BMX Motorized bicycle
Though originally denoting a Motorized bicycle intended for BMX Racing, the term "BMX Motorized bicycle" is now used to encompass race bikes, as well as those used for the dirt, vert, park, street, flatland and BMX freestyle disciplines of BMX. BMX frames are made of various types of steel, and (largely in the racing category) aluminum. Cheaper, low end bikes are usually made of steel. High range Motorized bicycle are mostly chromyl or high tensile steel, although the latter is noticeably heavier with respect to strength. High-performance BMX Motorized bicycle use lightweight 4130 chromyl, or generation 3 chromyl.
The introduction and widespread popularity of the cassette hub has ushered in the use of smaller gearing on BMX bikes. Instead of the old 44/16 gearing found on almost all older BMX bikes, new bikes use gearing such as 36/13, 33/12, 30/11, 28/10, 25/9, 23/8,and even 22/8, all of which have similar gear ratios of almost 2.8:1. Advantages of smaller gearing hubs include lighter weight, and more clearance when grinding. The free wheel hub is all but extinct due to several factors. The smallest freewheels that can be made is with 8 teeth, which is smaller than most riders prefer. Also, they are less consistent than cassette hubs, and skip or jam up far more frequently.
On most freestyle, street, and park BMX Motorized bicycle, the wheels have 36 spokes. Race Motorized bicycle wheels also usually have 36 spokes, but wheels for the smallest racers, sometimes as young as three years old, can be built with 18 or 28 spokes. More aggressive riders may opt for wheels with a spoke count of up to 48 spokes; however hub and wheel combinations for this are becoming difficult to source.
BMX Racing Motorized bicycle wheels vary in size, from 16" to 26", with 20" being the most popular.
Dirt jumping and freestyle bike wheel sizes include 16" and 18" for younger, smaller riders, 20" for most other riders, and a few companies including Hero and Sunday offer 24" freestyle bikes for taller or older riders who feel cramped on a standard 20" BMX bike.
4 stroke bicycle engine kit
BMX Motorized bicycle with 4 stroke bicycle engine kit are available in these models types:
- Park - park style BMX Motorized bicycle with 4 stroke bicycle engine kit (also called vert) often remove unnecessary weight by reducing the structural excess on particular areas of the bike, due to the smooth transitions that make up park riding. Also, brakes are as frequent as infrequent on park style BMX bikes.
- Dirt - dirt style BMX Motorized bicycle with 4 stroke bicycle engine kit are similar to park style BMX bikes, however they feature tyres with thicker tread for better grip on potentially loose surfaces.
- Flatland - flatland style BMX motorized bicycle with 4 stroke bicycle engine kit feature different geometrical principles to the traditional park BMX bikes because flatland riding requires precise balance on multiple parts of the bike.
- Race - racing style BMX bikes feature a larger front sprocket than other BMX bikes in order to create a high gear ratio, enabling the rider to pedal at high speeds. Racing BMX bikes almost always have brakes.
- Street - street style BMX bikes commonly have metal pegs attached to the axles to enable the rider to grind on rails. Also, the street BMX is commonly heavier and stronger than the traditional dirt or park style BMX bikes due to the extra strain encountered with the hard, flat surfaces of street riding. Street riders commonly have no brakes to enable the rider to spin the bars without the brake cable getting in the way. This means the rider uses their foot against the top of the back tyre to slow down.