The term “offset wheels” is loosely used to refer to an aggressive stance where wheels of a vehicle stick out of the fenders. A negative offset is what can create a larger lip or concave style, which will push the tyre out.
Offset is the distance from the hub-mounting surface to the wheel’s true centerline. It is quantified by an ET value and measured in mm. A positive offset means the hub-mounting surface is closer to the outside edge of the wheel, while a negative offset means the hub-mounting surface is closer to the inside edge of the wheel.
Automobile manufacturers design vehicle with specific offset that manifest a certain level of feel. Therefore, deviating from these preset measurements will cause the car to feel differently.
Reasons for deviating from OE specifications
There are a number of reasons why you may wish to deviate from manufacturers standard offset.
- You may wish to fit wider wheels and encounter clearance issues with the rear face of the wheel touching the suspension leg at standard offset.
- You may wish to give the car a more aggressive look so that the wheels and tyres appear to “fill” the arches better.
- Performance variants of cars employ something called “wide track”. Track refers to the width between the wheels measured across an axle. Tuners of aftermarket cars may want to achieve wide track for racing related purposes.
By deviating from the vehicle manufacturer’s offset figures, you change the geometry of how load is applied. This will have an impact on the performance of your vehicle: –
- Running a wide track through negative offset or spacers typically accelerates wear on wheel bearings, ball joints, control arm bushings, struts, strut perches, etc, because they are extra stressed.
- Changing offset will have the effect of lengthening or shortening the lower control arm which in turn will exert more or less force on the spring, therefore affecting spring rates.
- Most negative offset wheels are wide therefore requiring wide and low profile tyres. If you don’t install the correct width tyres, narrow tyres will be prone to injury and damage due to sidewall exposure.
Some negative offset enthusiasts argue that, most accelerated wear on components is negligible at worst. Observations however show that many components and driving aspects are affected the moment you vary from OE specifications.
If choosing an offset for an aftermarket wheel, it is important to take note of the space between the outer edge of the wheel and the fender, or keep a net variation of 3% from original equipment.