Chewed-up chainring

[Howzat]

I was cleaning the bike and noticed these chewed-up teeth on the front chainring (compact 50T). Any ideas as to what might have caused this?





The bike has only about 1000kms on it. I did have a chain break on me a couple of months back, but otherwise no unusual drivetrain incidents. The inner 34T chainring looks fine, and I spend about 50% of the time on each ring. Is it possibly just normal wear and tear?

[Jesmol]

Chainrings on my SRAM chainset look the same, in fact one of mine had bent slightly causing an issue when back pedalling. I suspect they're made of fairly soft material and dont really like the chain running at funny angles across them

[MattyK]

They make them like that to aid shifting.

[Howzat]

Interesting . I noticed the asymmetric pins and scalloping on the big chain ring, I have no idea how it is supposed to work.

I did find a metal shaving I removed with a file from one of the gaps between the teeth, and some other minor marks. But that those funny-looking short teeth are a design feature is good to know.

[jacks1071]

Get yourself a set of "Needle Files" from your local Bunnings or hardware store.



You can tidy up the chain ring with those, only remove as much material as is necessary.

As to the cause, the same thing that broke your chain would have damaged them - most likely shifting under too much load or an excessively worn chain. If the chain only had 1000kms on it then refer to the first cause.