Tyre decision : advice appreciated

[nickfrog]

This is the state of one of my front tyres, a Michelin Supersport. The car is a 125i on 130i power. The rest of the tyre is still on 6mm. It's the result of my stupid decision to run too low a pressure at Goodwood as the tyre was just scrubbed in and I assumed the tall blocks would lead to a lot of movement and overheating ; I went too low and made the issue worse it would seem by allowing the tyre to roll sideways too much under intense lat load. This was compounded by the heavy car, soft sidewall, not enough camber (just 1 neg deg) and dual compound (softer on the outside), plus Goodwood being mainly RHD corners. Since then I swapped both fronts to balance things a little and did a Ring trip (10 laps at 7 to 8 / 10th max).

I am doing another Ring trip in 2 months where I will need to do about 8 laps as I am getting a Swift anyway.

I will only cover 500 road miles until the Ring trip and as I now use higher pressures the wear seems to be under control.

The other front is in a much better shape, the transverse groove is still there.

What should I do :

- risk going to the Ring like that ? I am not concerned about the road miles but how much life is there left there for both road miles and 8 Ring laps?

- fit a new front and be back to square one of a lot of block movement ? (which this time I might mitigate a little better !!!).

Any suggestions would be welcome.

Edited by nickfrog on Sunday 3rd August 16:19

[brillomaster]

looks alright to me, just make sure you inflate them properly!

[BritishRacinGrin]

That tyre has some service left in it.

I'd suggest putting the lowest tyre on the least leaned-on corner of the car, i.e. Clockwise circuits- right front and visa versa.

ETA: I've just noticed- road use only? no worries. You'll probably be able to use all remaining thread on that tyre provided you don't absolutely hoon it everywhere.

[terenceb]

Looks ok but you have had a fair bit of understeer there, possibly caused by running the low pressure.Michelins need to be run to the manufacturers pressure at least.That will help in keeping the tread blocks apart, just how Michelin intended.It will also help in evening the wear out.Not the best tyre for track use though as they do suffer with tread roll, or where the hot surface rubber rolls to the edges of the tread.What event are you doing over here? (The Ring) that is.

[TrackMegane]

All depends how hard you'll drive the ring. Its a pretty harsh surface so that will go in no time. I pretty much wrecked a new F1 at the ring a few months back and i only did 8laps with them on

[nickfrog]

Thank you for all the feedback. I will be driving at 7/10ths on TF evening (02/10) and TF day (03/10) if they are not too busy (I am aware of the third party liability risk). Max 10 laps. My rears are fine so I supposed I could turn in slow and lean on the traction. When I damaged them at Goodwood there was little understeer actually, but huge front end bits and as it was a new car for me with very little feel I didn't realise they shoulders were rolling so much. I don't mind getting a new tyre as they are cheap but I am concerned that the very high tread might not be ideal either even at the optimum pressure.

[BritishRacinGrin]

If the inner shoulder isn't worn more heavily than the center of the tyre, I'd suggest that underinflation wasn't as big a factor as you're thinking. On the track at any pace at all you are always going to wear the front outer shoulders quickly on a standard tyre on a standard car with standard geometry. In this circumstance you can't expect even wear.
I ran a control tyre when racing which was a standard road tyre, and the camber wasn't adjustable so I had no more than one degree neg. Even though it was only a 520kg car (Caterham) and was otherwise very well balanced and set up, the outer shoulders always suffered fastest. The solution to the overheating problem was to have the new tyre buffed down to 5mm tread, which obviously isn't what something I would advocate for new Michelins on a road car with occasional trackdays.
I did accidentally fit a tyre on a rim the wrong way 'round once, so the 'outide' of the tyre was on the inside. I didn't notice this until I'd arrived at Castle Combe for testing. My lap times were no different. It was dry though. I suspect it wouldn't have killed me in the wet either but again not something I'd recommend!
There's many thousands of safe road miles left in that tyre in my opinion. Whether a traffic officer would overlook the fact the grooves are gone completely I don't know, I seem to remember there has to be 'visable tread' across the whole width of the tyre or words to that effect.

ETA: I've just had another look and a thought occurred. I've seen tyres, particularly Michelins, wear like this in normal use. It makes me wonder if it's just a normal trait of the tyre design? Granted it probably wouldn't ordinarily wear that much on the shoulder with 6mm remaining everywhere else...

Edited by BritishRacinGrin on Monday 4th August 15:48

[nickfrog]

Thanks for the input. Just bought a direct replacement off a forum with 6mm for £50 and not much shoulder wear so that will do nicely indeed...

[git-r]

You should post a video up of how you're driving - maybe you're using too much steering?

Looks like it's really been rolled over - did you know there are wear markers to indicate correct pressure?

You can easily buy tyres at the 'ring for a lot cheaper than UK. And anything we you need, especially in a BMW

Have fun

[git-r]

- I'd definitely keep and use that tyre, just keep an eye on that edge for missing chunks and canvas.

[nickfrog]

git-r said:

You should post a video up of how you're driving - maybe you're using too much steering?

That's a real possibility. I have been turning in a fraction too late at the time so I might have gone back the other way too, not sure. There is very little feel from the EPAS...

The damage happened a Goodwood (which is almost only right handers, I have swapped the front wheels since then of course).

I do think it was a combination of the heavy road car with heavy engine, not enough front camber, too low a pressure (the sidewalls are very soft) on a raod tyre, too many rh corners, not enough straights for them to cool, dual compound (soft on the outside which is only good if you have decent front camber).

No idea what parameters had more influence than others though.

https://www.youtube.com/watch?v=-dCaO2k3RX0

Edited by nickfrog on Friday 29th August 23:55