Rear tyre tearing

[scorry]

not sure if this should be in this catagory or racing or motards or maybe even suspension.

i took my ktm525 up to levels in the weekend to race in the clubmans class, wasnt expecting to do real good against the road bikes, but then it started raining.

I managed a 2nd in the 1st race, missed the 2nd race cos my feken bike wouldnt start.
Then i managed another 2nd in the last race and got 3rd over all.

but anyways the problem i am having is that my rear tyre is tearing mid way up the left side as per the pics attached.

the tyre is a metzler drift motard slick and it was running 30 psi and only did around 20 laps, the last 3 were in the wet (dont know if this has anything 2 do with it tho??) although they only started tearing up when it was wet.

i also noticed the pilot powers i used in the last race as wets also teared up just slightly tho, i have raced my bike at teretonga on those tyres and they didnt chew up like this.

the only change i have done is that i cranked up the preload on the rear by 2 turns, as i am didnt have the sag set up right.

so maybe this is the problem??

any advice is much appreciated, thanks

[puddytat]

wheel alignment?

[scorry]

wheel alignment?

if the alignment was out by say 1-2mm, would it effect it this much?

[driftn]

What compound are the tyres?
How warm was the track?

first thing I would be looking at would be the air presure dude.

30 pound may be a little hard.

[scorry]

What compound are the tyres?
How warm was the track?

first thing I would be looking at would be the air presure dude.

30 pound may be a little hard.

not sure what compound the tyres are but the track was pretty warm then it rained.

i was going to try running 32psi in the 2nd race but i never made it to the track.

im off to ruapuna this weekend so i will try play round with the pressures at practice on friday.

the thing is, when i used the pilot powers at teretonga they didnt do this at all, but when i used them in the last race at levels they did show signs of tearing alltho i was still using the same pressures.

got me stuffed????

[puddytat]

:

if the alignment was out by say 1-2mm, would it effect it this much?

It certainly can do.....I had new PR2's on at a trackday at Rua's & they ended up looking very similar, normal wear on edges etc but like yours the sort of middle third of the tyre looked rather sad..

Somone suggested checking my alignment using string & bugger me days it was 15mm out even though the swing arm marks said otherwise.
Adjustments were made & the problem dissapeared ....& now I know that I need to have nearly a whole mark differance to be running true.
It might'nt be the whole cause off your problem but its worth checking

[Nonbeliever]

it just looks like youve picked up some rubber off the track.
also,"tearing" normally occurs nearer to the edge of the tyre.

[scorry]

:

It certainly can do.....I had new PR2's on at a trackday at Rua's & they ended up looking very similar, normal wear on edges etc but like yours the sort of middle third of the tyre looked rather sad..

Somone suggested checking my alignment using string & bugger me days it was 15mm out even though the swing arm marks said otherwise.
Adjustments were made & the problem dissapeared ....& now I know that I need to have nearly a whole mark differance to be running true.
It might'nt be the whole cause off your problem but its worth checking

i know i had to offset the wheel slightly like only 1-2mm, otherwise my tyre warmers wouldnt fit in between the tyre and the swingarm
i will check the alignment tonight, cheers for that tho

it just looks like youve picked up some rubber off the track.
also,"tearing" normally occurs nearer to the edge of the tyre.

no its definatly tearing mate cos there is even more wear eg less tyre in that spot too, hopefully i can fix the problem and save the tyre??

[Robert Taylor]

not sure what compound the tyres are but the track was pretty warm then it rained.

i was going to try running 32psi in the 2nd race but i never made it to the track.

im off to ruapuna this weekend so i will try play round with the pressures at practice on friday.

the thing is, when i used the pilot powers at teretonga they didnt do this at all, but when i used them in the last race at levels they did show signs of tearing alltho i was still using the same pressures.

got me stuffed????

Apart from the sweeper at Teretonga you are on the side of the tyre at Timaru for a long time. It is simply out of its temperature window because of the suspension setup. Whilst not being on the spot the most likely causes are incorrect spring rate and low speed compression damping that is too weak for an application the bike wasnt primarily intended for. If the front is ( as I suspect ) also too soft that causes an imbalance and doesnt keep the rear loaded as it should be. If you are getting ''only 20 laps'' out of the tyre thats a figure that would make the 600 and 1000cc sports production riders very happy!

[scorry]

Apart from the sweeper at Teretonga you are on the side of the tyre at Timaru for a long time. It is simply out of its temperature window because of the suspension setup. Whilst not being on the spot the most likely causes are incorrect spring rate and low speed compression damping that is too weak for an application the bike wasnt primarily intended for. If the front is ( as I suspect ) also too soft that causes an imbalance and doesnt keep the rear loaded as it should be. If you are getting ''only 20 laps'' out of the tyre thats a figure that would make the 600 and 1000cc sports production riders very happy!

thanks for the reply, sounds like its not an easy fix for this weekend then as i dont have the coin at the moment for new springs.

im heading up to ruapuna on friday for practice as i have never been to the track before, is it ok if i pop down to your flash looking ohlins trailor for you to have a play with my suspension?

i read that you set quasi's 525 up pretty good

oh maybe i need a tyre sponsor if i am only going to get 20 laps out of a set of tyres

cheers