Tier Motorsports R1 concept motorcycle has just one front arm

This concept R1 motorcycle has a single-sided front swingarm and four-bar steering system that enables a vertical steering axis that's impossible to recreate with a traditional forked front. Fancy dreamers Tier Motorsports tout the following benefits:
1. More controllable motorcycle on rougher roads. Road imperfections tending to steer the wheel will not be fed back into the handlebars like it does on standard forks equipped motorcycles. This is illustrated here in contrast with a theoretical worst case 90 degrees steering axis (courtesy of Tony Foale): 2. Goodbye handlebar wobble (movement, sometime violent, of the handlebar occurring at higher speeds). This is a result of the actual parts moving during steering being much lighter than on conventional forks. Eliminating steering dampers also mean a quicker steering available to the rider. 3. Custom steering trail. The trail is set by 2 spacers that can be replaced in minutes. Trail being the key value controlling handling characteristics now let the user choose the right value to match the road condition and their riding style (lower = more aggressive; higher = more stable). 4. Reduced steering forces. Does not raise the height of the center of gravity while steering. 5. Reduced steering angle needed at the wheel to achieve the same turning radius as a standard fork. This is a great advantage over other front swing arm steering design as it allows for narrower swing arm which gives more ground clearance in fully leaned turns.
It's apparently a difficult engineer problem, though, and one that many other designers have failed in tackling in the past. The Biker Gene has a lot more detail — and more reasons why it may never actually make it to market. Tier Motorsports shows R1 concept with single-sided FRONT swingarm [The Biker Gene via Gizmag]
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6 Responses to Tier Motorsports R1 concept motorcycle has just one front arm

  1. ZoopyFunk says:

    Cannondale has had single sided front suspension for many years…yes, just a mountain bike, but I wondered how long it would take for it to show up on a motorcycle. Odd though, BMW motorcycles(and others) have also had single sided rear ends for many years. Odd to see that this bike did not include both.


    Tony Foale has been doing this type of design for decades. I recall reading a book of his in the mid 80’s. There are numerous inherent problems with conventional sliding tube forks (flex, stiction, dive, etc.), but they’re well developed and all of the alternatives are much more difficult to manufacture.

  3. Anonymous says:


    The Cannondale design just uses one side of conventional forks, presumably for less weight.
    This is about using a swingarm instead of forks, which allows for fixing some of the issues that forks create, eg. the steering geometry changing under brakes because the front dives and the forks shorten.

  4. Anonymous says:

    Looks like what Yamaha did with the GTS 1000 about 15 years ago.

  5. Anonymous says:

    What irony, yamaha actually built a hub steering motorcycle in the early 90’s called the GST. I really really wanted one, they are impossible to find now.

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