yeah this is stupid, but how do i know whether i've got a 1/8" or 3/32" chain & cog? measure the distance between the plates of a link in the chain? measure the thickness of the cog? don't laugh, jerks

well, if you're used to you can spot it by eye. But you're not. If there is a bike with a derailleur handy anywhere compare your chain to it and if it's beefier than the one on the derailleur bike then it's a 1/8" if you have a chainring or sprocket loose you can set it in a chain on a derailleur bike and if the teeth don't fit it's 1/8"

um, no derailler bikes around. can't i just bust out the ruler?

Does it have a master link? Did it come on the bike or did you buy it? If you bought it and the box said 'For BMX or Single Speed Bikes' it's probably 1/8".

came on the bike, and needs to be replaced. as well as the chainring. i got a cog when i fixed the sucka but being less informed at the time, i don't know whether i got a 1/8" or 3/32" cog. are there 1/8" and 3/32" chainrings as well?

From the great Sheldon;

Chain

Modern bicycles use roller chain to connect the cranks to the rear wheel. Chain drives are among the most efficient means of power transmission known.

Chain size is specified by pitch and width. The pitch is the distance between rollers (1/2" on all modern bicycle chain). The width is the internal width where the sprocket teeth fit in. Bicycle chain comes in two basic widths:


1/8" chain is used on most single-speed bicycles, and bicycles with internal gearing.


3/32" chain is used on derailer equipped bicycles that have more than 3 speeds.

Chains for derailer applications also come in various external widths. Newer clusters which have more sprockets use chain with thinner side plates and flush rivets.

so i can assume that it's 1/8". but i'd rather know for sure. i'm just gonna measure it when i get home.

Make no assumptions, especially if it's something someone else built. Something else that may help, does the chain have ramped plates for shifting? (the 8 shaped plates, are they completely flat, or beveled on the insides?)

hmm. i'll check that too.

Actually, tell us what it says on the chain, too.

you could bust out the calipers, but a ruler probably ain't going to cut it.

alrighty. i'll go do my homework and check back later.

late homework will not be accepted.

Just stop at some bike locked up somewhere and compare sizes. It's pretty obvious if they are different.