wheels speed calculator will allow you to check speedometer error and speed differences if you use different dimensions tires on your vehicle than manufacturer recommends. Tires size could be selected from R4/80/25 to R26/460/100. You may also check what sizes tires would make minimum error for speedometer if you decide to use not manufacturer recommend wheel diameter. App will tell you one hundred tires sizes that would make smallest error to speedometer. NOTE: this app only calculates speedometer error. It does NOT suggests that you should use wheels or tires that are not recommended by manufacturer of vehicle.