BMW’s Next-Gen, Swingarm-Less Carbon Fiber Superbike

[Hugh Janus]

Overlaying the BMW patent drawing over a current S 1000 RR gives clues to what the unit could look like. (Ben Purvis /)

When it launched the S 1000 RR-based HP4 Race three years ago, BMW proved the carbon fiber technologies it has honed in racing and road cars could make the leap to two wheels. It’s only a matter of time before a more mass-produced carbon sportbike reaches showrooms, and a new patent from BMW hints that it could be even more advanced than its predecessor.

As a reminder, the HP4 Race was BMW’s range-topping superbike back in 2018, weighing in at just 377 pounds wet thanks to a carbon fiber frame, bodywork, and wheels. Its dry weight was an even more impressive-sounding 322 pounds, and thanks to an engine spec that was similar to the firm’s WSBK machines it achieved 215 hp. On the downside, it cost $78,000, could only be used on the track, and that exotic motor needed to be replaced every 5,000 kilometers, at a cost of around $20,000. That fun didn’t come cheap.

Fast-forward to 2020 and BMW’s basic, road-going S 1000 RR manages 205 hp, combined with normal service intervals and engine life, but in terms of weight its 434-pound mass is still significantly more than the HP4 Race. It’s safe to say BMW isn’t going to allow its latest-and-greatest superbike be overshadowed by a version  of its predecessor for long, so a carbon fiber-framed lightweight derivative is sure to appear at some stage in the model’s life.

Doing away with a conventional swingarm pivot, BMW’s patent shows a carbon fiber struction acting as the spring and support for the rear wheel. (BMW Patent Drawing/)

One element of the old HP4 Race that wasn’t carbon was its swingarm. While its closest rival at the time, Ducati’s 1299 Superleggera, used the material for its entire chassis, including the swingarm, BMW stuck to aluminium for the suspension. Now the firm’s latest patent suggests it’s not only planning to move to a carbon fiber swingarm but to do away with the conventional swingarm pivot altogether.

The new carbon BMW frame design, pictured above, looks basically like a hardtail; the rear suspension—it can’t really be called a swingarm as it doesn’t swing—is molded into the main chassis itself. However, BMW isn’t planning to go without rear suspension. Instead the idea is to use flexible properties of carbon fiber to allow the rear wheel to move vertically, but not side to side.

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BMW’s patent explains that by arranging four layers of carbon fiber above the rear arm, and another four below it, all with the fibers running longitudinally, it can create a flexible component that acts as a spring. Fiberglass and carbon fiber leaf springs have been around for decades—they were pioneered by the Chevy Corvette in the early ’80s and remained a key element to the car until the latest generation was introduced this year—and in this instance the leaf spring is basically the swingarm itself. An upper shock mount is still visible on the frame, suggesting there will still be a conventional strut to damp suspension movement, and perhaps an auxiliary coil spring to allow preload adjustment, but the main suspension job is performed by the flexible rear arm.

BMW has already fit a carbon fiber main frame to its HP4 Race model, but it used an aluminum swingarm. (BMW/)

If any company can pull off a design like this, it’s BMW. The firm is undeniably a   world leader in carbon fiber technology, having pioneered mass-production techniques that have allowed carbon vehicles to be made relatively quickly and cheaply. Both the i3 city car and i8 supercar have all-carbon chassis, and several other BMW car models have structural carbon components including roof panels and pillars.

While the HP4 Race was a handmade machine, BMW has already patented methods to mass-produce motorcycle frames from carbon fiber. Whether the innovative flexible rear suspension makes it to the next S 1000 RR-based carbon bike remains to be seen, but it’s clearly under serious consideration.

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[Pedro]

I had a nice close look at an S1000RR the other day, at my mechanic's place. Fucking awesome to have a bike that is 200hp and only a little wider than it's rear wheel. Only wish I had the physique to ride that thing, and the skill to do it properly too