Have a look at our visual car tyre size comparison tool. Its a recent addition to the site that you may find useful, compare your current wheel and tyre combination against the stock setup for your car and see how much your speedo deviates. It may surprise you.
The tyre size calculator page also includes a tyre size guide that provides background information on the different cconsequences that may arise from changing the wheel and tyre setup on your car.
Read on for the tyre size calculator and more information in the tyre size guide.