Cable guide

A cable guide is a fitting or part of a bicycle frame which guides a piece of bare inner bowdon cable around a corner. Most multi-speed bicycles have cable guides to get the derailer cables past the bottom bracket. Older derailer bicycles used either brazed-on or clamp-on guides just above the bottom bracket, but newer bicycles have a guide under the bottom bracket.

Below the bottom bracket

Cable guides below the bottom bracket can be cheaper, and, for some bikes with very small chainweels, eliminate interference between the rear derailer cable and the bottom of the front derailer cage. They also make for a cleaner appearing and easier to clean frame in the bottom bracket area. Poor lubrication of bottom-bracket cable guides is a common cause of autoshifting.

Above the bottom bracket

Cable guides above the bottom bracket allow a shorter cable, and the loop of housing at the rear derailer does not need to bend quite as tightly, since the cable stop is on top of the chainstay, rather than beneath it.

Beside top of seat tube

Some bicycles use a cable guide on one side of the seat cluster for a rear cantilever brake cable, rather than use a short length of housing between two housing stops.