Has anyone found a good solution to the perceptible clunk from some propedal shocks? It appears to be freeplay in the valve which let it slam shut at the start of the stroke rather than close by itself before the stroke begins.
Always worth checking, but I can guarantee no play in this current one.electrik said:Probably way off, but maybe something with the DU-bushing for the shock? Had a similar issue with a friends fox float and the clunk was triggered by the initial force to open the pro-pedal damper, it was causing the bushing to move and clunk first before beginning the stroke.
Fox switched to a grooved replenish seat in the reservoir back a few years ago. Quite common in dampers to reduce the area that a shims seals on, therefore lessening the chance of it to not seal properly causing gaps or clunks. If yours is this older model then that is most likely the cause. You can generally check this by increasing and decreasing the propedal using the external dial. If it get s better the softer you set the dial than this is most likely the culprit. With our services on these older shocks it's procedure for the techs to hand the reservoirs over to our machine shop to have the groove installed.I have this on a DHX 5.0 with Propedal, that came on a used frame I bought. It can feel like a loose bushing or loose headset. It drives me crazy!
Thanks for this info Darren. Guess I should send the shock in!:thumbsup:PUSHIND said:........Fox switched to a grooved replenish seat in the reservoir back a few years ago. Quite common in dampers to reduce the area that a shims seals on, therefore lessening the chance of it to not seal properly causing gaps or clunks. If yours is this older model then that is most likely the cause. You can generally check this by increasing and decreasing the propedal using the external dial. If it get s better the softer you set the dial than this is most likely the culprit. With our services on these older shocks it's procedure for the techs to hand the reservoirs over to our machine shop to have the groove installed.
Darren
He may also take a look at how many of the small PP spring preload shims were installed. Often decreasing the preload will work well also. I can't say I have ever needed to replace the piston retaining bolt to solve this but a bolt shy on drilling depth may need replacement to optimize the OEM PP settings.PUSHIND said:The stock FLOAT and Van-R shocks use a spring loaded plastic poppet valve built into piston bolt. This valve acts as a one-way valve so that the Propedal effect can be created.
The knock or slight gap in damping whether audible, or felt while pushing on the seat, is from the tolerance between the bolt and the plastic poppet. Shocks with higher levels of Propedal from the factory tend to exaggerate this noise or feeling.
In your case, you've either come across a couple that are a bit out of spec, or have highly preloaded compression valving.
It generally has no effect on the ride quality, but it some cases we do exchange the bolt for a different one when it shows up exaggerated on our final dyno inspection.
Darren
The shocks that he's referring to don't utilize PP spring preload shims so that couldn't be the issue. As I mentioned, the problem he's experiencing is pretty rare.He may also take a look at how many of the small PP spring preload shims were installed. Often decreasing the preload will work well also. I can't say I have ever needed to replace the piston retaining bolt to solve this but a bolt shy on drilling depth may need replacement to optimize the OEM PP settings.
Wow, that's weird. Glad you got it sorted out. I've been running my IFP at ~225 psi of air (not N2) for several months and it's been fine so far at my 140 lb weight. The RP23 has been my first air shock in the last 3 years (previously coils), and I'm actually quite impressed how good it feels when tuned right.Dougal said:Bit of an update, I found the problem and it was instantly obvious.
I assumed from the old "unscrew the aircan and push the shaft" method than the gas charge was still good. But it wasn't.
This shock had somewhere along the line lost enough of it's gas charge that it sucked itself full of air. Enough that venting the IFP valve sent the piston right down the bottom of the shock and still left pressure in the body of it. The oil came out as bubbly as a freshly opened coke can, similar colour too. It's back together as it should be and with no perceptible clunk so the propedal valve is indeed fine. To keep it that way I may need to invest in some high pressure nitrogen gear, 300psi probably isn't enough to keep the seal head pressurised in hard use but might be okay on the wife's intense.
Sitting in the top of it was a small but fragile wire clip, I have no idea why it was there and I've never seen one in the parts diagrams before. If anyone is interested I'll throw up a photo.