Freewheels and chain sizes

[Jonny69]

I'm trying to work out if I've got an odd freewheel on an old bike wheel or if they are all like it.

Basically my two racers and the shoppers all use the same size chain but I've got a BMX wheel with a 16T single speed freewheel that seems to have bigger teeth and they don't go in the chain. It would need a chain with longer links by the look of it. Is this normal? I thought BMX freewheels were the same as any other freewheel?

I guess now might be a good time to ask if they all have the same thread on them... I know there is a rare smaller BMX one but I don't think this is one of them.

 

[hamster]

There are several widths of chain - 1/8th which is old 5 speed and BMX, and 3/32" which is 7/8 speed. This requires narrower teeth.

You can get BMX freewheels in both tooth thicknesses.

 

[GarethPJ]

Sorry to take issue, but 5 speed chain is not 1/8" it is 3/32".

To answer the original question, it may appear that the single speed freewheel requires a chain with longer links becuase it won't drop onto the teeth. The vast majority of bicycle chains have 1/2" long links, known as 1/2" pitch. What you need is a wider chain. Single speed chain generally comes in two sizes 1/8" and 3/32", you need 1/8". Do not simply ask for BMX chain, since you can get that in 3/32" as well as 1/8" sizes, although 1/8" is more common.

Single speed chain (also used on hub gears) differs from derailleur chain in that single speed doesn't flex much from side to side much. In order to move from sprocket to sprocket and ring to ring derailleur chain needs to flex sideways so the sideplates are tapered slightly. Most older derailleur chain is 3/32" it's only when you get beyond 8 sprockets at the rear that you need narrower chain.

There did used to be 1 inch pitch chain also know as block chain, but you don't find that very much any more.

Some eejits do confuse matters by refering to the width of the chain as the pitch, so you'll hear some people talking about 1/8" pitch or 3/32" pitch, but the pitch is the distance between the roller centres NOT the width of the chain.