so.. I had a tire blowout at 120mph yesterday...

I was at the local racetrack, doing some laps on a sunny/hot track day...

third session out... 3rd lap on the main straight, flat out at 194km/h according to telemetry.... and the 500km-old front right tire, a pirelli p-zero, decided to delaminate in spectacular fashion (punched thru a corner of the quarter panel).
what baffles me is, I had the 4 tires pulled from the car and balanced the night before. I even inspected them personally and found them perfect. fronts were 500km olds pzeros, rears were brand new michelin pilot sports 4...

seriously, never been more scared in my entire life, than when i heard the noise, saw pieces flying and felt the steering wheel completely unweighted for a few miliseconds...
the entire tread was gone, fortunately it happened on a straight before the braking point... and I had enough time to lift off the gas and coast to a stop.

i really had not clue it was only a blowout at the time. Because of the noise (and being fairly new tires, and the pieces i saw flying away) i thought i had have clipped something and the entire wheel/hub was gone).

going back... am reaaally grateful it happened on the straight... had it been 500 yards before (in a middle of a 70mph left hander) and it would have hurt a whole lot more.... same if it had happened 100 yards in front, in the middle a 130-60mph braking zone...

i keep thinking about it, and I remember the car pulling hard to the right, and a mushy feeling in fast left handers (the tire was probably starting to delaminate there)... which i thought was just the tires getting greasy/hot; but the important thing is, I was very lucky and nothing more serious happened.

now, the time has come for a decision.

my c63 is way too fast for its own good... specially for a car without a roll cage on a race track, doing 80mph average lap times... its also very hard on tires (NEVER buying p-zeros again, am a michelin pilot sport /super sport convert now); am seriously thinking about giving up on fast cars and track days.... maybe get a beater with a proper roll cage, or a set of wheels with proper track tires (my street tires get pounded on pothole infested roads, which might have contributed to this); or forget about cars all together and start cycling back up again....

thats something am trying to understand.

the basics

1) Front tires were/are P-zeros 235-40-18, 95Y, rated for 186mph, and MO (mercedes approved for the AMG). They were bought and installed about 1 month ago (about 500km of use in the street and this was their 2nd track day), and have never been patched/plugged or anything. They were somewhat old tires though. Manufactured in April 2013. (almost 5 years old).
2) Rear tires are michelin pilot sport 4 (installed the night before the track day), which are the new version of the pilot super sports. (best tires ever, by the way.. they are like the minion dhf of sports car tires)
3) Car was perfectly balanced and aligned within factory specs. The car is stock, and there are no mechanical problems/previous crashes (always dealer serviced and it has less than 10k miles on the clock).
4) Track runs counterclockwise. Front right tire (outside) usually takes the blunt of work (I had the tires rotated because of this. the previous track day, they were on the inside)
4) Tread delaminated completely, and in the picture... it appears the failure started in the inner sidewall (where its missing a chunk)
5) Tire pressure when hot at the track was 41-42 psi (32 psi when cold). I doubt this is too low (MB says 35 psi for speeds under 155mph, 38 psi for speeds over 155mph, cold. Was monitoring tire pressure every session (12 laps)
6) Track surface was very hot (probably above 110F surface temp), bright sunny summer day with temperature in the 80s..
7) Wear was minimal, and did not reach deep into the shoulders/sidewall (see picture), which means tires were optimally inflated.
8) All 4 tires were inspected, by me and the tire guy, (off the car) the night before, as the michelins were mounted and balanced. They did not appear to show any crack/buldge the night before
9) The car started pulling HARD to the right on the last few laps (I was off my pace by 3-4 seconds per lap) in the previous session. The tires felt "gritty" (I believe at this point the tires were starting to delaminate). I thought they were just greasy/overheated, and pulled into the pits. Checked the tire pressure, but found it to be OK.
10) The car has seen almost daily use during the last month. I take my son to school, and then drive to work. Its about 7 miles per day of stop and go traffic, over REALLY bad roads (potholes in Lima are insane, I run them at 39psi to avoid damage.).
11) Before these P-zeros, I had some Continental Contisport 5 on the front. The pair was replaced when I found one of them had delaminated a little, a 10cm by 3 strip on the inner shoulds. (they were 5 years old at the time of replacement). They were tracked only once, and were used for about 9k miles. I thought it was odd they delaminated in a similar fashion as the p-zero.
12) The rumble strips in this track are somewhat agressive. There is a non-zero chance I might have stepped on them at some point (I dont really remember if I did... just trowing this idea out there. and If I did, it would have, coincidentally, happen to the front right).


what I´d like to know is exactly what happened, for peace of mind. at this point, the options are:

a) was is the tire because it was old?
b) what it because it was damaged by a pothole on the street, and I didnt realize because the damage was internal?
c) was it because my AMG is too heavy and I was trail-braking for most of the day.., which means am in the wrong car/tire? can this be fixed with michelin pilot sports 4?
d) was this because the roads are so bad in Lima,i cannot use the same tires on the street and track? (remember, I saw some delamination in a previous set of old continentals) can a dedicated set of track wheels/tires fix this?
e) freak accident? 3 more psi needed?

if I cannot be certain of what exactly happened and how can it be avoided, I´d probably wont feel much safe tracking my C63 again.
the fronts are kinda small for a 450hp 3900lb coupe; but again, I wasnt the only C63 on the track that day... there were 2 coupes, and a sedan lapping in about the same time as the 911s (I was the only one on street tires though).

cars).

Jm_ said:

I could understand if maybe you had a plugged flat or something that weakened the tire, but that's pretty crazy. I ran P-zeros for years on a few cars, in fact I think I still have a set in the garage that was my BMW summer-tire. That just looks like a a freak accident, unless you wore it down past the tread-wear indicators, what you've been doing is well within the parameters of that tire. I think the versions I've bought were 186mph rated or similar.

The new car has the goodyear F1 supercar tires, which seem to get good marks except for longevity. I read a consumer reports or other similar article a few months ago comparing the high end street tires (including P-zeros) it said the Michelin PIlotsport 4s tires were the overall best tire for that category. Additionally, it seems to be the go-to for most of the people that track the same car, as soon as the F1s wear out, people put the 4S tires on.

So is PIrelli going to pay for your repair work?

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stoney said:

That's an excessively large fender, even for an AMG. That's not a Black, is it?

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those are the fat fenders of a regular c63 coupe.

Toshi said:

I remember when people would take heavy, powerful cars out to autocross, like G37s and Legacy 2.5GTs. They looked horrible, and I can only imagine that the C63 is even more unbalanced when it comes to tires and brakes vs mass.

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funnily enough, the c63 coupe is a "lightweight" AMG, at 1750kg
thats within 120 lbs of a late model 911 turbo.

the brakes are more than adecuate (can actually lock up and engage abs at over 50mph) and fade free... but its seriously under-tired.
it should have been 295 in the back 255 up front, at least.