How to Measure Bicycle Chain Width

bicycle chain widthHow to measure bicycle chain width is a rather straight forward method of using a steel ruler to gauge the distance between the two inner plates. (W)

The width of a bicycle chain is related to the maximum thickness of sprocket that can realistically engage with the chain. Obviously the width of the bicycle chain must be somewhat wider than the thickness of the chainrings and cogs or sprockets.

A typical bicycle chain comes in two widths:

  • 1/8" (3.175mm) The standard width of a bicycle chain for BMX riders and also the older one and three speed bikes.

  • 3/32" (2.38mm) width The standard for all modern multi-speed bicycles. These chains are commonly referred to as "derailleur" chains, thus any bicycle that uses a derailleur to shift gears.


Thinner Chains to Accept More Gears:
Typical sprocket thickness range from 1.7mm to 2mm. As we push the boundaries of multi and more gear options on the rear cog the sprockets must be thinner to still fit on the standard hub. It follows then that the typical chain but also slim out to slide between say the 10 separate gears of a 10 speed bike.

To accomplish this, manufacturers of bicycle chains have made thinner inner and outer plates, moved to bushingless chains and developed technology to mount rivets flush with the outer face of the chain. These adjustments in chain design have reduced the OUTER width of the chain while still retaining the standard inner measurements (w)

Thus when buying a bicycle chain, they are often referred to as a 10s chain, meaning that it is designed to fit on a rear cassette that has 10 gears. A 10s chain by definition then is thinner than a 9s chain. Taken to the logical conclusion then, a 10s chain would often work on a 9s bike, but the reverse is not always true.

A 9s bicycle chain could be too thick to fit between all 10 gears on a 10 speed bicycle, or able to bypass the gears but cause excessive wear on the sides of the gears, when running in such tight quarters.

Caution: It is not always preferable to use a "more" gear chain (10s) on a lessor gear (9s) bike. By necessity the chain will be thinner and thus weaker for no reason.

Thus when looking at how to measure bicycle chain width, remember that most standard derailleur chains are 3/32" but it is the OUTER width that may be more relevant to your particular chain-cassette set up than the standard chain width specification.

More to Buying A Chain Than The Width:
As an added note, although there is a standard in width, that is not true in the shape of the gear teeth. Each manufacture designs the tooth shape on their gears slightly differently so finding compatible bicycle chain-gear-derailleur combinations is important before you buy.

Bike Chains: Length, Width, What's Best to Buy etc.

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copyright Jan. 2007