SMALL IS BEAUTIFUL

 Supercars use massive wheels to fit around big brakes, and wide tyres to handle huge torque. Car dealers sell us fashionable big wheels because there is profit in extras. But is big beautiful?

I ran a 2012 Prius on 17in wheels and 45-profile tyres. It had wooden handling and a harsh, rattling low-speed ride. Toyota also specify 15in wheels with deeper, 65-profile tyres. On these, it rides and handles better and hardly rattles. This is partly because each smaller wheel and tyre is about eight pounds lighter, so the suspension has less work to do.

It’s a cheap change. Small alloys cost about £300 a set.

Tyres for 15in wheels are about £100 a set cheaper than for 17in wheels. Official figures give a 2.5% fuel saving. It seems nothing but it matters, because most of us spend at least £1000 a year on fuel. Also, wheels are saleable.

Most CM readers don’t crawl under fast, exotic cars. For us, big wheels may be a mistake.

Wheel sellers think you’re barmy downsizing. Their computer programmes show what fits but say nothing about the effects of deviating from the manufacturer’s spec. It takes research and persistence. It is difficult to obtain the specified offset – the distance of the flange from the wheel’s centre line. Changing it alters the scrub radius, which is the distance of the tyre’s centre line at the road surface from the axis on which it pivots when steering. It may affect handling.

Big is not necessarily beautiful. Boy racers with giant wheels often compromise both comfort and safety.

Rev. Phil Regan