What metal tubing is commonly used for go-kart chassis?

Go-kart chassis are commonly made from chromoly tubing.

Chromoly is shorthand for chromium–molybdenum steel, an alloy valued for its combination of strength, toughness and relatively low weight. Kart builders form the tubing into a rigid-looking frame, but the chassis is deliberately engineered to flex because most racing karts have no suspension. That controlled flex helps the tires load and unload as the kart corners.

The frame must balance two competing needs: it must be stiff enough to transmit steering and braking forces, yet flexible enough to help the kart maintain grip over bumps and during cornering. Chassis setup can therefore change with track temperature, tire choice and weather. Some competition karts use removable stiffening bars to alter their handling.

Chromoly tubing is not the same as stainless steel, aluminum tubing or carbon fiber. Those materials can appear in other vehicle structures or components, but the traditional kart racing frame is a welded tubular steel chassis. The tubing itself is only one part of the kart: the complete machine also includes axles, steering components, brakes, seat and engine or electric drive system.