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+--- Thread: MPSC Pressures and Technical Info (/showthread.php?tid=1316)
- ninjabones - 08-13-2008
There was a lot of debate recently (at WGI) regarding optimum tire pressures for MPSCs. I came across this great 42-slide presentation from Michelin specifically on Porsche applications. This presentation contains a ton of information on the design of the MPSC, wet/dry handling characteristics, ideal operating temperatures and pressures, as well as specific guidance for different porsche vehicles. Thought I'd share:
http://www.cb-racing.com/PilotCup_Presentation.PPT
- emayer - 08-13-2008
This is awesome thanks!
Been noting the tires are a bit greasy once hot, have been gradually lowering pressures to find optimum. Part of the issue at WGI may have been the changing weather conditions also. Plenty to learn on this subject...
- bobt993 - 08-14-2008
Glen,
Good source of info. No real surprises there. As I had suggested, the staggered pressure setup is suggested for the larger tire combo and heavier cars (most similar example was the 996 combo). The 235 is better for turn in over the 225 (and threshold braking). The most important note is the operating temp of at least 160 degs. Most drivers do not get these tires hot enough to see this performance range.
- ninjabones - 08-14-2008
Yeah bob, you're recommendations were spot on. I was not generating enough heat at WGI (temps were just shy of 160, with a wee bit of extra heat on the inside edges vs. outsides)... probably because I was driving like a wuss (ARMCOPHOBIA).
I was able to push the tires a lot more at Thunderbolt last week (that course inspires a lot of confidence due to the incredible surface grip and tons of runoff). Best lap was a 1:36.47. Anyway, 32 fr / 36 rr (hot) was about perfect for me at that track (translated to about 25/27 cold). I have just over -2.5 degrees of negative camber front and rear.
After 14 heat cycles on the tires, they are grippier than ever... in my opinion much stickier than the NT01s once up to temp, but a bit more finicky in terms of reaction to temp and pressure changes; and also slippy as hockey pucks when cold. The NT01s were pretty grippy right out of the paddock and weren't quite as scary when cold.
How many heat cycles can I expect to get out of the MPSCs?
- bobt993 - 08-14-2008
If your alignment is good, they will not cord before falling off (avoid excessive toe in the rear) and make sure the kinematic toe is set properly (see Larry Herman for this cure). Tires will start losing grip at about 25 heat cycles. They are great tires for learning on. The lack of grip when cold is synonymous with true slicks and you learn to scrub them hard while getting heat into the them. It is almost impossible to overheat them, but you can "over inflate" them by not starting at the correct cold temps.