Bent two chainrings on my mountain bike. How to know what size or brand to replace?
Question:I don't have any local bike shops near by. Wanted to buy online but not sure which one to buy.
How can I know? Do I check size? Brand? Will any fit?
It's a 24 inch mountain bike. Thanks.
Answers:
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It would help if you supplied the brand and model of the crank or the brand and model of the bike.First you'll need to determine whether you can indeed replace the chainrings. Look closely and see if there are bolts holding on the rings or just rivets that LOOK like bolts. This is easily accomplished by looking atthe back of the connector and seeing if there is a nut or just a swage stamping.
My guess, if it is a 24" wheeled bike that it has riveted rings.
If the rings are riveted on you'll need to replace the entire driveside of the crank... it is good advice to replace the whole thing while you're at it. Be sure that the crank arm lengths match. Usually arm lengths are stamped on the back of each arm.
If they are bolted on, remove the rings and measure the distance between centers of 2 neighboring bolt holes in millimeters. You need to be pretty accurate on this because some replacement rings are as close as 1mm different from the next. This measurement, along with the number of teeth will give you the correct size of chainring regardless of brand.
If you have a bike with a one piece crank it is a simple matter to remove the crank and take off the rings all in one piece. If this is the case the bike is strictly an on-road bike and you shouldn't be placing it in a situation where the rings could get bent.
Keep in mind that the vast majority of 24" wheeled bikes are NOT mountain bikes- they are ATBs, or all terrain bikes meant for on road and off road on smoother trails. Soooo, if you are beating the bike up by ramping and hopping logs you are likely going beyond the limits of the bike anyway.
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it is probably best if you replace the entire crankset (with chainrings)... look at the existing set for the crank arm length, and the teeth numbers will be somewhere on the arms or rings themselves... if they are missing or rubbed off, you will need to count the number of teeth.so, consider upgrading to a better crankset (Shimano or FSA).
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i recommend just getting an entire new crank set. chainrings cost $20-$60 EACH, depending on size. lets say you need to replace the two largest rings, thats around $80 or so. you can get a whole new set for $50. if you do that, make sure you get a crank that fits onto the bottom bracket spindle. look at the axle where the cranks spin around, it its square you need a square taper compatible crank. other styles are splined and isis drive (the Truvativ variation of splined), but most likely it will be square taper.check out jensonusa.com. they are my favorite online store and have pretty decent prices. look for a new set of cranks there.
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