Both in visual terms and for the sake of handling and roadholding, the first move you should make when tuning your car is in the wheels and tyres department. A nice set of alloy wheels with low-profile tyres really sets a car off even before you get involved in uprated suspension and body styling. The difference is instantly visible when you compare the car to a standard one of the same type, and the low-profile rubber gives you better handling, grip and braking, making your car safer as well as more satisfying to drive.
The larger the wheel, the lower the profile the tyre needs to be to maintain the same gearing and rolling radius (important for speedometer calibration). A larger wheel looks better and helps to fill out the wheelarches visually. It also exposes the brakes to better airflow and thereby aids brake cooling when the car is being driven hard. For early cars which came on 5.5J x 13in wheels, the natural upgrade was the so-called Plus One conversion. Using 185/60HR14 tyres on 6J x 14in wheels, this provided the same rolling radius as the 175/70HR13 standard rubber but put more rubber on the ground. The Plus Two system was 195/50VR15 rubber on 6J x 15in alloys. This was the largest size that could be accommodated under standard arches. The use of this tyre size with 7J x 15in alloys is possible, but on some cars the wheelarches have to be radiused or contact will be experienced over big bumps or when the car is loaded.
The very latest trend is to 16in diameter wheels as with the Nothelle package for the Golf Rallye, but only a car with as much wheelarch clearance as the Rallye can use these wheels without arch modification. The tyre size in 205/45VR16. When going to such wheel sizes, always bear in mind that the larger the wheel and the lower profile the tyre, the greater the chance of wheel damage on rough roads. Large potholes have been known to bend expensive alloy wheels, so if you live in an area with badly made roads, both ride comfort and your wallet may dictate no more than a Plus One wheel and tyre package. Also, when you are considering putting more rubber on the road, remember the law of diminishing returns. A 20% increase in tyre width gives you a 10% increase in grip – but only up to a certain point. Complications like over-sensitivity to changes in road surface such as patches and white lines, and a sharp deterioration in grip and steering feel under difficult conditions – when there is standing water on the road, for example -can set in if you pursue the wide tyre philosophy too far.