tyre wear question

scooble · Post by **scooble** » Mon Aug 20, 2012 6:37 pm

I have a michelin SM front tyre which looks like this;

the depth of the rippling is much deeper which isn't brought out in the picture.
Is this evidence of an underlying suspension issue, if so, what could possibly be the cause

Luders · Post by **Luders** » Mon Aug 20, 2012 6:47 pm

how does the front end feel?

It looks like your getting a bit of front end chatter.

I don't use these tyres, but what pressures were you running.

scooble · Post by **scooble** » Mon Aug 20, 2012 7:08 pm

I run 26 front cold - bike seemed to behave ok with no evidence of instability, although when I jam on the brakes hard, the front does then patter, however, if I brake progressively it doesn't do it.

dave32 · Post by **dave32** » Mon Aug 20, 2012 9:20 pm

Its not right,it shouldnt rip up like that,i would say 26psi front is too low and that could be the cause (thats near the pressure on use on the h***a RS125,which weighs 70kg).
ON my TZ with dunlop inters i run between 29 to 31 front and 27 to 29 rear cold,depending on the outside temp (cold day use the higher pressures).
I use the same pressures on the KR,no evidence of tearing,just a nice grained surface.
What is the rear tyre like compared to the front and are you running more ride height on the rear or stock?
How far through the yolks are the forks dropped?,i wouldnt go more than 20mm.

scooble · Post by **scooble** » Tue Aug 21, 2012 7:50 am

the pressure i use is that which is recommended on the Michelin web site for these types of tyres. The rear height setup should be standard, although I do have an R6 shock, but it has been modified to the standard KR height.
The front is a ZX636 setup and has been dropped 10mm through the yokes.

On the rear I used a Michelin power one and it looked pretty smooth.

Can anyone recommend a good suspension setup guide?

dave32 · Post by **dave32** » Tue Aug 21, 2012 3:08 pm

but there designed to be used on supermotos that dont have much weight over the front...
you would probably be better with a matched set of tyres,it maybe the cause,whats the gain in running a different front and rear?
Suspension settings really go out the window if your using a different front end and shock,are the forks and shock revalved for the lighter bike?

scooble · Post by **scooble** » Tue Aug 21, 2012 3:48 pm

yes, both the forks and the shock were sent to Russ at Mick Gardner racing to modify. The shock was shortened, re-valved and re-sprung and the forks were re-valved with racing and track days in mind.
The rear shock sag was setup by Racelab suspension services a few years ago at a Brands Hatch track day, they also set the compression and rebound damping, the front was setup by Mick Gardner as it left their workshop.

Although I am aware that these are supermoto tyres, I believe a lot of 250 riders use them.

Luders · Post by **Luders** » Tue Aug 21, 2012 5:00 pm

I think Dave is just saying that the tyre is being subjected to more braking and weight forces, than what a super moto would put on the tyre and therefore the recommended pressure may not apply in your case and a couple more psi would be required.

KFOR · Post by **KFOR** » Tue Aug 21, 2012 5:38 pm

Looks very much like a rebound issue there, take it back 2 turns and im sure the tyre will clean up

Rocket · Post by **Rocket** » Tue Aug 21, 2012 5:50 pm

I thought the mich supermoto and the mich power 1 were the same compounds, just different tread patern for legality (road use).

if supermoto and kr weigh same then when breaking hard and rear wheel off road, won't there be same force through the front tyre.

I run much lower pressure than this in supermoto and dunlop inters and it works for me, maybe my bikes are set up compleetly different though (kr1s forks(slid up through yokes), r6 or penske(same length as r6) shock, raise rear ride height via r6 shock, std r6 rear shock)

Luders · Post by **Luders** » Tue Aug 21, 2012 6:06 pm

what psi do you run in these michelin SMs Mark?

JanBros · Post by **JanBros** » Tue Aug 21, 2012 9:45 pm

Is it on both sides the same ?

26 PSI is about 1.8 bar ? that's not much

I' d recon that's a presure for supermoto's including ofroad sections no ?

I've used Continental supermoto tires on my KR, and I ran 2.3 bar front and 2.2 bar rear (in fact I don't care what tires are on the bike, I always use those presures on track).

Rocket · Post by **Rocket** » Wed Aug 22, 2012 9:26 am

[what psi do you run in these michelin SMs Mark?]

23 front, 23 rear cold

scooble · Post by **scooble** » Wed Aug 22, 2012 10:52 am

to be honest, the first track day I did with these tyres, I used 28psi cold and got the same kind of wear pattern as I did with 24psi cold on my last practice day.
Although, I agree, that the higher pressure is probably the way to go, I suspect there is still some underlying suspension issue that needs to be resolved.

The pattern doesn't appear on the left, possibly because there are only two left handers at Brands and I still haven't got them sussed yet and I feel uncomfortable on the bike.

on a seperate but slightly related question, what compound would you recommend front and back for a pair of Pirelli Supercorsa tyres?

Luders · Post by **Luders** » Wed Aug 22, 2012 11:21 am

I have an SC2 rear and SC1 front.

As Kev suggests, when you see deg on the tyre like that, it could be down to rebound damping.