X-Fusion's Prototype Shock - Sea Otter 2015
Hot on the heels of the news of their upcoming Roughcut damper, X-Fusion is now attracting attention with a prototype shock that uses an interesting dual Internal Floating Piston (IFP) arrangement. The coil sprung version was spotted on bikes at the Lourdes World Cup, and an air sprung version has been revealed as well, one that's likely a better visual indication of what the final configuration will look like. The underlying goal of the new design is to create a shock that has increased small bump sensitivity yet doesn't sacrifice when it comes to big hit performance.
An early version of the shock had two separate chambers, each with their own air valve.
Housed inside the shock's piggyback reservoir are two internal floating pistons, one that has 50psi of back pressure and the other that's inflated to 300psi. The earlier coil sprung prototype has two air valves that lets each of these pressures be individually adjusted, but it's now looking like the pressures will end up being pre-set, and contained in one chamber with the pistons oriented concentrically. The differing pressures allow for the shock to feel more sensitive earlier on in its stroke with less breakaway force needed to get things moving. Once the shaft is compressed enough for the secondary piston to kick in, a rapid ramp up occurs to prevent the shock from bottoming out harshly. By changing the position of the higher pressure IFP, the shock's ramp up point can be altered (that's what the blue knob at the back of the reservoir is for).
The shocks are still months away from going into production, and it currently looks like it will be late 2015 or early 2016 before they're available. Until that time, watch for various iterations to appear on the bikes of the Dirt Orange DH team and the Ibis enduro team.
In addition to changing the position of the IFP, the shock's rebound plus high and low speed compression damping will be adjustable.
Turning the blue dial changes the point in the shock's stroke where it begins to ramp up.
Be sure to check out all of our Sea Otter Classic images in this gallery.
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I'm still waiting on the inverted revel that was first shown like 2 years ago!
Wtf?!?
content.mtbr.com/images/Tradeshow/13/253/prodimg2.jpg
Once IFP is set high enough to hinder the formation of gas bubbles (cavitation) in the damping oil the amount of damping (i.e. friction created by damping oil passing valves and shims) will not increase due to oil being virtually incompressible. Manipulating the IFP pressure and volume beyond this will simply turn it into a secondary spring for the bottom half of travel to a larger or lesser degree.
Methinks this has already been done in the underrated manitou isx-6 series of coil and air shocks.
With this new dual IFP, X-Fusion are creating a 2-stage effect with the same system. The first (low pressure) piston is activated as soon as you compress the shock. But the second (high pressure) piston only activates when the shock is compressed further into the travel.
This is why you can have both a supple small bump sensitivity at the start of the stroke AND a big spring rate increase deeper into the travel. Having your cake and eating it, if you like.
www.youtube.com/watch?v=IyH8hNLr1m0
But I'm very curious to see, how it'll change the behaviour of the coil shock.it is already so plush initially :-)