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Michelin Sport Cup 2 Falls of GT3RS at Track... A must read for all track guys!
So I was at Streets of Willow this weekend and honestly can say I had an awesome time but the last lap of the whole weekend during TT my Michelin SC2 literally dislodged from the rim inwards.
Tire temp was 29psi on both back tires as I was waiting for my turn to go and on second lap of the TT as i was coming into turn 3 around the start of the second gator the car over steered and then a bam from the rim hitting the ground, but luckily I was able to keep the car on the track, and safely remove it from the track, wasn't sure if someone was coming behind me, but again my good luck they had not sent the next group out yet, as i waited for help.
So not sure what to do about all of this... if anything.
Tires were just installed a couple weeks ago by local dealer, and to make things worse the other rear tire had a bad leak the first session of the first day so I had to take tire to the tire shop, they checked the whole tire looking for a leak and couldn't fine anything so I asked him to check the valve stem and sure enough he was able to get a couple turns on it and it fixed the problem so not sure how happy i feel about that and just makes me go hmmm.
I know the risks I take when I go track my car but this kind of sucks, and last month same thing happened to my friend at California speedway on his GT3 on same tires so not sure if it is a problem with Michelin, bad install from the dealer, or just the kaka that happens when you play like this.
Curious to know if anyone else has had this issue with these tires and if they were able to get any recourse out of it.
Here are a couple of pics of the tire/rim, and I am uploading a video of the actual event from my Gopro so will update later.
9/10 times this happens (leaky tire, dislodged wheel) you have / had a slightly bent rim already before and that leads to a wiggle in the tire bead. Streets of Willow is a crappy surface and those curbs and gators can yoink the tire right off the rims.
When we are racing GT3 cup, our starting pressures are some times under 20psi. 18/19 generally. They come in pretty well but if you hit a big curb in the first lap you'll destroy a tire or bend a rim (no cushion for the pushing when you are at 19psi)
So, my theory is you have a bent rim, and if you don't get it replaced you will keep having tire issues especially on track.
I had the same problem on the front left tire at Barber. Car had the original tires and was untouched from the factory. Turned out the outer portion of the valve stem sleeve was loose from the factory - was not tight at all.
9/10 times this happens (leaky tire, dislodged wheel) you have / had a slightly bent rim already before and that leads to a wiggle in the tire bead. Streets of Willow is a crappy surface and those curbs and gators can yoink the tire right off the rims.
When we are racing GT3 cup, our starting pressures are some times under 20psi. 18/19 generally. They come in pretty well but if you hit a big curb in the first lap you'll destroy a tire or bend a rim (no cushion for the pushing when you are at 19psi)
So, my theory is you have a bent rim, and if you don't get it replaced you will keep having tire issues especially on track.
I did not go off track all weekend nor did I hit anything and that tire was holding pressure all weekend so not sure about that theory.
Also when i drive I have the TPM showing at all times which is how i caught the leaking tire on the other side Saturday morning because the PSI got down to 16 and I immediately got off track.
Also if you look at video there is nothing showing the car was unstable until that point.
Saw similar happen to a 991 RS at Atlanta Motorsports Park back in April at Smokies event. While I don't have the full details you could ping user 991GT3 for details.
Saw similar happen to a 991 RS at Atlanta Motorsports Park back in April at Smokies event. While I don't have the full details you could ping user 991GT3 for details.
CJ is right. Keep in mind the wheels on these cars have a tendency to bend easily. You do not have to go off the track or slam into a curb for them to bend. They just bend sometimes.
I've gone through more than a dozen sets never had a problem.
You had bad luck with hitting a curb at low PSI.
Or maybe bent rim.
Don't worry about it after checking it out.
This weekend I had to start at 22PSI and ended up 32PSI.
I have to take it easy for 3 laps, a shame because they are only fast for 3 laps.
Ideally I go out at 26 and drop them after 3 laps.
The 3 laps is very true... While others people might be doing 12+ laps per session I usually stop at 5 to 7 laps because tire temps just get to high and I don't like to go over 35psi hot because I don't think getting tires to hot is a good thing.
I think if it is not another valve stem that got loose (have not touched it yet), then it is the combination of a tire that gets hot to fast, which requires them to start at lower then normal temps and with the side wall being so short things like this can happen.
I start my temps at 24 fronts, 28 rears cold and they get to their proper 29/33 after 2/3 laps, but then after that they continue to go up and around the 6ish lap they are at 32/35ish if not higher which is when I get off track.
Are you adjusting based on the TPM? I don't think I would rely on the TPM system for this. The variance seems pretty high to me. If you are dropping the pressure based on TPM, you could be dropping it way too low by mistake (just a theory, I'm not accusing you of anything).
Get a really good, very precise tire pressure gauge with the ability to adjust in small increments with a pressure release valve.
Get the tires hot after a session and drop the pressure to what you want to see as a max (35 is not outrageous) while the tires are hot, then leave it there. If you are really worried about pressure variance, fill with nitrogen (you'll never have to worry again).
CJ is right. Keep in mind the wheels on these cars have a tendency to bend easily. You do not have to go off the track or slam into a curb for them to bend. They just bend sometimes.
Why are they so delicate? I thought they'd be tough since they're forged (unlike GT4's which are cast). Is there just too little material in the name of weight saving?
Are you adjusting based on the TPM? I don't think I would rely on the TPM system for this. The variance seems pretty high to me. If you are dropping the pressure based on TPM, you could be dropping it way too low by mistake (just a theory, I'm not accusing you of anything).
Get a really good, very precise tire pressure gauge with the ability to adjust in small increments with a pressure release valve.
Get the tires hot after a session and drop the pressure to what you want to see as a max (35 is not outrageous) while the tires are hot, then leave it there. If you are really worried about pressure variance, fill with nitrogen (you'll never have to worry again).
I only use TPM for monitoring when I am driving, when I get off track I check and adjust each tire accordingly with a TireTek Flexi-Pro Tire Pressure Gauge which I believe is pretty precise.
Why are they so delicate? I thought they'd be tough since they're forged (unlike GT4's which are cast). Is there just too little material in the name of weight saving?
Don't believe there is that much weight savings on these wheels since they are made for daily driving as well.
After market forged wheels are much lighter in comparison.
I think part of the problem with rim bending is running a low profile tire and running into the curbing. After every track day, I always remove and inspect them for damage inside/out, but even I know there could be things that I can't see with my eye.
05-22-2017, 04:20 AM
Michelin Sport Cup 2 Falls of GT3RS at Track... A must read for all track guys!
