Motorcycles

Aussie suspension guru builds hybrid double-sprung dirtbike front end

Aussie suspension guru builds ...
Laurie "Suspension" Smith has designed a hybrid double suspension system for dirtbikes that he calls the TwoEvo
Laurie "Suspension" Smith has designed a hybrid double suspension system for dirtbikes that he calls the TwoEvo
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Side by side with a standard dirtbike you can see how much more vertically the forks are mounted
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Side by side with a standard dirtbike you can see how much more vertically the forks are mounted
Those steering linkages don't look quite heavy duty enough to us
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Those steering linkages don't look quite heavy duty enough to us
It's a jarring sight alright!
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It's a jarring sight alright!
The TwoEvo suspension allows the entire triple clamp assemblies to be suspended, leaving the standard forks in place as well to vastly increase travel
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The TwoEvo suspension allows the entire triple clamp assemblies to be suspended, leaving the standard forks in place as well to vastly increase travel
Laurie "Suspension" Smith has designed a hybrid double suspension system for dirtbikes that he calls the TwoEvo
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Laurie "Suspension" Smith has designed a hybrid double suspension system for dirtbikes that he calls the TwoEvo
An earlier iteration of the TwoEvo front end out in the dunes
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An earlier iteration of the TwoEvo front end out in the dunes
View gallery - 6 images

Yes, that's a Kawasaki KX450F with a Hossack-style front end supporting a set of regular telescopic forks. Australian motorcycle suspension tuner Laurie "Suspension" Smith has created this confronting-looking jigger, claiming it makes for a better ride.

The TwoEvo suspension, as it's called, adds an extra layer of suspension to the bike's front end, suspending the triple clamps and steering axis that hold the bike's stock forks, and radically changing the angle of the forks. Where the standard bike offers 304.8 mm (12 in) of front wheel suspension travel, the TwoEvo system gives you 375 mm (14.8 in).

Because there are two suspension systems operating at once, and on different angles, the path of front wheel travel can be quite complex instead of more or less straight up and down like you'd get on a regular tele-forked bike, giving the bike a wider range of "ideal" bump shapes it can deal with.

Those steering linkages don't look quite heavy duty enough to us
Those steering linkages don't look quite heavy duty enough to us

Smith's theory is that the forks themselves might be more effective at handling the vertical component of bump handling at the steeper angle they're mounted on, as well as suffering from less dive under brakes, while the additional suspension does a better job with the horizontal component of the force.

In an interview with Australian Dirt Bike Magazine, Smith conceded that the system adds about 3 kg (6.6 lb) of weight to the bike, requires some pretty substantial frame modifications, adds potentially fragile complexity and gives the bike a "slightly odd look." It also adds significant complexity to the suspension tuning process, as the tuneable Fox shock on the head adds extra layers of adjustment possibilities to a complicated and dynamic system.

Still, when ADBM ride tester Mitch Lees took it for a ride, he was impressed with the overall feel of it, noting that "it made the small choppy bumps smoother and the big hits less harsh. It was incredible! The upright action of the fork helped it feel plush while the MTB shock allowed for superior stability like a normal bike at speed as if it was raked out. When braking it didn’t dive, which I knew it wouldn’t because of the rake angle but, to my surprise, it didn’t tuck. With a fork so upright I expected high-speed ruts to be a disaster but they weren’t."

An earlier iteration of the TwoEvo front end out in the dunes
An earlier iteration of the TwoEvo front end out in the dunes

Smith sees the system as something that would ideally find a home on an OEM bike, since an aftermarket kit or putting the system on bikes on an individual basis wouldn't be simple or cheap. But we applaud any effort to surpass the venerable telescopic fork, and this device, the result of several years of work, is a unique approach to the problem.

Source: Suspension Smith via Australian Dirt Bike Magazine

View gallery - 6 images
3 comments
zr2s10
I'm very surprised this helps, especially given that such a vertical set of forks doesn't help with the horizontal aspect of impacts. At the very least, I think fork seals would wear insanely fast, since they're bowing backwards as they travel.
Nelson Hyde Chick
Just the twenty to thirty pounds this adds to a bike would make it not competitive against its lighter rivals.
Mike Johnson
Very interesting idea for students of MC suspension. Experiments were done decades ago on nearly vertical forks that produced very strange looking bikes that worked very well with a stress point at the the conventional steering neck. If developed this system might resolve these difficulties.
Note in the image above the very steep fork tube angle!