The natural rubber comes from Southeast Asia
The racing tyres Dunlop supplies to the BTCC come from an unlikely source. We track their journey
What do tree plantations in Thailand and the perimeter of Brands Hatch have in common?
Red-tailed tropical birds? You won’t find many of those fluttering along Clearways. Grandstands? Not sure folk have the patience to watch trees grow. Burger vans? No, the answer is rubber. Lots and lots of natural rubber.
Admittedly the rubber in Thai forests is a liquid that seeps out of ‘wounded’ tree trunks, while at Brands Hatch it’s the primary material in the ‘well worn’ racing tyres that make up crash barriers. But these two rubbers toresexist at the start and finish of the same process: racing tyre production.
Making the rubber that will be used on track requires a different process to ones that end up on our road cars. Take the 18in tyres fitted to the 32 British Touring Car Championship entries, for example. They use material that is grown, sourced and manufactured entirely by hand, a process which is almost the polar opposite to that used by the manufacturers of road-going tyres. Road tyres use much higher levels of man-made silica and are produced via a more automated process.
“We use natural rubber in racing tyres because it has a higher stretch ratio, so it’s more resistant to tearing,” says Dunlop race tyre engineer Stefan Nasello. “Silica has benefits in road tyres but in racing we need the strongest material because teams have a habit of pushing things over the limit.”
Nasello works at Dunlop’s main racing tyre production facility, which is located at the tyre firm’s factory in Hanau, Germany, a site that recently celebrated its 125th year of work. These days the factory specialises in high-performance tyre production, making boots for only the fastest of supercars, such as the Porsche 911 GT3 RS, and for Dunlop’s racing activities, which has included supplying the whole BTCC grid with its tyres since 2003.
“We also supply tyres to teams in the LMP2 and GTE classes of the World Endurance Championship, as well as teams in the VLN endurance series in Germany,” says Nasello. “In these cases there’s tight competition against other tyre brands, so we’re always working flat out.”
That’s what makes the tyre production process employed by the 37 operators at the Hanau racing tyre facility so crucial. One tiny mistake in the manufacturing process, one millimetre’s worth of misaligned material, and the results might not reveal themselves until a racing car suffers a mid-race blowout two weeks later. That’s not something Dunlop, or any racing tyre manufacturer for that matter, wants to endure.
“Racing tyres are actually made of fewer parts but they have to deal with much, much higher loads, so our operators are highly trained,” explains Nasello as he shows us around the factory “It’s a very detailed job, yet we produce around 150 tyres per day, all by hand.”
There are 18 parts in each racing tyre compared with 22 for a road tyre, because each component is focused on one job: to provide grip. Road tyres, on the other hand, have to work in a much wider variety of conditions, while acting as a component of the car’s suspension and, increasingly in recent times, offering low rolling resistance.
Yet it’s the work of a racing tyre maker – not a road tyre-making machine – that is most impressive. Watching one in action is a bit like observing a bespoke tailor demonstrate their craft. They stand in front of their workstation and slice and fold rubber with the same conviction as a Savile Row sewist. Each can roll sheets of this material, which has been supplied to Dunlop from contracted rubber tree farmers located in Thailand, Malaysia and Indonesia, at such pace that it takes just 15 minutes to create a racing tyre’s internal carcass. This rubber carcass is not visible once fitted to a wheel, but is key to its performance because it ensures the tyre can sustain substantial loads, such as surviving a 20-minute race around an abrasive circuit such as Thruxton at an average lap speed of 115mph.
Race tyre makers then add an internal belt, which enhances overall strength further by tightening the layers together. Interestingly, while Le Mans tyres are equipped with belts made from Kevlar – to cope with the higher endurance required from multiple stints during the 24-hour race – BTCC cars use steel belts like road cars, because they have to cover far fewer laps.
This, says Dunlop motorsport centre manager Mario Korn, is what makes the transfer of technology from BTCC to road much closer: “Racing tyres have sidewalls that are about one millimetre thick, whichis thinner than a road tyre’s. That’s purely because they have to cover far fewer miles.”
The final layer to be added to the tyre is the ‘tread’ compound, which varies depending on the specification of each tyre (BTCC competitors use two compunds of Sport Maxx tyre at each race meeting). This is the part that makes contact with track surface, so its importance is clear.
Tyres are then cured in specially designed ovens heated to 180deg C, in which they are pressed into their final shape inside moulds, clamped with a force of 112,000 kilograms. After 22 minutes in the oven, they emerge as racing tyres, and those destined to become ‘BluResponse Wet’ tyres have grooves cut into them by steady-handed tyre makers.
“We inspect every single racing tyre that is produced here at Hanau,” says Korn. “The quality control for the tyres destined for the BTCC, and all motorsport for that matter, has to be second to none.”
The natural rubber Dunlop uses comes from Thailand, Malaysia and Indonesia, because rubber trees grow best in the rainforests of those countries. To extract the rubber, farmers ‘wound’ a tree’s trunk with a cut and capture the liquid latex that spills out.
This latex (or rubber milk, as it is sometimes known) is filtered …read more