Chainring or crank spec help

Ok, so I am trying to locate the outer chainring size on my TREK but I cannot locate the crankset specs anywhere and cannot pull them off to accurately check the size.. I have searched and searched and maybe someone out there knows..

The bike - TREK 800 Singletrack(year unknown)
Crankset - Shimano Acera X - 175mm - FC-M291 - Triple

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Permalink Reply by Craig S. on May 4, 2010 at 6:22pm

OUCH!

Chainring size may be stamped on the left, the inside of the ring. If you can't find it, you can always count the teeth.

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Permalink Reply by millenial removing Bernie tattoo on May 4, 2010 at 6:57pm

Do you mean the Bolt Ring Diameter?

You can figure it out with a ruler:

http://sheldonbrown.com/gloss_bo-z.html#bcd

If its the toofcount, just mark the fist toof and count them like craig said.

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Permalink Reply by Craig S. on May 4, 2010 at 7:18pm

Good call, I didn't even think of the bolt ring diameter.

If this were me, I'd take the bike to my LBS and let them deal with it.

envane x said:

Do you mean the Bolt Ring Diameter?

You can figure it out with a ruler:

http://sheldonbrown.com/gloss_bo-z.html#bcd

If its the toofcount, just mark the fist toof and count them like craig said.

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Permalink Reply by S on May 4, 2010 at 7:44pm

Shimano says 104mm BCD for the outer chainrings and 64 mm for the inner gear. The large chainring is either 48 or 42 tooth, I'd suggest getting a 48 tooth ring as a replacement since it's a triple and a 48 will give you a better top end speed.