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1682 Views 10 Replies 4 Participants Last post by  Ultra Magnus
Anyone have a pretty good handle on how the propedal damping works? Also any one have much experience on a propedal ava. Does it only affect slow speed like fox is claiming or does it effect the whole range? Also does it effect the plush linear feel of the ava?
Any info would be great.
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Depends on what "propedal" we are talking about, most fox "propedal" shocks simply have more low speed compression damping with a blowoff, although its not a huge amount more, and it blows off easily. The new fox DHX on the other hand has "adjustable propedal", I have mine in the mail, but at this point it doesn't seem like it works the same, or is at least a good deal more complex.

The regular propedal shocks are a fairly good compramise, but they are still much more like the regular "fox" shoxs rather than like a 5th element or manitou swinger...
I believe they just restrict the free compression bleed. In a non propedal shock, oil can flow freely on compression at low speeds through the rebound bypass. You may notice that if you take a normal fox shock and bottom the rebound adjuster, and push it by hand (off of the bike, no spring - if an air shock, unscrew or remove the air can) it becomes MUCH more difficult to compress. Low speed damping goes way up, but of course, you can't ride it like that. All it takes is a rebound check valve to accomplish that. 5th shocks use a rebound check shim stack, so essenstially, 5th shocks have two rebound shim stacks. Minute forks use a spring loaded rebound check valve. Don't know what swingers use, but I imagine a shim stack like the 5th due to length/packaging constraints.
My propedal is an 04 AVA R. If that helps any? I was wondering if you run lower pressure do to the propedal damping? Also you said it was pretty mild compression. I weigh #150 with gear? Do you think the standard propedal is about right? I am still tuning it looking for that sweet spot.
Thanks for any additional info
tom schoonveld said:
My propedal is an 04 AVA R. If that helps any? I was wondering if you run lower pressure do to the propedal damping?
nothing, it's mechanical and not dependant on air pressure like the 5th element is.
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.


Darren Murphy
Push Industries
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The check shim stack does in fact operate like an additional shim stack. There are a number of "tunes" for both the main piston shim stack and the check shim stack. Our check shim stack is often referred to as the "low speed stack" where the main piston shim stack being heavier requires more force to open (in fact, they both affect the overall range, neither are isolated as low speed or high speed only). Partly, this is to keep the shock from acting like a pogo stick on the rebound stroke even if the rebound adjuster is turned all the way out. Also, both the main piston stack and check shim stack are dished, allowing for preload that is adjusted with clamp shims or negative clamp shims. The rebound needle basically adusts what point, or speed the main piston stack takes over.

From the sounds of it, you work for Progressive. As for the check stack producing rebound forces, that's interesting for sure. With hydraulic forces being what they are with high leverage frame designs, and with such a small stack c-cliped to the bolt, you must me getting just the slightest amount of force being created.

Well, it is preloaded, and it is a relatively small shim (od) for the size of clamp diameter. You are referring to the old bolts, since I took over the 5th line of shocks in my employment here (the 5th coil's been around about a year longer than my employment here), that bolt irritated me. I've changed it to use a button head cap screw as a check shim clamp.
platform damping

Hey guys,
It's great to see you interacting with the forums. You guys are way over my head. Does platform damping such as propedal affect mid to high speed and the way the shock acts thruoghout its stroke or is it only low speed? Also can you run lower air pressure in a platform shock?
Any info would be a huge help.
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.
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