Race car suspension Class

Ranger Mike

So there I am under the car at 4 in the morning changing ball joints. I pressed the new one in but manager to ding up the threads so the nut will not properly follow the threads. Ok, out comes the tap and die kit..to my horror its a metric thread.

Even worse, it is a relatively rare thread as it is M 14 - 1.5 which is the fine thread. No where in 30 miles will I find a metric die to re-thread the stud and I don't want to remove the ball joint and replace it. I can't use a small file to chase the damaged threads..

solution

I hack sawed a slot in a good M14 - 1.5 nut, spread the slot apart with a chisel (careful not to mess up the treads at the bottom of the nut). I opened the slot enough to be able to slip it over the damaged thread until it fitted over the good undamaged threads. I used a pair of Vise Grips to tighten the nut just enough and rotated the nut off the ball joint stud thus chasing the damaged threads. I did not clamp the nut totally tight as I did not want to ruin the threads on the nut. I did this four or five times, each time closing the slot gap a little more until the threads were repaired enough to run a good M14 - 1.5 nut up to the good threads and permitted me to tighten the nut to spec.
just thought I would pass this on.

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WN9Y

How many beers does it take to come up with such ideas?

Ranger Mike

4 to 12??

necessity is the mother of invention

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British Menac

Hehe .... nice humour aswell as interesting thread Mike.
When finnished with your project I do have an interesting question for you.
For now, I would like to follow this project if I may.
BM

Ranger Mike

Welcome...always like input from our Brit connections..Pardon me..project?

British Menac

Yes Mike .... Your present project here on Designing a suspention set up from scratch.

My question involves a design which would not involve accomodating a driver ..... :-)

Very good information here.

British Menace

Ranger Mike

some of the drivers I had to work with could in fact fulfill this requirment...i.e. the guy behind the wheel could not be considered a driver..

British Menac

Hehe .... funny Mike. I trust they are not the sort to read threads like this?
BM

chriswh86

Hi everyone,

Chris here from BC-Canada! Just had a look over a few of the pages in this thread. Amazing information. I dont have much of a background in racing as I just got into asphalt dwarf racing 2-3 years ago; A bit of time spent in the drivers seat, more time spent tinkering in the shop, reading books, using a computerized suspension program and going to race nights with my friend to help pit/tune/work on his car on race and practice nights.

I find dwarf cars to be quite interesting considering a coil over independant front suspension and solid axle, 3 link rear suspension. ~1210pound cars and the ability to try some wild suspension setups/ideas/parts/motors and so on

Anyways, just wanted to start out by saying hi and I will definantly be looking at having some questions answered in the near future. Im just 25 and ive got a lot of learning ahead of me. I still have a lot of learning to do on setting up a car before race day. Im not yet consistant on taking a LOT of notes and doing the same very involved overview and setup of his car before race day.

My friend is the type of, if it aint broke, dont fix it, and if the car is resonably fast leave it, and just put a round in here or out of there. So its hard for me to try any changes that i want to try.

Anyways, I would like to see if I can get a couple questions answered without jumpin in on the threads above on designing a suspension system from scratch. Im looking to see if you all have some good information on string lining a car, i cant afford lasers so what is my best bet on string lining the car, what should I look for and so on and how should I do it. Also, is it best to use the string line setup to check/adjust toe out or is there a more percise route to take to get a consistant toe out measurement. Our current way of measuring toe out is horrible, im embarrased to say how we do it. Anyways, I just dont like the idea of measuring off the tire as Im sure there are to many imperfections/writing on the tire to make for a bad toe out measurement. is it best to use a toe bar and a tire scrib to scribe a line on the tire tread and use the toe bar to measure from that?

Thanks all,

Chris,

Ranger Mike

Welcome Chris..we have these at the local tracks...nice clean racing...see post 293 on stinging the car..measuring toe is best deon with scribing a line on the tire but this takes two people t o scribe the line and hold " dumb end " of the tape measure....we use a toe gage..i will see if i can get photo of this on line..onme person can check the car and adjust...really close results..the Legends or Dwarf cars are real fun but rules say you can not do a lot to them..which does keep cost down...

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chriswh86

interesting. here are a couple items I found at longacre

tire scribe
toe gauge that will measure to 1/32"

seems like a good setup.

Yah the dwarf cars are pretty cheap to run. We are just a local club so we designed our own rules theres a lot of grey areas etc but they also state if its not in the rules you cant do it so im not to sure. But you can still design the setup however you want pretty much, which is quite nice.

I will look over the string line post. Thanks!

Chris,

Ranger Mike

Anti-dive and anti-squat ( I didn't explain calculations on post 314 so here it is)

Please read post 314 on page 20-

I had a question from Conrad on setting up his front suspension. Both Anti Dive and Anti-squat refer to the front diving under braking and the rear squatting under acceleration. They came about because passenger cars would require very stiff springs to counter act braking and acceleration forces and the difference in design is due to the different design goals between front and rear suspension, assuming symmetrical design between the left and right of the vehicle.

Percentage is the method of determining the anti-dive or anti-squat and this depends on whether the suspension linkages react to the torque of braking and accelerating. For example, with inboard brakes and half-shaft driven rear wheels, the suspension linkages do not, but with outboard brakes and a swing-axle driveline, they do.

To determine the percentage of front suspension braking anti-dive ( outboard brakes like GM metric chassis uses)

1. Determine the tangent of the angle between a line drawn, in side view, through the front tire patch and the front suspension instant center, and the horizontal.

2 Determine the percentage of braking effort at the front wheels.

3. Multiply the tangent by the front wheel braking effort percentage.

4. Divide by the ratio of the center of gravity height to the wheelbase.

A value of 50% would mean that half of the weight transfer to the front wheels, during braking, is being transmitted through the front suspension linkage and half is being transmitted through the front suspension springs. Passenger cars are as high as 30%, stock car racers run 5 to 7% if they even bother to figure it.

For inboard brakes, the same procedure is followed but using the wheel center instead of contact patch center.

Forward acceleration anti-squat is calculated in a similar manner and with the same relationship between percentage and weight transfer. BUT..you can have Anti-squat values of 100% and more (common in drag racing). all of the weight transfer is being carried through the suspension linkage but remember, this does not mean that the suspension is incapable of carrying additional loads (aerodynamic, cornering, etc.) while braking or during acceleration. 50% or less are more common in cars which have to undergo severe braking. Higher values of anti-squat commonly cause wheel hop during braking.

chriswh86

Off topic

we run a 235 60 13 tire in our dwarf car class, ive seen some people running 13x7 rims but most on 13x8 rims that stretch the tires out pretty good.

I am wondering if there would be much benefit to going to a 13x9 if that would pull the side walls a little straighter and maybe take away some tire roll...

Chris,

Ranger Mike

like everything in racing , its all about compromise..we went thru this mind drill in FC ( Formula Continental) a few years back. In a class that races open wheel and limited horsepower the traction benefits of wider boots on all four corners may not be worth is. The key factor is engine output ( torque and HP). Open wheel cars get killed with big aero drag and tires account for at least 40% of total drag.
If.. and this is a big if the tire and wheel combination is the same as your current combination, and yoor wheels are under the car not hanging out in the air stream..Id run them. But if they are heavier than the current set up (come on...it takes more metal to make them... more metal = more weight). There's also more rolling mass. More rolling mass = slower rotation = slower speed. Figure about 2% more grip per inch tire width you add,,,but,,,parasitic drag is a BEAR...esp in open wheel limited hp racing.

see post below on General Physics forum,

How does traction compare to the width of a tire?

Mar17-12, 07:03 AM
Mender had some good insight

Liju GKM

sir, we are participating in mini baja. can you tell the steps of designing suspemsion in the correct order??????

Ranger Mike

how high is the sky?

chriswh86

Interesting question im having a hard time figuring out.

As ive seen, most circle track cars run some sort of offset on the rim backspacing to create more left side weight?

I recently got a newer used dwarf car which has set multiple track records, multiple points championships etc and it runs 13x8 aero rims @ all 4 corners with 1" backspacing.

Im having a hard time figuring out what the benefits of running this type of offset is at all 4 corners. theres a few other cars in the club running 1-2" backspacing at all 4 corners and they are fast as well.

Is it a way to better load the contact patches on acceleration? I just cant seem to get an answer i understand as to how this works.

Chris,