Propedal?

And stuff

The "ProPedal" system that is used in the Fox Vanilla, Float and DHX line of shocks is based on the system of preloaded valving. With a standard valve stack, the piston shims sit flat on the face of the piston. Because of this, when oil starts to flow the shims immediately start to bend open allowing the fluid to pass through. As the shims bend, the resistance to allow the oil to flow increases. With a Vanilla or Float "Propedal" valve stack, the shims are preloaded which causes a delay in the opening of the stack. Imagine instead of the shims sitting on a flat piston face, they're sitting on a concave face which causes them to be preloaded when you tighten down the piston bolt. When you pedal your bike it's not a constant motion, even if you do try to pedal perfect circles like Lance, so the valve delay keeps the shock from moving under this frequency. When you hit bumps, the frequency of the impact is significantly higher and more forcefull than pedaling, so the preload on the stack is overcome allowing the shock to move. So, for tuning, different levels of preload and shim profile allow us to alter the characteristic of the "ProPedal" feature. And, because the system is a shim based system, the mid and high speed damping characteristcs can still be tuned while maintaing the same "Platfrom" feel.

In the DHX, instead of building the "ProPedal" feature into the piston, they utilize a seperate valve located in the reservoir of the shock. It also is a preloaded system with the benefit of being able to adjust the preload externally with a dial which is nice. The "ProPedal" valve also functions off of the displacement of the piston rod, which again is great for tuning because it allows vast changes to be made more easily to the shimmed piston which is operating in the main cylinder independant from this valve.

As for the 5th and Swinger shocks, they both utilize a check system built into the piston bolt, however it doesn't operate like an additional rebound stack, due to the fact that it doesn't generate any force on the extension stroke of the shock. The rebound in both of these shocks is still controlled buy the rebound bleed hole, as well as the rebound piston stack.

Thanks,

Darren Murphy
Push Industries

I'll let Darren speak for the Fox stuff... There's a lot of theoretical stuff you can throw around. I've read some of Race Tech's literature regarding thier Shock Clock (a simple data aquisition device, and I think Darren uses it), and basically they explain the difference between static sag and dynamic or average sag.. (I'm reciting this from memory, and it's been a while since I've read thier information) For example, high rebound damping will make your suspension pack up a bit or a lot, but if it's only a bit, then on average as your ride around your sag will be lower. higher compression damping on average, by not letting the suspension compress as much over impacts would cause you to ride higher in your travel. True or just their marketting dept creating a need to sell their product, either way, food for thought.

Now, as far as the 5th dampers go, being position sensitive they allow you to run lower spring rate and conversely lower air pressures because the damping helps resist bottoming, not just the spring. In the end, experiment, and ride what works for you. If you can ride lower pressures w/o causing excessive sag and messing up your bikes handleing, also while not bottoming excessively, than it'd probably be more comfortable.