Michelin Slicks Malfunction

[OLLIE_NZ]

Hi guys,

We took our R32 GTR out to the circuit last weekend and everything was great until we got the car home and up onto the axle stands to inspect everything.

When we took the front tyres off we noticed the inside wall of the tyres was starting to come apart (see pictures)

We don't feel we ran them too low pressure wise (we started off with 28 psi cold) and then worked towards a 32psi hot on all four tyres.

There's no visible damage to the outside wall of the tyres

The main tyre that is really bad is the left hand front tyre (inside wall), the two main almost hairpin corners at the track are right hand corners and the track is predominantly right hand corners and quite high speed.

Any thought as to what has caused this? The New Zealand Michelin Motorsport tyre distributor has told us we ran the pressure too low which we dispute.

Tyre size is 240/640R17

Prior to this session at the track the slicks had done twelve laps.

[scooby36]

looks like theyv rubbed on the sidewall, no marks on anything under there? the coilover itself? or the little metal 'protector' lip on the chassis rail?

add 5mm spacer and drive em till theyre finished :]

Edited January 31, 2012 by scooby36

[OLLIE_NZ]

Rubbing wasn't the issue if you look at the last two pictures you can see the writing on the side wall perfectly untouched and also the ribbed lines the run across the sidewall.

[blackrex]

Did you take pyro readings for the tyres? I have seen that happen before on tyres that got too hot and over pressurised.

[LSX-438]

wow that looks really weird. i've used a lot of michelin slicks and never seen that. are you 100% sure there was no rubbing?

[R32 Stuart]

So what was the days temperature, any idea on track temp, camber and toe settings

We have been having the same issues with another tyre over here on V8 touring car only on hot days and extreme loads.

Don't try and run the tyres again chords are broken

If you are sure pressures were correct, pending on camber and toe settings, tyres look to have been very hot? - if not, I would say - its a tyre case issue

Hi guys,

We took our R32 GTR out to the circuit last weekend and everything was great until we got the car home and up onto the axle stands to inspect everything.

When we took the front tyres off we noticed the inside wall of the tyres was starting to come apart (see pictures)

We don't feel we ran them too low pressure wise (we started off with 28 psi cold) and then worked towards a 32psi hot on all four tyres.

There's no visible damage to the outside wall of the tyres

The main tyre that is really bad is the left hand front tyre (inside wall), the two main almost hairpin corners at the track are right hand corners and the track is predominantly right hand corners and quite high speed.

Any thought as to what has caused this? The New Zealand Michelin Motorsport tyre distributor has told us we ran the pressure too low which we dispute.

Tyre size is 240/640R17

Prior to this session at the track the slicks had done twelve laps.

[OLLIE_NZ]

Thanks for the replies so far chaps,

To answer a few questions in no particular order

- No pyro reading as we don't yet own a pyrometer

- The temperature on the day was no more than 20 degrees, it was an overcast day so not too hot. Not sure on the temperature of the track surface itself

We started the day with 28psi cold all round and worked from there We were aiming for 32psi all round hot and were pretty close to that after letting one or two psi out after our first session. We took pressure readings immediately after pitting the car and took note of them. (off the top of my head the highest reading I would have seen was 34psi hot and the lowest 32psi hot)

There is very slight rubbing on the front plastic wheel arch liner but the is only on near full lock and only affects the outside wall of the tyre.(there's no way we would see anywhere near full lock at this track)

If there was rubbing elsewhere surely that would show up on the tyre itself wouldn't it? There is very little evidence that I can see looking at the pictures that I can see.

Picture of the car (sitting far too high as we had just put new springs in the front)

Camber 4 degrees, caster almost 7 degrees, Front toe 0mm

[r32-25t]

You really should be aiming for 30psi hot with michelin slicks, but 2 psi still shouldn't cause that, I'd contact Michelin and see what they say

[blackrex]

What does the inside of the tyre look like?

[Munroman]

I have seen that before with that size and compound tyre - even with brand new stock - especially on powerful cars.

I always recommend 270 68 18 for the R32 GTR. It's the rear tyre of the old Porsche Cup cars (not the Carrerra Cup 30 68 18 or GT cars as in Cup S and Cup RS 31 71 18)

[Fatstig]

It's looks like a hinge joint failure. Yokohama has a similar problem in the v8 brute ute class hence why they have little front end camber.. I've had this happen before at over 3.5 deg

On an off note if you can afford new slicks why not a cheap pyro?its one of the most important setup tools in racing

Edited February 1, 2012 by Fatstig

[OLLIE_NZ]

Hi guys,

Thanks for the insights

To answer a few more questions.

- blackrex, we've not had the tyres off the rims yet so aren't sure but should go ahead with removing them as they're only good for the bin now.

- Munroman, have you managed to fit a 680 rolling diameter rim under an R32 GTR? We'd love to go down this path as the Porsche Cup slicks are a dime a dozen over here. We did look into this before we went for 17"s but were told a 270 68 R18 wouldn't fit.

- Fastig, we can't afford new slicks (these were bought from Michelin New Zealand second hand) they had done a 12 lap test with them when we bought them. But will definitely get pyrometer