Bending a chainring

Harrybelafonte

Bent a Sram inner chainring which I forgot was missing a chainring bolt at the weekend. Anyone ever had luck bending one of these back? It's on a carbon crank so I don't want to go all hammer and tongs on it.

seamus

Most chainrings are alloy. Once they're bent, they're ****ed. They won't have the strength for anything but very light spinning.

Harrybelafonte

Yeah, am looking for a replacement, but wanted to try and sort something temporary

seamus

You might get away with bending it back and bolting it in place, but I've had one bend between the bolts before, it was only fit for the bin. When I bent it back, it just bent again straight away under any force.

Raam

You got lucky. I lost some bolts and ended up wrecking the chainring completely, damaged the crank so that it is no longer useful and also cut a nice groove around the BB from the chainring.

JBokeh

I've bent them back on MTBs with varying degrees of success, how bent is it? A dirty trick i've done to keep me going for a while until I got a new one, is to mark where the fold is, and grind off some of the teeth, furthest from the centre line of the bend, it stops the chain from putting as much force on the chain ring at the point where it gets the most leverage, which stops it from folding again, makes it very bad at shifting, and it makes a bit of noise, but strangely enough doesn't affect the way it pedals. The way i look at it is that the ring is shagged anyway, may as well sacrifice it.

I straighten it between 2 bits of steel in a vice, having heated the relevant parts until they just start discolouring, and fine tune it with an adjustable spanner and a vice. To cool it I point a heat gun at it and try to let it cool slowly, this stops the alu from weakening as much as the bend points, but it is still weakened, just not as much as it would be if you cold bend it. It is a very temporary solution, but one has only bent again on me, however I've only ever used them for a couple of rides until I got some new ones of ebay or CRC

Harrybelafonte

Raam wrote: »

You got lucky. I lost some bolts and ended up wrecking the chainring completely, damaged the crank so that it is no longer useful and also cut a nice groove around the BB from the chainring.

Came very close to destroying chain stay tbh. Really stupid of me tbh. Should have fixed it ASAP.

Harrybelafonte

JBokeh wrote: »

I've bent them back on MTBs with varying degrees of success, how bent is it? A dirty trick i've done to keep me going for a while until I got a new one, is to mark where the fold is, and grind off some of the teeth, furthest from the centre line of the bend, it stops the chain from putting as much force on the chain ring at the point where it gets the most leverage, which stops it from folding again, makes it very bad at shifting, and it makes a bit of noise, but strangely enough doesn't affect the way it pedals. The way i look at it is that the ring is shagged anyway, may as well sacrifice it.

I straighten it between 2 bits of steel in a vice, having heated the relevant parts until they just start discolouring, and fine tune it with an adjustable spanner and a vice. To cool it I point a heat gun at it and try to let it cool slowly, this stops the alu from weakening as much as the bend points, but it is still weakened, just not as much as it would be if you cold bend it. It is a very temporary solution, but one has only bent again on me, however I've only ever used them for a couple of rides until I got some new ones of ebay or CRC

Thanks for the details. Tbh it sounds like my new one would have arrived before I got a chance get any of that done. Thank you though.