jrgordonsenior

While I've never had the bubbling problems as seen in your pics, I have had some cording problems with MPSC's that I believe are associated to with car weight and pressure. I am now a believer in running more pressure back there in heavier cars. I drive a 993TT which is similar in weight to both your car and the 996TT. I run 34-35 fronts, and 40-42 rears with 3.0 neg camber front, and 2.5 rears. I always cord out my driver's side rear on the outside edge, usually in about 4 track days or 20 heat cycles. My fronts seem to last forever...Temps range from 190 inside to 165 out so camber seems appropriate. As previously stated, run more pressure back there until you start to skate....

Larry Herman

I too have had problems with suspected sidewall failures (and subsequent rapid deflation) on the inside left rear tire on my car. It happened at both Watkins Glen and Summit Point, and ironically both during the 7th session on the tires. They were Pirelli slicks, and there was plenty of rubber left on the tires. I then corded the inside of the left rear using Dunlop SSRs at VIR last fall after 12 sessions. It also got very greasy after the 8th session.

After a lot of input, I surmised that I was overheating the inside edge of the tread, and so I dropped the rear camber from -3.3 to -2.5 and reduced the toe from 3/16ths total to 3/32s total. Not only did this improve the grip at the rear of my car, but so far very even rear tire wear and no problems with flats this season.

DrJupeman

I still need to figure out how to fix this problem, but Michelin is refunding me the cost of the failed 295. They are also sending me UPS ship tags so that I can send them back the damaged tire...

Mike Buck

My buddy got the pictures I sent him and is forwarding on another at Michelin. I'll let you know.

DrJupeman

Great, I'm still awaiting technical advice/feedback from Michelin.

MB965

Charlie,

What, if anything did you hear from Michelin about your MPSC failure?
Just mounted a new set of 235-18 and 285-18. I am finally getting tires which are new 2304 and 0205. I was getting tires which were more than 2 years old!

Thanks,

Mike

TD in DC

Charlie,

I have the Longacre probe pyrometer (with memory) and like it very much. Please keep us informed on what you learn. On a related note, I cannot seem to find the presentation on cold and hot tire pressures that Michelin recommends for the PSCs. I did a search, but the links I found appear to be broken. I am trying to find recommended cold and hot pressures for my 944 n/a (approx 2,500lbs) with 15x8s all around.

Thanks,

TD

dwe8922

I too have ended up with higher hot temps for my 993c2. I'm running 35 Frt 37 Rear hot, with -2.5 Frt -2.0 Rear camber. I ran 10 sessions at road atanta last weekend w/o switching left to right, and noticed higher outside edge tire wear on the left rear. I attributed it to all the left hand corners there, and normally I switch them left to right half way through. I'm also still experiencing greater inside wear on the right front. I had toe out on the car, and have changed that back to neutral. I thought that would fix it, but it didn't. Other than that, my tire wear has been even across.

Manny Alban

If you see the Michelin guys at the club races, use them. They don't advertise very well, but they will take your tire temps and air pressures for any session or sessions you want (as long as your running Michelins ). They always sit on the pitwall. I just look for the guy in the blue and yellow shirt holding the pyrometer, air guage and clipboard. They helped me get the right amount of camber as well as offer solutions to handling issues. They don't attend all over the races, but I know they were at Watkins and Sebring.

ceboyd

we've gone through several sets of MPSCs (including 285 30 18s rear) and never had a problem.... no problems like that with DSSRs either (although the DSSRs corded whereas the MPSCs gave out long before getting anywhere near cords due to too many heat cycles) ..and obviously MPSCs last longer..

38D

Jupe can fill in the details, but net-net he has raised his rear tire pressures to ~38 hot and had no issues since. I've been running 32-33 hot front & rear all year and had no issues either (but my car does weigh 274lbs less and have 40hp less than Jupe's car). I have 20 days on my practice set of MPSCs and 3 qualifyings, 2 sprint races, and 2 enduros on the race set of MPSCs. I think I'm going to retire the practice set, since they have zero grip left (thought there is still plenty of tread remaining).

George A

Ok, here is my question on the MSCP's: How far down the sidewall are you going in hard cornering? I'm really getting down there and it's making me nervous. I'm running 34 hot all the way around on a 3100 lbs 993 and am only having a rollover issue at the rear. My temps are the same all the way around in the rear and if I add more pressure, the center temp raises. They feel great at 34psi, better than at 36 or 38psi which I've tried. Anyway, here is a pic from the last club race of my rear tire in action.

George

DrJupeman

My update. Michelin never took back my tire, yet they said they would. They also never gave me additional setup advice, yet they said they would. These were the two things I asked for.

They did give me my money back, which I did not ask for. Go figure.

Anyway, I've upped my hot pressures to ~38 psi and have had no problems. The car does get squirrely after a bit if the pressures creep up to 40+ or so. One just has to tune the pressures to nail 38. This just takes some experimenting each day.

Fwiw, here's a picture of rear tire action on my car, this is a slow and cambered turn, so compression on the tire might not be as dramatic as it could be elsewhere.