Inch Up / Size Up / Conversions

Inch Up / Size Up / Conversions

This process replaces the original tyre fitment of the vehicle with a larger wheel and wider tyre and making sure the overall diameter remains the same.

Increasing the wheel size means that you now have a wider tyre which has a larger contact area. The contact area is the part of the tyre that is in direct contact with the road. This means there would be more rubber on the road which allows for better handling and braking of the vehicle.

Why does the Overall Diameter have to be kept the same when upsizing/ inching up

As mentioned above the overall diameter has to be kept the same when upsizing your tyres for the following reasons:

·         Speedometer accuracy

·         Odometer accuracy

·         Gearing influencing power and fuel consumption

·         Handling of the vehicle

·         Maintaining un-sprung mass

The items mentioned above will all be affected negatively if the overall diameter is not kept the same.

Why people upsize/ inch up their tyres

People upsize their tyres for many different reasons. Some upsize their tyres to make the car look sportier which is a better look for them and some may want to upsize to increase the overall road grip performance of the car.

People may want to upsize because the original OE fitment tyre may be scarce and therefore expensive. Upsizing would be an option if the tyre size used is more common with better availability.

Pros of upsizing and inching up

·         Better look and road grip performance of the vehicle

·         Better braking performance

·         Quicker steering response

·         Handling

·         Better lateral stability

Checks to be done after fitting bigger wheels

  • Turn the steering wheel from lock to lock to check that all wheel and body components are clear of one another.
  • Make sure wheels don’t touch the inside wheel arches and suspension and brake components as this would damage the relevant items.
  • Make sure there is enough space between the tyre and the wheel well in order to allow for full suspension travel.

Always confirm modifications to a vehicles rims and tyres with the manufacturer of the vehicle to ensure safety and legality. Some Owners Manuals list the various options for a particular vehicle. Reputable Tyre Dealers should have conversion tables available.