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Discussion Starter · #1 ·
Hi all,
As the title says, what does pro pedal actually do?
Is it a general compression damping, or a low speed only damping that blows off in big impacts?
In another word: Does Pro pedal affect the bike's bottom out resistance?
 

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Nightmare on Lyrik st. VI
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No. Once the shock starts moving, it's like it was never on.
 

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Pro Pedal was developed by Fox to help eliminate pedal bob. Its a great system that really works. Next time you have your bike, put your weight on the saddle with Pro Pedal on, and then off. You will see how much more sag there is with it off. With the Pro Pedal off, it allows the shock to become much more active on a discent or in another sketchy environment without letting the shock bottom out. For racing most will just leave Pro Pedal on, because it makes the bike more stiff and less prone to suspension dive when climbing or sprinting. Pro Pedal basically is a damping system, it would be like cranking up the air pressure in your shock. When Pro Pedal is engaged it compresses where all the air is in the shock, to a smaller portion of the air canister. When Pro Pedal is disengaged, it allows the air to move into a bigger space, therefore letting the suspension more a lot more freely.

Hope it helps!
 

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Propedal is a marketing term created by FOX to describe a digressive compression damping force curve. Digressive force curves have been around long before bicycles had suspension. Digressive compression tunes use preloaded valving to build compression quickly in order to give a firmer feel at low shaft speeds. It does effect the total compression curve and will have an effect on full travel or bottoming, but it puts more emphasis on the low speed characteristic of the shock.

Propedal has nothing to do with the air system of the shock. With adjustable systems such as the RP3 or RP23 you can activate a bypass hole in the shock which allows oil to free bleed past the valving. Propedal "off", and the bypass hole is open allowing fluid to move freely. Propedal "on" and the bypass port is closed off forcing the oil through the preloaded stack.

Darren
 

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I get the digressive damping curve concept here, but would anyone care to really explain how such a damper works? Just out of curiousity.
 

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Discussion Starter · #6 ·
Sorry, I'm not very smart...
The shock I'm talking about is a DHX 5.0
So according to Darren, if I turn the Pro pedal knob to the + direction, I get a bit more damping through all the compression travel, even it's a high speed (big hit) compression.

I'm I correct?
 

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PUSHIND said:
Propedal is a marketing term created by FOX to describe a digressive compression damping force curve. Digressive force curves have been around long before bicycles had suspension. Digressive compression tunes use preloaded valving to build compression quickly in order to give a firmer feel at low shaft speeds. It does effect the total compression curve and will have an effect on full travel or bottoming, but it puts more emphasis on the low speed characteristic of the shock.

Propedal has nothing to do with the air system of the shock. With adjustable systems such as the RP3 or RP23 you can activate a bypass hole in the shock which allows oil to free bleed past the valving. Propedal "off", and the bypass hole is open allowing fluid to move freely. Propedal "on" and the bypass port is closed off forcing the oil through the preloaded stack.

Darren
Money. Best description ever. :thumbsup:
 

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I came here to ask a question about propedal and its already being discussed! Any way, I bought a fox rear shock on ebay. I think it is a R2 or R3, I really cant remember. I know that it is from 2004 or 2005. The previous owner had it sent to PUSH for the total rebuild. The shock has a blue lever and a red dial. The blue lever was disabled when they installed the pro pedal. So my question is, what does the red dial do? What does turning it all the way clockwise do as oposed to counter clockwise? Ive done small tests with it both ways, just dropping of a curb, but I cant tell much difference. But, I really dont know what I need to be looking for either. Anmy help would be greatly appreciated.
 

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EDR
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Red dial = rebound adjuster, at least on every fox shock I've had.

You should see a great difference from full CW to full CCW in how fast the bike pops back up (rebound) when you throw all your weight on the saddle .
 

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, but would anyone care to really explain how such a damper works? Just out of curiousity.
>>>>
Propedal has nothing to do with the air system of the shock. With adjustable systems such as the RP3 or RP23 you can activate a bypass hole in the shock which allows oil to free bleed past the valving. Propedal "off", and the bypass hole is open allowing fluid to move freely. Propedal "on" and the bypass port is closed off forcing the oil through the preloaded stack.
Push tuned an RP3 for me one time to make the Max PP feel like a lockout but with great blowoff and the Min PP setting (no off setting on RP3) as if it was off.
So, basically they made the bypass valve hole smaller for Max and larger for Min.
Btw, if you don't have PP on a shock you can simulate it a bit (but without the shock able to sit high in sag) by turning red knob to min. rebound and then for more active, to more rebound.
 

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Thanks, I get it now. Now I want to find an exploded view of the damper.
 

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PUSHIND said:
Propedal is a marketing term created by FOX to describe a digressive compression damping force curve. Digressive force curves have been around long before bicycles had suspension. Digressive compression tunes use preloaded valving to build compression quickly in order to give a firmer feel at low shaft speeds. It does effect the total compression curve and will have an effect on full travel or bottoming, but it puts more emphasis on the low speed characteristic of the shock.

Propedal has nothing to do with the air system of the shock. With adjustable systems such as the RP3 or RP23 you can activate a bypass hole in the shock which allows oil to free bleed past the valving. Propedal "off", and the bypass hole is open allowing fluid to move freely. Propedal "on" and the bypass port is closed off forcing the oil through the preloaded stack.

Darren
I digress but what does 'digressive', in relation to suspension technology, mean?
 

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GrantB said:
Thanks, I get it now. Now I want to find an exploded view of the damper.
There is one out there somewhere, I saw it in some bike magazine along with the DT Swiss Nude shock for the Spark. (Several years ago.)
 

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campisi said:
I digress but what does 'digressive', in relation to suspension technology, mean?
anden had a good go at explaining it.

Digressive means that the graph of force against shaft speed starts steeply and then levels off. The implementation usually involves a port orifice and a preloaded shim stack that opens up to allow extra oil flow as shaft speed increases.

The example of a classic digressive damping characteristic is given by the red line in the graph below (by anden):

 

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Slow Patrol
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foxracing said:
So according to Darren, if I turn the Pro pedal knob to the + direction, I get a bit more damping through all the compression travel, even it's a high speed (big hit) compression.
I have never liked the characterization of high speed damping as "big hit". I read this used all the time. It is really how fast the axle tries to move and not how big a movement. A .5" rock can be a "big hit". On the uphill at 4mph this would be a low speed thing but on the DH at 18mph it will be a high speed damping thing. At least that is the way I see things.
 

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Elitest thrill junkie
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NormanPCN said:
I have never liked the characterization of high speed damping as "big hit". I read this used all the time. It is really how fast the axle tries to move and not how big a movement. A .5" rock can be a "big hit". On the uphill at 4mph this would be a low speed thing but on the DH at 18mph it will be a high speed damping thing. At least that is the way I see things.
It's not, the guy you quoted was not correct in his terminology. Drops and jumps are low shaft-speed events, medium sized bumps or just sharper transitions cause high-shaft speed impacts, and yes even very small bumps can easily be high-shaft events, so high/low speed is all about the shaft speed, not the bike's speed. The original guy is right that increasing the propedal affects the entire range (what the guy from Push was saying).
 

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Equal opportunity meanie
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amillmtb said:
Pro Pedal was developed by Fox to help eliminate pedal bob. Its a great system that really works. Next time you have your bike, put your weight on the saddle with Pro Pedal on, and then off. You will see how much more sag there is with it off. With the Pro Pedal off, it allows the shock to become much more active on a discent or in another sketchy environment without letting the shock bottom out. For racing most will just leave Pro Pedal on, because it makes the bike more stiff and less prone to suspension dive when climbing or sprinting. Pro Pedal basically is a damping system, it would be like cranking up the air pressure in your shock. When Pro Pedal is engaged it compresses where all the air is in the shock, to a smaller portion of the air canister. When Pro Pedal is disengaged, it allows the air to move into a bigger space, therefore letting the suspension more a lot more freely.

Hope it helps!
The PP thing is just for damping....so how would your sag change at all? Damping = speed control. Spring and preload = ride height = sag.

Turning the adjuster has nothing to do with where the air goes either. Air only goes in one place in any DeCarbon style shock. Do you have any idea how a standard shock even works or are you just doing your best to recite the most recent Fox advertisement you saw?

My assessment of the whole PP valve on the DHX is that it's nice for pedalling and chassis control, but is nowhere near as digressive as it needs to be to avoid high speed spikes, which end up being spikes at mid-speeds with how restricted it is once it's anything but 1 or 2 clicks in.
 

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The PP thing is just for damping....so how would your sag change at all? Damping = speed control. Spring and preload = ride height = sag.
I don't know how, I just know that it does. Iow setting pp, shocks sit more into the travel when weighted, less into travel on the higher pp setting when weighted.
Most XC/Marathon/Endurance oriented riders prefer this as it allows them to sit higher with higher pedaling leverage for climbing what they often intend higher platform for.
Thanks for graph above.
 

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Code Burr
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DHidiot said:
My assessment of the whole PP valve on the DHX is that it's nice for pedalling and chassis control, but is nowhere near as digressive as it needs to be to avoid high speed spikes, which end up being spikes at mid-speeds with how restricted it is once it's anything but 1 or 2 clicks in.
I totally agree and would even add that with 1 or 2 clicks in it spikes on mid speed stuff. I run mine with no propedal about 99% of the time to avoid this. So how do you fix it? Can you just pull or swap one of the shims out to make it more digressive?
 

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I have never liked the characterization of high speed damping as "big hit". I read this used all the time. It is really how fast the axle tries to move and not how big a movement. A .5" rock can be a "big hit". On the uphill at 4mph this would be a low speed thing but on the DH at 18mph it will be a high speed damping thing. At least that is the way I see things.
Correct....good example.

Drops and jumps are low shaft-speed events
Actually, drops and jumps are generally very high velocity events. Depending on the slope of the take-off, the face of a jump can be a low speed event, but generally not.

The PP thing is just for damping....so how would your sag change at all?
The reason it effects sag, is because with shocks that have a very high level of Propedal the riders weight doesn't overcome the preloaded stack. So with the PP "off" the shocks bypass port allows oil to freely pass and the shock can easily compress into position. With the PP "on" the bypass port is closed and the valving also remains closed making the damper ride higher in it's stroke because of the high force required to open the valving.

My assessment of the whole PP valve on the DHX is that it's nice for pedalling and chassis control, but is nowhere near as digressive as it needs to be to avoid high speed spikes, which end up being spikes at mid-speeds with how restricted it is once it's anything but 1 or 2 clicks in.
The PP valve is actually extremely digressive and un-restrictive once open. What you're sensing has to do with other settings in the shock.

So how do you fix it? Can you just pull or swap one of the shims out to make it more digressive?
The PP/Boost system in a DHX is not a shimmed mechanism.

Darren
 
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