In a spin

One of the most important, yet most often forgotten, set-up items in engineering a racecar is the differential. The reason it is so important is it plays a critical role in both power delivery and car handling. Ignore both at your peril.

A couple of years ago I addressed this matter at length, but recently received a great question on what your ballpark differential wheel speeds should be. That offered a perfect opportunity to re-visit this important chassis engineering topic.

The principal problem we have with the differential is we have two wheels moving at different speeds, as illustrated in Figure 1.

The reason tuning the differential is such a mess is that for a given forward speed, V, and a given yaw rate, r, because the wheels are separated by a track, t, we have the inside wheel velocity at V-t.r/2 and the outside wheel velocity at V+t.r/2.

Making an already tricky situation