Track gurus - setup questions

I took my newly acquired '02 C2 to Sears Point this weekend, and had a great time. I do have some questions on fine tuning the track setup and I am hoping to get some opinions from the more experienced track gurus here. The car has no PSM, PSS9, GT3 sways. The PSS9 settings are 2F, 2R. The GT3 sways are set at one notch above full stiff both front and rear. Tire pressures cold are 36F and 38R on Bridgestone S02s. (I know I probably need to lower this), but I will be running r-comps by the next track event. Camber setting is -1.2F and -2.2R. I can't remember the toe settings - I think it's 0 toe F and can't remember the rear. I think the car is still pushing just a bit and I would like more responsive turn in, so I will probably want to put some camber plates up front to get more negative camber. I will also move the rear sway bar to full stiff and that should help. What's would be a good camber setting for a track setup? I would like to learn some of the settings that people run here as a starting point before I talk to my local alignment shop. Also, when I am trail braking, I feel a twitch or wiggle in the back. I understand that's probably a characteristic of the rear weight bias, and I probably need to adjust / smooth out my inputs. The twitch did go away when I smooth out the inputs and extend my braking zone, but I am carrying less speed into the corner than I'd like. I feel the car has some more to go but that twitch is holding me back. I am wondering if something can be done about this (other than the driver ). I called TRG and they suggested a toe link. said that there are many rubber bushings in the rear suspension and they flex when not under full compression, and the toe gets out of alignment when that happens. A toe link would with monoball bushings will lock in the toe and help with the twitch. They also said that it's the first thing they would do to the car. It makes sense... do track guys here run a toe link? Any thoughts on this topic? The final recommendation is rear monoball shock mounts. I am not sure how much that will help with just rear monoball shock mounts but everything else in the rear suspension is still rubber bushing. For people who have monoball shock mounts, do you really feel a significant difference that's worth $650 or so? Thanks!

I'll pull up a chair, as experience on this front would be highly valuable to me as well.

I run Pilot Sport Cups (225/265) and PSS9s, set at F1/R1. I'm no expert, but here's what I would try: I would suggest you start out by firming up your rear sways and setting rear dampers to 1. If you're moving to R-compounds then DON'T DO ANYTHING ELSE until you've been back on track. The tires will make a big enough difference that the other stuff is as likely to hurt as it is to help. There's a huge gap between S02s and PSCs, for example. One thing to note as well is that you might want to try a 265 or 275 section in the back, as running a F225/R285 setup is going to cause some push. Some will say this last suggestion is stupid. Once on track if you're still getting some push then you might dial the front dampers back to 4 or 5. The nice thing about this is you can do it between sessions. If that doesn't do it, then you can soften up the front sway (not sure if you can do that at the track), but you're probably doomed to get a camber kit. If you go this route a) I would start with no more than -3 degrees, especially if this is a DD, and b) I would also lower the suspension some, especially in front. Not knowing your current height makes that last suggestion iffy, but lowering in front should reduce push and increase grip.

I'm not going to claim to be a guru but here are a couple ideas. You're headed in the right direction. With your soft suspension you'll benefit from long, light braking. It is much faster in a 996 then braking late and upsetting the car. I agree with TRG on the twitch. The rear toe links are a weak link and should be replaced. By chance do you get a twitch when lifting to change gears on a straight. If so, it's a clear indication of a worn toe link. I'd go through four sets a season before getting the newer motorsport version. For the push, is it under braking, neutral throttle or acceleration. It makes a lot of difference. As for alignment, it obviously depends on your tires but you'll want a bunch more camber in front if you can get it. 1/2 degree more in front than in back is a pretty good rule of thumb. Something like -3.25f and -2.75 back works well. Toe should be around 1 mm out in front and 1-2mm in on back. I would be more inclined to soften the front sway than stiffen the rear. Just some ideas. Jim

For what it's worth I Run with the following....... PSS9's at 5 front and 2 rear.... I have found that the softer setting in the front helps with turn in... but does tend to increase the tire wear..... I am not fortunate enough to have adjustable sways or I would adjust them to compensate for the tire wear. I have the monoball shock mounts and feel they were the best upgrade for the buck... the turn in issue has improved greatlly.... 3 degrees on the front and back and 2 mm toe in on the rears......... running on MPSC's All in all I'm still working this out but am more comfortable with these settings that the previous ones... Oh and I do not have the twitch.... I would check your toe links...... Hope this helps.

Great, thanks! The information was really helpful! Good to know that it's not all just (the lack of) driver talent that I am getting a twitch Looks like I will go with the rear toe links. I will most likly go with the front camber plates in the front as well, as I want more negative camber. Thanks for the recommendations on alignment settings as well. Really helpful to know that 0.5 degree separation between F and R is a good setting. The push is under acceleration. I feel that the car still understeers a bit coming out of a corner, and I have been taking later apexes than I am used to - but it could just be first time out in a new car on street tires etc. I am going with the front camber plates to improve turn in response anyways, so I guess I will see how the car feels after I get some nice negative camber up front. If there is still some push, I think this is something that can be tweaked and dialed in on a combination of sway bar setting, PSS9 firmness setting, and tire pressures. Are there any additional modifications that you guys would suggest? For instance, I do not know that the rear toe link is a weak point that a lot of people beef up. I am not really interested in HP mods becuase I am already getting a 50% upgrade in HP and 10% reduction in weight from my BMW, and that's plenty. I am really interested in setting up a good suspension. So far I have PSS9s and GT3 sways, and I plan on adding front camber plates, rear toe link, and rear monoball shock mount (?). Am I missing anything else? Someone suggested a motorsport motor mount as well. Damn this is a slippery slope. RamVA - I plan on running F225/R275 Toyo RA-1. I ran with these for 5 years in my BMW and I love them. I may eventually try the Nitto NT-01 since many BMW club racers I know rave about them a lot. I may run rear sway at full stiff and rear PSS9 at 1 for a day to see how it feels before I go with further additional modifications. JimB - how do you get -3.25 up front? I think the lowered pss9s can get to -1.5 or so, and then the plates will add another degree. Will I need some major modification to get to -3.25? I see your race car and you seem to run in stock class... hopefully that means I can get that kind of camber without some major modifications and $. SMR996 - Do you have the rear monoball shock mount? Your message wasn't quite clear on whether you were talking about the front or rear. I talked to TRG again. It seems like having the toe link in the bottom and the monoball shock mount on top will really lock down the rear suspension nice and tight, short of going full monoball everything in the back suspension. TIA!

Listen to what Jim is saying, he really knows what he is talking about. Also, frequently issues like understeer and oversteer are the result of driving technique as much as they are the result of car setup. In other words, if you drive your car incorrectly, you can cause understeer and oversteer. If this is the case, and I am NOT saying it is, searching for setup fixes would be a mistake. Just my two cents.

Galun, (is that your real name?) I'd much rather have GT3/cup car lower control arms than camber plates. They will provide you with more camber flexibility and the ball joint bolt is much stronger than the stock piece. Actually I would put them on back as well just for the safety of the stronger ball joint bolt. For the tires you plan to run I might run a little less camber. Maybe someone has a better suggestion but I'd guess around -3/-2.5 or so. I run 245/315 Hoosiers on my stock 996 racecar. I should have mentioned you don't want to apex late in these cars. Long braking, early apex. They really don't like harsh inputs. Now for the push. If you had two way adjustables I'd say to take out a little rebound in front but with PSS9s I guess your best bet is to stiffen up the back a little to keep it from squatting quite as much. I think you were on 2. Maybe go to 1 in back and 3 in front. I'm not sure about that though. It worth messing around with. A sway bar adjustment should help as well. Good luck. Jim p.s. Thanks Todd!

Jim, my real name is Gary. If I get GT3 lower control arms for front and rears, I probably will not need camber plates up front and monoball mount in the back? Seems like a simple swap to two piece control arms, slip in some shims, and I can push the wheel out to get some more negative camber. Do I need to do something to the top as well? Will the stock top mounts handle the change in suspension geometry? Hehe, yes, I realize there is still a lot of upgrading in the driver to go! Let's say you guys have my car and my current setup (Pss9, GT3 sways). What would you do? Thanks!

Let's get started: 1. Have you checked your hot tire pressures? Based on your cold pressures, you should be very high. I would recommend 32/36 as a good place to start. Try to keep the rears hot around 38-39 psi. A pyrometer may be a better gauge so you can see if the centers are getting too hot. Too much pressure = too little grip. Running lower pressures will help some with the tail stability. 2. You have a few things wrong with your setup. Your rear camber is too high for your front. Best guess is you had them align the car to max the camber all the way around without looking at how it would balance. This is the first reason why it is pushing. If it was really loose, I could see going higher; but that is not the case. Keep in mind you are running street tires and not race tires like MPSCs. You don't as much camber for an S02 as an MPSC. -2.5 degrees on race tires like Hoosiers will definitely stick, but you will be running on the inside edges on street tires. You can verify this with a pyrometer. With your rear camber, you will find the outer outer edge 10-15 degrees colder than the inner when you get off the track. I would reduce your rear camber to -1.6-1.8 and would not recommend to increase it until after you start running race tires. S02's have stiff sidewalls and they are going to move around in a straight line with this much camber. On my street S03's it is a little nervous, but on MPSCs my car is perfectly stable. You can toe in for some stability, but this will slow turn-in more. Unless you are going full monoballs and Motons, skip the toe links. They can't compensate for the deflection in the rest of the suspension. 3. You need to adjust your sway bars. Both your poor turn-in and your pushing balance are both due to the front bar is set way to stiff. This is very common from people who don't know how to dial in a car. Do sway bars increase or reduce grip? Its the opposite to what you think. Stiffening a sway reduces grip. This is compounded more when you increase spring rates. Start off soft and work your way up, not the other way around. Move the front to the softest or next to softest setting and both your turn-in and neutral balance will improve. 4. For tires, why are you looking at running 225/275 Toyos? The problems with the Toyos is the sizes aren't right for a 996. It is a bad compromise anyway you want to look at them. The NT01 is a decent tire, but it doesn't hold up to an MPSC or a Corsa. MPSCs work well in warm climates, but need a lot of camber (-1.5 is absolutely minimum). Corsas are less tolerable of heat, but can grip extremely well at low camber settings (-1.0). I run 235/40 MPSC's on 18x9.0" wheels up front and 295/30 MPSC's on 18x11.0" out back at the track. I run -1.6/-1.9 and on MPSCs with GT3 control arms and M030 sway bars. Keep in mind with the GT3 control arms that you also gain about 1" in track, which also helps turn-in. The downside is you can't get a lot of extra camber before the suspension starts binding up. With 27 psi front and 28 psi rear cold pressures, both ends heat up to 34-36 psi. With the pyrometer, the front outers are 5-8 degrees lower than the centers and inners. Out back, the temps are dead even across the tires. With this setup, my car is perfectly neutral both ways on the skidpad; which is my driving preference.

I think I know only enough to be dangerous, but I'm pretty sure I disagree with both these points. It might be worth the debate... 3. It is mis-leading to say that increasing sway stiffness reduces grip. The thing that "reduces" grip when you increase sway stiffness is the change in RELATIVE roll stiffness F-to-R (or R-to-F). If you're front is much stiffer (in roll) than the rear you will get push, and vice-versa. That said, if you increase total roll stiffness in balance at both ends you will increase grip, not reduce it. The increase in grip in this case comes primarily from the minute reduction in CG height and the minimization of suspension deflection/camber change. This also generally aids turn-in and transient response, assuming that relative stiffness (F-to-R) is in balance. Point being, in general more roll stiffness is better (presuming it does not limit wheel control), but relative roll stiffness (F-to-R) is important to get right. That said, to fix a push specifically on corner exit, I believe softening the front rebound damping and sway sitffness and increasing rear compression damping (and perhaps spring stiffness) is the right course. 4. I'm not sure if you're point is that 225/275 is too narrow for a 996, or if it's that it's the wrong F-to-R balance. In any case I think the Toyos are a fine choice for the car, especially given the meaningful cost difference (price and life expectancy) relative to the MPSC and Corsa. It seems to me all are good answers (and I'll probably stick with the MPSC) but there are good reasons to think about the RA-1. It's not the right way to get right to the 996 performance envelope, but it HPDE is your thing it's a decent way to save a few bucks. If the point you're making is that the 225/275 relationship is wrong for the 996, I'd like to understand better why that is, for my own education. Your post is obviously a thoughtful and well-informed one, so please take my comments in the spirit they're intended. To the OP (some of this may controvert my earlier advice): A. Most of the changes that we've been discussing run the risk of reducing your traction on corner exit. The 996 is obvioulsy strong in this arena, but increasing rear roll stiffness and/or decreasing rear tire width will have a measurable impact on corner-exit traction, which I would probably assert should be your first priority. B. Most of these changes will also likely introduce or exacerbate looseness on corner entry, especially if you like to trail brake. That's not a bad result, as long as you can take advantage of it. You're moving in the direction of a setup that favors a looser style, which you should be prepared for. C. All of this assumes a relatively smooth track surface. I don't know Sears Point, but if you run anything as rough as Summit you might should bias toward softening the loose end as opposed to stiffening the other. I think I end up at: stiffen the rear dampers, soften the front sway, and get your RA-1s on, make sure you're getting the rear end around before the apex, and then see how you feel before you do anything else.

Thanks for the feedback so far! I should have stated up front that the settings I posted were the settings that the previous owner had for the car. Unfortunately I was not able to change anything at the track this time. I am still trying to figure out how to get all my usual track tools into this car. For instance, now I have to go buy a smaller jack becuase my old jack won't fit in the front trunk. Fun little interesting problems! I am running Toyos becuase I had been running them for quite a while, and it's just a personal preference. I can also get a discount on them through BMW club racing teams that I work with. I know 275/35/18 is not the exact right size for the back, but at this point I guess I will compromise a bit. 02 Carrera - You said "Keep in mind with the GT3 control arms that you also gain about 1" in track, which also helps turn-in. The downside is you can't get a lot of extra camber before the suspension starts binding up." Can you explain this downside that I cannot get a lot of extra camber before the suspension starts binding up? My understanding of the GT3 control arms is that it's a 2 piece design, and the size of the shims will get you to the negative camber that you need. When you can suspension starts binding up, is it a function of you using 235/245 tires up front? Jim - "I should have mentioned you don't want to apex late in these cars. Long braking, early apex. They really don't like harsh inputs." I felt the car pushing a bit on exit and that's why I had been taking a safe late apex while I learn the car. But to your point - I can understand the smooth braking part to not upset the car due to the weight distribution, but what do you mean by early apex? Do you mean the ideal line of the 996 would have an earlier apex than normal? RamVA - My personal preference is to setup a car so it rotates really well, and require smooth precise inputs to drive well. I think it's a great challenge and it makes the perfect lap that much more enjoyable. I also spoke with Austin at TRG extensively over the last few days. I will most likely have those guys setup the car once I decide what I want to do. At this point, I plan on nailing down a solution to get the negative camber up front, get the RA1s mounted, and see how the car feels. I also have to figure out this puzzle of fitting 4 wheels, jack, jack stands, tools, water, day bag, etc.... into the car. That may be a bigger challenge!

Gary, First, I should mention that I assumed this was primarily a track car. I would set the car up very differently if you use it on the street quite a bit. Having said that, don't listen to anyone on this board if you're going to have TRG do the work. They know more about making 996s go fast than anyone here. (Well actually I regularly beat their cars when I was racing stock C but they do know a bunch. ) If you are going to be working with them you should take advantage of their expertise. Jim

Thanks Jim. This is primarily a track car, but I plan on driving it to the track. I will just throw on some cheap street tires and take the tire wear on the street as the cost of doing business.

Before I did the swap, I asked the same questions (search for the thread in the modification or racing sectiosns) and received very little accurate information. The advantage of the GT3 control arms is there is an inner and outer arm that uses shims in the middle. The greater the shim thickness, the longer the control arm. So if you can picture the geometry, the upper mount stays in the same position while the lower arm mouts out, increasing the track. It increases a little over an inch on my car. If you look at the front geometry, the track arms mounts through the end of the lower control arm. What do you think happens when you move the hole location in the end? The track arm now rides in a different postition. This is immediately an issue if you run the front control arms on the same sides as a GT3. In the center hole, even stock front wheels and tires rub at full lock on the front of the fender wells. In the offset holes, they rub worse. The caster increases substantually, but well out of range. As a result, to fix the issues you run the right arm on the left and the left arm on the right so the offeset holes are facing forward (i.e. RSR style). In this case, caster in in the 6-7 degree range and there is no rubbing at full lock. With my race wheels and tires, 18x9.0" CCWs with 235/40 MPSCs up front, I still get a small amount of rubbing at full lock. Reversing the control arms and using the offset holes allows the track arm to reside more in its correct position. It also pre-loads the track arm the further it moves out. The more you move out the end, the more the track arm is pre-loaded and twisted in rest position. If you overload too much, you will tear the track arm and inner control arm bushings. For this case, monballs would be the answer. I am running about a 7mm shim pack right now and it is already hard to line up the track arm to get it in. In fact, I had to loosen the shim nuts to get them in. If you need to run a larger shimpak than this, there are options. A couple after market companies make outer control arms with adjustable plates for the track arms. They also make replacement mounts to go into the stock arms where you push out the original ones with a press. Last, you can drill additional holes to set the track arm location.