# Calculating torque/hp losses from wheel choices

 Sci Advisor P: 674 Rotating components add an effective mass to the car for the purposes of straight-line acceleration. For a wheel/tire, that mass (beyond the normal one you'd find using a scale) is $$m_{\mathrm{rot}} = I / r^2,$$ where I is the wheel/tire's moment of inertia, and r its radius. I depends on the way mass is distributed in the wheel. If it's all at the rim, it would be $m_0 r^2$, where $m_0$ is the wheel's ordinary mass. Realistically, it's going to be less than this (say 1/2). So this effect is not very significant. Rotating components closer to the engine can be much more important in lower gears due to their much higher rotational speed relative to the wheels.