The frame is the main part of the bike, the literal framework that supports everything. When choosing it, there are many factors that should be taken into account. A modern BMX frame should be strong, lightweight and have a comfortable geometry for the rider.
The strength and weight of the frame are affected by the material and reinforcement of the frame. The most commonly used material on the market is steel, usually in two grades: hi-ten 1020 and cro-mo 4130. Hi-ten 1020 steel is easy to process and a quite reliable and cheap material, but it is inferior in strength to its counterpart. Cro-mo 4130 steel is more expensive; this alloy is stronger and lighter.
Reinforcement in the frames is usually provided by gussets, as well as by heat treatment. Gussets strengthen the frame, prevent loads from tearing off the headtube or altering the spacing of the chain stays, but they add some weight to the frame. Also, the expensive batting technology is designed to achieve more strength and less excess weight. It is all about reducing the thickness of the tube in the frame, where it does not experience strong stresses, and at the same time, the nodes, in which the maximum loads are concentrated, are made thicker. Heat treatment of metal is a big and important thing. A properly hardened frame does not get dented when struck, but if you make a mistake in temperature conditions, you can end up with the strength of glass or plasticine, instead of the desired result.
Geometry is a very important aspect when choosing a bike. A long frame will not work for a rider of a small stature, and spinning is easier to do with a short frame, although a long frame is more stable in flight. When choosing a frame, you need to pay attention to its height, usually it's the length of its upper tube in inches:
If you want to use brakes when riding, you need to pay attention to the modification of the frame – find out if it has a brake mount.