Rims feel slightly concave

[mcshroom]

I've just been working on my tourer's front wheel and I've noticed the braking surface feels a little concave to the touch, but there is still a visible 'wear indicator' groove on the wheel. The wheel is 4000 miles old and is a pretty standard double walled job, and the brakes ared Oryx cantis.

Is it normal for the rim to feel a bit concave for a while before it goes? I've never got a wheel to this distance before.

 

[brockers]

The mileage does seem low tbh, but this is apparently what happens to wheels before they go BANG! (convex, though surely - the walls bend outwards?). I wouldn't risk it. Let a good mechanic have a look at it.

 

[fossyant]

Just keep an eye on them - getting towards end of life. Both my rims on my fixed are pretty worn, so I'm keeping regular checks.

 

[Angelfishsolo]

The mileage does seem low tbh, but this is apparently what happens to wheels before they go BANG! (convex, though surely - the walls bend outwards?). I wouldn't risk it. Let a good mechanic have a look at it.

I would agree with the OP. As the walls wear the surface becomes thinner and this concave. If the rim reached a point where is became convex I would have thought it would be seconds away from snapping in two.

Anyone want to confirm or deny this please. My head hurts from lack of sleep (again)

 

[HLaB]

I think my much abused rear rim on the Ridgeback got 6500 miles before it bulged and burst but touch wood the better maintained kinesis has done 8600 miles an its still OK.

 

[Red Light]

Do the test recommended by Chris Juden at the CTC. Pump the tyres up to 50% over the maximum pressure on the sidewall. If the rim is going to go it will go when you do this. If it survives, let the pressure back down to normal and you're done. If you have some wear marker left though its almost certainly OK even if it is concave provided the wear is centred on the wear marker (where it is most concave.

The time it takes for a rim to wear out depends on a number of factors - how you ride, how hilly it is (i.e. brake use), riding conditions (dry or wet and muddy) and local soil type. For example in Yorkshire gritstone areas rims and brake blocks can wear very quickly.

 

[mcshroom]

Thanks everyone.

I've tried that test Red Light and the rim seems fine. The wear indicator is pretty much centre of the concavey bit as well, so I'm pretty happy it's ok.

[It's definitely concave (slightly hollowed out in the middle of the braking surface. If it was convex the wheel would be off my bike VERY quickly.]