Quote:
Originally Posted by cxp213
RE-71Rs (and Rival S 1.5) are one of the best, legal street tires you can get that's still reasonable in price (unlike Sport Cups). There's a reason why many people run these tires at national level events.
Your pressures are WAY too high. You need to be in the mid 30s if you want grip. Given that these tires have stiff sidewall, you don't need to run as high of pressure.
Tires definitely heat up (although not as much as a track session) and it's a little more than 3-4 psi if you're pushing the car enough and the tires are sticky. The interval between your runs varies by club, but you actually need to be constantly checking/adjusting your pressure before/after each run until about your 4th run or so.
Get some chalk and mark your tires from the edge of shoulder tread block to the sidewall, so you can see how much rollover you're getting (will vary based on tires, camber, psi, etc). Then find the tread marker on the sidewall of the tire to see where the rollover needs to stop ideally. From there, you just adjust tire pressure and camber as appropriate. Having a pyrometer helps but I wouldn't worry about that now. Of course, if you don't have enough seat time, none of this should be your primary concern, but that's another point.
BTW, for FWD, you want more pressure in the rear so you can get the rear to rotate easier. By adding pressure (and that much at that) to the front, all you're doing is introducing more understeer.
No offense, but I think you need to start making friends at your local autocross who is national level or very competitive locally, because I get the feeling you're doing things without proper guidance or someone's feeding you bad advice. 
What clubs are you racing with in Chicago? |
Thanks for the advice.
I do all the stuff you mentioned above. (checking pressure, marking with chalk...etc)
I ran with CCSCC in rantoul, IL little over 2 yrs.
I did about 20+ autocross event 7~8 years ago but I was not that competitive driver anyway.
I did Autocross class they offered and I did learn a lot of what you explained.
They do have several good drivers.
For my current car, it's got MPSS. That side wall is soft.
I started at 40 psi but it rolled down to sidewall. lol
So I had to keep pumping up. It was stable around 45~46 after 3 runs. (peaked at 48)
Rear was good at 35 psi.
Maybe I will start with 35~38 psi next time see how far I wear down on the sidewall.
Once I get RE71 later, I will try lower pressure.
I saw couple of E90 M3 running 33 psi in front with RE71. So It will be good starting point.