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Michelin Sport Cup 2 Falls of GT3RS at Track... What to do?

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Old 05-22-2017, 04:09 PM
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GrantG
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Originally Posted by GT345
After market forged wheels are much lighter in comparison.
And stronger too?
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Old 05-22-2017, 04:31 PM
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I think the car isn't over steered but the tire was "blown" or flattened before your turn in to left corner.

How hard is the breaking before this corner? I've heard that Trofeo R tires "spin" on the GT3 RS rims under the heavy breaking (No kidding!)

Your are lucky that this wasn't the fastest corner on the track!
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Old 05-22-2017, 04:32 PM
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TRAKCAR
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All tires pretty much spin on the rims, that's no reason for a flat.
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Old 05-22-2017, 04:41 PM
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Originally Posted by TRAKCAR
All tires pretty much spin on the rims, that's no reason for a flat.
bent rim + tire spin on the rim + turn in = result (maybe)

Actually I marked my tires last track day (drive hot 2.0 bar) and no spin (have two very heavy breakings on the track)
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Old 05-22-2017, 04:45 PM
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Originally Posted by GrantG
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?
I don't know. I know it's not just me, though
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Old 05-22-2017, 04:46 PM
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I use the TPMS to check while driving too. And it has been very accurate related to the gauge I use. So if someone's isn't accurate maybe they should be replaced?
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Old 05-22-2017, 04:53 PM
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Originally Posted by mwar99
I use the TPMS to check while driving too. And it has been very accurate related to the gauge I use. So if someone's isn't accurate maybe they should be replaced?
The TPMS is probably +/- 1 PSI compared to a gauge because I know that there are certain values the TPMS never seems to show on my car... I have never seen 31 or 34 psi on the TPMS... Only 30/32 and 33/35
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Old 05-22-2017, 04:59 PM
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Originally Posted by C.J. Ichiban
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.

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.
Originally Posted by orthojoe
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.
CJ is spot on. The only time I've seen this happen to guys is: going hard when pressures too low, a defective or damaged wheel allowing the bead to unseat, hitting something that catches the tire.

If its my car I'm replacing that wheel and get 2 new rear tires.

Don't chance it.
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Old 05-22-2017, 05:34 PM
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Originally Posted by TRAKCAR
I haven't bent one and Sebring isn't a pool table.
I avoid the rumbles at Sebring in my street GT3 for just this reason. Probably cost 2sec+ a lap, but they are brutal. T7 is like the surface of mars.
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Old 05-22-2017, 05:38 PM
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Well I just looked at it and I can wiggle the valve stem and turn it by hand.

OMW to dealer, this should be interesting.
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Old 05-22-2017, 05:39 PM
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Originally Posted by Earlierapex
I avoid the rumbles at Sebring in my street GT3 for just this reason. Probably cost 2sec+ a lap, but they are brutal. T7 is like the surface of mars.
Yes, it is a bit cratery but I pound them all and no problem so far

Originally Posted by GT345
Well I just looked at it and I can wiggle the valve stem and turn it by hand.

OMW to dealer, this should be interesting.
I bet you just got your answer
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Old 05-22-2017, 05:41 PM
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Originally Posted by tqevo
The TPMS is probably +/- 1 PSI compared to a gauge because I know that there are certain values the TPMS never seems to show on my car... I have never seen 31 or 34 psi on the TPMS... Only 30/32 and 33/35
Close enough, I always have one eye on the display.
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Old 05-22-2017, 05:52 PM
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Wow thats crazy. Glad to see the car is still ok but let us know what happens at the dealer....
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Old 05-22-2017, 06:06 PM
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Originally Posted by tqevo
The TPMS is probably +/- 1 PSI compared to a gauge because I know that there are certain values the TPMS never seems to show on my car... I have never seen 31 or 34 psi on the TPMS... Only 30/32 and 33/35
I'm guessing that the TPMS measures in bar, not psi. Thus, when it converts from bar to psi within the number of decimal places of precision it has available, it never shows certain psi values. You can see the problem in the below conversion chart:

1.9 bar = 27.55722 psi
2.0 bar = 29.0076 psi
2.1 bar = 30.45798 psi
2.2 bar = 31.90836 psi
2.3 bar = 33.35874 psi
2.4 bar = 34.80912 psi
2.5 bar = 36.2595 psi
2.6 bar = 37.70988 psi

For when it measures 2.2 and 2.4 bar, respectively, it likely rounds up to 32 and 35 psi.
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Old 05-22-2017, 06:07 PM
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Originally Posted by RyanSD
Wow thats crazy. Glad to see the car is still ok but let us know what happens at the dealer....
You should see what happened to the tire on 991GT3's. Much more tire folded under. Looked like half a rear tire...
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