Just a curious thought…..
A little while ago I was having bad chainsuck, XT hollowtech II setup, the chain hanging on to the granny ring whilst trying to change up to the middle ring. I always clean the bike after a trip and haven't overly used the setup, I'm not hard on kit. After a while, I removed the cranks and one tooth had a burr along it's edge, something you could feel and see too. I gently stroked it with a file and removed it. That seemed to do the trick. Got a little chainsuck at the end of my last ride, not a long trip, but muddy. Now wondering if burr has returned or it could have simply been muddy conditions, though it wasn't that bad.
I'm no chainring masher, couldn't jump a log to save my life!
….so if if has burred again, how did it burr?
answers please!
cheers
Q

Sorry if I am stating the obvious but why not check it rather than ask here?

It's just wear on cheap chainrings btw

If the chain stretches (which they all do) the roller between links no longer sits neatly between the teeth on the sprocket, instead the roller starts to catch on the top of the tooth before it settles into the valley between teeth. This is why you get sharks fins, burrs etc. Tis also why changing your chain regularly extends the life of the sprocketts.

When the chain rings are badly worn, or you put a new unstretched chain onto worn chain rings the chain catches instead of smoothly releasing.

Burs also occur due to physical impact on the chainrings.

Buy a chain checker, I'd recommend the Park Tools one, and then change your chain at 0.75% wear, works out cheaper in the long run than constantly replacing chain rings and cassette.

cynic-al: I was trying to establish *what* causes a burr, apart from actually bashing it on logs or steps, something I don't do.
If I don't make a habit of bashing the ring, then how does it actually get the burr?
I didn't realise simply wear will cause that.

stumpyjon: yes I have often wondered about a chain checker as an addition to the tool box. That way I'd know if my chain had stretched or not, as opposed to thinking 'it can't be worn yet….'. Maybe I've to invest in one and stop guessing!

ta
Q

My answer is perhaps empirical but I've seen this more on cheap rings (which are admittedly moe common)

Depending on how they are manufactured, chain rings can have burrs from new, and these can get worse with wear.

This is my first experience with 'modern' XT, and hollowtechII stuff. The only things I've read ( on here ) is that apart from the bearings being poor, the chain rings " are made from Swiss Cheese…"
Maybe I'm now experiencing first hand that fact!
At the weekend ( in the light! ) I'll check the condition on the rings, and I think will have to treat myself to a chain checker, then I can keep an eye on that for wear too.
cheers
Q