toe overlap with the front wheel that is not an issue for velodrome riding but can make slow-speed turns awkward if the bike is used on the road. Material Frames are assembled from tubular elements (typically with round or elliptical cross sections), or cast in a mould for "one-piece" type models. The most popular materials for frame building include steel, aluminium, or titanium alloys, carbon fiber, or a combination of these materials. Carbon fiber frames are most common at the professional level. Gear ratio Track bicycles have only one drive sprocket (or cog) and one chainring, so the size ratio is relevant. A lower gear ratio allows quicker acceleration or 'jump' but can limit top speed. A larger gear ratio makes sustained speed easier, important in pursuit racing, time trial and bunched races such as points or scratch events. Without a good jump, the rider risks opponents accelerating away; without good sustained speed, the rider will be unable to keep up with a fast race. Track sprinters make a compromise by using particular gear ratios that allows them to reach race speeds at a relatively high cadence (pedalling), around 130-135 rpm (revolutions per minute). Long-distance attempts such as the hour record sometimes use high gear combinations such as 52x12 or 55x14. Ondřej Sosenka used 54x13 with cranks to set the 2005 record. Chain Bicycle chains used in track, fixed gear and single speed cycling come in two common roller widths (the internal width between the inner plates): inch (3.18 mm) and . The chainring, sprocket and chain should all be the same width. Although a wider chain will work on a narrower chainring or sprocket, it is not ideal. A narrower chain will not work on a wider chainring or sprocket. Newer bicycles with derailleur gears use bushingless chains which flex, making gear changing possible. There are also inch bushingless chains on the market, which can be lighter or cheaper. Track bicycles, however, need increased strength rather than a lightness or a flexibility, so most of the track chains still use the full-bushing design. Tires Tubular tires are most often used in track racing and training, though advances in clincher tire design have seen them being used somewhat more often. See also Outline of cycling Path racer Keirin References Cycle types Track cycling