JAX Tyres also offers a range of great value wheel and tyre packages.
Wheels and the Law Measuring Offset and PCD
Each state has certain legal requirements, when wheels outside the manufacturers recommended range are fitted to a vehicle.
These requirements mainly relate to wheel rim widths, the fitting of nuts and studs and the increase of track measurement.
Modifications outside the legal guidelines are not permitted and the correct matching of wheels and tyre is vital to ensure the continued safe operation of the vehicle. See your JAX Tyres wheel specialist for the best advice on all performance and safety aspects.
Wheel Care and Maintenance
For lasting care of your alloy wheels it is recommended you clean them regularly with soap and water. Check first before using automotive detergents, as they may corrode the alloy metal. Re-tension your wheel nuts or studs with a wheel brace on a regular basis.
Please make sure that you check with your insurance company to ensure that your choice of wheels is compatible with your car.
Measuring Offset and PCD
There are two ways of measuring offset. Centre line offset is the distance from the centre line of the wheel to the face of the wheel mounting surface. Back space offset is the distance from the extreme back edge of the rim to the wheel mounting surface. Pitch Circle Diameter (PCD) is the diameter of the bolt circle.
The centre bore is the location hole that is machined in the centre of the wheel. This will vary from one vehicle to another. It is essential to have the correct centre bore for the vehicle to avoid wheel imbalance problems, which will lead to poor ride comfort.
Wheel manufacturers and distributors have universal fittings and are drilled to fit a wide range of vehicles. In order to obtain the correct fitment for a particular vehicle, a correct locating or spigot ring most be inserted into the rear of the wheel.
PCD is an abbreviation for pitch circle diameter and is the diameter of the circumference of the centreline of the stud fixing holes on the wheel mounting face.
The offset of the wheel is a fundamental technical parameter that must be carefully considered when choosing replacement wheels.
The offset of the wheel is defined as the measured distance in mm from the hub mounting face to the centreline of the wheel.
Fitments of Wheels with an Incorrect Offset
Care must be taken to not fit wheels with incorrect offsets, as this could influence negatively the vehicle's handling performance. Other areas that may be affected are wheel bearing loading and bodywork clearance. The best option is always to follow the manufacturer's recommendations.
Wheel Offset Types
- Negative Offset
This is where the hub mounting surface is positioned towards the internal side of the wheel. This type of offset is used on wheels fitted to rear wheel drive vehicles. If an offset is described as 35N this is an indication that the measurement is 35mm from the tyre's centreline with a negative offset.
- Zero Offset
This is where the hub mounting surface is even with the wheel's centre line
- Positive Offset
This is where the hub mounting surface is positioned towards the external side of the wheel. This type of offset is used for wheels fitted to front wheel drive vehicles. If an offset is described as 35P this is indication that the measurement POsItive offset is 35mm from the tyre's centreline with a positive offset.
Calliper Clearance (X-factor) is the amount of clearance built into the wheel to allow for the vehicle's disc brake and calliper assembly.