Bicycle Mechanics - Chainring wear - replace along with chain?

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ReelExterminato
03-28-10, 06:06 PM
I've got about 3500km on my chain. Yesterday I noticed that the chain was riding up a little bit at the top of the ring on which it was sitting. Taking out a stretch tool, the 0.75 end went in easy, and I was also able to force the 1.0 through the link - time to replace the chain! Fortunately I have a extra new one lying around.

I'm trying to determine if I should swap the rings and/or cassette while I'm at it. The teeth on granny ring are pretty symmetrical while the middle (which I use the most) and the big rings look a little bit funny, though no 'hooks'. Teeth on the small sprocket still have flat tops, but the dip in between them is also a bit lopsided. Should everything but the granny be replaced? I'd rather not spend the money if I don't have to, but if it needs to be done then I'd prefer not wasting a $40 chain to find out. Thanks!

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prathmann
03-28-10, 06:32 PM
I would just change the chain. Then if the new chain skips on the old cassette you'll need to replace that as well. The chainrings still look like they'll work ok to me - and I presume you haven't had any issues with the chain slipping on them.
Kimmo
03-28-10, 11:44 PM
If you get a whirry, throbby sort of vibration while pedalling hard with the new chain then change the affected rings; otherwise they're fine.

They look like they've still got a fair bit of life left.

ReelExterminato
03-30-10, 02:32 AM
Excellent, no problems with the new chain. The only hitch occurred when I tried to take off my square-taper crank with the ISIS bit on the puller in order to clean it more thoroughly - yay for evening mechanics and stripped threads :) Pulling it off later will be interesting...
DMF
03-30-10, 08:50 AM
You'll know a front ring is worn out when you put some serious power into it and the pedal suddenly drops to the bottom of the stroke without resistance. It will get your attention! A worn out rear cog will skip, but nothing like that.

Ride the rings until you can't, then replace the one that needs it. Usually the middle.
IK_biker
03-30-10, 04:29 PM
Your rings look fine, but you should go by feel after installing the new chain.

On my MTBs I get an average of 850 miles per chain (that's what the muddy terrain I ride in Western NC does to me), and need to change the cassette once in 3 to 4 chains, and the chainrings - 1 in 6.
On the road bikes I get around 3000 miles per chain, and have not yet changed c/rings due to wear.