Kawasaki pretty much stole the show in 2014 with the Ninja H2R (less so the H2) featuring the first supercharged bike in many years and one that jumped performance ahead by a considerable margin. But is their next trick a brand new front end setup that evolves the tried (and generally unsuccessful) center-hub arrangement? Patents published this year say, well, maybe.
By and large, almost every motorcycle since the 1930’s has used the traditional telescopic fork setup and for good reason. They’re extremely cheap to manufacture, they’re mechanically very simple and compared to other options, provide a good level of feedback to the rider. But they’re not without drawbacks which is why center-hub steering arrangements have popped up now and again since 1918 – most recently with Bimota.
With center-hub steering, the front wheel is able to rotate both left and right on its axle, in addition to turning on its pivot like a traditional motorcycle. The main advantage to this is improvement in the physics of front end design as it separates the steering, braking, and suspension functions from the forks. The forks on a motorcycle extend vertically, save for a few degrees of rake. Yet, when you brake, forces are exerted along the horizontal plane – effectively the forces are working against the forks and therefore front suspension. This means that the bike isn’t working in an optimal fashion under braking which is one of the reasons why the front end dives when you hit the anchors.
On first glance, the patent images from Kawasaki look like just another center-hub design. But there’s a few more things going on here. Here’s the abstract from Kawasaki’s patent:
A front wheel supporting structure for a straddle-type vehicle includes a front arm which supports a front axle and which extends rearward from a front axle to a location behind a front wheel, and a pair of upper and lower link members which is turnably connected to two vertically separated portions of a rear end of a front arm. The link members extend rearward. Rear ends of the link members are turnably connected to a vehicle body-configuring member. The front wheel supporting structure includes a front suspension mechanism which suppresses turning motion of the front arm.
Translated into something more like English, what Kawasaki has done is is quite different from traditional center-hub design. The ‘swing arm’ holding the front wheel doesn’t swing as such but instead is connected to two arms behind the front wheel which themselves swing and provide the vertical movement of the wheel. You can see in the patent images there’s also a horizontal spring and shock absorber in play as well. So it takes all the benefits of center-hub steering but into a more compact and lightweight arrangement.
Negatives? Yes, there’s a few. Cost would be a major factor – what Kawasaki has designed here isn’t exactly simple and uses a fair few more components than telescopic forks. The biggest problem however is that the system effectively turns the steering mechanism into a ‘turn by wire’ setup. In this patent, Kawasaki has employed cables to translate inputs on the bars, through the linkages and on to the wheel. Given how important front end feel is on a motorcycle – being able to have direct steering inputs is a big deal – this system would mean you don’t have any direct interaction with the front wheel and therefore you’ve got far less idea what’s happening when you’re leaned into a corner at high speed.
That could be a deal breaker. However, if Kawasaki’s system creates a giant leap forward in handling then perhaps drawbacks would be worth overlooking. Regardless, it’s unlikely that this is a motorcycle design that will be mainstream in the foreseeable future. But perhaps after the excitement of the Ninja H2R finally dies down, Kawasaki will look to this as the next big thing to steal the spotlight.