Hi guys.

A friend of mine just passed his test and has come out with us on a ride. After about 30 miles we stopped off for a drink and i noticed the wear on his rear tyre. On the side where his chicken strips are the new pattern from him is a wavy line?

I have searched on the internet and looked at cupping, but that is not it, there are no dip in the actual tyre, just a wavy line down the side wall almost like a really elongated "S" shape, all the way round.

To my his tyres look under inflated as the bike had sat in his garage after he bought it for 8 months till he passed his test. He also wen't a bit silly after buying it and tried to learn down a private road, coming off and breaking his collar bone at about 30mph. He snapped his rear brake lever, bent his front fork, needing new ones and a few other bits and bobs.

But its the rear wear pattern that concerns me.

Mine is pretty much a straight line with a little feathering on the extreme edge, same as my mates, but his is a solid wavy line?

 

I'd agree with under-inflation
Maybe an old tire too...........delamination is possible.
Parking a bike with a flat tire then riding it could also be to blame but I'd say most likely is under-inflated. I'd change it.
Lucky he stayed on this time too

 

Cheers... He's going to be changing his tyres anyway as they are almost on the limit in the middle, previous rider was a little conservative in his riding.

He's a little nervous on corners and roundabouts, but is not getting ahead of himself this time, think his fall made him think about it.

 

Faulty or incorrectly set suspension may cause that was well.

 

Is the rear axle running true - and square with the swingarm ? - if not, maybe.......
But if the suspension is running "soft" it would do as Zaq says also.

 

Sounds like he needs to go over the bike entirely and make sure everything is correct pressure and suspension setting wise.

 

entire bike should be gone through.