Lemming

I'm heading to Roebling Road next weekend for the NASA DE. I have 5 track days in my 924S (plus two more in my M3). Up to this point I have been running street tires (Kumho MX's; 205/50/15; -2 front, -1 rear, 0 toe front and rear) and at my last DE it was clear that I was pushing them to their limit. Although the car was sliding like crazy, I never had an off-course excursion and maintained a good speed. Some of the instructors and advanced drivers suggested it was time to go to R-compounds. So, I purchased a set of 7x15 phonies and mounted some Toyo RA1s (225/50/15). I have heard that the Toyos like more negative camber and am thinking of going to -3/-2 (F/R) and staying at 0 toe.

Questions.

1) Does this camber sound about right? Or, I am better off staying at -2/-1 for this DE since changing too many parameters between runs may be too much.

2. I purchased a smart camber and planned on doing alignments myself. The fronts are easy to align but I really don't see how you set camber on the rear. Any good DIYs out there for the 924s/944?

Thanks.

Lemming

I forgot to mention, this is a dedicated track car and has Koni Sports all around. I should be upgrading to larger sway bars in a month or so.

M758

I run -3.5 front and -2.5 rear on RA-1's Zero front toe and like 1/16 or 1/8 rear toe in rear. There rear toe in helps to counteract the natural suspension flex that causes toe our.

Be sure to get your pressures right too. Look for 38-40 hot. I start at 32.5 usally and come off track 38 or 39 all 4 corners.

PS... you can fit 225/50's to 7" wide wheels. Easy in the rear, but might need a small spacer to clear the front spring. 944-spec 924S cars run 225's easy, but often need the narrow diameter "coilover" front spring to ensure clearance to the 225's especially with lots of negative camber.

hdemas

I would change the camber to a minimum -2.5 front and -1.5 rear, and probably a little more negative. I don't see any reason to stick with your current camber--all you will do is excessively wear the outsides of your new tires. Changing only one thing at once makes sense when you are fine-tuning the car, but your car is currently so far off where it should be that I think it is a no-brainer that you increase the camber. You might also want a mm or two of toe-in at the rear, just for stability.

I have done an alignment on the rear of a 944 more times than I'd like to remember, but couldn't describe it other than to say there are two things you adjust on the trailing arm. There is a special tool you need, though, in order to do either toe or camber--can't remember which, but you must get this tool to do the rear as changing either camber or toe will change the other. You'll need strings or some other means of measuring front toe as well as it will change when you change the camber. The tool for the rear is something on the order of $20, and is basically an eccentric that a slips into the trailing arm and which you put an allen into to adjust. ...probably something you need to get from the dealership.

M758

The tool adjusts rear toe. You can adjust the bolt that sway bar mounts to when adjusting rear camber.

RedlineMan

Hey;

I'm gonna get the usual grief for this, but you can't just do a 944 alignment any old place. It is a pretty difficult job to do on an alignment rack. To try and do it on the ground is folly. There may be people that do it, but I'm just not that ambitious. Try it - if you must - and you will see.

The front is relatively easy, especially if you have camber plates. I would think you could get it done professionally once to set the rear, then fiddle to your heart's content with the front.

It would be my judgement that anything over -2.0 is a bit premature, given your driving experience. I would suggest you try -1.8 front and -1.3 rear, or there abouts. You will know if these settings suit you by how the tires wear. Anything in excess of this will likely give you a really darty car and lots of INNER tire wear.

Work up to it. That is the best approach.

Lemming

Thanks for the input.


Yes, after installing my new wheels and tires I noticed that it was fairly close. Right now I cannot go past about -2.2 without rubbing in the front. I took the cheap way out and ordered 7mm spacers as opposed to the narrower springs.

I ordered that last week along with the smart camber tool, unfortunately the tool is not yet here.

I am currently running -2/-1 (F/R) and am getting excessive outside wear. Is there reason to suspect that the Toyos will be different??

boxsterpontus

I discovered a few weeks ago that with some easy moves I could get up to 5 degrees camber in the front of my (pure race) 944. I modified it to 4 degrees camber up front and headed of to the evening practice with my local race club. In the rear I had only about 2 degrees camber.
From being a civilised drivable car it turned into a uncontrollable oversteering monster. Not funny. But the car showed that some more camber up from really gave me more grip. I added some camber in the rear as well (a real pain) and the car was a a bit more balanced. I managed to improve the laptimes with over one second only with theses changes! The McPherson suspension and a lowered car without any geometry compensation requires a lot of camber.

I have also tried to drive the car with toe-out in the rear. That makes the car really unstable when breaking and turn-ins into a real challange keeping the back end in order.

Be careful when adjusting the car, the rear is not easy to adjust and the settings can really upset the balance of the car.
The thing with the 944 that has saved my many times is that the masses of the car is positioned at the ends. It gives you a lot of time to react before the backend goes past you in a corner.

hdemas

I don't have experience with the Toyo's, but generally the R-compound tires have stiffer sidewalls than normal street tires. This would help reduce the amount of wear on the outside edge. On the other hand, R-compound tires will generate more lateral grip than the normal street tires so the tire will be subjected to much higher lateral loads, which will tend to negate the effect of the stiffer sidewall. I'm not sure if your excessive outside wear will get a little better or a little worse with the other tires, but I stand by my recommendation that you try to dial in more camber.

RedlineMan

Hey;

If your car is still on stock springs, then that and those skinny tires will have you rolling quite a bit. You might indeed need to go with more camber, but it is not in my experience that novice drivers drive hard enough (or well enough) to warrant it.

You may be an exception!

M758

If you ARE getting outer shoulder wear then add more negative camber. Your soft spring do contribute to the outside tire wear since the chassis moves so much as to induce postive camber.

In my case 2450 lbs car with 350 lbs front and 30 mm rear torsion bars and weltmeister 28 mm and 22 mm sway bars the 3.5 and 2.5 camber setting work quite well. I always have a very event tire wear. Remember too much negative camber compromises braking traction in front and power application (esp inside rear wheel) in the rear. I had run as much as 4 deg negative, but I think that is too much.

You can get a 1/2 decient alignment at home if you have a camber gauge, tape measure and some patience. No it will not be as good a shop aligment with the proper tools, but it can get you by. I ran for a long time on home aligment. It worked, but went I went racing I knew I needed more and got my car aligment and corner balanced by a real pro. It did make a subtle, but noticable difference.

trumperZ06

Lemming,

Watch for tire wear on your left side, especially the left front! Roebling is tuff on tires, easy on brakes! Some guys flip their tires from side to side each day.

Cya @ Roebling this weekend.

Trumper

GUMBALL

I would suggest starting with the following settings:
3 degrees ft and 2 degrees rear negative camber
1/8" to 3/16" total toe out-front
1/16" to 1/8" total toe in-rear
as much positive caster as you can get - make sure both sides are equal

check tires with tire pyrometer after each run, adjust camber accordingly
ft toe out reduces corner entry understeer - I run more on short twisty tracks
under load, the rear wheels on the 924/944 tend to toe in, so don't start with too much - rear toe-out will cause corner entry oversteer.

Have fun.....

Lemming

Trumper,

Look me up, I have the black exploder pulling the featherlite (with red 924S). I'm leaving in 5 minutes for GA, spending the next 24 hrs with the folks and then to Savannah tomorrow night. I'm going to drive RR on Friday with Seat-time (www.seat-time.com) and then NASA on Sat and Sun.

Tim

trumperZ06

I'll be with 2 other instuctors.

We all drive 2004... Z06's, one yellow & two are Silver!

Mine is Silver # 11X, Cya @ the track!