Tyres: the differences between off-road and racing cars

Driving a racing car that has slick tyres fitted is a real eye-opener and it means you can drive around a racetrack at very high speeds. Courtesy Michelin

Let's face it, tyres are not glamorous. They might be the only things that connect your car to terra firma, yet they're largely unsung heroes.

For example, when you go to the showroom to buy a new car, the chances are that the salesman will bang on ad nauseam about the state-of-the-art infotainment system, safety features, performance capabilities or other attributes. What the salesman will not do is give you a spiel about how tenaciously grippy or durable the tyres fitted to the vehicle are.

For most of us, tyres are just utilitarian elements that are merely a necessary part of a vehicle, much like brake pads, oil filters, shock absorbers and engine oil. You simply use them until they have no more to give, then replace them with new ones. There’s usually not a whole lot of thought about the process. It’s an inevitable part of the ownership experience. Even when we do hand over the cash for a new set of black boots, it’s a somewhat grudging outlay.

But here’s the deal: there is arguably no more vital component that contributes to the safety of your vehicle and its occupants than its tyres. They could make the difference between you having a big accident and not having one at all. That extra little bit of grip afforded by a quality set of hoops might just enable you to swerve around an unexpected obstacle or bring the car to a safe halt rather than ploughing into it. They could also mean you stay in control of the vehicle in treacherous wet conditions.

Some may think of tyres as being a simple entity that’s easy to churn out. They’re just large bands of rubber, right? Actually, no. The modern tyre has to meet many conflicting requirements – yes, their primary purpose is to provide good grip in wet and dry weather, but they also have to last for 30,000 kilometres or more (depending on the type of tyre and how it’s used), deliver low rolling resistance for energy efficiency, generate low noise across varying road surfaces and provide good ride comfort. As a result, developing and manufacturing these black bands is a complex process.

Believe it or not, more than 200 raw materials go into the manufacture of each tyre, and even the design and construction is arrived at after a lengthy scientific process. Michelin spends more than Dh2.6 billion in research and development each year, and performs more than 1.5 million measurements over the same period in its quest to continually develop better tyres.

As you may have guessed, rubber (both natural and synthetic) is the main commodity that makes up a tyre, but other key components include carbon black (a waste product of the petroleum industry) and silica to significantly boost the lifespan of the tyre. In addition, there are metallic and textile reinforcement cables that serve as the “skeleton” of the tyre, forming the geometric shape and providing rigidity. Then there are numerous chemical agents that help provide properties like low rolling resistance.

It’s very much a case of horses for courses when it comes to tyre design and manufacture, as the requirements for a set of boots fitted to a hardcore off-roader are very different to those affixed to a 300kph-plus supercar. In the former case, the priorities are to provide maximum purchase when traversing mud, sand and boulders, while resisting the relentless attack of sharp rocks and sticks seeking to gouge a hole in the tread or sidewall. A supercar tyre, on the other hand, is designed to provide maximum grip on smooth Tarmac (be it wet or dry) and must be able to withstand the heat generated by sustained running at high speeds, often with high G-forces generated by hard braking, acceleration and cornering thrown in.

To gain a feel for the contrasting properties provided by different types of tyres, I travelled to the Sepang International Circuit (home of the Malaysian F1 Grand Prix) for the Michelin Pilot Sport Experience, as part of which we got to shave a few millimetres of rubber off the diverse hoops fitted to a track-prepared Renault Clio touring car, Citroen DS3 rally car and Formula 4 racer.

It was not a tyre test per se, as there were no offerings from rival manufacturers, but it did provide an insight into how different types of tyres deliver contrasting characteristics. Given that they were designed to do their business on billiard-table-smooth bitumen, the Clio touring car and Formula 4 were shod with slick tyres (those devoid of any tread), enabling them to generate neck-straining levels of cornering grip around the Sepang Circuit.

If you’ve never driven a car fitted with slick tyres (I’m guessing most of you haven’t), it’s a real eye-opener to glean just how resolutely they cling to the Tarmac. The result is that you can circulate a racetrack at warp speeds, which, of course, is precisely the aim of the exercise.

You may ask how any of this relates to real-world driving. Well, the tyres you’d find on a high-performance road car are somewhat similar in conception to those fitted to the Clio race car I’d just sampled. Next time you spot a Lamborghini Huracan or BMW M4 parked up, check out the tyres and you’ll notice they have a low-profile sidewall (viewed side-on, they look almost like rubber bands), which means they flex less under hard cornering, making for instant response when you tweak the steering wheel. What’s more, their treads are made up of wide, flat blocks and relatively shallow grooves (these are there to channel water away in wet weather), putting as much of the tyre surface in contact with the road for maximum grip. They are, in essence, a semi-slick.

The Citroen DS3 rally car rides on altogether different rubber, seeing as its playground is mud and gravel. Consequently, it’s fitted with a knobbly treaded tyre that can eke out traction on the slippery clay-like rally stage prepared for us by the Michelin team. The driving style required for this exercise is also different, as you need to fling the car around – thereby getting through corners sideways – as opposed to taking neat, slide-free cornering lines that proved most effective in the circuit-prepped Clio and Formula 4.

The tyres fitted to a rally car prepared for a mud/gravel surface are most similar to the rubber you’d find on an off-roader such as a Nissan Patrol or Jeep Wrangler. Most noticeable is the aggressive tread pattern that’s designed to dig into the surface and extract grip in muddy or sandy places where a smooth road-biased tyre would spin helplessly, getting you mired in the process. Off-road tyres also have a taller sidewall that can flex a little to help absorb the large irregularities in the surface below. These sidewalls are also reinforced with a variety of materials to make them more resistant to puncture.

As mentioned, the modern tyre has to satisfy a myriad of criteria to make it marketable, and even the hoops affixed to a humble Toyota Camry are the result of intensive research and development. Consequently, they deliver (in most cases) a blend of decent grip in wet and dry conditions, good wear properties and low levels of noise and rolling resistance. Importantly, they have to do all this at a competitive cost in a cut-throat market. Herein lies the challenge for tyre manufacturers.