I was going to ask if I need to replace it but I'm certain the responsible answer is yes (comments welcome). How do I find and replace the outer chainring?

Specifically find the right model or compatible part and the dummys checklist for doing the task at home, perhaps some good links. According to the Kona Cindercone 2011 specs the chainring is the 44 tooth "42/34/24" (incorrect spec) on a Shimano FC-M521 crank arm.

chainring missing tooth

Notice how I haven't even worn off the stickers... yes I am a newbie who either broke the tooth tumbling off an intermediate trail, or worse still hopping a curb.

  • 1
    Chainrings are fairly standard items -- your LBS may have one in stock, or you can order it. The only problem is that yours is a 4-bolt ring and most are 5. (Looks like it might be a Shimano SLX, which of course are twice as expensive as standard 5-bolt rings.) Used to be you needed a special wrench for the back side of the bolts -- don't know if that's still true. Jun 1 '12 at 3:00
  • Yeah Shimano SLX sounds right. Are any crank/chainring/derailleur parts interchangeable with other models? Possibly other 4-bolt options within the Shimano range
    – KCD
    Jun 1 '12 at 3:41
  • In general you've got 4 variables -- the number of teeth, the number of bolts, the bolt circle diameter, and the thickness of the ring (related to the chain width which relates in turn to the rear cluster geometry). The thickness is probably the most confusing but also most forgiving. Jun 1 '12 at 11:01
  • It's not the SLX aka FC-M660 it is the "Non-series" FC-M521. Interestingly I can get the whole SLX set with bottom bracket for not much more than a new chainring. I can source the SLX chainrings too I might research if they are compatible
    – KCD
    Jun 2 '12 at 22:49

Just buy a 104 BCD (Bolt Circle Diameter) chainring with the same number of teeth (probably a 42 tooth on this model). Try searching for '104bcd 42t' on google.

Unbolt the chainring bolts (you may need a chainring nut wrench to hold the bolts while loosening or tightening them like the Park CNW-2C) and then put the new ring on and bolt it back up. You may need to remove the crank to get this on, but usually you don't have to worry about that for larger outer chainrings, so I think you'll be able to skip that step.


Not positive, but it looks like you can replace it without even pulling the crank. Just remove the 4 allens and slide it up over the crank arm then just do everything in reverse putting it back on. Make sure to drop the chain off the whole thing to keep it out of the way.

Worst case is you will have to pull the crank. If so, there is a chance you will need a crank-puller (ex: http://bit.ly/Lclgtv), some cranks use tapering to keep from wiggling loose, and since I dont see any locking bolts from this angle I will assume that is the case. You will only need to use it to pull the crank and when you tighten it back on it will basically self adjust (you will want to check it a few times the next couple of sessions). You might be able to take it into a bike shop to have them pull it, I know the shop I worked in would have done it for free in a matter of seconds.

  • If the crank arm is removed (which is highly advised) then one must be sure to properly torque the bolt on reinstallation. Otherwise the arm is apt to come loose and be damaged. Jun 1 '12 at 11:02
  • you are right, proper torque is advised, if you can find the specs and a torque wrench. Even then, I still check all my nuts/bolts the next few times I go riding. I have seen 14mm axles snap just because the nuts were a little loose...
    – BillyNair
    Jun 12 '12 at 2:24

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