Unanswered how do teeth get bent on a sprocket? can they be straightened?

[pgrbff]

My son was complaining that his gearchange wasn't working particularly well. On inspection the sprocket is bent, two teeth are anyway. How do they get bent? He says he has no idea but then he is 13 so he wouldn't tell me if he did. I assume I can change the single sprocket but Haibike can't tell me which cassette he has so here we go again. It's a Deore 11 speed, how do I know which cassette to buy? Are there many options?

 

[pgrbff]

Scrub the last bit, I can just make out it is a CS-M5100-11. He has done about 1200km, would it be better to change the whole cassette?

 

[VWsurfbum]

How did he do it, you'll never know.
what can happen is sticks or branches in the chain etc.
it sucks, I did it last winter on a reasonably new cassette.

 

[urastus]

Scrub the last bit, I can just make out it is a CS-M5100-11. He has done about 1200km, would it be better to change the whole cassette?

That's a fair bit, especially if it is the original chain too. If it is the original chain, it is probably better to replace cluster, chain and chain ring.

If the bent teeth are on a reasonably large sprocket (chain is supported by more teeth), you could try cutting the teeth with a cutting wheel holding it vertically between the sprockets - just cut the bent bits off. I imagine they'd just break if you tried to straighten them. There should still be some nubs left, which will do something.

 

[pgrbff]

It's a middle sprocket. Just thought if I'm going to have to strip it maybe better to change them all. That's going to cost a small fortune!

 

[urastus]

It's a middle sprocket. Just thought if I'm going to have to strip it maybe better to change them all. That's going to cost a small fortune!

Try the cutting wheel - it should buy you some time. Don't dismantle anything - well take the wheel off and lock the cluster somehow (with zip ties?) so that it doesn't spin around while you're playing with the cutting wheel. Run a rag with a bit of kerosene between the sprockets to get rid of any steel grindings.

 

[pampmyride]

Just bend 'em back. Did this 400 miles ago, still going great. Assume E-bike.....then clumsy fast gear shifting under power can tangle chain.

 

[steve_sordy]

I'd go with the straightening attempt first. If it doesn't work, you will end up with stubs anyway. But it might work and you will be better placed.

 

[All4Fun]

Take the cassette from the hub and you can straighten almost every single cog.
Use a flat surface as a controlling base.

https://si.shimano.com/api/publish/storage/pdf/nl/ev/CS-M5100/EV-CS-M5100-4665.pdf

 

[RustyIron]

How do they get bent? He says he has no idea but then he is 13 so he wouldn't tell me if he did.

Shifting under power and smashing into things.

 

[pgrbff]

Park Tool chain wear tool just arrived. 0.5 just about slips in. It's an 11 gear does that mean time to change chain?
Can you just change the chain on it's own? I gently tapped on the teeth with a piece of hardwood and hammer and whilst they are still bent the gear changing has improved.
How easy is it to know when the cassette and chain ring are worn to the point they need changing?