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Why fitting low-profile tyres to your SUV is a terrible idea

13 March 2020 - 07:21 By Denis Droppa
Big wheels with low profile tyres might look great, but don’t make good friends with potholes. Picture: DENNIS DROPPA
Big wheels with low profile tyres might look great, but don’t make good friends with potholes. Picture: DENNIS DROPPA

It’s not for me to question how car buyers spend their hard earned money, but I do despair at the pointlessness of a high-riding SUV wearing low-profile tyres.

It’s well known that most people buy SUVs or crossovers not because they necessarily want to go offroading but because they like sitting a couple of centimetres higher than in a regular car.

The popularity of SUVs is also driven by the belief that, because of their higher ground clearance, they’re more suited to SA’s potholed tar.

They aren’t.

You don’t need an elevated ride height to deal with potholes; you need high-profile tyres. But our roads are populated by a growing number of SUVs fitted with low-profile tyres that not only provide a less comfortable ride, but also puncture more easily and more readily lead to bent wheel rims if subjected to potholes or stony gravel roads.

Low-profile tyres generally regarded as those with an aspect ratio of 50 or less have much smaller sidewalls with less cushion to absorb impact from potholes. This can lead to structural damage to the sidewall, which could exhibit as a bulge or bubble in the sidewall much like a hernia. It’s the reduced rubber cushioning of low-profile tyres that also makes wheels more prone to buckling when hitting a pothole.

The statistics are clear: about 70% of pothole-damaged tyres brought for replacement into fitment centres are low-profile tyres, according to Riaz Haffejee, CEO of Sumitomo Rubber South Africa which handles the Dunlop, Falken and Sumitomo tyre brands.

It’s a case of cosmetics trumping common sense. Customers choose big alloy wheels mostly for their aesthetic appeal as larger wheels simply look better, and nobody can deny that a set of megasized 22-inch alloys give an SUV more kerb appeal than smaller wheels.

But don’t try driving that SUV onto kerbs or attempt any kind of offroading, because the larger the wheel size, the lower the profile of the tyre must be. This is because the car’s speedometer and gearing are finely matched to the combined wheel/tyre circumference, so if you decide to buy a sweet set of larger new mags for your ride but try to retain the same tyre profile, the overall circumference would increase and result in the car accelerating slower and the speedo giving the wrong readings — apart from the fact that the whole caboodle might not even fit inside the wheel arches.

So to summarise, big wheels require lower-profile tyres which are more prone to pothole damage and negatively affect ride comfort.

Such tyres make sense on sports cars because the smaller sidewalls have less flex, which improves handling sharpness. The decreased pothole protection seems a more logical trade-off in cars that are purpose built to go around corners fast. On an SUV, not so much. Apart from the aesthetic appeal, low-profile rubber on such vehicles makes about as much sense as a hippo wearing running shoes. Why buy a top-heavy, soggy-handling SUV in the first place if handling sharpness is what you’re after?

High-powered sports SUVs are even more of an enigma. Build a heavy, high-riding SUV, stick in a monster engine, fit low-profile tyres and drop the suspension voila, you have a duck-billed platypus: a mishmash of a thing that makes no sense. It can’t go offroad unless you want to damage those expensive 22-inch tyres and rims, and on the road it doesn’t handle as well as a regular car.

Don’t get me wrong. I’m not immune to the charms of aesthetics, and plumage taking precedence over practicality. Possibly the best example of a duck-billed platypus, the Mercedes-AMG G63 racecar-meets-SUV, is one of my favourite toys despite it being so illogical. Brutally powerful, top heavy, and you can’t take it offroad because it wears ultra low-profile tyres.

But as a motoring journalist, like the uncle to a baby, I only get to play with such things for a short while before giving them back. Living with it on a daily basis is a different prospect.

My advice, if you want to navigate the real world of potholed roads and you want SUV-like space with car-like handling, buy a station wagon (with high-profile tyres of course). If you can handle not sitting a couple of centimetres higher.