A person who has not seen a BMX must be living under a rock. A BMX, the abbreviation for Bicycle Motocross, is a popular bicycle used for both sports and casual use. This manual powered version of the motorbike is designed mainly for dirt and motocross cycling.
Originally intended for BMX racing (the counterpart of motocross), the sport has branched out to multiple disciplines such as dirt, vert, park, street and flatland. The acronym is now used broadly to encompass race bikes and those used for the different categories.
Construction
Various types of metals are used to build BMX frames. Aluminum is primarily used in the racing category, while steel is common in less costly and low end bikes. Chro-moly (a family of high strength and low alloy steel) or high tensile steel, almost the same in weight and strength, is mostly used for mid range types. Modern adaptations of the high carbon steel, like 4130 chro-moly and generation 3 chro-moly are used for high performance BMX bikes.
There are also two main hubs used in the construction of the bike: the long-standing freewheel hub and the more contemporary, and swiftly becoming more widespread, cassette hub. The introduction of the latter has ushered in the use of smaller gearing which gives the rider the advantage of lighter weight and more clearance when grinding. The gears are where the chain would rest and the entire mechanism is what makes the bike move with every pedaling of the rider.
Older BMX bikes with freewheel hubs usually have 44/16 gearing (44 teeth for the bigger gear where the pedals are connected and 16 teeth for the smaller gear attached to the rear wheel) or the smallest possible gear with 13 teeth. More modern bikes with cassette hubs use gearings such as 36/13, 33/12, 30/11, 28/10, 25/9 and even 23/8.
The ideal ratio for both gears would be 2.8 is to 1. The popularity of the cassette hubs because most riders prefer smaller gears with more consistent performance (less skip or jam up).
The wheels themselves would customarily have 36 spokes on most freestyle, dirt jumping and street BMX bikes. Due to the extra strength afforded them, more aggressive riders use 48 spoke wheels. Smaller race bikes can also be built with 18 or 28 spokes.
These are for younger riders, as young as three years old, thus the corresponding wheels would be from 16 to 18 inches. Most other riders use the most popular 20-inch wheels. Other wheels can even reach anywhere from 25 to 26 inches, such as those created by reputable BMX manufacturers Haro and Sunday.
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