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How are tyres made?

How are tyres made
Jonathan Manning
7 Dec 2015

Upgrading your tyres can be the cheapest way to improve your ride, but do you choose? We break down how they're made and work.

It sounds like science fiction, but the introduction of space-age materials to road bike tyres could give them a form of virtual intelligence. When you’re riding along a flat, smooth road, the rubber in the tyres will automatically harden to reduce rolling resistance, but when you brake, accelerate or take a corner it will soften to create more grip.

The magic comes in the form of graphene – the wonder substance setting hearts aflutter in the field of material science. Graphene is a one-atom-thick layer of carbon that is incredibly light, strong and flexible. It could lead to folding mobile phones, dramatically lighter aircraft and, er, the thinnest, most impenetrable condoms (the Bill & Melinda Gates Foundation has donated $100,000 for investment into graphene to create a safer contraceptive with better sensation).

It’s also set to transform the world of cycling, including the road tyre, and you won’t have to wait decades to test its effects. Italian company Vittoria has just launched a version of its popular Corsa tyre with added graphene in the tread compound, and it claims the result is a 19% reduction in rolling resistance compared to its predecessor, as well as greater puncture resistance and big improvements in overall longevity. 

Making bicycle tyres

While it’s too early for Cyclist to verify these claims, it’s certainly evidence that tyres, despite being among the least glamorous components you’ll find on a bike, are at the forefront of scientific development and have a far greater impact on ride quality and performance than they are often given credit for. Good-quality tyres are perhaps the cheapest and easiest upgrade you can make to your bike, so it’s worth understanding a bit about what goes into those rubber hoops. 

Circle of compromise

Minimising rolling resistance, maximising grip, cushioning the ride, all while fending off the continual threat from glass, flint and thorns – tyres are impressive feats of engineering. Manufacturers have to balance these competing demands when developing new tyres, and it’s no easy task, as Benjamin Blaurock, product manager for Continental’s road tyres, explains. ‘If you increase one of these parameters it will influence at least one of the others,’ he says. ‘For example, a very hard compound would lower rolling resistance but decrease grip, plus it would feel very wooden to ride. If you want high puncture resistance you can add a thick anti-puncture layer, but that adds weight, and pushes up rolling resistance.’

Such inescapable compromises explain the wide spectrum of road tyres available. At one end are stiff, heavy, durable and highly protected tyres best suited to touring and commuting, where puncture resistance has a higher priority than outright speed and performance. At the other end are super-light, grippy, supple tyres aimed at racers who are prepared to accept an increased risk of a flat tyre and reduced longevity for the additional performance gains that might secure them a win or a new PB come race day. 

As Blaurock points out, ‘It’s important to have a great feeling from your tyres, and they can influence the performance level
in a very significant way.’ He also reminds us that some people are prepared to shell out upwards of £2,000 on top-end carbon wheels, while the difference in price between a mid-range and a premium-quality tyre is barely £50. Tyres represent a relatively cheap upgrade.

Schwalbe Durano

With so little contact with the road surface – less than a thumb print – how can a tyre make such a difference to the ride feel? Unlike mountain bike tyres, where the tread pattern is crucial for grip, road tyres rely more heavily on a combination of the compound of the rubber and the suppleness of the carcass. In the wet, a road tyre will cut through the film of water (and not aquaplane on top of it) and hence even a totally slick tyre can still provide sufficient grip to keep you upright. Even tyre manufacturers admit that having any kind of tread pattern on a road tyre is more for the psychological benefit of the rider than any contribution to grip. What this demonstrates is how important the construction of a road tyre is to every aspect of its performance, so let’s peel back the layers. 

Roll-up, roll-up

Tyres are typically an assembly of four elements. The quality of the materials used for each of these is important, but it’s how they interact that really determines performance. Working from the outer layer inwards, first comes the tread or rubber compound that contacts the road. Next is usually some kind of puncture protection layer and finally comes the carcass that gives a tyre its structure. The fourth element is the inner tube, which is either fully enclosed within the carcass, as with tubular tyres, or fitted as a separate component, as per clinchers.

Schwalbe claims its Pro One tubeless tyre has 25% less rolling resistance than a comparable clincher tyre with an inner tube

Tubeless tyres, described by German tyre manufacturer Schwalbe as ‘the technology of the future’, do away with the need for an inner tube and therefore reduce rolling resistance by taking away the frictional losses created between the tube and tyre as the tyre rolls and flexes. Schwalbe claims its Pro One tubeless tyre has 25% less rolling resistance than a comparable clincher tyre with an inner tube, which highlights the influence the inner tube alone has in the tyre system.

For race day, pros across disciplines including track, time-trial, road and cyclocross use tubular tyres, where the tread, casing and tube are sewn into a single structure. Despite the nuisance factor of having to glue these tyres to wheel rims (they don’t engage via a hooked bead as per clinchers), the pros favour the tubulars’ smoother ride, proven lower rolling resistance and the reassurance that even with a flat, the tyre stays on the rim. 

Tyre tread

‘The physics of that perfectly round cross section shape gently hugging a (usually) latex inner tube is optimal for a soft, supple system because it will deform perfectly in every direction,’ says Morgan Nicol, chief technical officer of Challenge Tyres, a company specialising in handmade tubulars. A typical clincher tyre is constructed with a pronounced U-shape and will not deform as uniformly. 

Why does this matter? To lower rolling resistance a tyre needs to be supple enough to deform and absorb any imperfections in the road surface, allowing the momentum of rider and bike to continue unimpeded. 

The alternative, says Nicol, is that each time a tyre hits a stone or uneven surface it bounces back by a tiny fraction (which is happening many times per wheel revolution), resisting forward motion. If you scutinised even a super-smooth road surface under magnification, its profile is far from flat. On a microscopic level, tyres experience something akin to bouncing over the cobbles of Paris-Roubaix every single ride, losing energy as the wheel is repeatedly airborne. This is why skinny, highly pressurised tyres are gradually being phased out in favour of wider tyres run at lower pressure, as it has been proved the wider, lower-pressure tyres create less rolling resistance because they deform more readily and thus bounce back less.

Challenge Paris Roubaix Open

Eric Gertner, Bontrager’s chief tyre engineer, says, ‘Everyone used to ride 19mm-wide tyres pumped to 120psi thinking it was faster. But we now know that’s not the case. From what we have seen in testing, a higher-pressure tyre will bounce you around more and that bouncing around is actually energy being bled off into the universe. On a polished velodrome a 19mm tyre might be the fastest, but on a road the optimum is definitely bigger to take that road noise out, and a lower pressure, within reason, is a good move for a lot of people.’

Suppleness, it seems, is a tyre’s greatest asset, and even more so when cornering, especially in the wet or on rough surfaces. Nicol says, ‘As you come into corners where the road surface is not perfect, any bouncing over bumps will tend to unweight the tyre.’ If water is added to the situation it acts as a lubricant, and you’re likely to slide onto your backside unless the suppleness of your tyre can retain contact with the road.

‘Suppleness depends partly on the thickness and flexibility of the tread, but really it’s the casing that plays the dominant role in a tyre’s performance,’ says Nicol. This casing consists of layers of woven and bonded threads. The higher the number of threads per inch (TPI), the thinner each thread is and the more supple the tyre will be. Race quality tyres can have up to 320TPI, while winter training tyres might have just 60TPI. But be careful when selecting tyres, because manufacturers will often quote TPI rates based on multiple layers of carcass. For example, a 180TPI carcass might be three layers of 60TPI.

Materials matter here too, with top-of-the-range silk (used for track tubulars) being softer and more supple than cotton threads, which in turn outperform nylon. But as Continental’s Blaurock pointed out at the beginning, you can’t have it all. High thread count, cotton carcasses and softer durometer rubber treads may be the most supple but they lack the durability and resistance to cuts of more rigid nylon and harder rubber compounds. 

As yet, nothing has been able to defy these compromises and produce the perfect blend of suppleness and durability. But who knows what might be coming down the road once the graphene revolution takes hold?

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