Curious tyre wear around cuts in the tread rubber

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Samuel D
Posts: 1785
Joined: 8 Mar 2015, 11:05pm
Location: Paris

Curious tyre wear around cuts in the tread rubber

Postby Samuel D » 19 Oct 2017, 10:24am

The 6 mm long cut on this Schwalbe One HS 448 tyre occurred when the tyre was new. It was at a shallow angle but it was deep, penetrating the puncture-protection strip though not the casing plies.

Image

Click here for a larger image.

I’ve put a few thousand kilometres on the tyre since, mostly on the rear wheel, and it now has pronounced square shoulders (possibly aiding the formation of the micro-cracks seen at these shoulders).

It is plain to see that in the vicinity of the cut the tyre has worn in a different way: smoothly, without the ripples that show elsewhere. A similar effect can be seen around the much smaller cut in the bottom-right of the photograph. In fact, I have seen this around many cuts before.

What cannot be seen in the photograph but in real life is that the rubber has also worn less around the large cut. The tread is perceptibly thicker around the cut. (This is in addition to the tread being raised there by the lack of tension.)

I’m interested to hear your thoughts on this wear mechanism.

Brucey
Posts: 26874
Joined: 4 Jan 2012, 6:25pm

Re: Curious tyre wear around cuts in the tread rubber

Postby Brucey » 19 Oct 2017, 10:46am

when the tyre rolls over a section of tread, the tread and carcass deform. The loads required to do this contain elements that are related to tyre pressure and elements that are related to the bending stiffness of the tyre tread/tyre carcass. I'd suppose that the latter are greatly altered by the presence of a cut. The cut will tend to close up as the tyre rolls over it, which means that something very different is happening to the rubber in that vicinity.

It is possible that the rubber elsewhere squirms until it is in intimate contact with the road, then sees a force that stretches the rubber surface as the tyre rolls out of contact. This may be the cause of the patterning (micro-tearing?) in the tread rubber, (which you don't see in every tyre BTW).

BTW that the tread wear is not uniform means that the rubber showing around the cut is possibly not 'the same' rubber as elsewhere in the tread, either by virtue of the way the tyre is made or by virtue of the wear rate ( the surface could be 'newer' or 'older', relatively speaking).

cheers
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