Tyre sidewall cracking...does it matter?

mjcaskey

Hi,

I went to swap tyres on my venerable Dawes Galaxy commute bike to 'Summer' continiental city speed tyres, used last year. They are hardly worn at all but there are now a few craks in the rubber of the side walls. On looking at my other road bikes I nitice the same on two yeal old Michellin pro race 2s and another continintal tyre set (can't remember the type, could be 3 years old now. A few google searches suggest that as long as the tyres are not deformed they should be fine. I have never had this problem with previous MTB tyres.
What do you think? Do I need to change them all??

Weejie54

Put it this way: If they were on a car, and were severely cracked, it would fail an MOT.
If you can see the casing through the cracks it is not good.

night_porter

I have to disagree, according to Sheldon Brown the only purpose of the rubber in a tyre is for adhesion to the road.

"The rubber is mainly there to protect the fabric from damage, and has no structural importance."

Therefore of the rubber has no structural purpose the cracking should make no difference whatsoever.

Have a read here http://www.sheldonbrown.com/tyres.html

Cars weigh a lot more and go a lot faster than bikes so I will guess that would be the reason for an MOT fail?

Weejie54

"The rubber is mainly there to protect the fabric from damage, and has no structural importance."

Like damage from stones, glass etc.

If it wasn't needed, it wouldn't be there - as weight saving is all important.

If the casing is exposed, the tyre is vulnerable. Not the thing to be flying downhill at 40+ mph.
Not the kind of thing I would like to put to the test.

Minor cracking is probably OK but you only have one life - as a cyclist, anyway.

freehub

The rubber is very important, if it was not there you'd not be able to have tyres...... And obviously when the thread starts showing, you bin the tyres.

4kicks

Meanwhile, having actually READ the OP..

Small (ie mms long) cracks in the rubber sidewalls are not a problem. I live somewhere hot and leave my bike outside and they happen after about 2000kms/2 months. Michelins are particularly prone to them, dunno why

Im pretty sure there are tyres, like the Vittora Open Corsa EVO, which actually dont have rubber on the sidewalls, just the fabric. upon whch a narrower rubber tread strip is glued.

Once they become big cracks, or you can see the material under, of course its a different case and its impossible to tell which they are without seeing them

mjcaskey

Thanks everyone.

After some consideration I think the cracks do not pose much threat, but I have decided to change the tyres anyway for the sake of a few pounds and peace of mind.

Mike