Yes, you may not have believed it but you can actually have the wrong sized tyres fitted to your vehicle. The manufactures recommend the correct tyres for a vehicle but you can chose to have different ones fitted, or sometimes they are fitted by the garage incorrectly.
Converting to a different size of tyre is possible, but it must be done within strict criteria. If you get it wrong, the consequences can be dire.
If you want to change the wheel size of your car it is possible but it may mean that you need to also change other parts on your car to accommodate the new wheels and tyres. It is important to remember that you should remain as close to the original wheel diameter as possible. Diameter is important because your car speedo, braking system, traction control and gear settings are all based around the diameter of the wheels that are built on the car when it is manufactured.
