Renn 951

I'm running my 1988 951 in its first Drivers Ed event tomorrow and looking for any recommendations on tire pressures. I've got Kumho 225/45/17 tires on the front and 245/40/17 on the rear.

I was thinking of starting out about 38 psi cold all around and then adjusting based on temperatures and handling. If anyone has experience with 17" tires on the track and any recommendations to accelerate my learning curve I'd appreciate any advice! <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

David Floyd

Which Kumho's street or slicks ?

I set my 17" Kumho 712's at 34 lbs cold and keep a check on pressures after each run about 40 lbs hot is what I have been told to shoot for.

Maybe some serious track junkies can be a little more specific.

<img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />

Mike S.

Check this out:
<a href="http://www.homestead.com/redlinerennsport/DriversEdEd.html" target="_blank">http://www.homestead.com/redlinerennsport/DriversEdEd.html</a>

Read Article #15

Have a great time.

Mike

Renn 951

David: thanks, your info was just what I was looking for! These are street tires, 712 Ecsta's. They are at 34.5 right now sitting in the garage, and it will be a bit colder in the morning so I may be set up just about right. I'll shoot for 40 psi hot as you suggest.

Mike: thanks for the link, that is a great website! I've bookmarked it for future reference.

I also got the original 16" phone dial wheels from the PO and I'll probably get some track tires to fit those wheels this spring. I happen to have a $100 discount certificate for a set of Toyo tires, so I might as well put it to good use.

Jerry

I agree with 40 lbs front and rear when full hot for a 944. To get this you can learn from experience where to start with when cold based on the temp of the day. The tires will go up 7 or 8 lbs. from wherever you start them out in the morning. If it is going to be a 60f day set cold at 34 lbs. If it will be a 70f day set cold at 32 lbs. A 80f day 30 lbs. A 90f day 28 lbs. In this last example if you just let your car sit still and checked the tires during the hot part of the afternoon your 28 lbs in the morning tires will be at 33 lbs. Unless or until you have your susption set just right you can make improvements in handling be changing your tire presures but this is the incorrect fix but it will aid you to decide whats needed for the correct fix. Two last points, you won't get max heat build up unless you are out of the lower run groups / runnng hard and it should take two laps.

jason952

I also shoot for about 40 hot. As the track warm throughout the day, more and more may need to be let out. Then you gotta refill the next AM when the track gets cold again. May be real cold where you are though.

Jason

Mike A.

Check your hot temps as soon as you're off the track, the sooner the more accurate. 40 psi hot sounds good, but to really know, check tire temps.
Tire temps are accurate if taken immediately (after afew hot laps) before they begin to cool off. If the middle of the tire is hotter than the edges let air out. If the edges are hotter than the middle, add air. You want to see all three temps within 10 to 20 degrees of each other provided your suspension settings match your driving style.
No matter how you do it, make sure you check the pressures/temps after each run since the ambient temp and your lap times (therefore the tire pressures/temps) will change through out the day.
Have a blast.

Renn 951

Well, 40 psi all around seemed to be just about right! The car was well balanced and the Kumho 712 Ecsta's had great grip. I might even try a little less pressure next time as the wear on the tread contact wasn't quite reaching the sidewall. On my Audi S4, even with pressures above 40 psi hot, I'd get a little scuffing on the top part of the sidewall of the Michelin Pilot Sports I've been running with. Of course, the Audi is a good bit heavier than the 951.

Thanks to everyone for the advice! I had a blast yesterday and I'm really looking forward to a fun track season! <img src="graemlins/wave.gif" border="0" alt="[byebye]" />

Richard C2S

Was that taken at FATT? I thank you for your input on Friday afternoon relative to the 951 I'm looking at. The camera guy did not stick around for the Mercedes event on Saturday and Sunday.

Richard

Renn 951

Richard:

Yes, that pic was taken at the FATT, along with this other one. I'm a little surprised they bailed before the MB event, but I guess considering the very cold and very wet weather forecast they decided not to stand out in the rain all morning! At least we had a nice and sunny (if chilly) day on Friday.

I enjoyed talking with you, and I'll see you at VIR next month!