer the Instant Center the less the IC will move around during rear chassis roll, wheel and suspension links moving up and down and will provide the driver with a more stable feeling under acceleration. I think we ran a pull bar from the traditional mount on the Quick Change all the way to the transmission chassis hoop one time.
The whole point of this is try to maximize the control of the rear ends rotational torque for optimum tuning. The big draw back to anti-squat is that it will have an equal and opposite reaction under Braking. You could suffer wheel hop and a light rear end under braking conditions.
Bottom line is – Any time you can have an Instant Center closer to the front of the race car, it will have less movement during chassis roll. You will have a longer lever to counter rear end axlel wrap. This will make for a more stable car under acceleration and braking.
One note for the readers who are trying to understand the forces we are dealing with. Think Drag Racing.
Anyone who was around in the 1960s ( I was) will remember the Detroit Iron Muscle cars were the rage and just about every Camaro and Mustang had traction bars sticking out in from of the rear tires. No one bothered to tune them but the looked mean as help and did manage to hook up half way good. Of course the Chrysler boys engineered the proper set up and had a pinion snubber working with Hemi leaf springs but that is another matter.
There are three points to ponder here. Traction Bars use rear end rotation to slap the traction bar to the chassis and hook up the tires under acceleration. The Suspension links still formed an IC. Traction bars were mounted only at one end. Again, Anti-squat causes the rear end housing to apply more force to the chassis and down load the tires for more traction. We get 100% anti squat and we do a wheelie! Not good in round track racing!
- #955
drobbie
- 36
- 2
So from what I hear you saying about anti-squat, is 50% the best number to achieve a balance of wheel hop under deceleration and traction under acceleration? Or am I better off assuming it is car specific and just another tool to be used for tuning.
The other part I would like to understand is the left or right mounting. Up here they use a left side pan hard rod with a right side Torque arm and vice versa. From what I have read here you want the third link to be in line with Left Side weight distribution. Seems to me this configuration might make it hard for cars with large LS weight.
The other part I would like to understand is the left or right mounting. Up here they use a left side pan hard rod with a right side Torque arm and vice versa. From what I have read here you want the third link to be in line with Left Side weight distribution. Seems to me this configuration might make it hard for cars with large LS weight.
- #956
- 2,444
- 429
One can not make blanket assumptions with race cars simply because the cars are not symmetrical.
There is too much variation on the left side weight , rear % weight, cross weight.
Ref- torque arm mounting – as I posted a few posts back- try to push that chainsaw with that broom handle at a location other than center of mass.
As you stated correctly, for best results the 3rd link or torque arm should be mounted at same % as left side weight. I know the practical side of things mean you mount it as best as you can but try to hit a happy balance . You have to decide if the % of races you have won is because of out accelerating the other guy or out braking?
That will ultimately determine the locations.
There is some fuzzy thinking on the mounting location for the top link. When looking to the front from the rear end of the car, the engine torque twists counter clockwise. The thinking was that this loaded the left side more than the right side. Since the left was loaded more the car would shoot toward the right side because of this twisting motion. So this ideas was to mount the third link more toward the passenger side or right side to counter this. Maybe in drag racing but not on a round track.
Looking at this in detail as torque is applied from the driveshaft to the rear axle, multiple forces begin to leverage the car. Engine torque multiplied by the transmission gear ratio and axle ratio generate a few thousand ft. lbs. of twisting motion. The first thing the pinion gear tries to do is climb the ring gear. This forces the nose of the rear axle upward. As the car begins to accelerate, the torque wants to lift the front of the carupward, causing more down force on the the rear tires. As viewed from the rear of the car, engine torque twists the body clockwise, lifting the left front and compressing the right rear spring. As the pinion continues to apply this massive torque through the ring gear, the rear axle housing is also being leveraged in a counterclockwise direction lifting the right side of the axle and planting the left. As the car accelerates, it appears to be planting the right rear tire but is really unloading the tire, thus reducing traction. Torque over steer.
You can still see this dramatic body twist at the drag strip. You have very sticky drag slicks ( not hard spec tires that you have to use) you have 50-50 left to rt side weight % and up to 100% anti squat. All the linkages are set up to do one thing, provide maximum down force to the rear tires under acceleration. The body is really twisted under axel wrap. Because this car was originally designed to be a family grocery getter, the suspension was made to give the softest ride with best the best handling and comfort. The 4 link rear suspension gave good traction in rain and snow. When it grew into a romping stomping muscle car with a 396 cubic inch engine, spring rates were upped and heavy duty shocks were added as were bigger tires. The design was still based on the comfortable balanced 4 link package. No wonder the darn thing wants to climb to one side and fish tail out of the gate!
The classic 3 link suspension negates a lot of this simply by the fact that you have only one top link. Where it is mounted and the angle it is mounted relative to the rear end is critical. If the link is not mounted at the center of weight of mass of the car the tire loading will not be equal when accelerating. It is that simple. On a locked rear end you need to load both rear tires equally.
Power torque over steer is negated by cross weight or wedge. When you put that greasy 1/2 socket on the floor jack and jack up the rear end, the right rear tire moves about 3 inch off the floor before the left rear does. Wedge or cross weight.
You use this static set up to counter the force of inertia created when entering a turn. It is a must for you to properly apply power equally on the rear tires on turn exit.
When you bomb into turn one, think of three vectors or force arrows. 1. from the rear to the front. 2. from the left to the right. 3. from the left rear tire to the right front tire. These three vectors are the momentum forces at work. The entire spring / ARB/ shock package and the tires are for countering these forces. You have good phase one and phase two handling and now want to exit.
You ROLL on the gas and power torque over steer putting down force on the left rear tire. This is some what canceled out because the whole chassis was trying to lift the left rear tire due to that diagonal force vector #3. You are still in the middle of the turn and the right side springs are still compressed some what. If your top link is mounted correctly and at the proper angle you will be putting some down force on the rear tires ( commonly know as weight transfer) by lifting the chassis through the linkages. If you have the right cross weight you should have equal traction as tire temperatures will tell you.
There is too much variation on the left side weight , rear % weight, cross weight.
Ref- torque arm mounting – as I posted a few posts back- try to push that chainsaw with that broom handle at a location other than center of mass.
As you stated correctly, for best results the 3rd link or torque arm should be mounted at same % as left side weight. I know the practical side of things mean you mount it as best as you can but try to hit a happy balance . You have to decide if the % of races you have won is because of out accelerating the other guy or out braking?
That will ultimately determine the locations.
There is some fuzzy thinking on the mounting location for the top link. When looking to the front from the rear end of the car, the engine torque twists counter clockwise. The thinking was that this loaded the left side more than the right side. Since the left was loaded more the car would shoot toward the right side because of this twisting motion. So this ideas was to mount the third link more toward the passenger side or right side to counter this. Maybe in drag racing but not on a round track.
Looking at this in detail as torque is applied from the driveshaft to the rear axle, multiple forces begin to leverage the car. Engine torque multiplied by the transmission gear ratio and axle ratio generate a few thousand ft. lbs. of twisting motion. The first thing the pinion gear tries to do is climb the ring gear. This forces the nose of the rear axle upward. As the car begins to accelerate, the torque wants to lift the front of the carupward, causing more down force on the the rear tires. As viewed from the rear of the car, engine torque twists the body clockwise, lifting the left front and compressing the right rear spring. As the pinion continues to apply this massive torque through the ring gear, the rear axle housing is also being leveraged in a counterclockwise direction lifting the right side of the axle and planting the left. As the car accelerates, it appears to be planting the right rear tire but is really unloading the tire, thus reducing traction. Torque over steer.
You can still see this dramatic body twist at the drag strip. You have very sticky drag slicks ( not hard spec tires that you have to use) you have 50-50 left to rt side weight % and up to 100% anti squat. All the linkages are set up to do one thing, provide maximum down force to the rear tires under acceleration. The body is really twisted under axel wrap. Because this car was originally designed to be a family grocery getter, the suspension was made to give the softest ride with best the best handling and comfort. The 4 link rear suspension gave good traction in rain and snow. When it grew into a romping stomping muscle car with a 396 cubic inch engine, spring rates were upped and heavy duty shocks were added as were bigger tires. The design was still based on the comfortable balanced 4 link package. No wonder the darn thing wants to climb to one side and fish tail out of the gate!
The classic 3 link suspension negates a lot of this simply by the fact that you have only one top link. Where it is mounted and the angle it is mounted relative to the rear end is critical. If the link is not mounted at the center of weight of mass of the car the tire loading will not be equal when accelerating. It is that simple. On a locked rear end you need to load both rear tires equally.
Power torque over steer is negated by cross weight or wedge. When you put that greasy 1/2 socket on the floor jack and jack up the rear end, the right rear tire moves about 3 inch off the floor before the left rear does. Wedge or cross weight.
You use this static set up to counter the force of inertia created when entering a turn. It is a must for you to properly apply power equally on the rear tires on turn exit.
When you bomb into turn one, think of three vectors or force arrows. 1. from the rear to the front. 2. from the left to the right. 3. from the left rear tire to the right front tire. These three vectors are the momentum forces at work. The entire spring / ARB/ shock package and the tires are for countering these forces. You have good phase one and phase two handling and now want to exit.
You ROLL on the gas and power torque over steer putting down force on the left rear tire. This is some what canceled out because the whole chassis was trying to lift the left rear tire due to that diagonal force vector #3. You are still in the middle of the turn and the right side springs are still compressed some what. If your top link is mounted correctly and at the proper angle you will be putting some down force on the rear tires ( commonly know as weight transfer) by lifting the chassis through the linkages. If you have the right cross weight you should have equal traction as tire temperatures will tell you.
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- #957
CGruhlke
- 1
- 0
Ranger Mike,
I signed up so that I could participate in this thread. This thread contains an amazing amount of information and there's a good chance this question has been asked and answered but it's so long I hope you'll forgive me if I'm duplicating your efforts.
I'm a Certified Mech Eng Tech up in Canada. I'm in the process of building a 2 seat tube chassis track day car which is based roughly on Mazda MX-3 chassis dimensions, but uses C5/6 Corvette running gear. I've used the stock C5 pivot points and BJ locations to identify the RC and IC's and I've manipulated the track width slightly and using Suspension Analyzer I've decided that the small decrease in width hasn't had a dramatic affect on the roll characteristics of the suspension. My question is in regards to the roll axis.
My wheelbase will be in the neighborhood of 18" shorter than a stock C5 Vette. If the front and rear RC heights don't change, the shorter wheelbase will cause a somewhat significant change in the roll axis angle. How will this affect the handling of the vehicle? I anticipate it will have the most impact on dive but will it affect roll?
thanks for any insight you may have.
Charlie
I signed up so that I could participate in this thread. This thread contains an amazing amount of information and there's a good chance this question has been asked and answered but it's so long I hope you'll forgive me if I'm duplicating your efforts.
I'm a Certified Mech Eng Tech up in Canada. I'm in the process of building a 2 seat tube chassis track day car which is based roughly on Mazda MX-3 chassis dimensions, but uses C5/6 Corvette running gear. I've used the stock C5 pivot points and BJ locations to identify the RC and IC's and I've manipulated the track width slightly and using Suspension Analyzer I've decided that the small decrease in width hasn't had a dramatic affect on the roll characteristics of the suspension. My question is in regards to the roll axis.
My wheelbase will be in the neighborhood of 18" shorter than a stock C5 Vette. If the front and rear RC heights don't change, the shorter wheelbase will cause a somewhat significant change in the roll axis angle. How will this affect the handling of the vehicle? I anticipate it will have the most impact on dive but will it affect roll?
thanks for any insight you may have.
Charlie
- #958
- 2,444
- 429
Welcome Charlie and thanks fro the kind words.
Please see post # 264 on page 14 of this post. Has benefits of long vs. short wheel base. Given a mandatory weight and no stated wheel base, go with the shortest practical.
Biggest advantage to a shorter wheel base is weight. If you can chop out the extra frame length and shorten the wheel base, you can then place the required weight ballast to where it will be at polar moment and do the best for you. The additional advantage of shorter wheel base is the ( I hate to use this ) weight transfer occurs faster. As you have read in previous posts THERE IS NO WEIGHT TRANSFER! The ability of the shorter wheel base car to react to the inertia ( momentum ) caused by cornering takes less time than a longer wheel base car. The untold advantage of a shorter wheel base car is it can fit in holes better in traffic.
In a purely technical point, this momentum is directly proportional to the weight of the race car , the height of the Center of Gravity and the rate of acceleration in Gs. It is inversely proportional to the wheelbase.
Why are you selecting a wheelbase like 87”?
any idea % ft to rear weight?
Ifin I remember correct the CR corvette has about 2.4 inch front roll center and 4” rear rc on 105” wheel base
real good package developed over years of solid engineering
the mazda miata has about 91 inch wheel base and 2.4 inch frt rc and 4.7 inch rear roll center
so if you are going the short 87” wheel base using the C5 geometry you should have a nice handing package
If i remember right, the shelby corbra had a rear roll center lower than t he front on a 90 inch wheel base. i think the front rc dove to one side on wheel turn in and the darn thing pushed. i think it did not turn in well. i drove a replica of one of these that had a small block chevy v8...but that was years ago. i remember it was tail end loose but with that much power...it had to be.
Check out LG Motorsports drop spindle to lower the car 1 inch and use same stock geometry
https://www.lgmotorsports.com/corvette-c5-parts-1997-2004/c5-chassis/lg-corvette-drop-spindles.html
Please see post # 264 on page 14 of this post. Has benefits of long vs. short wheel base. Given a mandatory weight and no stated wheel base, go with the shortest practical.
Biggest advantage to a shorter wheel base is weight. If you can chop out the extra frame length and shorten the wheel base, you can then place the required weight ballast to where it will be at polar moment and do the best for you. The additional advantage of shorter wheel base is the ( I hate to use this ) weight transfer occurs faster. As you have read in previous posts THERE IS NO WEIGHT TRANSFER! The ability of the shorter wheel base car to react to the inertia ( momentum ) caused by cornering takes less time than a longer wheel base car. The untold advantage of a shorter wheel base car is it can fit in holes better in traffic.
In a purely technical point, this momentum is directly proportional to the weight of the race car , the height of the Center of Gravity and the rate of acceleration in Gs. It is inversely proportional to the wheelbase.
Why are you selecting a wheelbase like 87”?
any idea % ft to rear weight?
Ifin I remember correct the CR corvette has about 2.4 inch front roll center and 4” rear rc on 105” wheel base
real good package developed over years of solid engineering
the mazda miata has about 91 inch wheel base and 2.4 inch frt rc and 4.7 inch rear roll center
so if you are going the short 87” wheel base using the C5 geometry you should have a nice handing package
If i remember right, the shelby corbra had a rear roll center lower than t he front on a 90 inch wheel base. i think the front rc dove to one side on wheel turn in and the darn thing pushed. i think it did not turn in well. i drove a replica of one of these that had a small block chevy v8...but that was years ago. i remember it was tail end loose but with that much power...it had to be.
Check out LG Motorsports drop spindle to lower the car 1 inch and use same stock geometry
https://www.lgmotorsports.com/corvette-c5-parts-1997-2004/c5-chassis/lg-corvette-drop-spindles.html
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- #959
Ronorlin
- 2
- 0
Greetings!
it took me about three weeks on and off to read this thread. Awesome information. I am hoping to ask a few questions of you all. Especially Ranger Mike. First time poster.
I run a asphalt sportsman/streetstock type car. Camaro clipped metric rear, ford 9". Impala spindles, howe adjustable parts in front.
Ive read all the books by SS and Bolles I could get. I have his roll center software and would like to know your thoughts on using a 1" taller BJ on the right to aide my geometry. You have been so adamant about where the roll center should be located I just have to ask. I really don't want the difficulty of different spindles right and left. Crash repairs are excruciatingly slow as it is.
After losing track of things during the season, and repairs, I just blue printed my front end and the roll center was 4" up and 10" left! I can't even explain how i let that happen. I am mandated to run a 1.5" bar. I've seen you mention Salem a couple times. Thats a tough place to go and race against guys that have been doing for a ton of years. Mixed results there, crashed bad once, 14th next time.
Thanks in advance, I look forward to the info. I am leaving for the week tomorrow so getting back on here may be a few days. Thank you.
Ronorlin
it took me about three weeks on and off to read this thread. Awesome information. I am hoping to ask a few questions of you all. Especially Ranger Mike. First time poster.
I run a asphalt sportsman/streetstock type car. Camaro clipped metric rear, ford 9". Impala spindles, howe adjustable parts in front.
Ive read all the books by SS and Bolles I could get. I have his roll center software and would like to know your thoughts on using a 1" taller BJ on the right to aide my geometry. You have been so adamant about where the roll center should be located I just have to ask. I really don't want the difficulty of different spindles right and left. Crash repairs are excruciatingly slow as it is.
After losing track of things during the season, and repairs, I just blue printed my front end and the roll center was 4" up and 10" left! I can't even explain how i let that happen. I am mandated to run a 1.5" bar. I've seen you mention Salem a couple times. Thats a tough place to go and race against guys that have been doing for a ton of years. Mixed results there, crashed bad once, 14th next time.
Thanks in advance, I look forward to the info. I am leaving for the week tomorrow so getting back on here may be a few days. Thank you.
Ronorlin
- #960
- 2,444
- 429
welcome Ron, good to know I have fellow Salem racer here. Salem is a fast 1/2 mile high bank track and you need lower roll center to race there. You need good camber curve as well.
see post # 284 on page 15 and post #809 on page 41,
A stock Camaro has a centered roll center about 0.5 inch above the ground. Swapping in Impala spindles was a trend to assist the camber build curve slightly and all things being the same a taller spindle makes the top A-arm angle more down hill and thus raises the roll center. Let's say your camshaft centerline is 18.5” above ground. This is a good approximation of the Center of Gravity. In stock form you have a Moment (lever) 18 inches long between the stock roll center (.5” above ground) to the COG. When you raise the roll center to 3.375” you reduce the Moment to 15.125” long. Less body roll and better camber curve. There are other advantages covered in this thread previous posts I won't go into like jacking effect, tire loading etc..
You said you have front RC 4 inch height and 10 inch to the left. I doubt you have enough down force to plant the right front tire to turn the car to be competitive.
If you want to WIN, you need to do the following:
1. Buy Street Stock Chassis Technology by Steve Smith. see www.stevesmithautosports.com
This book details how he took a Stock Camaro and made it competitive. The track rules he had to go with did not permit him altering the suspension enough to place the roll center where it should be but it was a lot closer than wheat you now have.
2. You will need to swap out spindles and ball joints to move that Roll Center 3 inch to the right of center and 3.375 height. It needs to stay on that side during roll and dive.
3. You will need to modify the cross link so your bump steer is correct. This is critical.
4. You have the best tool available. the software. Use it to bench mark your current set up and run it thru 4 inch of bump right side and 4 inch rebound on left side.
5. This will take much work and some $$$ initially but once you got it you can be competitive with those hard spec tires you have to run and can start winning.
FYI
Big metric spindles everyone talks about are Chevy Impala/Caprice 1977- 1996 spindle is identical to
Camaro/Firebird 1970-1981 spindles but much lighter, is 8.75” tall, 2.5” pin height.
Next up is the popular 7 1/4 tall spindle used in
1967-1969 F body Camaro / Nova
1964 –1972 A body Chevelle, Maibu ,GTO, LeMans 442 Cutlass, GS, Skylark
1968-1974 X body Nova, Apollo, Omega, Ventura – all with spindle height is 7.25”
1982 –2004 Chevy S 10 2wd pick up truck 7.5 “ spindle height
1980-90 GM full size car (Impala/Caprice) spindle has overall height of 8.6875”
"Short Arm" Metric Spindle. Based on a 1979-Up GM Metric midsize spindle- This spindle is 7 1/2" tall and the spindle snout is 1 3/4" up from the bottom of the spindle.
1974-1980 Ford Pinto and 1974-1978 Mustang II spindle is 7 5/8” tall and 2.4” pin height.
With your software you can plug in suspension numbers and figure how to get the roll center to proper offset 3 inch to the right.
If you are limited to stock A-arms, and you are permitted to replace ball joints, you can grind the Ball joint hole oblong to offset the ball joint by up to 3/8” to the inside on lower left side or outside on lower right side. and weld in Screw in ball joints like Chryslers. These will stick the spindle up about 3/4 “ higher from bottom A-Arm and move the upper A-Arm 3/4” higher for even more angle. Afco, U-B Machine , Speedway Motors, Coleman racing, have these. Check our Colman racing. Adjustable upper ball joints.
http://www.colemanracing.com/Integral-Ball-Joints-for-Lower-Control-Arms-P6201.aspx
http://www.colemanracing.com/Ball-Joint-Mono-Ball-Upper-GM-18-Degree-P3688.aspx
Don’t forget. You can move the A-arm inner mounts as well so there should be enough wiggle room to get the roll center close to the proper height and offset.
see post # 284 on page 15 and post #809 on page 41,
A stock Camaro has a centered roll center about 0.5 inch above the ground. Swapping in Impala spindles was a trend to assist the camber build curve slightly and all things being the same a taller spindle makes the top A-arm angle more down hill and thus raises the roll center. Let's say your camshaft centerline is 18.5” above ground. This is a good approximation of the Center of Gravity. In stock form you have a Moment (lever) 18 inches long between the stock roll center (.5” above ground) to the COG. When you raise the roll center to 3.375” you reduce the Moment to 15.125” long. Less body roll and better camber curve. There are other advantages covered in this thread previous posts I won't go into like jacking effect, tire loading etc..
You said you have front RC 4 inch height and 10 inch to the left. I doubt you have enough down force to plant the right front tire to turn the car to be competitive.
If you want to WIN, you need to do the following:
1. Buy Street Stock Chassis Technology by Steve Smith. see www.stevesmithautosports.com
This book details how he took a Stock Camaro and made it competitive. The track rules he had to go with did not permit him altering the suspension enough to place the roll center where it should be but it was a lot closer than wheat you now have.
2. You will need to swap out spindles and ball joints to move that Roll Center 3 inch to the right of center and 3.375 height. It needs to stay on that side during roll and dive.
3. You will need to modify the cross link so your bump steer is correct. This is critical.
4. You have the best tool available. the software. Use it to bench mark your current set up and run it thru 4 inch of bump right side and 4 inch rebound on left side.
5. This will take much work and some $$$ initially but once you got it you can be competitive with those hard spec tires you have to run and can start winning.
FYI
Big metric spindles everyone talks about are Chevy Impala/Caprice 1977- 1996 spindle is identical to
Camaro/Firebird 1970-1981 spindles but much lighter, is 8.75” tall, 2.5” pin height.
Next up is the popular 7 1/4 tall spindle used in
1967-1969 F body Camaro / Nova
1964 –1972 A body Chevelle, Maibu ,GTO, LeMans 442 Cutlass, GS, Skylark
1968-1974 X body Nova, Apollo, Omega, Ventura – all with spindle height is 7.25”
1982 –2004 Chevy S 10 2wd pick up truck 7.5 “ spindle height
1980-90 GM full size car (Impala/Caprice) spindle has overall height of 8.6875”
"Short Arm" Metric Spindle. Based on a 1979-Up GM Metric midsize spindle- This spindle is 7 1/2" tall and the spindle snout is 1 3/4" up from the bottom of the spindle.
1974-1980 Ford Pinto and 1974-1978 Mustang II spindle is 7 5/8” tall and 2.4” pin height.
With your software you can plug in suspension numbers and figure how to get the roll center to proper offset 3 inch to the right.
If you are limited to stock A-arms, and you are permitted to replace ball joints, you can grind the Ball joint hole oblong to offset the ball joint by up to 3/8” to the inside on lower left side or outside on lower right side. and weld in Screw in ball joints like Chryslers. These will stick the spindle up about 3/4 “ higher from bottom A-Arm and move the upper A-Arm 3/4” higher for even more angle. Afco, U-B Machine , Speedway Motors, Coleman racing, have these. Check our Colman racing. Adjustable upper ball joints.
http://www.colemanracing.com/Integral-Ball-Joints-for-Lower-Control-Arms-P6201.aspx
http://www.colemanracing.com/Ball-Joint-Mono-Ball-Upper-GM-18-Degree-P3688.aspx
Don’t forget. You can move the A-arm inner mounts as well so there should be enough wiggle room to get the roll center close to the proper height and offset.
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- #961
Luke Doolin
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Hello, another newbie here. I run an ex-Cup car in scca road races. 3200 lbs approx. When I have the chassis side to side level at front and rear I have about 250 lbs more lr weight than the rr. I know the car was a converted oval car so I can't move too much static weight around. To get more wt on the rr to balance it I have to jack quite a bit on the screws and then my ride heights get way off. The car gets a bunch of tilt (right higher) from jacking weight into the rr. It looks to be not right for a road race car. A buddy told me not to worry about it because the cross weights are actually fairly close... and to not worry about balancing the rear tire weights. Thoughts?
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Welcome and good to have you going left and right!
You have a big problem. That car was made with lots of low left weight. Using jack bolts will not get you handling where you need to be. If i remember correct, the car is build with 1/2 " offset from center line. I suspect the engine, transmission drive shaft are offset. I know you have battery and dry sump mounted on left side and fuel cell is probably offset to the left too. Maybe even the rear end is bolted in offset from the center line. This will be a major rework project. Also you may have lower trailing arms of non equal length and odd angle to each other. Unless you can get 50-50 left to right weight you will have tuff time getting a checker.
Welcome to road racing
You have a big problem. That car was made with lots of low left weight. Using jack bolts will not get you handling where you need to be. If i remember correct, the car is build with 1/2 " offset from center line. I suspect the engine, transmission drive shaft are offset. I know you have battery and dry sump mounted on left side and fuel cell is probably offset to the left too. Maybe even the rear end is bolted in offset from the center line. This will be a major rework project. Also you may have lower trailing arms of non equal length and odd angle to each other. Unless you can get 50-50 left to right weight you will have tuff time getting a checker.
Welcome to road racing
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- #963
Ronorlin
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Hey RR,
Thank you for the reply and the info. I will be back to my car next week and I already have Steve Smiths book! Thing is, I didn't remember about the camaro work he did because my car was all metric when I bought it. I had it clipped. (out of necessity) A wall at the Rock.
So let me get back into this in a few days. And I have a coleman spindle option allowed now. I will get the part number for you and discuss further. I am going to run out of time quick as I run at Memphis first weekend in Oct. Just won't have time to re-vamp it all by then. May need a "band-aid" approach for that race. But rest assured, I will this winter. I look forward to future dialog, and thank you. So i may have to run that 1" taller upper BJ on the RF to get the geometry close.
Ron
Thank you for the reply and the info. I will be back to my car next week and I already have Steve Smiths book! Thing is, I didn't remember about the camaro work he did because my car was all metric when I bought it. I had it clipped. (out of necessity) A wall at the Rock.
So let me get back into this in a few days. And I have a coleman spindle option allowed now. I will get the part number for you and discuss further. I am going to run out of time quick as I run at Memphis first weekend in Oct. Just won't have time to re-vamp it all by then. May need a "band-aid" approach for that race. But rest assured, I will this winter. I look forward to future dialog, and thank you. So i may have to run that 1" taller upper BJ on the RF to get the geometry close.
Ron
- #964
Luke Doolin
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What about cross weights, if they are close or very close? Should I worry as much about the lr weight?
The car BTW, has even a arms, engine is evened up as the rear and trans...it's only when I put MY weight in that the problem surfaces...250 lbs is less than 10 % of total car weight.
What about actually adding ballast to the rr? Bad idea?
The car BTW, has even a arms, engine is evened up as the rear and trans...it's only when I put MY weight in that the problem surfaces...250 lbs is less than 10 % of total car weight.
What about actually adding ballast to the rr? Bad idea?
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luke
On a left and right turn car the closer you get the left to right side weight the better you will handle. This is with driver and full load of fuel. Shift the battery to the right side. Add right side ballast. I would center up the fuel cell. You would only change front to rear weight if this is done as you burn off the fuel. Dry sump may be too much trouble to change over but think about this as you have several gallons of oil and it all adds up. One thing you can do is count up the large right and left turns, not the sweepers. Is your track biased to the right or left?
On a left and right turn car the closer you get the left to right side weight the better you will handle. This is with driver and full load of fuel. Shift the battery to the right side. Add right side ballast. I would center up the fuel cell. You would only change front to rear weight if this is done as you burn off the fuel. Dry sump may be too much trouble to change over but think about this as you have several gallons of oil and it all adds up. One thing you can do is count up the large right and left turns, not the sweepers. Is your track biased to the right or left?
- #966
Luke Doolin
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The battery is in front of the lr and that could be changed. The dry sump is in the lf fender behind the wheel and would have to be moved inside the cage on the rh side. Hot! unless I build a box around it. I shudder to think of actually adding ballast weight to a race car where there is no minimum but I have considered it before. Most road courses have dominant right hand turns with the exception of Daytona which has the two important right hand hairpins but the rest is pretty much left hand turns. I am talking about the tracks in the SE US, like Road Atlanta, Sebring, etc.
The cross weights are close but the lf is much heavier than the rf.
The cross weights are close but the lf is much heavier than the rf.
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this is a great link to read when converting an oval car to road course..
left vs right side weight is 50 to 52% but you want right side bias so should be 52% on right side for the " hot setup".
I would think about re-locating the dry sump, oil cooler, and fuel cell to the right side. when you burn off the fuel you may end up back at 50-50 left vs right side weight.
http://www.hotrod.com/how-to/chassis-suspension/ctrp-0011-race-car-weight-distribution/
left vs right side weight is 50 to 52% but you want right side bias so should be 52% on right side for the " hot setup".
I would think about re-locating the dry sump, oil cooler, and fuel cell to the right side. when you burn off the fuel you may end up back at 50-50 left vs right side weight.
http://www.hotrod.com/how-to/chassis-suspension/ctrp-0011-race-car-weight-distribution/
- #968
drobbie
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Just saw this picture of our race car from last weekend. I softened up the suspension all around and now I see the RF rolling under (blue arrow). Trying to figure out if I should stiffen or soften the RF spring. Any idea why this might be happening? Several cars had this same look.
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- #969
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I believe the original problem could be defined as "lateral tire deformation". A tire is just a bag of air, and it's shape can be influenced by many factors.
When a car is cornering, the tire is attempting to deal with the immense forces pushing sideways. Where the tire meets the track, it deforms.
In the picture, it illustrates how the tire is being forced out of it's inflated shape by cornering loads. Obviously, one fix is just to add pressure. What tire pressure are you using on the rt ft. tire?
Tire temperature should tell the whole story. What is the temp at the three points on the tire? what is the Average temp of all three compared to the other tires averages?
When a car is cornering, the tire is attempting to deal with the immense forces pushing sideways. Where the tire meets the track, it deforms.
In the picture, it illustrates how the tire is being forced out of it's inflated shape by cornering loads. Obviously, one fix is just to add pressure. What tire pressure are you using on the rt ft. tire?
Tire temperature should tell the whole story. What is the temp at the three points on the tire? what is the Average temp of all three compared to the other tires averages?
- #970
drobbie
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I am away on business right now so I do not have the tire temps in front of me, but from memory, the RS average was about 20 degree more than the Left and the rear about 8 degrees hotter than front. Also they did not look unusual with maybe a 25 degree (?) differential across the face. The pressure in the tires is 17.5 -18 hot (starting at 14). The car only weighs 1925 pounds to begin the race and 58% left and 49.5% rear. The track is a 1/3 semi banked oval with fast sweeping corners so you spend a bunch of time in the corner.
- #971
drobbie
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Here is the RF tire temps 164 168 180
Average of the tires are LF 121, RF 171, LR 150 RR 178
Average of the tires are LF 121, RF 171, LR 150 RR 178
- #972
loganc_racer
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In a matter unrelated to the current conversation. I put to use some of the information I gathered from this forum earlier this year, and ended up 2015 Champion of the Street Stock division at Sandusky Speedway. Thanks Mike and others for your input.
- #973
Jared0020
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Ronorlin are you running that GARS race at Memphis
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good jog loganc,
sandusky is a beautiful track..you don't need me to win..you just need to learn this stuff and properly apply the physics..
droobie is the temps you posted with same roll over tire condition?
Tempes show right front tire is toed in too much or has too much camber. 20 degrees on outside edge indicates this. Fix this first.
The left front is way cooler than the rest and is not doing its job. Needs more static weight or needs to start carrying more of the dynamic load.
Even if the car feels balanced it will go faster if you can shift some ballast on left side forward. Right rear is 7 degrees hotter than the right front indicating oversteer. Right rear should be 10 to 15 degrees cooler than right front tire. Both rear tires should be 10 to 15 degrees cooler in fact. Left rear is not carrying enough load either. You are very close to ideal so a little tweaking can go a long way. I would shift more ballast to left side and get the heat up the left rear and left front.
sandusky is a beautiful track..you don't need me to win..you just need to learn this stuff and properly apply the physics..
droobie is the temps you posted with same roll over tire condition?
Tempes show right front tire is toed in too much or has too much camber. 20 degrees on outside edge indicates this. Fix this first.
The left front is way cooler than the rest and is not doing its job. Needs more static weight or needs to start carrying more of the dynamic load.
Even if the car feels balanced it will go faster if you can shift some ballast on left side forward. Right rear is 7 degrees hotter than the right front indicating oversteer. Right rear should be 10 to 15 degrees cooler than right front tire. Both rear tires should be 10 to 15 degrees cooler in fact. Left rear is not carrying enough load either. You are very close to ideal so a little tweaking can go a long way. I would shift more ballast to left side and get the heat up the left rear and left front.
- #975
drobbie
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Ranger Mike thanks for the info and yes this is the same car. I can definitely make the frong end changes.
My goal all year has been to get the weight to the left front and currently there is 125lbs of lead at the lf. There is not a lot of room left in there for any more and I am well above the minimum weight now. Fyi, this is the only place i have lead mounted in the car.
I would much rather try to get the Lf to carry more of the weight dynamically if possible. What would you suggest?
Thanks for hosting thisforum.
My goal all year has been to get the weight to the left front and currently there is 125lbs of lead at the lf. There is not a lot of room left in there for any more and I am well above the minimum weight now. Fyi, this is the only place i have lead mounted in the car.
I would much rather try to get the Lf to carry more of the weight dynamically if possible. What would you suggest?
Thanks for hosting thisforum.
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thanks for the nice words..
are you running ARB (sway bar)? what is it?
what is car weight and what are spring rates?
are you running ARB (sway bar)? what is it?
what is car weight and what are spring rates?
- #977
drobbie
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Yes to the Sway bar. #95 rate
Springs from this picture are LF 325 RF 375 LR 165 and RR 150.
Car weighs 1940 with 58% Left and 49.5 Rear. Our minimum weight is 1900 lbs after the race (25 laps) and max 60% left. We generally burn 2-1/2 gal of fuel for a race.
Let me know if you need any other info.
Doug
Springs from this picture are LF 325 RF 375 LR 165 and RR 150.
Car weighs 1940 with 58% Left and 49.5 Rear. Our minimum weight is 1900 lbs after the race (25 laps) and max 60% left. We generally burn 2-1/2 gal of fuel for a race.
Let me know if you need any other info.
Doug
- #978
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we ran an outlaw super late model on year with 2400# weight
had 220# arb, had LF 300, rt ft 325
lft rear 175 and rrear 150# springs...
the heavier car had darn near same rear springs as you run
i would consider ft spring change with only 25 # split and go to heavier ARB
like maybe 300 lft ft 325 rt ft but be prepared for possible too loose condition.
once you get it too loose start going up on spring rates..watch tire temps
had 220# arb, had LF 300, rt ft 325
lft rear 175 and rrear 150# springs...
the heavier car had darn near same rear springs as you run
i would consider ft spring change with only 25 # split and go to heavier ARB
like maybe 300 lft ft 325 rt ft but be prepared for possible too loose condition.
once you get it too loose start going up on spring rates..watch tire temps
- #979
drobbie
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Sounds similar to what I am looking for.
How much stagger and cross weight did you run with this car?
How much stagger and cross weight did you run with this car?
- #980
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droobie, this is straight out of the tech books..3/8 track medium banking, 55 to 57% cross weight
stagger is what works for you..1 to 4 inch typical ..try 3 inch, could be 3.5"
stagger is what works for you..1 to 4 inch typical ..try 3 inch, could be 3.5"
- #981
drobbie
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Yup sounds like the numbers we ran in our late model years ago and not far from what we are using now. I'll be softening the front springs for next week's race. The issue I may have with the car in the picture is the ride height is only 2" at the LF and 2.75 at the RF. There really is no significant travel to be had. Too soft a spring and your hitting the race track.
But now, I have a another question we have been kicking around here, one to ponder and I am sure there would require some calculation and testing.
What if you used a lighter say bar and a stiffer RF spring to control roll instead. Could you get away with using less cross weight and possibly less stagger? Less stagger would mean less drag and less cross weight would allow the car to transfer the weight easier.
But now, I have a another question we have been kicking around here, one to ponder and I am sure there would require some calculation and testing.
What if you used a lighter say bar and a stiffer RF spring to control roll instead. Could you get away with using less cross weight and possibly less stagger? Less stagger would mean less drag and less cross weight would allow the car to transfer the weight easier.
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the photo of the car and tire temps all point a classic push going in-tight off condition. Where is the front roll center height and offset?
- #983
drobbie
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Roll center is 3-3/4" above the ground and 1-1/8" to the right.
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the front roll center needs to move to the right two more inches. There is not enough down force on the right front tire with current position. We need more down force to increase traction with body roll. The right front is plowing and the rt frt spring is too heavy. The left front can not lift under acceleration to plant the right rear tire. So we have a push going in lose off condition.
- #985
Gilbert33
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Is there a way to measure the body roll in cornering..? I have measurements from acelerometers for lateral forces, but I would like to substract the effects of the body inclination when cornering. How it will be possible to measure the body roll degrees...? I'm talking of market vehicles...
A Gyro will provide that body roll measure along the Y axis..?
A Gyro will provide that body roll measure along the Y axis..?
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welcome gilbert,
you need to state the question a little more precise. are you asking how to determine body roll of stock production automobile?
what kind of car is it?
need a lot more info to proceed and this may not be best place for this question.
in general we measure body roll using rubber stops on the dampers ( shock absorbers). This tell us us compression on one side but have fabricated brackets and a rod to measure droop on the left side as well. This means drilling and cutting the car body..not good for you if its not your car...
you need to state the question a little more precise. are you asking how to determine body roll of stock production automobile?
what kind of car is it?
need a lot more info to proceed and this may not be best place for this question.
in general we measure body roll using rubber stops on the dampers ( shock absorbers). This tell us us compression on one side but have fabricated brackets and a rod to measure droop on the left side as well. This means drilling and cutting the car body..not good for you if its not your car...
- #987
Gilbert33
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Thanks!
Well, yes I'm talking about stock cars. I have using my 2008 camry for tests. I'm using accelerometer to measure the developed cornering foce. But as the car transfers weight when cornering, I begin to be interested into how much it tilts, so I can compensate the amount of force measured by the accelerometer, due to gravity.
That's a excelent idea I had not in mind about measuring shock absorber displacement!
Well, yes I'm talking about stock cars. I have using my 2008 camry for tests. I'm using accelerometer to measure the developed cornering foce. But as the car transfers weight when cornering, I begin to be interested into how much it tilts, so I can compensate the amount of force measured by the accelerometer, due to gravity.
That's a excelent idea I had not in mind about measuring shock absorber displacement!
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as cheap as go pro cameras are , you could stick two in the wheel wells and glue up a couple of 1 foot plastic rulers to measure things as well.
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In Car Racing I can not stress enough that you have to keep your eye on the Checker Flag. Last race weekend we tried a new set of tires from a new manufacturer. total junk. My driver who has 30 plus years winning drove to second place only with great skill and personal tenacity. It sure was not the tires. The track was terrible on Saturday morning. 48 degree temperature, cold dreary day and NO GRIP. A pencil eraser would not scrub off on that track! Things did not go well in afternoon after dropping the air pressure. We ended up running the back up set of tires that had seen a lot better days. We got another second place and that is as good as the last race of the year did us. It was my call to go with the new brand..I had a couple long conversations with the tire engineer ...all very professional but you would not want to be in ear range when the car was sliding all over the track. Keep your eye on the flag and know the guy who screws up the LEAST will win, caz you will screw up..how much and how bad is the only question..but you will screw up..Top top it off some one backed into the tow vehicle and now I need some body work. At least the car is in one piece and all the wheels are pointed the same way...live to race another season..but them tires...
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New car or refine older one??
recent rules changes in SCCA now permit the 1995 and older cars to compete in the class we race. My team has been in deep discussion on changing over our SF88 rocker arm suspension car to the push rod design car, RF95, that dominated the class since its introduction in 1994. We had to spend some time gathering data but the bottom line is as follows.
Both cars must use same power plant and have dimensional limitations on length width height and weight.
Our car has about 1.4” longer wheel base.
Rear width is 2 inch wider in the newer RF95 car.
and RF95 car has wider front by 4 inch and slight aero advantage as it is a narrower car. Is it worth getting a 5 year newer car?
Stay tuned...it sure looks like i will be rebuilding a new car next year
That is the question?
recent rules changes in SCCA now permit the 1995 and older cars to compete in the class we race. My team has been in deep discussion on changing over our SF88 rocker arm suspension car to the push rod design car, RF95, that dominated the class since its introduction in 1994. We had to spend some time gathering data but the bottom line is as follows.
Both cars must use same power plant and have dimensional limitations on length width height and weight.
Our car has about 1.4” longer wheel base.
Rear width is 2 inch wider in the newer RF95 car.
and RF95 car has wider front by 4 inch and slight aero advantage as it is a narrower car. Is it worth getting a 5 year newer car?
Stay tuned...it sure looks like i will be rebuilding a new car next year
That is the question?
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- #991
GoneRacin
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Can someone explain why a vehicle's roll center axis is typically not HIGHER than the center of sprung mass?
Can we discuss some advantages and disadvantages in designing a race car with the roll axis higher than the center of sprung mass?
Thank you, in advance.
Can we discuss some advantages and disadvantages in designing a race car with the roll axis higher than the center of sprung mass?
Thank you, in advance.
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welcome goneracin
pls see page 12 post #229
RC over the COG ..not a good idea
pls see page 12 post #229
RC over the COG ..not a good idea
- #993
GoneRacin
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Thanks Ranger Mike.
I have read the post.
The part I am having difficulty understanding is, "If the roll center goes over the Cg, the chassis will actually "jack down" and start to roll to the inside of the turn."
Why would this be a bad thing?
Please note that the roll center would always be higher than the Cg, not "flipping" over the Cg.
Thanks again.
I have read the post.
The part I am having difficulty understanding is, "If the roll center goes over the Cg, the chassis will actually "jack down" and start to roll to the inside of the turn."
Why would this be a bad thing?
Please note that the roll center would always be higher than the Cg, not "flipping" over the Cg.
Thanks again.
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When the RC is intentionally over the COG you have just turned a cars suspension into a very smooth riding Go Kart.
The lateral force is shearing the tire patch and not being scrubbed off in a controlled manner with the cars suspension springs and dampers (shocks).
Yes, the body rolls, and compresses the springs ON THE WRONG SIDE.
You are helping to plant the left front tire and unload the right rear tire in a left hand turn. Pushes going in loose off the turn.
The ‘”hot setup” on short track cars is to offset the roll center to the right (below the COG) so the body roll produces download of the right front tire and increase grip of that tire. It should be the hottest tire temperature on the car followed by the right rear tire, lft ft, ft rear tire.
If you did have a super sticky tire on the right front that could handle all the lateral shear force because the RC is so high the angle of jacking force from the RC to the tire contact patch would be 55 degrees and you would lift the left front tire.
The lateral force is shearing the tire patch and not being scrubbed off in a controlled manner with the cars suspension springs and dampers (shocks).
Yes, the body rolls, and compresses the springs ON THE WRONG SIDE.
You are helping to plant the left front tire and unload the right rear tire in a left hand turn. Pushes going in loose off the turn.
The ‘”hot setup” on short track cars is to offset the roll center to the right (below the COG) so the body roll produces download of the right front tire and increase grip of that tire. It should be the hottest tire temperature on the car followed by the right rear tire, lft ft, ft rear tire.
If you did have a super sticky tire on the right front that could handle all the lateral shear force because the RC is so high the angle of jacking force from the RC to the tire contact patch would be 55 degrees and you would lift the left front tire.
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- #995
GoneRacin
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Thanks Ranger Mike.
Let me ask a similar question, but in a different way.
Most of the textbook examples of roll couple distribution, roll axis, etc. assume the the roll axis is centered and the chassis will roll toward the outside of the corner.
Now, knowing that the roll axis can be offset and that it moves dynamically, it seems that it would be possible to roll the chassis INTO the corner. (Similar to a motorcycle leaning INTO the corner.)
An example would be a circle track car with a low Cg and high left side weight % on a very high banked corner with stiff springs on the right side, soft springs on the left side and a roll axis located near the right side tire contact patches.
Certainly this chassis could lean INTO the turn and not roll toward the outside.
It seems to me that there could be some advantages to leaning the chassis INTO the turn.
What would be the disadvantages?
Let me ask a similar question, but in a different way.
Most of the textbook examples of roll couple distribution, roll axis, etc. assume the the roll axis is centered and the chassis will roll toward the outside of the corner.
Now, knowing that the roll axis can be offset and that it moves dynamically, it seems that it would be possible to roll the chassis INTO the corner. (Similar to a motorcycle leaning INTO the corner.)
An example would be a circle track car with a low Cg and high left side weight % on a very high banked corner with stiff springs on the right side, soft springs on the left side and a roll axis located near the right side tire contact patches.
Certainly this chassis could lean INTO the turn and not roll toward the outside.
It seems to me that there could be some advantages to leaning the chassis INTO the turn.
What would be the disadvantages?
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Most of the textbook examples of roll couple distribution, roll axis, etc. assume the the roll axis is centered and the chassis will roll toward the outside of the corner.
My assumption is that it is easier to explain these chassis dynamics with a symmetrical set up. Laziness on part of the books author.
A motorcycle rider can shift his weight ( COG) to counter the effects of momentum ( in this case cornering force). A race car can not shift its COG as it is fixed.
A circle track car with a low Cg and high left side weight % on a very high banked corner with stiff springs on the right side, soft springs on the left side and a roll axis located near the right side tire contact patches WOULD PUSH LIKE A FREIGHT TRAIN.
Certainly this chassis could lean INTO the turn and not roll toward the outside. YOU HAVE TO HAVE GRIP TO DO THIS AND YOU WILL NOT WITH THIS SET UP.
It seems to me that there could be some advantages to leaning the chassis INTO the turn. SUCH AS?
What would be the disadvantages? NOT USING THE SUSPENSION TO HANDEL THE CORNERING FORCES TO THE DRIVERS ADVANTAGE.
I think you have not grasped the basics of handling regarding a left turn race car. Some how you got it in your head that a car will handle better if the chassis leans to the inside on a left hand corner. Take time to draw the force vectors and you will see this.
My assumption is that it is easier to explain these chassis dynamics with a symmetrical set up. Laziness on part of the books author.
A motorcycle rider can shift his weight ( COG) to counter the effects of momentum ( in this case cornering force). A race car can not shift its COG as it is fixed.
A circle track car with a low Cg and high left side weight % on a very high banked corner with stiff springs on the right side, soft springs on the left side and a roll axis located near the right side tire contact patches WOULD PUSH LIKE A FREIGHT TRAIN.
Certainly this chassis could lean INTO the turn and not roll toward the outside. YOU HAVE TO HAVE GRIP TO DO THIS AND YOU WILL NOT WITH THIS SET UP.
It seems to me that there could be some advantages to leaning the chassis INTO the turn. SUCH AS?
What would be the disadvantages? NOT USING THE SUSPENSION TO HANDEL THE CORNERING FORCES TO THE DRIVERS ADVANTAGE.
I think you have not grasped the basics of handling regarding a left turn race car. Some how you got it in your head that a car will handle better if the chassis leans to the inside on a left hand corner. Take time to draw the force vectors and you will see this.
- #997
GoneRacin
- 4
- 0
Hi Ranger Mike.
Yeah, I guess your right.
It was just more of a thought process, for me.
I had been told that the car would ALWAYS ROLL and we had to deal with some of the associated "disadvantages".
I was trying to think of a "new" way to get the car to lean into the turn by moving the roll axis.
Some of the advantages ...
It may feel more comfortable to the driver.
Less camber loss on the left front tire.
The front anti-roll bar could be eliminated, thus saving weight.
Better for fluids such as fuel in the carb. bowl, gas tank and oil in the pan.
Areo advantages by keeping the left front down and the right rear up.
In the unfortunate event of a rough track, the chassis would drag on the track surface as opposed to digging in or plowing it up.
Passenger cars... not spilling your favorite adult beverage.
Yeah, I guess your right.
It was just more of a thought process, for me.
I had been told that the car would ALWAYS ROLL and we had to deal with some of the associated "disadvantages".
I was trying to think of a "new" way to get the car to lean into the turn by moving the roll axis.
Some of the advantages ...
It may feel more comfortable to the driver.
Less camber loss on the left front tire.
The front anti-roll bar could be eliminated, thus saving weight.
Better for fluids such as fuel in the carb. bowl, gas tank and oil in the pan.
Areo advantages by keeping the left front down and the right rear up.
In the unfortunate event of a rough track, the chassis would drag on the track surface as opposed to digging in or plowing it up.
Passenger cars... not spilling your favorite adult beverage.
- #998
- 2,444
- 429
pretty logical thought process..keep up the good work!
rm
rm
- #999
no friends at
- 2
- 0
Ranger Mike ,#253, when you say left side of the car. Is that looking from the front or rear of the car. Left is driver , right is passenger? I have a 30" pull bar and 23.5" lower control arms. Are these to short for a 107" wheel base and 2200 lbs. of car? Dry sump tank, radiator. trans cooler, battery and fuel cell are all mounted in the rear half of the car. Only the radiator pod is aft of the axle. Engine is pulled back 12" and off set 3" to the passenger side. The chassis is 4" off the ground. Working on the body next. Looking to rake the windshield to super car status for less drag. 23 degrees from stock 35 degrees. Am i missing something besides a brain? lol Thanks RM
- #1,000
- 2,444
- 429
welcome no friend,
Left side is drivers side- always ..when I talk about it...to help you remember...when you see a driver who porked up over the winter..just tell him..more left side weight!
it a pit joke..
20 to 24 inch trail arms usually.
I assume you run paved track with three link.
in my opinion you can not change things unless you know what you got.
buy chassis software and bench mark the car.
front roll center – where is it ? how high is it? same on rear Roll Center
what is height of camshaft ( center of gravity )
what is left side weight % rear % , cross weight %?
do you have rear roll steer?
these are just a few data points you need to see where you are and change to a better handling car.
Left side is drivers side- always ..when I talk about it...to help you remember...when you see a driver who porked up over the winter..just tell him..more left side weight!
it a pit joke..
20 to 24 inch trail arms usually.
I assume you run paved track with three link.
in my opinion you can not change things unless you know what you got.
buy chassis software and bench mark the car.
front roll center – where is it ? how high is it? same on rear Roll Center
what is height of camshaft ( center of gravity )
what is left side weight % rear % , cross weight %?
do you have rear roll steer?
these are just a few data points you need to see where you are and change to a better handling car.
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