Jim Clark

Looking for some help with a race set up for an upcoming event at Daytona. I'm having problems with the tail all over the place under braking and just cornering at times. Car loves to turn in but tail is loose.
At present I'm not able to concider an LSD for tire spin but have done a bit of suspension upgrades for a start. Let me know what you think of the set-up and some ideas to move forward with. Thanks for the help.

Koni Sport Yellows all around - How many turns back from full?
30mm bars
400lbs springs. - should I go 450lbs ??
stock front bar 22.5mm
rear bar 18mm
Adjustable camber plates
present settings front -3.00 camber, 3.00 caster, 1/16 toe in
rear - stock settings
15" phone dials with 225/45 Kumho's
Alum. stock controle arms with rennbay kits - 968 rear bushings / stock front.
strut bar
Brakes - Hawk Blues
Ride height set at 5" frt/ 6" rear
Weight Balance is equal from side to side but heavy on the front by 10%.

Any help would be greatly appeciated

Jim Clark

I just found the posting for 350lbs Koni's. Information is great for the suspension part.

924RACR

Start by leveling the car. You'd probably get much better feel and performance running the same camber in the rear as the front, or at least 2.5 deg., but leveling the car will balance it out and keep the tail planted much better. You may find that you wish to take the front toe to zeroed or even a touch toe-out to regain some of the turn-in response.

Good luck, have fun!

M758

Toe in in the rear of the car will keep the suspesion from toeing out under braking.

I measured mine at 3/16" Front toe is zero on my car.

Yep also make sure the car is level at the rocker panels. Higher in the back = oversteer, lower in the back = understeeer, level = balanced.

joseph mitro

i was going to say the same thing as vaughan. he's got a lot more racing experience than i do, but the front toe out will help turn in and some negative camber in rear will help keep the suspension under better control. leveling the car will help. i have my ride height at 24 7/8" at all four wheel arches.

the only other thing is your rear sway bar seems pretty large compared to the front. that might be partially responsible for the rear feeling loose.

also, i found that (at yesterdays autocross at least), higher front pressures (38) helped turn in and lower rear pressures (32) kept it under better control. but i've got 1/16" toe out in the rear (which i'm going to have removed in the near future)

Jim Clark

Just want to navigate this a make sure I'm reading this right.

So the -2.5 camber in the rear will make the car understeer? Dosn't toe-out make the rear turn faster?
Do I need to adjust the toe for the rear too???
Any idea on the caster for the front?

The car is getting quicker and quicker but it handles like crap right now so I keep asking more and more questions.

joseph mitro

the negative rear camber will reduce the car's tendency to oversteer if there is that tendency. won't eliminate it if there are other factors contributing to that.

toe out should make the rear rotate more easily but also (from what i've been told and experienced on my own car) makes the rear feel more twitchy and, if you're not careful or inexperienced (like me), it could make it more likely for you to spin

Jim Clark

I'm getting a bit turned around.....How does this sound, am I getting it?

-2.5 camber front and rear.
lower the tail .5" lower than front should help oversteer or even for balanced.
Toe-in on the rear at .25"
Toe-in on front at zero, what about bushing flex - should it be 1/8th in to get to zero????
Any caster changes to the front???

M758

Ok,
Here is my aligment/suspenison settings

Front
350 lbs springs
Koni yellows camberplates, delrin bushings, 28 mm weltmeister sway bar
Camber = -3.5 Caster = 2.0, Tow = 0
Ride height ~ 4.0 inches (too low for ITS)

Rear
30 mm t-bars
Kon yellows, welt rear sway bar, Welt ploy bushings
camber -2.5, toe in 3/16.
Ride height ~ 4.0. Again too low for ITS, but level at rockers front and rear.

I run 225/50 R15 toyo's with no LSD. Hawk blues front and rear. Car is 2625-2660 with driver depending on fuel load. This set-up worked well at California speedway and the 130 to 50 mph braking coming off the banking.

PS I adjust the sway bars for balance front to rear and get even tire wear accross all 4 tires. I start at 32 PSI all 4 corners and come off track with all tires within 1-2 lbs of each other hot.

Jim Clark

Outstanding.....................this is great stuff.Thanks

roadblock

Hi Jim- I ran an ITS for 6 years -In the midwest -I had a problem with the rear brakes locking before the front -I put a Brake bias on and that solved that problem,otherwise you have to put to different brake conpounds on front and rear of car -This car had Full lock LSD -31mm torsion bars-sphrical bearings -Konis -Have you tried goodyear GSCS -they really last -The sway bar was Kelly moss -Blade style=Fat and rigid -I had 450 lb springs on the front -hope this helps

a4944

Hi Jim,
I have a 944 Turbo. See my sig. I'm running -2.3 camber front and -1.5 in the rear. It's not enough, i get roll over. I'll probably go with -3.0 front and -2.0 rear. I run the same spring/torsion bar combo as M758 but with M030 sway bars with the rear set at the middle. I run 245/45-R16 tires on all 4 corners. I have the koni yellow sports set to full stiff. I run only slightly lower than stock and have stock rubber busings. I've been very happy with the current set-up except for the tire wear at the outside edge. I was in a perfect 4 wheel drift through turn 1 at VIR and it felt very natural. I was surprised on how neutral and well balanced it felt. M758 has a good setup and gives good advice. It would be a good starting point.

Thanks,
Mark

924RACR

Copying blatantly, here's my current setup (car weighs 2620#):

Front
400 lbs springs
custom-valved 933 (aka 924 D Prod) Bilsteins, Paragon camber/caster plates,
spherical bearings, 23 mm stock sway bar (rubber bushings)
Camber = -2.5 Caster = 4.0, Toe = 0 to slightly positive.
Ride height 5.25 inches (marginal for IT)

Rear
30 mm t-bars
Bilstein Motorsports custom-valved shocks (revalved circle-track units), used 951 LSD
944 Cup Car rear sway bar (set in middle), Delrin t-bar bushings, RE Spherical trailing arm bushings
camber -2.5, toe in 1/16.
Ride height 5.25"

Further comments. I've been running Hoosiers (225/45/15), but will switch to 6" rims this year as I'm dropping back to ITB - may go to 205's, or stick with 225's, need to test. I will also be going to a much stiffer suspension; I've been having trouble with wearing the insides of my tires out, yet my tire temps are perfect - indicating good camber in the corners, but too much static camber. This indicates too much body roll. Wear is otherwise fairly even, wearing the rears slightly more than the fronts - but that I believe is likely my driving style (a little loose). So I'm going to 65% stiffer - 660# fronts and 34mm rears. IT doesn't allow coilovers. I'm looking to take out some static camber with this setup, perhaps a half of a degree or so. I am VERY happy with the balance and driveability of the car - it does exactly what I want it to do every lap of the race, without fade. It's wonderfully consistent, easy to drive, and easy on brakes (though a terror for the other cars under braking - I can make lesser drivers flub the apexes easily with just a look of the nose down the inside, I'm so well-known for being able to blow by other cars in the braking zone and still make the corner, car is VERY stable on the binders, classic Porsche braking characteristics).

Most important thing is to get the weight even. If you want a balanced (handling) car, you are best off starting with a (weight) balanced car! Level rockers will usually get you there; these cars are all very naturally balanced, and handle like it - it's only up to us to screw it up! Do this before all else - lower and realign that rear. Just get it level, no need or want to go lower.

John Brown

Support for and re-emphasis of Vaghan's suggestions. Especially the ride height as it presently is 'raked' but in a subsequent post the opposite was offered. Whereas I think the message was to not be extremem either way but try level first.

Also, the anti-sways you have are both stock and are not particularly strong in relation to your spring rates. So wouldn't worry much about them being the source of the problem.

M758

Well, My set-up was given above and I can also describe the handling. Note that for me this compared mostly to other 944-spec cars.

Balance.
Ride height. Since we don't have min ride height requirement in 944-spec, I set my car up also low as I could get it to minimize weight transfer. The height right now is such that there is may be 1" to a little more suspension travel till the car bottoms. When I lowered the car I was surprise by how close it was in front and in the rear. I did have some concerns about bottoming the car in places, but as I have been running it for 2+ years like this it seems to be ok. It can close a shock in front if you hit a big curb or something, but usally you don't want to do that anyway.

The car is level front to rear and has been corner balanced. Car is nose heavy by 1% or so.

I run 225/50's at all corners and every track day I rotate the tires to optimize the wear as most track will wear down one side or corner of the car more than the rest. Doing this and using the camber I have set in (3.5 & 2.5) has given me very even tire wear across all tires and across face of the tire. I have never been able to measure tire temps.

Balance...
I feel the spring rate set-up is well balanced, but have done quite a bit of fine tuning with sway bars to get the steady state balance where I like it and where it works for most tracks. I have considered, but do not run different set-up for each track I visit. My goal in setting up the car is to allow me to rotate the car at whim. Most track I visit don't have super high speed corners so I my car is setup to allow me to rotate it quckly and easly for most low to mid 3rd gear corners. Understeer is rarely present in these corners. I have few hard hard braking zones, but do have the car setup for trail braking as Turn 2 at PIR requires a lot of brake application while turning. The car is stable and introduce instability using the brakes at turn in so the car will rotate easily. Of all the spec cars observers feel that my car tends to be one of the better rotating cars for these low to med speed corners. How much of this driving style vs car set-up is unclear however. On corner exit the car rarely has understeer either. If it does understeer rather than make a set-up change I typically make driver adjustment either in line or technique to elimiate corner exit understeer. Most times this works well.

I do run without a limited slip so I must be carefull to get wheel spin exiting corners. Sometimes this requires power managment on corner exit and other time i tend to use a higher gear. There are places on a few tracks were other 944-spec drivers use a lower gear (mostly 2nd) getting out of a corner. I find that the extra power of the lower gear upsets the balance (either cornering or wheel spin) for the car more than lose in the higher gear. I also find that being in the higher gear forces me to carry more speed through the corner to ensure I have enough Revs to be in an ok spot in the power band on corner exit.

I have never played with the adjustments on my Koni yellows. My fronts adjustable while in the car, my rears must be removed. I have my rear set full stiff. This may or may not be good, but I have never changed them. Also given the number of miles I have on my Koni's and I know a few off course excusions have closed the shocks a few times I expect them to be quite worn. I am pretty certain I need new ones, but would rather not spend the money to fix them yet. So rather than inspect them and find they are bad I choose to not look. At least that way and guess that they are still good and think I will be fast on track. Given the way the car handles they must not be "that bad".

PS... Car weight also plays an important role in balacne and control. With my car full of fuel or with a passenger it tends torward understeer in steady state cornering and is noticable harder to "toss and roatate" for a corner. So if my car had to weigh in 200lbs heavier I would need to make some adjustments to regain the handling feel I have now. Current weight with driver, typ fuel load (Reserve Light to 1/2 tank) and required ballast is 2615-2650 depending on fuel level.