Tyre help

[soe8m]

As Dolomites have a lot of bump steer and all the rusty holes are panels again........

Jeroen

[paulsprint]

I would have thought the damage is being done in the corners as oppose to the straights. The tyre in question is doing all the cornering work as it is the outside one. So the tracking is of no really consequence as the car will follow the line of that wheel. The tyre on the inside would be effected be tracking in this instance, but due to cornering forces has very little weight on it anyway. Now the outside front tyre will deform in the corner (in effect as it try's to roll off the rim) if the tyre has the correct pressure it will keep an even load throughout its foot print. Too low a pressure and the tyre will fold in the middle, too high and the tyre will load to much on the inside edge. This will in turn reduce the footprint and therefore grip which in turn will increase under steer and tyre scrubbing. The tyre will then start to overheat and lose grip, over steering more which will cause more heat and the pressure goes up and we are now in a vicious circle.

[trackerjack]

I have been giving this little problem more thought and my car looks similar while cornering to yours and most Dollies.
I think the damage is being done under braking and would look for a loose rack mount or perhaps the drag link has too much movement but the wear is so severe that there has to be movement.
See mine is just the same but my tyres always wore evenly on track days.

[Mad Mart]

It's not so much the tyre wear Jon, but the fact that the tyres have ballooned in the centre.

[gmsclassics]

If you haven't experienced this before to any extent, and consensus seems to be that you are not doing anything that different to other Sprint users on the track, it could well simply be an issue with the specific tyre.

During the last decade or so of racing at 79 meetings (and counting) I've had a couple of Toyos delaminate and most recently a front Dunlop 03G showed a remarkable pattern of wear in the middle of the tread, something exactly the opposite to what I have seen before and would expect. The compounds used in race tyres have certainly got softer over time. I normally get a season out of a set, but after 6 meetings last year they were looking more like slicks and had to come off.

This is a pic from 2005 when I was running Toyos - different sizes to yours (195.60x14) and of course a stiffer suspension set up with less body roll, but the tyres do seem to be rolling over less at about 28psi front and 24 rear.

As far as i know tyres are still made individually, and I suspect you have just got a bad one or two. Maybe try something else next! A check alignment of toe, caster and camber might not go amiss first - cheaper than ruining another tyre.

TDC.JPG (26.8 KiB) Viewed 1988 times

[trackerjack]

It's not so much the tyre wear Jon, but the fact that the tyres have ballooned in the centre.

Ah now I see the problem and I had a set of Colways that did this. They delaminated and broke up just as a set of P6 tyres that I used for a race in my MGBGTV8 at Mallory did.............err duff tyres then

[SPRINTPARTS]

Looking at the photo of the tyre it appears that it has broken a belt or has belt separation. I have had this happen to both a Yokohama A032 and A048. In both cases the belt broke and the tyre went "egg" shape. Neither time could Yokohama give any real reason for this happening, except that in motor sport the tyres are pushed to the limit and sometimes over that limit.

I would imagine that these tyres are quite a few years old (tread depth has little to do with tyre life with these types of tyres), as I don't believe that A032's have been made for a few years now. From this year we have started using A050 tyres, so A032 are now 2 generation old technology.

Suspension set up is very much determined by circuit condition, driving style etc, etc. When we changed from A032 to A048 tyres we went up nearly 50% in spring rate. On a Dolly I have always run 3 to 4 deg neg camber, similar caster figures and and around 2mm toe in. From memory with A032 around 36 psi HOT, once again personal choice and what sort of car feel you want.

Mark