The original pit bikes were tiny machines made from spare parts lying around a motocross rider's trailer. Frames could be made from any type of metal, from steel to aluminum. Bicycles were even commonly used and modified with motors to allow riders to navigate the tight pit areas. The style of pit bike frame has varied significantly over the years, from simple scrap-heap frames to well designed, lightweight aluminum frames specifically designed for mini-motocross racing. The pit bike frame can still be made from scrap metal and other random parts, though frame technology and design has improved since people began racing these tiny motorcycles.
The two most common materials used for pit bike frames are aluminum and steel. A steel pit bike frame will be quite sturdy and strong, and steel is relatively easy to weld together. Many of the early pit bike frame designs were made from steel, both for the ease of construction and the availability of materials. The advantages of steel include durability, the ability to be hammered back into place should the frame get dented, and the ability to absorb shock and vibration while riding. Steel does rust, however, meaning the frame can weaken over time. It is also fairly heavy, making maneuverability an issue.
Aluminum as a pit bike frame material is a lightweight choice that will not rust. Many pit bike frame designs use aluminum because it cuts down the weight of the bike, making maneuverability even easier. Since most pit bikes will at some point become coated with mud or water, aluminum is a preferred material because it is rust and corrosion resistant. Unlike steel, however, an aluminum frame cannot be hammered back into place should it get bent; the material is likely to crack if this is attempted. It is also much stiffer than steel, meaning it will not absorb as much shock and vibration.
The frame designs of pit bikes have changed significantly over the years as well. While many pit bikes are motocross-style bikes that are designed for racing, other styles of pit bike have emerged. From road racers to chopper bikes, the range of designs very often mirror full-size motorcycles, and each design is good for different purposes. Chopper style pit bikes are showpieces, while superbikes are designed with a tight wheelbase good for maneuvering and cornering. These, too, can be raced and modified to go faster than they are normally designed to go.