A Complete Guide to Legality, Safety, Tyres, Fitment and Getting It Right Changing the wheels on a car is one of the most popular modifications people make. A larger set of alloy wheels can completely transform the appearance of a vehicle. A car that looks ordinary on standard 16-inch wheels can look much more aggressive and sporty with 18, 19 or even 20-inch alloys. But what happens if your car currently has 16-inch wheels and you want to fit 18 or 20-inch wheels? Follow Car Guru DIY Blog Is it legal? Will the car still pass its MOT? Will the larger wheels damage the suspension? Will the tyres rub against the arches? Will your speedometer become inaccurate? And perhaps most importantly:  how do you make sure the modification is actually safe? The short answer is that increasing wheel diameter from 16 inches to 20 inches can be possible, but you cannot assume that any 20-inch wheel will fit simply because the bolt pattern looks correct. The wheel, tyre, suspensi...