Single-speed Bicycle - Single-speed Cycle Conversions

Single-speed Cycle Conversions

Single-speed bicycle builders have converted many former multi-geared cycles into single or fixed speed through the removal of the derailleurs and associated hardware. The simplest conversion uses the existing freewheel/cassette and crankset, the chain being cut to fit the desired gear ratio. However this retains unnecessary weight and the chainline will most likely not be perfect. A more thorough conversion will involve replacing the freewheel with a single-speed one, and re-dishing the rear wheel. On bicycles with vertical dropouts, a chain tensioner is often required to allow the correct tension on the resulting shorter chain.

A very popular "off road" mountain bike gearing, for the 26" wheel size, is 39:18, approximately a 2:1 gear ratio and 56.35 gear inches, for versatile trail riding. A great "on road" gear ratio, for the 26" wheel, is 42:17, approximately a 2.5:1 ratio and 64.2 gear inches for versatile tour riding. Many British enthusiasts used to tour on 27–inch–wheeled ligtweights on a single fixed–gear of 69 inches before multi–speed gearing became universally popular, though this certainly made for tough work.

A reasonable "road" gear ratio, for the 700 x 28c wheel size a, is 46:17, approximately a 2.7:1 ratio and 71.75 gear inches, for very versatile asphalt riding, and a better lifespan with good road duty.

Fixed-gear setups work especially well with higher 40s chainrings, so the rotation ratio is closer to a wider 3:1, avoiding the tighter ratios, which will spin too fast, especially when descending steep hills.

Note that the larger diameter gear and chain ring, clearly, offers the best longevity, with much better wear characteristics than smaller gear and chain ring sets and less rounding of the teeth, over time.