Tyre screwed?

[ivan]

Any idea why a repair near the edge of the tyre is so much more of an issue. I've repaired a few like this,and not had any issue. The sidewall is obviously different - flexes a lot more, is more load-bearing and has a different construction. But the edge of the treaded section is the same as the middle isn't it? So I would have thought as long as there's room on the inside for the patch to sit, then it should work? Or is the 'not to close to the edge' thing because the patch can't be seated properly on the inside?

[Stinsy]

Any idea why a repair near the edge of the tyre is so much more of an issue. I've repaired a few like this,and not had any issue. The sidewall is obviously different - flexes a lot more, is more load-bearing and has a different construction. But the edge of the treaded section is the same as the middle isn't it? So I would have thought as long as there's room on the inside for the patch to sit, then it should work? Or is the 'not to close to the edge' thing because the patch can't be seated properly on the inside?

1) Against the law.

2) The reason it is against the law is because there is an unacceptably high risk of catastrophic failure.

Saying "I've done it a few times and been lucky so far" is hardly the ringing endorsement you seem to think it is...

[ivan]

Im not suggesting you're wrong. I'm interested in the mechanism which would render it unsafe. Understanding why repairs on the sidewall are not recommended is relatively easy - the side wall flexes significantly with every revolution of the tyre - which would put additional cyclic stresses on the repair patch. But this can't apply to the outer 1/4 of the tread. The only thing I can think of, is that if it is so close to the sidewall, then there isn't enough room on the inside of the tyre to vulcanise the rubber patch onto a flat area...and if some of the patch is extending slightly onto the sidewall, then that is subject to cyclic stresses. Or maybe it's because the outer part of the tread tends to wear down quicker than the centre? Wouldn't have thought that would have much bearing on the integrity of a patch though.

[chris_n]

Im not suggesting you're wrong. I'm interested in the mechanism which would render it unsafe. Understanding why repairs on the sidewall are not recommended is relatively easy - the side wall flexes significantly with every revolution of the tyre - which would put additional cyclic stresses on the repair patch. But this can't apply to the outer 1/4 of the tread. The only thing I can think of, is that if it is so close to the sidewall, then there isn't enough room on the inside of the tyre to vulcanise the rubber patch onto a flat area...and if some of the patch is extending slightly onto the sidewall, then that is subject to cyclic stresses. Or maybe it's because the outer part of the tread tends to wear down quicker than the centre? Wouldn't have thought that would have much bearing on the integrity of a patch though.

I would have thought the inside of the tyre would be curved in the outer 1/8th of the tread on most tyres. May not be the case with particularly wide tyres but almost certain to be on most. I don't know why they didn't specify a distance from the edge of the tread, 1/8th of the width is fairy significant on my 245's (about 36mm).

[Stinsy]

Im not suggesting you're wrong. I'm interested in the mechanism which would render it unsafe. Understanding why repairs on the sidewall are not recommended is relatively easy - the side wall flexes significantly with every revolution of the tyre - which would put additional cyclic stresses on the repair patch. But this can't apply to the outer 1/4 of the tread. The only thing I can think of, is that if it is so close to the sidewall, then there isn't enough room on the inside of the tyre to vulcanise the rubber patch onto a flat area...and if some of the patch is extending slightly onto the sidewall, then that is subject to cyclic stresses. Or maybe it's because the outer part of the tread tends to wear down quicker than the centre? Wouldn't have thought that would have much bearing on the integrity of a patch though.

When you drive around a corner a radial tyre flexes sideways. This means that the outside portion of the tread significantly and is subject to significant forces.