Hi!

I guess this has ben addressed before, but I cant find any threads, so I'll ask:

For a 951 track car with H&R CS coilover's (torsion delete) 18*10" 250 slicks, GT3 brakes. Had an incident, and needed to take averything apart. The car is weighted in pretty good, now ready setup, previous setup was

Camber: -3.5 front, -3 rear
Toe: pretty straight i think
Caster: dont know

What wheel allignment / setupnumbers du you guys use?

 

Alignment is subjective to personal preference.

Do you have power steering....?

Do you mean DOT treadless race tires, Hoosier, Hankook, BFG, etc. or do you mean real slicks like you'd buy off professional race team test days...?

Camber - for a 944 really hauling the mail, yes, -3.5 is in the ball park, in the rear we run closer to -2.5 but -3.0 would be inside my window. Again though, different tires, different sweet spot. I use the hot pits (right off track) with a tire probe at three intervals across the tire to determine if more/less camber is needed. You are trying to equalize tire temp across the outside/center/inside.
Err on the side of lesser for straight line braking contact patch.
Toe - Zero total toe is the generally accepted setting, which obviously would be Left toe = 0 and right = 0.
When you get into let's say, 1/8" (3mm) total toe in or out, you want to make sure each side carries the equivalent of half the total toe, so LF & RF = 1/16" (1.5mm) toe out each. Toe is a tuning aid just like camber and caster so it's a personal preference.
Toe in will give straight line stability and toe out will wander a little. For the same reason, toe out makes the car a little more agile and on a razor edge, ready to dart to exactly where you aim it.
Toe out turns in easier IMO so if you are competing against alike powered cars this can help you make an aggressive inside move to the corner first.
Caster - ride height changes when the steering is turned from side to side because the strut angle is levered forward from top to bottom with more caster, so the steering becomes more "weighted".
Difficult to describe without feel but the tires want to "fall over" on turn in (think wheelbarrow) but as you round the apex the car wants to go straight (think caster wheel on shopping buggy) and you have the sense that you are fighting against the weight of the front end as the steering wheel is unwound as you exit......because you ARE raising the front end.
On a 944, you'll just have to take my word for it....., I post it as a signature sometimes, "caster is faster".
The value that you can achieve will vary from side to side as much as by a full degree, so what you want to to is find the maximum allowable on both sides and set them both to the lesser maximum setting, meaning, you want the maximum symmetrical caster.

Anything more than this and I'd have to either have you sign a privacy disclaimer or send compensation....

T

 

^^^ I enjoy reading your responses T, you are a wealth of knowledge.

 

I'm still very much an amateur, but from what I've learnt so far I agree with all of what T says.

I run 18 inch wheels with 255 street/track semis all round on my car and these are my specs:

Camber: -3 front, -2 rear
Toe front: 0 (it was better with 1mm toe out either side, but it chewed through tyres very quickly)
Toe rear: 1.5mm toe in either side
Castor: Maxed out (about 4 degrees on left side, 3 on the right)

With these settings I'm getting even heat and wear across the tires. It does pull a little to one side though, so next time I get an alignment I'll need to even up the castor to 3 degrees either side, and that should fix it hopefully.

 

So caster is faster
Makes sense as the tires seat turned "naturally" and don't want to turn to straight so you're probably using a bigger patch...so...you can probably go faster without understeering.
But I guess the steering will feel a bit weird because as soon as you turn it a bit it will want to fall over turned and sit there.
So, symetrical camber + (max symetrical)caster for better front end grip.

 

I'm no racer, but even on the street and for autocross, I'll agree that more caster is more better on these cars. I have mine set at just under 4.5 on both sides, that's the most I could pull out while keeping them equal.

 

Even on the same car/weight/class and tire, no alignment settings are set in stone because the driver is the variable.

Late apex vs early turn in, trail braking vs. straight line braking, set and power through corner, etc., etc.

Negative camber increases as you turn the wheel when you have positive caster. So you may go from your setup static -3.0 to -3.5 while turning.

That's why you should err on the side of caution on -camber in exchange for maximum contact patch for straight line braking.

T

 

This is why most spec series state that "suspension pickup points shall remain as factory".

Some don't even want you to have an aftermarket camber plate set at anything other than -0-, only the camber achievable by the factory eccentric is allowable.

It would get out of hand if too much creativity were allowed by raising the a-arm, etc., and there is always performance left on the table with factory setting ranges.

I think adjustable bump steer kits are illegal in some cases.

Only thing we run, not counting sphericals, are the geometry correcting ball joints to keep the a-arm level with the ground at lowered ride height.

T

 

You would be better off getting those to match.

If you can't get 3.5-4.0 on either side, there was some kind of friction bind while setting that made only 3.0 achievable or you car may have been previously wrecked...?

T

 

Thanks a lot to T and the rest of you. What you say makes sence. Taking it to the "specialist", i guess he has an opinion to. At least i know a litle more now.

And i run slicks as in racingslicks. Yokohama supersofts. They stick.

 

Kul bil

Nice car, any specs on it?

 

Very nice.

The trend here is going back to the original wheel sizes or even down in size to 15" custom wheels due to the performance in gearing and the price difference in 18" race tires.

One of the top 944S2s in USA racing runs 15" rear wheels.

T

 

Thanks, you gain knowledge through experience and unfortunately, with that comes age....

T

 

Hi again!

EALokken, as i understand you are building youself a 944 T racer these days as well? 3L?
Engine is stock with upraded chip, W.G. spring and blocked I.C. necks. 260HP?
Panels are: Lexan sideglass, GF front and hood.
Under the car: H&R CS kit with stiffer springs, torsion delete, camberplates, GT3 322mm front brakes, LSD diff (porsche) Sanden early ET alu A-arm, 9products caster block, 968 roll bar aso.
The car isset up pretty nice, but could need som extra HP

1.37 Rudskogen.

 

re wheel size. I hear some talk about historic racing becoming popular over here as well, ie originality becomes an issue. But i need some inches to fit 330mm brakes under