Any ideas? Damping not functional for initial 10mm of rebound stroke - '12 Float RP23

[brettf]

Damping not functional for initial ~10 or ~15mm of rebound stroke.

Shock is 2013 or 2012 Fox Float RP23 (not CTD) Kashima-Coat with high volume sleeve.

The shock compresses normally. However, as it begins to rebound, the first 10mm or so of rebound stroke is undamped (or barely damped - hard to tell) - it pops back quickly in initial rebound and then almost feels like it tops out/catches, and the rest of the rebound stroke is damped as the shock continues back to sagged position.

So it almost feels like it tops out - like a clunk/thud as the initial rebound is "caught" before the rest of the rebound stroke is damped. Obviously, it's not actually topping out because it is nowhere near the top of the stroke, but that's how it feels when it catches.

Quick check shows it is holding air, has Float fluid, seals appear normal. Internal volume spacer is in normal position. Same behavior at low pressures (can be experienced by hand with shock off bike) and at high pressures (as felt on bike). I did not remove high volume sleeve or replace can with low volume to test, but popped can open to take a look inside.

Crashed my brains out recently; seems like timeframe of this starting roughly coincides, but not exactly... not that there is any indication of the shock taking a hit when I crashed.

Any ideas?

[kidwoo]

Crashing isn't going to do anything to your shock.

Fox air shocks just do that when they get used. It's annoying. I've never popped one open to look at the damper but I've always assumed it was either shims breaking or the damper fluid has off-gassed enough that you have a void in the fluid before the rebound shim stack catches.

What bike is it on? If it's something with a vertical shock mount, turn the shock upside down and see what happens.

Either way, it's time for a rebuild.

[brettf]

It's on a TRc, that while relatively new, has seen a ton of time. Shock displays same behavior upside down, right side up, sideways, shaken, or stirred.

[300hp]

There is air in the oil, or oil in the air of your damper, depending how you want to look at it. The dampening oil is kept under pressure by the internal floating piston, which has a 300-400 psi nitro charge behind it. Some air has gotten into the dampening oil. Since fox is butt-tarded you can't service it yourself. Send to push or fox service center, depending on how long you want to wait. Might get a discount from fox or free service if it's new enough. I had a dhx air start doing that after a few weeks of riding and they took care of it for me. For the price the rebuild will cost, might want to consider a used monarch or a dhx air if you had any desire to go that direction. Both are easy to service/bleed yourself with a little know-how which is nice if you ride all year round and want to save some cash.

After alot of riding, every rp will do that, and you'll have to do the same thing to it (unless you have a friend who services snomo/atv suspension and has a nitro tank and nitro needle and some 7mm o-ring cordage)

[brettf]

My buddy at PUSH thought it was aerated, crimped check shim on rebound circuit, or general boost valve shittiness. I really hate RP23s. Officially, that is.

Thanks dudes.

[kidwoo]

I really hate RP23s.

That makes most of us.

It seems like that shit happens far too soon and far too often.

[Finstah]

Yeah, I think that actually has something to do with the Boost valve. The Boost valve is supposed to be position sensitive and kick in when the shock gets deeper in it's stroke. You may just be feeling that compression spike on the back end when the shock is rebounding.

I could be completely wrong too. Get the damper serviced and that should answer some questions. Or, just roll it as it does sound kinda par for the rp23 course.

Edit : sounds like 300hp may have a good idea of what's going on too...

[300hp]

srsly, if your frame can fit it, and you have a choice, go dhx air every time. You can put a shim or two in the high volume can to give it some ramp up, and it doesn't have a nitrogen charge. With a little know how it is super easy to purge a little air out of the oil if it gets in there, and if you are hands on, there are a bunch of good threads on mtbr about bleeding and oil changes. Still not a great shock in my opinion, but way better than rp23z. If you don't mind a little weight, the roco air is, in my opinion, the best air shock out there. Shreds all day long, great coil feel, the wc has useable high speed compression, and it has lots of mid stroke support. Also, you can call marzocchi tech support, and they'll answer the phone in a few rings, talk to you like a real person, answer your question, even if it involves modding, servicing, or taking something apart, and help you get riding again. I've had 100% positive experiences dealing with them. Even on something like my frankenfork I built. One of the guys had built his own, helped me sort things out, and never said anything dumb, like "you voided your warranty" or plz send to push.

[brettf]

I've never used a Roco, so that's good feedback on that - I may have to check one out one of these times.

X-Fusion is shipping me a 2012 O2RCX shock. It should hopefully work well on the bike with an X-Fusion fork already on the front end. I can finally ditch the entire 'high-end' Kashima coat bullshit on my bike. The O2 is coming with a 'custom tune' for my frame, whatever that means, so we'll see how that works. Pricing is too good to pass up and I'm impressed with my XF fork and its damping.

I really miss the old Fox stuff. All metal dampers (or at least more metal), lasts forever, amazing damping (especially when modified to run heavy oil), just quality stuff. The new Fox stuff just doesn't hold a candle. I mean, it's light, has high-tech slick coatings, cool features, but c'mon. Build dampers that actually, uhh - damp, and build them to last.

This is all IMHO of course. I do know plenty of people who really like the new Fox stuff. They really like it. Like-like it even... but not me. Hate-hate it. End rant.

[300hp]

yeah, I got to test an 02 rcx on the single speed slope frame my friend built. Really nice shock. Rides taut and firm without being too jarring. You know that ride quality BMW gets? like that.

[brettf]

Taut and firm... just like my haunches.

Good to hear on the O2. I'll post up my thoughts on it.