dkmtr

My wife has an 1991 GT All-teran mtn bike. In a rotine inspection of the bike I noticed the sprockets on one of the front chain rings was bent. I need to replace it as I think it would make it difficult to shift on the font gears. My question besides price and crank length is there other factors i have to be concerned with? I know I need a crank puller

thanks

catonec 

if just the teeth of a chainring are bent, you can try to bend it back with a pair of pliers and a table vise.

also if its only bent teeth you can replace just one chainring. You will need to know the number of teeth and the BCD (bolt circle diameter) to insure that it lines up w/your crank.

If you need to replace the entire crank, yes you will need a crank puller but you will need match the interface of your bottom bracket spindle. ie. square taper, isis,

dkmtr

thank you that was a lot of help

dkmtr

hanging the bike from the rear tire, and citing on a fixed object i.e. the front derailer, if I spin the crank by hand the large chain ring moves up and down. I think the crank might be bent. i also have no reason to beleave that it didn't come from the factory like that.

lopek77

I believe all cranks are little "off" to help chain to jump on to chain ring. Check online pictures for closeups and compare it to the look of your crank. 91's chain rings are most likely made from hard metal/steel, so pretty hard to bend it accidentally.

LesterOfPuppets

Sounds like Biopace or Oval Tech or ...

If so, the rings are non round by design.