Single-sided front swingarm could steer the way to better motorcycle handling


December 2, 2008

Tier Motorsports' R1 design study, with single sided front swingarm

Tier Motorsports' R1 design study, with single sided front swingarm

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December 2, 2008 If center-hub steering like that found on the Bimota TESI 3D isn't radical enough for you, perhaps this'll do the trick: Tier Motorsports have released a set of concept illustrations featuring a Yamaha R1 that's been modified with a single-sided front swingarm. The aim of the design is to provide a completely vertical steering axis for the front wheel, making for a much more direct and responsive steering effect than is possible with angled forks - and the idea also opens up the possibility of virtually frameless bikes, in which both the front and rear swingarms mount directly from the engine and no heavy steering stem/headstock is needed. Fascinating stuff.

Telescopic forks, which have become by far the most common front-end suspension solution on modern bikes, are far from a perfect design. Their angle and leverage exert powerful forces on the steering head of the frame, necessitating heavy, reinforced frames. They cause the bike to dive forward under braking forces, changing the steering geometry and reducing the suspension travel available to deal with bumps and maintaining traction.

Motorcycle buyers, however, have generally resisted change to the trusty forked front end. BMW's telelever front suspension has been the only commercially successful alternative in recent years - and possibly mainly because its workings hide behind the bikes' bodywork and the system looks pretty much like a set of forks. It does an admirable job of separating braking, suspension and cornering forces.

The hub-center steering employed on the Yamaha GTS1000, and more recently the Bimota TESI 3D and Vyrus 985, employs a front swingarm suspended by a monoshock - a similar arrangement to what you'd usually find on a rear wheel. The difference is that the wheel hub tilts back and forth on a central pivot, pushed by two large steering arms that are operated by the handlebars. By all accounts it provides an uncanny ride experience with huge mid-corner front end confidence and exceptional performance on the brakes deep into a corner.

This latest design from Tier Motorsports re-envisions the hub-center model using a single sided front swingarm and a four-bar tilting mechanism in the hub that allows the wheel to pivot on a perfectly vertical axis for maximum responsiveness to steering inputs. Presented here as a Yamaha R1 mockup, the system could bolt straight in to modified engine cases, removing the need for a strong, heavy frame at the front end of the bike.

Otherwise, the system should enjoy most of the advantages of hub-center arrangements as well as their drawbacks - high costs, limited steering lock, and a perception among the oddly conservative motorcycle market that it doesn't look like a 'real bike.' Still, these striking mock-ups certainly stir the imagination and it would be great to see what designers could do with the concept given a blank sheet. Here's hoping the Tier Motorsports system makes it up to and through the prototype stage so we can get a closer look.

More information and photos at TheBikerGene.

Loz Blain

About the Author
Loz Blain Loz has been one of Gizmag's most versatile contributors since 2007. Joining the team as a motorcycle specialist, he has since covered everything from medical and military technology to aeronautics, music gear and historical artefacts. Since 2010 he's branched out into photography, video and audio production, and he remains the only Gizmag contributor willing to put his name to a sex toy review. A singer by night, he's often on the road with his a cappella band Suade. All articles by Loz Blain

The advantages for hub centre steering are best seen by changing not just the geometry of the front end, but the whole concept of how to build a motorcycle. One of the inherent advantages of this type of front end that has only rarely been seen is the ability to make the frontal shapes that are optimised for low frontal area, drag and improved aerodynamics. At the present moment modern motorcycles represent a level of advance somewhat akin to the early air racers of the late twenties. Massively powerful engines, but all the aerodynamics of a house brick.

This is nowhere near innovative, as even this has been before. What is really needed is a fresh approach to motorcycle design - why not take advantage of the single-sided systems front and rear to put the pivot point for the rear swingarm where the front is, and vice versa? All the benefits of long wheelbase, none of the demerits. Why not seat the rider in a semi-reclined position, back braced and hip positioned in the ideal ergonomic relationship, as defined by billions of dollars of research into high-g fighter jets? This would also enable a much more aerodynamic bodywork package. Performance is no use in this modern, fuel-scarce age unless it comes with massively improved fuel consumption. Drag increases as a square of the speed. So to go faster you need to reduce drag. Lower drag means less fuel need be carried for a given range. Fuel represents a major element of mass centralisation and weight distribution in a modern sporting motorcycle. Reduce the fuel load and you make a lighter bike, which accelerates faster. A longer swingarm would enable reduced lift under acceleration, which would enable the bike to accelerate faster, as would 2wd, easily implemented in a single sided front end The HCS permits all this, and som much more, yet this designer does nothing- absolutely nothing - to take advantage of these other elements.

This isn't innovation, it's a shameful waste of computing resouces.


What I disagree with in the article is this statement:

"buyers, however, have generally resisted change to the trusty forked front end. BMW's telelever front suspension has been the only commercially successful alternative in recent years - and possibly mainly because its workings hide behind the bikes' bodywork and the system looks pretty much like a set of forks."

As if we're just too stupid to recognise progress. Noooo. IMO It's the because designs so far have not proven thier merit in terms of performance, cost and complexity when compared conventional forks. Not to mention if the performance was trully superior; race teams would be using them.

Much like essentially all current alternative energy automobiles...

Finally - a "modern motorcycle". I'm still riding a 1979 sport bike and I love it but this might be reason enough to buy something more modern. I'm not at all happy with the crouched riding position, and forget reclined seating, I'll gladly stay with my current setup - my level seat allows me pelenty of options from sitting up to crouched forward - freedom to move around, I'm not shoved up against the tank by a highly sloped seat and I don't drive on a race track. All that aside, I like this - while it isn't novel (there have been several front swingarm designs proposed) it is certainly innovative in execution.

Bring it on - maybe Ducatti will build one.


Everyone can remember the Dodge Tomahawk in its Annyversary 3, with one sided springarm as well.

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