MotoGP tech to improve airflow is set to make its way onto road bikes

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If you’ve had even a passing interest in MotoGP over the last few years you’ll have noticed there’s something of an aerodynamic revolution underway for motorcycles.

And some of that work is trickling though to road bikes, with virtually all of the latest superbikes sprouting wings, and now attention is turning to other areas where gains are to be made. New patents from Yamaha show they’re focusing on forks and how to improve airflow around them.

Yamaha have already tested their new aero fork shrouds, running them at a Jerez test last November, but the patent explains how they work and illustrates why fork covers could be a fertile area for future development.

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Ducati’s GP machines are also running their own variation on the idea this year, albeit only shrouding the upper section, while Aprilia and Suzuki’s bikes entirely cover the lower part of their forks.

The problem that they’re all trying to solve is that forks, by their very nature, have a round cross-section. As well as giving a blunt front edge facing the wind, they also create turbulence as the air rushes in to fill the space behind them.

It’s not just about pushing the forks themselves through the air: that turbulence has a knock-on impact on everything behind the forks, notably the radiator and oil cooler on a MotoGP bike or on a modern sportsbike.

Making air pass the forks more smoothly should let the bike’s cooling system work more effectively, potentially allowing smaller, lighter radiators and a smaller cooling intake.

There are also potential benefits on the road. You might not notice a fractional improvement in aero efficiency on a superbike, but as firms turn towards electric bikes – putting a huge focus on range – anything that makes them cut through the air better will be a welcome development.

Ideally, the fork shrouds would be completely enclosed, tapering to a point at the back to give a classic ‘teardrop’ cross-section, but it’s not as simple as that.

Yamaha’s patent points out that forks need to turn, and an elongated shroud would act rather like a vertical rudder, with a potentially destabilising impact when the bars are turned or if there’s a crosswind.

As a result, Yamaha’s designs cut the rear taper of that ‘teardrop’ off, a well-known aero trick called the Kamm-tail – named after 1930s German aerodynamicist Wunibald Kamm who discovered that slicing the tail off an aerodynamic teardrop shape leaves a wake that mimics the effect of having the original, long tail in place.

A Kamm-tail design cuts the air cleanly

MotoGP aero technology explored

  • Cowled lower Even though the mudguard largely covers the fork lower, the aero cross-section is kept around the forks, so air that sneaks between the wheel and mudguard is cleaved by the fork shroud.
  • Kamm-tail A full aero teardrop shape would be susceptible to sidewind effects when turned so Yamaha have sliced the rear off, creating a Kamm-tail that cuts the air cleanly but with half the amount of side-on area.
  • Earlier inspiration Yamaha’s patent gives a nod to earlier Suzuki designs for motocross fork shrouds, which reached production on the 1996 RM250, and to a 1989 Honda patent that appears to show a very early iteration of the bike that would later become the Blackbird.
  • Sliding sections While Ducati’s latest GP bike has upper fork shrouds, Yamaha’s design includes sliding lower aero sections that overlap the upper ones, making the whole front of the fork cut the air cleanly. The small gap allowing the two parts to slide is designed to shed water without allowing dirt into the gap between them.
  • Improved cooling Normal forks disrupt airflow, creating turbulence behind them. The cowled versions give smoother, uninterrupted flow to the radiator and oil cooler.
Ben Purvis

By Ben Purvis