I have a box o parts that I've had for awhile. Now that my chain has stretched beyond the wear markers it's time to replace. I have a front sproket that I can't identify as 525 or 520 and need some help.

Currently I have 16/46 on a 525 chain and am happy with that setup. The "new" front sproket says 15E Made in France. How do I tell if it's 520 or 525? I'm guessing 525 as the teeth don't quite match perfectly to a 520 rear I have that I'm comparing to.

 

do you have some measuring calipers? if so, use them to measure the width of the teeth on the 525 front sprocket, and then measure the teeth on your new sprocket and compare.

 

No I can't measure, but an eyeball comparison side-by-side leads me to belive it's 525.

 

well according to this site, the difference between the 2 is that 520 is 1/4" while 525 is 5/16". maybe just measure the one that you have out? also, try sticking it into your chain and see how much it moves it side to side

 

The 520 will not be centered. The teeth are offset. They are this waybecause the rear center is now closer to the rim because the sprocket is thinner. So as you look down on it where the it groves down to a round surface on side will be wider. you cant just make the front thinner because it has to come out and make contact with the bolt.

 

Thought I had something with Axsys' suggestion. I put it in my 525 on my bike and it didn't move as freely as I thought it should. Chain does have some wear and stretching and is sharpening sproket teeth now. So I figured it's a 520. Well, it's not off-center as Rodantking suggested. I dunno...(shaking head)