Why are my tyres cracking?

**Zapf** · 2nd January 2015, 09:08

These are a dual purpose Pirellie MT90 mounted on a 650 single thumper.

I am noticing these cracks in the blocks. should I be concerned about how i am riding them?

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**haydes55** · 2nd January 2015, 10:52

They look all good to me. Gravel can have sharp edges that start a split, then fast cornering can open it wider. Unless the tire is old, or sits in the sun all the time, it shouldn't have hardened and gone brittle.

**AllanB** · 2nd January 2015, 11:01

Just ride in the mud more - it fills up the cracks.

**Motu** · 2nd January 2015, 11:24

You should use tyres, that could be the problem.

**Waihou Thumper** · 2nd January 2015, 11:37

A couple of cuts, yes..
Gravel and cornering does that and like the rest of the inmates say, just ride...
Nothing wrong here, move right along please...

**mossy1200** · 2nd January 2015, 12:19

Originally Posted by Waihou Thumper

A couple of cuts, yes..
Gravel and cornering does that and like the rest of the inmates say, just ride...
Nothing wrong here, move right along please...

Think OP is more concerned with the multiple small cracks between the knobs. Easiest to see when expand 2nd photo.
Wonder if the knobs are flexing to much because pressure is to low in tyre.

**Waihou Thumper** · 2nd January 2015, 12:30

Originally Posted by mossy1200

Think OP is more concerned with the multiple small cracks between the knobs. Easiest to see when expand 2nd photo.
Wonder if the knobs are flexing to much because pressure is to low in tyre.

aah, yep, see now. Normal...Had a look at mine, pressures? Think it is flex. These are going to flex no matter what surely?

**mossy1200** · 2nd January 2015, 12:38

Originally Posted by Waihou Thumper

aah, yep, see now. Normal...Had a look at mine, pressures? Think it is flex. These are going to flex no matter what surely?

Not sure. Idd think normal but im not an off road rider.

**Ocean1** · 2nd January 2015, 14:27

Looks like cold tearing.

Don't worry about it, won't kill you on those.

Maybe choose something different next time if you're going to push it a little on the road.

**R650R** · 2nd January 2015, 16:52

What pressures are you running? maybe too high.
I have same on front of my DR and they stick to tarmac like slicks, absolutely brilliant for an 80/20 tyre. Will take a pic of mine later.

**R650R** · 2nd January 2015, 18:46

Here's how mine is looking roughly after 2000km... has been few slow rides lately so not as feathered up as it has been in the past

The front tyres on the DR don't really do any work, I find the rubber goes hard/off after about 8000km even though plenty of tread left, well on trailwings anyway.

https://drive.google.com/file/d/0B0N...ew?usp=sharing

**Zapf** · 2nd January 2015, 23:02

Originally Posted by R650R

Here's how mine is looking roughly after 2000km... has been few slow rides lately so not as feathered up as it has been in the past

The front tyres on the DR don't really do any work, I find the rubber goes hard/off after about 8000km even though plenty of tread left, well on trailwings anyway.

https://drive.google.com/file/d/0B0N...ew?usp=sharing

Wow your tires are scrubbing off nicely on the edge...

Originally Posted by haydes55

They look all good to me. Gravel can have sharp edges that start a split, then fast cornering can open it wider. Unless the tire is old, or sits in the sun all the time, it shouldn't have hardened and gone brittle.

sounds like what maybe happening. the tire was made mid 2014 so shouldn't have hardened. But yes have been riding on gravel and fast south island sealed corners.

Originally Posted by mossy1200

Think OP is more concerned with the multiple small cracks between the knobs. Easiest to see when expand 2nd photo.
Wonder if the knobs are flexing to much because pressure is to low in tyre.

been running 26 psi front and 30 psi rear. so should be high enough?

Originally Posted by Ocean1

Looks like cold tearing.

Don't worry about it, won't kill you on those.

Maybe choose something different next time if you're going to push it a little on the road.

possible.... so that is from riding hard when the tires are still cold?

Originally Posted by R650R

What pressures are you running? maybe too high.
I have same on front of my DR and they stick to tarmac like slicks, absolutely brilliant for an 80/20 tyre. Will take a pic of mine later.

26 psi front and 30 psi rear. yes they have stuck well and I have not fell off yet :P Have done 4'000km's on them in the south island roads now.

**zoomzoombounce** · 4th January 2015, 05:41

Looks very normal to me

**Ocean1** · 4th January 2015, 09:28

Originally Posted by Ocean1

Looks like cold tearing.

Originally Posted by Zapf

possible.... so that is from riding hard when the tires are still cold?

On modern road tyres, yes, usually because of over-inflation, (doesn't allow the tyre to work and warm up). Not sure that'd apply to those tyres, although I'd be running that rear at closer to 25psi.

Given the size and pattern of the tears I'd lay at least some of the blame on the large and very sharp chip-seal they use down there, it has to put more shear pressure on a smaller area. It certainly wears tyres, I can trash a rear on a trip from Picton to Invercargill and back.