Are carbonfibre wheels actually worth it?

I’m almost kind of half-thinking about maybe being convinced by carbonfibre wheels. Almost.

In next week’s issue, you will find our annual Britain’s Best Driver’s Car contest, two of whose competitors (not a spoiler alert, I don’t think), the Alpine A110 R and Ariel Atom 4R, arrived on composite wheels. Both were expensive cars, but previously I’ve generally tried rims like this on high-end supercars.

Just a few weeks ago, I drove a Porsche 911 S/T, which doesn’t have composite wheels but does have magnesium ones. Porsche’s engineers were keen to point out the similar reason why they had used this material: a reduction in wheel weight.

In particular, it’s a reduction of unsprung mass: the bit on the road side of the springs, so the tyres, wheels, hubs, brakes, wishbones and so on. Reducing this is helpful dynamically. The lighter it all is, the easier it is to control the wheel’s movement.

I wondered if lighter wheels improved a car’s ride: the 911 S/T rolls more easily than the 911 GT3 Touring, with which it shares suspension hardware. But no, not particularly, said the engineer from Porsche.

What they do help is traction (because a lighter wheel is deflected less by bumps and then finds the road again more quickly) and acceleration and braking (because a lighter wheel has less rotational inertia than a heavier one). So it’s easier to get it going and easier to stop it. The car therefore feels – and is – more agile.

Again, this isn’t a spoiler, because you will have had the chance to read about them already, but the A110 R and Atom 4R do feel particularly feathery. Mostly this is because they are: the Ariel weighs 700kg, the Alpine 1082kg. But I do wonder how much the way they respond to even small throttle inputs – and they are particularly responsive – is down to their light rims.

I haven’t done back-to-back testing. One day I will. But in the past, I have noted the difference between Porsches with iron and carbon-ceramic brakes. And when I fitted lighter wheel rims (not carbonfibre) to my mountain bike, it steered, went and stopped a lot more easily. Those rims are a bigger proportion of the machine’s weight, though, so they will have a greater influence.

Australian company Carbon Revolution will make the carbonfibre wheels for the next Range Rover Sport SVR. It reckons it can make a 24in wheel that’s as light as an 18in alloy one; and that it can enhance stiffness in particular directions to reduce road noise transmission, or increase lateral stiffness, or mould more aerodynamic shapes, because it can choose the direction of the fibrous structure.

That fibrous structure, though, eh? I know what you’re thinking: they may be strong, but they’re not immune to kerbs and potholes. And I’ve had my eyes opened wide by the insurance excesses on test cars that have arrived with carbonfibre rims. 

When I buckled an alloy once, a place in Northampton locked it into a contraption that rolled it round again in a few seconds. There certainly wasn’t a CT scan, as offered by some carbonfibre wheel repairers. So they’re probably not for me.

What’s more, I can’t quite shift that nagging feeling that seeing most cars on carbonfibre wheels would be like spotting a podgy cyclist wearing the full Lycra get-up. Yes, I’m sure the material offers aerodynamically sleek and easy-moving performance benefits, but if you really wanted to make a difference, you would probably start elsewhere.