Cycle News

VOL. 55 ISSUE 36 SEPTEMBER 11, 2018 P99 Why do you think a produc- tion customer would choose an alloy wheel over a carbon wheel? Do you think it's just down to looks, or is there a major performance difference between the two? You've got your three core technologies, which are cast alu- minum wheels, forged aluminum wheels and carbon wheels. If you take car wheels and bike wheels, typically, if you go from a cast to a forged wheel, you're taking about 15-20 percent of the weight out. If you go from cast to carbon, you're talking about taking about 50 percent or more weight out. If you go from forged to carbon, you're taking 25-30 percent out. It varies by design and style, but that's roughly what you're looking at. Magne- sium has a very similar weight to carbon, but it doesn't have the durability of carbon. And the costs for magnesium are going up, where the cost of carbon is coming down. So, the way I see this mar- ket playing out technically, the OEMs are all moving towards forged aluminum as the standard away from cast, except for the low-value bikes. Then with the upgraded packages will be car- bon rather than magnesium. The proper technology will be forged aluminum and carbon. That's why we've chosen those two tech- nologies and so far, that's proven to be a good decision. We raced our carbon wheel in the Endurance World Cham- pionship in 1997 and won the title. What it did was it massively reduced rider fatigue on these endurance races, but because World Endurance follows World Superbike, when they banned carbon from superbike they banned it in endurance. Unfortunately, that was a step back for those endurance riders because of the fatigue issue. We are considering bringing that three-spoke wheel back into pro- duction because a lot of people like the look. Can you explain in layman's terms the benefits of light- weight wheels? Whether it's a car manufac- turer or a bike manufacturer, to get performance you're trying to get weight out wherever you can. That's a big driver. There are three fundamental reasons why wheels are so much more focused on than any other part of the car/bike: The first reason is the un- sprung mass, which means that everything above the spring sus- pension is static or sprung mass. The un-sprung mass is the tires, wheels and brakes. Taking weight out has a big impact on the rideabilty of the bike. When you go over a bump, the energy the bump generates is greatly reduced, thanks to the lower un-sprung mass. Therefore, the bike handles better, rides bumps better, absorbs much of the shock, and as a result, by reducing the entire weight of the vehicle you get a much better tire contact patch. There's less energy for the bike to absorb. The second reason is it's a big lump of rotating mass, which means it's like a big disc. The heavier the wheels are, the more energy [torque] is required to accelerate the motorcycle, and the bigger the brakes must be to decelerate them. If you can reduce that weight, you reduce the moment of iner- tia. The bigger the wheels are, and particularly on the outside where the tire meets the flange of the wheel, the mass or mo- ment of inertia [energy] increases exponentially as the weight moves out from the center of the axis of rotation. As the wheels get bigger and heavier you need much more energy, and it's a function of a square of the distance from the bearings, effectively. You're hav- ing to accelerate this big, rotat- ing mass. Thus, the moment of inertia is the second big issue. Then you have a third issue which is the gyroscopic impact. When you are going through chi- canes and bends and cornering, the high-speed rotating masses/ discs tend to want to pull you outwards. If you can reduce the weight of the high-speed rotating rear tire, basically you can flick through the chicanes and tight bends much, much faster, much quicker. The bike feels much lighter. It's much more control- lable. It's got three key factors as opposed to a kilogram on a bike anywhere else, which is only about weight. CN

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