Hello,

I was considering buying an old track crankset that currently has a 51t 3/32" chainring. If I were to get a new chainring with fewer teeth could a buy one in 1/8"? If so, would it still be flush with the crank spiders?

yes

you could fit a 1/8" chainring on your spider, but you'd have to switch to a 1/8" chain as well, and will maybe need to replace your stack bolts. as for if it will be flush with the spider, i don't know. i'm guessing not.

Excuse my newbie question, how do you measure the chain to know it is 1/8 or 3/32? Thx,

So you're saying that the difference in the thickness is just in the teeth?

the chain has "inside" and "outside" links



1/8" and 3/32" is a measurement of the space between the inside links. 1/8 is obviously slightly larger than 3/32 (obvious provided you remember how to do fractions)

There's a fairly visible difference. A 3/32" chain is designed to flex a bit when changing gears on a road bike so the walls of the chain are a thinner.

the difference in thickness is the entire chainring sometimes, sometimes not (as the chainring can be thicker than the teeth in both cases, but it shouldn't make any difference in fitting on your cranks.

so the 1/8" or 3/32" refers to the "thickness" of the chain. 1/8" chains are thicker than 3/32" chains, and 1/'8" chains are used mainly for singlespeeds and bmx bikes. if you switch your 3/32" chainring out for a 1/8" chainring, you're switching to a thicker chainring, and your old 3/32" chain wouldn't be able to fit on it because it's too narrow. you'd have to switch your chain to a 1/8" chain so that it would be compatible with your new 1/8" chainring.

also, if you switch to a 1/8" chainring, keep in mind the possibility of having to also switch out your chainring bolts. because the 1/8" chainring is thicker than the 3/32" chainring, the bolts need to be slightly wider to accomodate the 1/8" chainring. you might be able to get away with using the same bolts, as the difference between the old and new chainrings is just 1/32". but if you want to stay on the safe side, look for stack bolts that are compatible for 1/8" cranks...they're like 5 bucks at your lbs.

So? How does that affect how wide the chainring is at the point where the chainring bolts go through?

Before you buy that crankset, please make sure you can actually get 3/32 chainrings in that BCD, for that crank. Assuming it's not obsolete.

Thanks