Reverbs stop working on a somewhat regular basis. RS will repair or replace them, but sending them back takes time. So... can we fix these ourselves?
RS now offers the IFP height tool and a bleed tool. They don't seem to have published instructions however. Does anyone have accurate instructions for doing the IFP bleed?
The "push IFP all the way down and fill the inner tube with oil" approach isn't right. It results in incorrect IFP position.
I got seemingly good results by:
1.) Pushing the IFP all the way down.
2.) Filling the inner tube with oil.
3.) Putting the small piston back in the inner tube and screwing the cap on.
4.) Pushing the inner piston down with button depressed to displace oil into IFP chamber.
5.) Unscrewing the cap and checking IFP depth with IFP tool.
6.) Screwing the cap back on, moving the inner piston as needed to adjust IFP height (repeat 5 and 6 until IFP height is right). Finish with the inner cap on and tight.
The IFP height should now be right... next bench bleed and get the inner piston back to the fully extended position....
7.) Removing the small snap ring on the top of the post, pull out the washer and top cap, pull out the remote circuit piston with needle nose pliers. The IFP chamber should be separated functionally from the inner tube now since the remote piston is out.
8.) Pull the inner tube piston out until in fully extended position.
9.) Add oil through hole where remote piston goes until it is filled up to the narrow hole the thin part of the remote piston goes into.
Now IFP height should be ok, and your inner tube piston should be in fully extended position.
The result is a post that is firm when pressing down on the seat. Feels perfect, no movement. But... when the post is partially compressed, if I lift up on the seat the post extends. When I put the bike down it goes right back where it should, like there is a vacuum somewhere in there. I don't remember it doing this before...
What could be wrong? I am certain there is no air in the circuit.
That is the procedure for bleeding the remote line, not for bleeding the internals of the post. Bleeding the remote line is very easy, doesn't really require instructions. The internals are the mystery.
I'm coming up short on some comprehensive instructions too. I just started running a reverb and will undoubtedly be popping mine open at some point. So far so good, but its just a matter of time. I'm hoping its user serviceable as well.
I've been pouring over your procedure for a while now. It seems sound. FYI - i did just go check mine (only 3 rides old) and it extends the same way when lifting the bike. I have to "help it a bit by lifting the seat and pushing down on the frame at the same time. Same result that you have, seat lifts then when released suck back down. The "vacuum" is probably just the air chamber behind the IFP pulling back down.
Okay so I've successfully done mine now. I didn't use a...."bleed tool" or an "oil height tool". Instead of the bleed tool I just stuck a snug plastic pipe into the post head and clamped it with one of those red clamps.
Here is the reason for the "oil height tool": You want hydraulic fluid/oil above the bottom of the "poppet" valve (in green below), but you don't want fluid in the black (gap) next to the valve. It needs air in that black space, so that the valve can move downwards. When you press the button on the handlebars you are trying to move that valve downwards - but it won't be able to if you've got incompressible hydraulic fluid in that gap.
I just sucked a bit of fluid out with the plastic tubing - guessed it. I've probably got a little air in the internal hydraulics but not enough to notice any difference in performance.
p.s. Using a picture of the oil height tool, figuring out it's approximate real-world diameter, and doing some scaling I worked out that the markings on the height tool are, in fact, 100mm and 125mm from the bottom of the tool. Quite convenient. I have a 125mm travel post so pushed the IFP in 125mm.
p.p.s. You DO have to bleed the remote hose after this because you have opened the remote hydraulic system as soon as you remove the "poppet" valve.
I recently purchased a used Reverb which had about 1-2" of sag when fully extended. Once below about half length, the sag vanished.
After a lot of Googling and several trial-and-error attempts, I thought I'd document here how I fixed it as it may help others:
First I bled the remote circuit as per the SRAM instructions using the two syringes from the bleed kit (actually, a third party Avid kit, but it worked ok ) - no change to the sag
I then repressurised the air cylinder, which was a little low on air - no change
I then watched the four "full service" videos on the SRAM page, which while being cool, seemed to need proper parts to sort. "Specialist tools? We don't need no steeenking specialist tools...."
Here's how I finally fixed it. Assuming that the sag was air, I decided to try to get rid of it:
Depressurise the cylinder and, using the remote, fully depress the seatpost. Depressurise the seatpost again! You really don't want any air left in it or you'll get a face full of oil and metal when you remove the top circlip!
Clamp the post into a vice, taking care not to scratch it. I had no aluminium jaws, so used cardboard - worked ok
Very carefully, remove the small circlip at the top of the post. Even when pressure is removed, it comes out with a pop - be ready to catch the bits!
Remove the circlip, retaining washer and small metal top cap
You should now be able to see the main valve. Using needle-nosed pliers, remove it using the spike on the top.
You can now peer down into the main oil cylinder. I then carefully added enough oil to reach just past the bottom of the piston. (see below)
Replace the piston - it needed a firm wiggle to get it properly seated and pushed down.
Replace the small metal cap, washer and circlip.
Re-bleed the actuator circuit, as you've just emptied half of the oil out of it
Hopefully, you're fixed!
I had to repeat this three times until I found the correct amount of oil to have in the cylinder. Once done, however, the post feels like new and I'm well chuffed. Obviously, you can change any seals you come across, but I didn't bother. I'm going to see how I get on with it over the coming weeks.
This process is miles and miles from the one in the SRAM videos and, ultimately, sucks as it's hard to get all of the air out this way, but it's easy (takes me 10 mins) and needs no specialist tools other than the bleed kit (which you *do* need to bleed the actuator circuit and will need if you remove the top cap like I did).