Track day tyre wear, is this right?
 

my first track day on a circuit that was n't covered in standing water yesterday and my rear tyre seems to have blistered and chunked itself apart in the most odd way, - and other Ducs were n't.
Unfortuantly I know it was n't me riding the thing to fast, - as I was not having a good day, (not in the right frame of mind, but more of that in general messages).

The front tyre looks as a normal track day tyre would, - even blistering accross the width of the tread, however the rear ( a Michelin Pilot sport with only 150 miles on it) was what looked like tearing chunks off of it about 3/4 way accross the width of the tread. The Michelins have diagonal slash cuts going accross the tyre and it was from the leading edge of of this slash cut starting about 1 1/2 inch wide narrowing to a point just in front of the slash cut behind. Looking at the cut tread of that slash cut now it looks to have chamfered off itself, - to me this is odd, andnot right. Checked the presures in the paddock 36psi rear, 32 psi front, perhaps a bit high, but not enough to make a difference. We checked the rebound, it was a bit slow, so slackened that off 1/2 a turn, - next time out the effect was not so extreme, but still there.

The other mates that i was with thought it to be the way I was riding (like a pussy), - i was not carrying enough corner speed through the 2 main corners (Lydden, so there are only 2 fast corners really), - i was doing my braking before the bend, - and whilst the bike was still leant over feeding in the power from low revs as I rode through the corner, - to me this is how you ride a Duc, - (ok with a bit more bottle on the way in). At first we thought it might be the v(L?)-twin torque ripping at the tyre, - but had a look around the paddock, and it was just me.

So if anybody has any clues of experience I would love to know what is going on, - could it be a sign of a dudd rear shock?

it sounds like the tyre pressure is to high
30 front/30 rear also have you set the suspension up as if it is not set up properly it will just rip the tyre
:sing:

[Edited on 15-6-2003 by scoot]

How strange ,can you give me a little more info on the tyre?

How old is it (the date not how long its been on the bike!)

A little prev history

The pressure of 32 psi when hot seem to low to me. I suspect the tyre had to little air in the extra deflaction has casued it to over heat.

what was your pressure cold (about 29psi!!) seems to low me.

What circut was it?

It really isnt my area trhis need to get someone who knows what there doing.

What did the instructer say on the track day?

Kev

Track day tyre wear
 

29 to 30 psi rear when cold and speed up the rebound. you will also need to chuck the tyre as this is now scrap. If the rebound is to slow, or to quick for that matter it causes the tyre to skip under load, you may not notice this but it manifests itself in a rear tyre that has chunked as you described. :devil:

thanks guys.

The pressures cold were 34 rear, 31 front, which is what I ride them at on the road, I left them at that, and checked them after a session, they were 36 rear 32 front. Track was Lydden, and it was hot yesterday. Lydden is all right handers except one left so the effect is mostly on the right side. The tyre, Michilin Pilot sport was fitted about a week ago, how do you tell when it was manufactured? Wheels are light, - Magnesium Marchesinis if that is of any relevance.

I did not ask the instructor, - I know, duh, but I really was not happy with myself as I was Mr Slow on slow day and was sulking to myself. The ride home from the track has removed most of the chunking effect, but you can still see it is not the usual neat blistering, - I will try and get a picture posted.

My original statement of chunking itself apart is perhaps more dramatic than it is, but it was almost looking like it was cutting into existing rubber and moving it back around the tyre as a lump adding to the profile. This is tough to describe.

I run 30/30 pressures when cold...
 

...your rear pressure seems way high...

Not sure if that was the problem though, but on a hot day, those pressures are bound to increase considerably.....


Tim

I really dont know anything about the bikes or modern tyres but 30/30 seems way to low to me.

I tend to run nearlly all modern bikes 36/42 for road use.

if the tyre was only a week old and its a popular make, which it is , it cant be old.

Tyre pressure does seem high for the track. I run 30/28.

If your shock is set up too hard it will chew the rear tyre up really badly, the same if theres too much weight over the rear tyre, also if the seal is failing (like mine :( ) it will have the same effect, I did the CSS at cadwell and wasnt riding anywhere near the speed I wanted to (loadsa slow riders on unpredictable lines so couldnt pass - 8ft CSS rule) and my rear was tearing up on a damp track!

PS the CSS technician lowered our tyre pressures to 30/32 on the day - maybe your tyres are overheating?

[Edited on 16-6-2003 by DJTera]

NO NO NO DJ, if the shock is set too soft it will chew the rear tyre to much, not if its too hard!