Alloy wheels are fitted as standard to many cars these days, mainly for their good looks, though there are other benefits. You may consider changing your wheels, either to different alloys or to replace steel wheels. Alloy wheel retailers can help you find wheels which will fit, but if you want to know a bit more, we run through the essentials below.
Bigger, smaller, wider?
Bigger wheels have more visual impact, but keep in mind that larger wheels are generally going to be heavier (other than some very expensive designs), which can have a negative effect on your car - a small but potentially noticeable reduction in acceleration, braking and/or handling performance. It's usually possible to fit wheels an inch or two larger in diameter, as long as you can still get suitable tyres - see below.
You may wish to fit smaller wheels. This can have a positive effect on acceleration and braking, as long as the wheels are still a sensible size for your car (they fit over your brakes). Smaller wheels should have tyres with a higher sidewall, which can improve ride comfort if that is your goal.
You should only consider wheels of a similar width to standard, to prevent potential issues with rubbing bodywork or suspension (also affected by offset - see below).
Pitch Circle Diameter
Find out the Pitch Circle Diameter or PCD of your car's wheel hubs if you're looking to buy wheels for your car. PCD describes the number of wheel bolt holes and the distance between them, for example a PCD of 5x100 means that the wheels have 5 mounting holes which are arranged in a circle of diameter 100mm.
Offset
Wheel offset is also important. Offset is a measurement of the distance between a line through the very centre of each wheel (in the same plane as the wheel's outer face) and the mounting face of the wheel where it meets the hub of your car. The offset can be positive (nearer to the outside of the car) or negative (closer to the centre of the car) and affects whether a wheel sits further out towards your wheel arch or deeper into the arch. Positive offset is more common.
You should aim to buy wheels with an offset as close to your standard wheels as possible, as too great a difference can affect suspension geometry and therefore the handling performance of your car.
Tyres
To ensure the overall diameter of your wheels and tyres together is as close to standard as possible, if you fit larger wheels the tyres need to have a smaller sidewall and vice versa. There are online wheel/tyre fitment calculators which can help you compare your standard wheel and tyre size to that of a wheel and tyre combination you're considering. You must keep to within a few millimeters difference or your speedometer won't be entirely accurate.
These are the most important considerations when choosing alloys, but if you're in any doubt about what you need it’s always best to talk to a wheel retailer or trusted garage.