This post will give overview of bicycle driving chains standard dimensions. Each chain has three important dimensions: pitch, inner diameter and outer diameter.
Chain pitch is the distance at which the pins are placed. It is measured by measuring the distance between 3 links, then dividing it by two.
For detailed explanation of chain pitch, and why measuring three pins gives a more accurate result read the post Chain wear (“stretching”). For this post it suffices to say that bicycle chain pitch is exactly 1/2 inch (12.7 mm). This goes for all the bicycle chains, regardless of the speed number.
Inner chain diameter is the spacing between a pair of inner plates. It is marked in the picture 2.
For inner chain diameter there are the following standard dimensions:
- Single speed chains have inner diameter of 1/8″ (3.175 mm).
- Multi speed chains, from 5 to 8 have inner diameter of 3/32″ (2.38 mm).
- Multi speed chains from 9 to 12 speeds have inner diameter of 11/128″ (2.18 mm).
- “Exotic” standard for freight bicycles is 5/32″ (4 mm).
Chains for one and multiple speeds differ from each other by the outer diameter. The more “speeds” a chain is designed for, the thinner the outer plates and shorter the pins are (and they protrude less) – so the outer chain width is smaller (i.e. chain is narrower). Inner diameter (width) of all the multi speed chains is almost the same – with only single speed chains having a significantly larger inner diameter.
As can be seen from the picture 3, the outer diameter differs mostly. This is important for bikes with multiple sprockets, so the chain doesn’t get stuck (too wide), or drop between the sprockets (too narrow). Table 1 gives an overview of chain outer dimensions, by number of speeds.
|Number of sprockets (speeds) a chain is designed for||Chain outer diameter (width) in mm|
|All 6 speed||7.8|
|All 7 speed||7.3|
|All 8 speed||7.1|
|All 9 speed||6.6 – 6.8|
|10 speed old Campagnolo standard||6.2|
|All other 10 speed||5.88|
|All 11 speed||5.62|
|SRAM 12 speed MTB||5.25|
|Shimano 12 speed MTB||n/a|
For overview of which chains can be combined with which sprockets, read this post: Bicycle chains compatibility: