Chain/Belt Interface

A bicycle chain consists of several small parts such as the inside & outside plates, rollers and pins. The inside width of the plates dictates what size of tooth it can fit onto. The most common inside width for shift-able chains is 2.4mm or 3/32" regardless of what speed they are designed for. The outside width of the plates is what dictates the speed of the chain. The outside width get smaller and smaller as the number of speeds increases since the gap between sprockets gets tighter. Chains that aren't required to shift are usually a bit wider; 3.2mm (1/8") and 4.0mm (5/32") are most common on single speed bikes.