Bob Silver

I have a stock 96' C4S with 18" S02' Bridgestones. I have been trying to find the optimum tire pressure for the track (and street as well). I had initially set them at the factory recommended settings and other C4S owners told me that was much to high. I have tried 30lb front and 38lb rear and do not feel I am getting that great traction. Frankly I have been rather disappointed with the grabbing ability of my car. I am new to tracking the car (3 times so far) and could use all the help I can get.

B-Line

Hey Bob,

I would highly recommend that you get a dedicated set of track tires. The difference is night and day. You can buy Hoosiers which cost a bit more than some other options (and don't last as long.)

I use Kumho's which are heat cycled and shaved. They do not have the performance of the Hoosiers but they last a long time and are cheaper.

If you plan on continuing to track your car, long term. Your much better off with a dedicated set.
Good luck..

Martin S.

I second B-Line's suggestion. I have run the SO2s at the track, briefly...15 minutes. At $>250 a tire for replacement SO2s, I went to Kumhos on 17" Cup wheels. You can get these wheels fairly cheap from Wheel Enhancement in Culver City, CA. The next big hassle is finding someone to truck your tires, assuming you don't trailer thr car. It can be done...I do it all the time...it just costs me a meal or two, some race gas, whatever.

Or, there is the option of buying a little trailer to pull behind your 993. It can be done...the big drawback has been a hitch for the 993..I understand one is available...somewhere.

Martin <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />

Dbltime

Bob,

I would NOT recommend track tires. You learn track driving skills sooner using street tires. With three track days under your belt stay with street tires and follow the tire temps and increasing pressures. This is where you develop your handling skills. Loose screaming street tires are happy tires. Losse screaming Hoosiers are pissed. Do you want happy or pissed? Plus you have the added enjoyment of driving to the track.

Track tires... then a trailer... bigger truck... then new suspension... spare wheels...

RESIST BOB, BE STRONG!!!!!!

Hank Cohn

Bob:

First, your question about tire pressures. I have never driven my S02s on the track but I would think the 8 psi. differential you are using is too much. My 18” S02s have a maximum inflation pressure of 44 psi. I am assuming the 30/38 numbers you are trying are hot tire pressures and not cold starting pressures. Tires will grow 8-11 psi from cold, so start conservatively and bleed off excess pressure when hot. I would shoot for 34/36 f/r hot as a baseline and see how that feels. Add pressure from there maintaining a 2 psi differential front to rear. My only real experience with street tires is with the Toyo tires we use in Speed World Challenge. They seem to perform well at about 39-41 psi.

I mostly agree with other responses to your post. Buy a set of 17” takeoff Porsche wheels and mount some Kumho’s on them. Unless you are driving in super hot conditions and can really push the tires consistently, I would buy them at full tread depth rather than shaved. I mount my Kunho’s at home and drive to and from the track on them all the time (90 mile round trip). Should it start to rain, just be careful and use good common sense. They work well in the rain on the track anyway. Track tires do not have any radical “at-the-limit” characteristics at all. The Kumho’s especially are very linear in their performance even at the limit.

By the way. Because I use stock 17” Porsche wheels, the Kumho sizes I use are 205s and 255s. this works well on a two wheel drive car but I wouldn’t know about a C4.

Hank

H. Miller

I have the same car and same tires as you do. At my first event, I too had too much air (in my tires). This past weekend I went with 34 in front and 36 in rear COLD and the track surface was cold too. This worked very well for me (although I am no track expert). You do need to experiment a little. Change the pressure after each run if you have to.
Good luck.

Ray Calvo

I'll go along with some of the other experiences re Kuhmos. I have them on my 2wd 993, sizes 225/45 and 255/40 X17. Used them for the first time at a very wet Mid-Ohio track two weeks ago; I also drove to and from the track in them. In the rain, they are better than BFG R-1 (last track compound I ran), but still have to be cautious. On wet track or roads they're OK; in heavy downpours watch for the standing water/puddles (had to slow to 50 on PA Tpke on drive back home in raging thunderstorm; car was darting/hydroplaning all over the place). Dry traction (on the one session I tried them) to me was good. I'm still playing with tire pressures; I use 36 psi on streets all around, was starting with 32 psia all around on Kuhmo on the track.

Hank Cohn

Kim:

Unless you are going to turn your car into a serious track machine, I would stick with 17” wheels. The tires are significantly less expensive and most tires are widely available. If, however, you have access to some inexpensive 18” wheels that you are sure are strong enough for the track, then by all means get them. 18’s are a little better because the sidewall is shorter and therefore stiffer giving crisper turn in and a higher effective wheel rate.

Hank

B-Line

Hey Bill,

Not trying to start an arguement here, but don't you think 3 track days is enough experience to switch to a better compound.

I think a solo driver should be on a shaved tire. And I would assume that most 3 timers are solo or at least border the solo line.

It is much easier to be a consistent, methodical driver if you don't have to compensate for a lack of grip. Granted screaming Hoosiers are dangerous. And it is easier to loose control if you pass the grip potential of the tire. But it takes some real stupid driving to push Hoosiers to a screaming point at a DE.

I totally agree that a first time/second time driver should not be toying with suspension, tires, etc. But I also have to believe that someone with 3 days experience should be ready for some grip and control.
I believe that a learning curve on street tires peaks very early. A car understeering all over the track does not make for a better driver.
Shaved tires make the car much more neutral. They can bite you in the butt, but only if you are driving beyond your limits which I don't recommend on street or shaved tires..

Just my opinion!
B

Greg Fishman

I personally don't think that someone that has 3 days of track time is ready for R compounds but I can understand why they would want them and think it is more dependent on the driver having his head on straight.
I would suggest something in between, the BFG KD's. I drove and instructed a friend of mine last weekend with these tires and I was impressed. They had great grip and were very predicatable. His Boxster was also a treat to drive, much more neutral than a stock 993 and very tossable. The PSM was a nice backup if you made a mistake or overcooked a turn.
Greg

STLPCA

B-line, Martin, & Ray:
With due respect, I disagree w/your R compound suggestion for Bob. I've got 3 DE weekends behind me. You guys probably have a hard time remembering back to that level of inexperience. I know I have NOT reached the track potential of my 2WD coupe w/stock suspension & 17" MXX3 street tires. I still need to work long & hard to refine technique, brake later, accelerate harder & continue to build confidence & skills. I'm not seeking faster lap times or a faster car, but rather a better, smoother driver. R tires won't get me to my goal faster, just make it more likely I'll be over my head at a higher speed. My first instructor told me to plan to progress using "baby steps" & I think it was good advice.

As to tire pressures, I've been happy w/34-36 cold & have had very even track wear across the tread.

Just my $.02.

Anir

Bob,

You've already received a lot of great advice, but I'll chime in since I was in exactly your shoes last year. I did six DE days in my car (also AWD) on my everyday S-02s. Just drove to the track and home, with no real investment of time other than bleeding the brakes prior to each weekend.

The tires performed beautifully in this novice's hands. I was able to consistently achieve 40 psi hot all around when starting with 32 front and 34 rear cold. I was throughly enjoying the sliding, which allowed me to play with different slip angles through each corner.

Only downside with the S-02s is that they suffered a significant loss of grip and finesse in street driving after the six track days. With 8000 miles on them, I just replaced them with S-03s despite the fact that half the grip was still remaining. Simply too greasy after living the "good life" at the track.

For this DE season, I'll be running Pirelli P-Zero C's. I plan to wait until next year for the Hoosiers. I chose this sort of a stepwise approach based on Greg's advice, which echoes the sentiment of many others on this board that you will learn more, and play it safer, by sticking with stock tires for now.

But, keep in mind that you could take this argument to the extreme. All of us would probably benefit from starting in karting, or maybe Formula Fords, etc, prior to PCA events, if all we cared about was ultimate driving abilities in the long term. We do PCA events because they are fun, even though our cars (especially newer models with PSM) are so forgiving that you get away with mistakes that should bite you.

Best of luck with your decision.

Edward

Bob,

I've got the Kumhos and, like the others, I like them a lot. And, like the others, I recommend getting a decent set of dedicated rims as there are lots of good 17inchers to be found at good prices if you're willing to wait and keep hunting --I found OEMs here, courtesy of another kind Rennlister.

Still, I agree with Bill et al. regarding waiting on R compound. I went through what seems to be the same thing as you: seeking higher performance at the track. The advice I got: WAIT, and get REALLY comfortable with the car's dynamics on the track with street rubber. I even had greater than 3 DE weekends at that time, but I took the advice and I feel I am all the better for it, and more skilled (thanks E.J.!). I resisted the urge to improve the car and worked on the nut behind the wheel. Remember that the driver is ultimately responsible for the performance of the car; tires, suspension, HP, be damned if the driver is not up to the task (this is not MY opinion, but that of others with far more experience than I). I have been bettered by others in far "lesser" cars and, likewise, have passed others in better tracked-prepped cars. You draw your own conclusions. Again, just my opinion from this side of "expert." Good luck and remember that the track is supposed to be FUN <img src="graemlins/jumper.gif" border="0" alt="[jumper]" /> regardless of how your car is prepped. (Sorry for the longish post )

Edward

Hank Cohn

Greg:

I have read some of your other posts where you argue compellingly that street tires will teach you how to drive better because their limits are lower and therefore you must develop good car control and you get to do it at a lower speed. I get that, but we aren’t talking about slicks here. Kumhos or Toyos are, in my opinion, fine for even a novice driver. As instructors, it is our job to manage the new pilots and we really don’t want to teach them to react to the car, but rather to plan ahead and interact with car and track. I know this is easier said than done sometimes. It has been my experience that Kumhos are very linear and exhibit no nasty habits at the limit or even beyond the limit. The biggest issue for me is cost. You can buy a set of 17” cup takeoffs for $800-$900 and a set of Kumhos for $500 delivered to your door and you’ve only spent ~$1300 and they will last a novice pilot 5-10 DE events depending on conditions… SO2s or KDs are going to ragged within 2-5 events and cost $1500 to replace and you are putting your pristine street wheels at risk. Plus the street tires get rubber build up and make the car feel like it has lost all four bearings for about a week.

Dan:

I understand your point and agree that it is a valid one. However, would you buy a crappy set of golf clubs to learn to golf, or a Wal-Mart tennis racquet to learn to play tennis? I do think R compound tires will get you to your goal faster. They allow the car to perform better. You can accelerate out of corners faster and brake deeper. R compound tires are made for the track – street tires are not. Tire choice has less to do with lap times than the pressure on the accelerator pedal has - at least in the beginning that is true. I agree that baby steps are a good way to learn to drive, but those steps need to happen in rapid succession to get better at this sport. Practice doesn’t make perfect, but perfect practice does make perfect. If you learn bad habits like sliding street tires around corners or early braking corners because of street tire limits, you are getting imperfect practice. The law of primacy says that the way we learn to do things the first time is the way we will continue to do them.

B-Line:

Don’t get too hung up on shaved tires. I have used Kumhos shaved and at full tread depth. If I know I am running them in the Dog Days of summer, I will order them shaved. If the temperature is less than 80 degrees, full tread depth is works just fine. I have used abut 8 sets each way.

Lastly, (I know you are all saying FINALLY) by R compound, I am not talking about Hoosiers or Goodyear GSCS or slicks. Those tires, in my opinion, are for racing or race practice. You have to take care of them to make them last. They could get a new pilot in some trouble because they have incredibly high limits when new. I have just been sent a set of Toyo R compound tires and will post my findings after I use them. They are supposed to be a nice tire.

Hank

PS. I am not advocating that a first time DE student go out and buy some R compound tires. I would advocate that the person who is committed to running 4 or more track events per year for the purpose of getting better and possibly moving up to racing should consider the R compound route.

B-Line home

Very good points everyone...

Dan, Maybe I am forgetting my level of experience back then.

I have never driven on hoosiers, just Kumho's..
Heat cycled/shaved. Looking back maybe it was a good thing that I waited a long time before trying this setup. But I did spend a lot of money on very expensive street tires that did not last very long.

Hank, I live in Miami where it's always at least 80 degrees

I guess it's not fair either to make such a broad statement that a third time driver should be solo or on track tires. Everyone has different comfort levels, learning curves, etc. It's important to recognize you skills and weaknesses as a track driver before biting off more than should be chewed.
I guess part of my reasoning also comes from Skippy. After their three day racing school, they put you in a R/T 2000 with slicks.

I guess the time to move to a more aggressive tire comes from driver desire and ability, not a general consensus.

Although somehow I can't help but feel that having better grip is a good thing. If you can hit the same spot on the track every time. Heel/Toe downshift, Threshold brake, hold consistent lines, consistent times and drive the car at 10/10's safely, confidently, securely..

I guess then it's time to upgrade..