Race car suspension Class

Ranger Mike

All things are relative so i would make small changes like when you are on on a wet tacky or very tight track you want to loosen the chassis up on corner entry. Use a tie down shock on the Left front. This lets the left ft. drop down easily at corner entry and takes weight off the RR tire. This makes the car pivot around the Left Ft which makes it easier to steer in the the corner. The tie down shock delays weight transfers off the lefty front. In the middle of the corner when the chassis is transferring weight to the RR., it keeps the LF tied down to prevent a quick weight transfer to t he right rear. A stiffer LR shock with stiffer rebound holds the weight on the LR longer at corner entry not allowing as quick a transfer to the RT FT tire.

THORPE

Ok I see where you are going with this and it makes sense. Thank you for your time.

I got off track a little after reading this article about initial weight transitions.

http://www.circletrack.com/chassiste...g_your_shocks/

THORPE

I did exactly this ^^^^ yesterday for practice and absolutely love it.

Also found a problem I've been fighting for while now. My upper links.
When I drew out the geometry I must have misinterpreted something and had the inner links higher. Thought I was lowering my rc but instead had raised it.

Made the swap real quick to lower them and WOW. All I can say. It was that great. Finally made everything I've been working towards come together for a great setup.

Thank you for your knowledge you are willing to share on here I know it has helped me tremendously

Ranger Mike

Thanks for the kind words..Ifin we were racing each other on the same track I doubt I would be as Christian...seriously I appreciate it.
I hope everyone realizes I have sourced some pretty good books and if everyone bought these, they would we able to figure things out..all I do is save a little time in the process and hopefully do not impart BAD advice that screws up some ones good set up...Like Jimmy Johnson just demonstrated, you have to FINISH to win. So this winter is the time to check and inspect every nut and bolt on the car. When in doubt ,,replace it!

Ranger Mike

Real good questions hear. Stagger – on open diff car , it is a waste of effort. The differential is doing its job and tire size will not impact the drive motion at all with this setup. Are you running stock diff or Ford 9 inch model?
But...you can use stagger on right front to add or take out wedge or cross weight. So when you are tire matching keep this in mind and 1/2 inch will do some good for you. Now back to the spring thing...wedge bolts or jack bolts are for at the track FINE TUNING ......period. If you go to the track without knowing where your Roll Center is and what's base line spring rate be you have no business cranking on a stupid jack bolt!..
You have restrictive rules on weight jack bolts..ok..use the stagger to tune it. You can buy spring rubbers to add more rate.
Sway bars ( anti roll bars) ..get as many different ones as will fit and know their spring rates and swap these out at the track until you figure out proper spring package. Shocks...you should have a good base line on these but I assume nothing and we can revisit later.


Not knowing all the rules you face all I can do is suggest.

I recommend you spend the $ 100 for Roll Center software. Measure the car, find out where the Roll center is.. Next , before you do anything, look at the rules to see if you can change the roll center height, legally. As a minimum, change the Front RC location to offset it to the right to plant some down force on the right front tire. Then see if you can drop the front RC and still keep it 3 to 3.5 inch to the right. When we drop the RC we kill off camber build and the jacking effect on the right front. Rear RC should come down as well and again depends on rules and you can get different spring heights and spring rates as the software tells you.

Next work on eliminating bump steer and know your camber build curve over +/- 3 inch travel.
More tips are to concentrate your efforts on going after big chunks of things like horsepower. Do look at a trick 2 barrel carb ( why put on a 4 bbl. carb when the tires cant possibly hook up.)
Hedders are good, after market ignition is good if..if... you have battery big enough to run the car all night without the alternator. I like a point eliminator type distributor kit like a photo cell and straight coil..no CD ignition. Simple and easy to trouble shoot at the track. In fact , forget roller rocker arms, big intake valves, trick engine stuff.. just the basics..keep cost down for more tire money. Spend it on brake caliper upgrades and better lighter rotors. Add brake bias pedal so you can dial in front to rear brake bias. Eliminate all the rubber suspension bushings and replace with brass or aluminum. But I am sure you fellows are already on top of this..my point is to show the newbies some areas to improve..economically..

mustngthundr

I'll be at IMIS- and the ARS chassis seminar

mustngthundr

I haven't been to it yet either, but iv heard there's lots of good info. I'm looking forward to it

missile07

Which roll center software package do you prefer? I have been looking at the Performance trends & Auto-Ware. Both look similar but Auto-ware looks more up to date and more user friendly.

Ranger Mike

I use perfomance trends and recommend you call Kevin Gertgen, who I have worked with since 1999.

BTW..i am honored to be nominated for an award on Engineering Forum poll

Threads in Forum : 2012 PF Member Awards

...thanks guys, I appreciate the votes!

Ranger Mike

Auto Ware software is a good product from what I can see..

I think Kevin and the Performsnce Trends software is a little more advanced in that it has the higher end capabities of watching dive and roll dynamically and can use data loggers to collect the data input..plus i have many legacy programs already form over the years...

any serious racer needs at least one of these to find Roll Center and adjust accordingly

my opinion

Ranger Mike

A lot of you sent private messages to me about running in very restrictive stock classes and what “ advantages” you can make over competition.
One area often overlooked is the Rear ARB or Sway Bar. We have discussed the Soft Spring Big Bar set up in pretty great detail in previous posts here.
The whole idea of using a BIG Bar on the rear is to permit spring squat and thus more traction coming off the corners. Since you are forced to run hard spec tires, any advantage to putting more traction down will be a great advantage 9 all other things considered.)

A quick review of the ARB - sometimes also called anti-sway bars or anti-roll bars. Their purpose in life is to try to keep the car's body from "rolling" in a left turn.
When you are inside the car, you know that your body gets pulled toward the outside of the turn. The So the right part of the car on the outside of the turn gets pushed down toward the road and the left side part of the car on the inside of the turn rises up. In other words, the body of the car "rolls" 10 or 20 or 30 degrees toward the outside of the turn. If you take a turn fast enough, the tires on the inside of the turn actually rise off the road and the car flips over.

Too much Roll is bad. It tends to put more weight on the outside tires and less weigh on the inside tires, reducing traction. Proper amount of body roll will load the right front tire and assist in improving traction through the turn. Ideally, we would like the body of the car to remain flat through a turn so that the weight stays distributed evenly on all four tires.

ARB tries to keep the car's body flat by moving force from one side of the body to another. When you go into a turn, the front suspension member of the outside of the turn gets pushed upward. The arm of the ARB gets pushed upward, and this applies torsion to the middle section. The torsion moves the arm at the other end of the rod, and this causes the suspension on the other side of the car to compress. The car's body tends to stay flat in the turn.

If you have too much ARB, you tend to lose independence between the suspension members on both sides of the car. When one wheel hits a bump, the ARB transmits the bump to the other side of the car as well, which is not what you want. The ideal is to find a setting that reduces body roll but does not hurt the independence of the front or rear springs.

Back to the “ street Stock “ set up. If we replace the spindly stock “ sway bar’ with a much beefier one, and we switched to much softer rear springs, we still control the body roll and at mid turn after the weight transfer has zeroed out, we can point the car and jump on the throttle much quicker since we wil be loading the rear tires to more of a degree than with our previous set up. Just something to think of when its snowing out side..

Ranger Mike

Excellent points..pls look at page 2 on how we figured weight that was transferred and look at page 20 for rear motion rates.. We really got to be on top of the front ‘ spring rates’ ( and ARB) to control roll and proper rt ft wheel loading.. the rear...well... we are not talking about a heck of a lot of transfer...i.e. we got a 3100 pound street stocker...going into a medium to high bank turn..
on stock hard tires...for the sake of this discussion we assume we corner at 1.3 G...way high but the figure is common in prior posts so here is the math..
3100 pound car times .35 means 1085 weight transfer up front and left to right. We figured that 75% is going up front so 75% of 1085 is 814 pounds...so both springs and the ARB have to handle 272 pounds with motion rate is figured in...mean while we have 25 % of 1085 pounds or 271 pounds going from left to right in the rear. This is not a lot of weight for the springs to handle. In fact , if we add in the rear ARB we have 271 / 3 = 90 pounds for each spring and the ARB to deal with.
Typical ( per post 308 page 20) Ford 9 inch rear end has a .688 Motion Rate (MR)... so we have the formula WR = (MR x MR) x SR (spring rate).. just FYI...a .688 MR squared is .473
so if we want to handle 90 pounds of weight with each spring ( ARB calculated separately but to have same effectiveness) the math is
90= .473 x SR so...SR= 90 / .473 or 190 lbs. spring....typical stocker run 250# or so Rear springs WITH OUT the ARB.

So you see , the opportunity of using the rear ARB to counter left to right roll and potential for rear squat to really hook up the tires is pretty good.


One rumor from the NASCAR side of the house was the rear ARB was mounted in such a way as to close the skirt gap of the skirting on both sides of the new Car of Tommorow..AT SPEED...which is very difficult to detect when going thru tech inspection. Somebody talked and now the ARB links have to be perdendicular to the ground as viewed from all sides. Seems some enterprising team chief figured out if you can seal up the skirting better than the other guy, you got more grip going into the corner and could run deeper..so...if you use some really compliant mounting bushings and angled them ....???

Ranger Mike

Again many of you have messaged me on advice on gaining an advantage “ legally”.
I looked up my notes from flogging the old GM metric chassis during my door flapper days. I was into chassis measurements big time and wanted to MAP the rear end movement relative to ride height and was trying to understand what was happening when the car was in the turn.
I found that by setting the chassis on stands and mapping the rear end movement using 3 inches of right rear down and 1 inch left rear up, the metric chassis pulled the right rear tire forward almost 3/8 inch more than the left. This was AFTER I loosened the bolts holding the trail arms ..etc... as the stock serrated teeth bound up the components when “ properly tightened”. Anyway, this movement when rolling into a turn, would have the effect of tightening the car on corner exit or anytime the power was applied. I learned three things here. 1. Stock rubber bushings flex and can be to your advantage. 2. I had to free up the components to swing free when race ready and replacing the inner metal spacer that had teeth with a smaller diameter non toothed spacer was a must. Also I replaced the stock bushing bolt nuts with lock nuts at could be run down tight and then backed off a turn to prevent bind. 3. As the venerable Stroker Mcgurk once said..” If some is good and more is better then too much is just enough “ so I went on to see how much flex I could get out of the rubber bushing. More on this later.

You have to measure your car to find out where you are relative to where you want to go. If the rear axle pivots so the right-rear pulls forward, this will tighten the car. If the left rear pulls forward, the car will be looser.

Roll steer can be affected by using very soft rubber bushings. I tried the old tire softener trick but it seriously and quickly deteriorated the bushing and was a mess. With softer bushings on the right rear lower trailing arm, you have roll steer loosening the car on entry. This would reverse with the power on and tightens up the car on corner exit. The soft bushing allows the right rear wheel to pull rearward under braking. With acceleration, the right rear will push forward and this tightens the car on corner exit.

You can soften these bushings by drilling holes in them parallel to the bolt. This permits more compressibility..
Before you loosen up all your bushings, you better think about it.

If you want more roll steer to tighten up the car on corner exit you would soften the bushings on the right lower trailing arm. This compresses the wheel base on that side during acceleration by pulling the right rear forward. It would then steer to the inside. Softening the left side lower trailing arm bushings would offset much of the right side compression. This would loosen the car. Softening both might be an aid to forward traction because the rear end bottom mounting points ( trailing arms) shorten up and thus move forward in the chassis adding weight to the rear tires and more traction.
Beware- If you are using roll steer to tighten the car on corner exit, it may loosen the car on corner entry.

So why do all this...so you have an advantage over the other racer who looks at other areas for an advantage, The rules say stock trail arms and mounting locations and in some cases, no eccentric bolts...so...think about it...you could get up to 1/2 inch movement that could make all the difference.

Ranger Mike

Happy New Year and you got the best present possible...yeah I agree. Shock location half way between the mount point and Ball Joint will be pretty in effective. The closer to the BJ the better and if rules say you got to run stock location on the shocks...run a racing shock. And you MUST run a shock ( damper) to complete the proper susension. In some cases we need to run a tie down shock to keep transfered weight where we want. Stock location is not excatly racing ideal but as a minimum you need a shock and automotive engineers spent millions on designing the set up and it is a compromise for ride comfort, performance and economy of manufacture.

Stock shocks will not stand up to the abuse of racing. We run Penske 3 way shcoks and have to rebuild every year. The shock oil deteriorates and the thin metal shims wear out. You get alot of heat when you dampen the suspension and this is the main culprit.

Ranger Mike

Speedway Motors has a bunch of racing shocks specifically for your class..I like this one myself..affordable and who is going to claim your " used shocks" for $ 50.00..never seems to happen..make sure you paint them same as your original shocks and smear a lot of grease and dirt on them....

http://www.speedwaymotors.com/QA1-St...ing,31463.html

Maliwagon99

Notice my postscar were gone? I gotwas deleted forand being a spammer somehow? Anyway now that im back up and running I can ask more questions. On the rear ARB will a aftermarket stock mounting one suffice? I have seen some that mount to the rear end with similar bushings as the front mounted on the housing then the ends hooked to the LCA ahead in the front with some adjustable links ie http://www.hotchkis.net/_uploaded_fi...455image_2.jpg . Since it doesn't say anything in the rules about it id like to try but I have a good feeling if I start winning that will be the first "gray" area fixed and that bar mounting system isn't cheap. Your thoughts?

Ranger Mike

I would mount a stock appearing ARB on the rear as close to " stock " location as possible and I do not think they will say anything because the car came with one from the factory..right?