Dunlop’s race to road motorcycle technologies
Tyres & Accessories recently visited the Dunlop Motorsport tyre factory next to Goodyear Dunlop’s UK headquarters at Tyrefort in Birmingham. While around half of the 1,200 tyres produced on-site daily are designed for four-wheel use, Dunlop was showing T&A its motorcycle range and how motorsport tyre developments have “cascaded down” to the Dunlop brand’s road going range, in the words of Mark Sears, chief design and development engineer for Dunlop motorcycle tyres.
Sears is part of a research and development team of 22 on the site, which includes a computer design and simulation suite and a motorsport tyre store capable of holding 50,000 tyres – when T&A visited, it was holding stock of around 32,000 tyres, a figure that was in the process of “creeping up” during the winter months in preparation for the summer season.
Sears presented the Tyrefort plant as a nimble, flexible research and production unit able to “produce a tyre from scratch in five days”; make short runs of bespoke products to support motorsport series’ particular needs; and react to feedback from the track quickly. The plant is ultimately able to function alongside Dunlop’s central European technical centre as an important step in the evolution of new Dunlop technologies, two of which are particularly present within the latest range of road-going Dunlop Sportmax motorcycle tyres: multi-tread compound technology and “N-Tec construction”.
Multi-tread compound technology is a result of technology “developed from 250GP, Superbike, Supersport, Endurance and Road Racing around the world”. Simply put, the technology involves matching the compound to the area on the tyre where it will be needed most – an idea Sears illustrated to T&A through Dunlop’s computer simulators. Because most road-going bikes will only ride on the centre of the tyre most of the time, a strip of the “more durable traction compound” is placed in this central area. It is cooler-running, which helps to increase tread life and maintain straight-line stability and traction under acceleration and braking. This compound also extends underneath the “lateral-grip compound” – around “30 per cent softer” than the central compound, according to Sears – used either side of the tyre’s centre to enhance cornering grip. This, Dunlop says, helps the tyre to warm up quicker, while simultaneously control heat generation, enabling it to improve stability in corners.
The “central compound also comes to the surface” in a triangular wedge placed in the middle of the softer, explains Sears. “This suppresses wear in this region, and gives it some extra stability. The more it wears, the wider [this strip] gets The technology is present in the Sportmax GP Racer D211 track day and hypersport street tyre, the Sportmax SportSmart hypersport street, occasional track day and light touring tyre – both of which were new for 2010 – and the Sportmax Qualifier II supersport street tyre.
The N-Tec construction technology is used to help rear tyres run at much lower pressures on track than on the road – Dunlop exemplifies 25psi for the GP Racer D211 – while helping the same tyre achieve better on-road stability, grip and handling. Running at lower pressure on track yields the advantage of a larger footprint providing additional grip, though the casing stiffness lost would normally reduce cornering stability seriously; N-Tec helps to provide stiffness in corners despite the low pressures.
As “part of the N-Tec package”, Dunlop also employs Jointless Belt, or JLB, technology, which helps to reduce circumferential deformation, especially at higher speeds. JLB is comprised of a jointless nylon bandage that helps stability at high speed, therefore leading to smother wear and increased wear resistance. Once again, this technology is partially a result research and development work carried out at the Birmingham facility on race tyres.
Emphasising the success of this technology, Dunlop points to its on-track success in 2009, 104 world and national motorcycle championships were claimed on tyres containing N-Tec construction, with all series but the American Motorcycle Association events supplied by multiple tyre providers. N-Tec is available in both the tyres debuted in 2010 – the GP Racer D211 and the SportSmart, both of which are designed for use on trackdays, exemplifying the race to road journey of the technology they contain.
These technologies – along with a patented “seven zones” technology that works with the two compounds to enhance the tyre’s characteristics most useful in each area of the tread – represent a perfect example of “cascading motorsport technology” working its way into Dunlop road-going bike tyres. “Everything we learn on the track, we develop in this office and can put into standard production tyres within a year,” says Sears. “Although this plant makes some standard production tyres, it is not the mainstream plant that produces most of Dunlop’s motorcycle tyres.” This production is carried out at the company’s production plants in Japan, the USA and in France. The latter location at Montluçon “produces the majority of the tyres for Europe. From Montluçon come the GP Racer, GP Racer Slick, D211, Qualifier RR, SportSmart and RoadSmart.” All the technology from motorsport development carried out in Birmingham will “cascade” where it is needed throughout this motorcycle range.
“Some need it and some don’t,” continues Sears. If a technology is developed for more enthusiastic use, it will cascade to the areas of the range where it will be most appropriate. For example, “the Qualifier was just a single-unit tread – one compound all across – whereas the new Qualifier II is multi.” Sears explained the manufacturing technique of “extrusion” helps to pre-form the compounds into a tread, while another method is called “strip winding” in which a small slither of rubber, “about 5x5mm is wound on from one side to the other. The advantage with that type of technology is that the overall stresses of the tyre” – caused by unevenness created when shaping rubber – “is all but eliminated” in the process of winding small strips of rubber around a predetermined shape. Both extrusion and strip-winding are techniques used at the Dunlop plant.
Of course, the technology used in track tyres can often represent “overkill” when it comes to producing road-going tyres. While it may be necessary for the Dunlop factory to react to specific tracks’ needs by producing seven compound tyres, this kind of technology is unnecessary for most riders, who spend the vast majority of time on the centre of the tyre. However, Dunlop’s small manufacturing unit, where tyres are handmade, can deal with producing these short runs, allowing for the experimentation that leads to the sorts of new technologies that do make it into the major Dunlop range.