Efore you start calculating speeds and what effect a differential or tyre change will have on top speed in each gear, you need to calculate your overall tyre height, which can be done by using the sum outlined on the opposite page. We used 265/35R18 and 2
To make things easier later on, we’ll convert the circumference to metres — so, 2.018m. One way to increase acceleration at the expense of top speed in any given gear is by changing the tyre size.
We’ll use a common size of tyre in this scenario — one that people might have upgraded from: a 205/50R16. Now that you have the overall tyre height, you again need to calculate the circumference.