The unsprung mass of a vehicle is the mass of the suspension, wheels or tracks, and other components directly connected to them. This contrasts with the sprung mass supported by the suspension, which includes the body and other components within or attached to it.

Why is unsprung weight bad?

The issue with unsprung weight is simple — it offers no performance improvement whatsoever. On the contrary, it reduces performance. More unsprung mass means that your suspension components have to work harder to keep the wheel on the ground.

What is meant by unsprung weight?

The unsprung mass (colloquially unsprung weight) of a vehicle is the mass of the suspension, wheels or tracks (as applicable), and other components directly connected to them.