• 06-15-2014
    shupack
    1 Attachment(s)
    First Rebuild (RS Revelation), big glob of grease..???
    Was surprised to find this when I removed the air shaft:

    Attachment 901323

    That's probably 1/4" glob of grease on top of the piston. The manual says a liberal coating of grease, but that seems excessive to me.

    Is there any valid reason for this? or was it some tech's last day and he just DGAF? It's working fine both before and after the rebuild.

    2012 RS Revelation RLT Ti (sat for 2 years, I bought it "new" this January)
  • 06-15-2014
    mtnbikej
    As you ride....the grease seems to migrate up. Even when I service my fork, the next time I open it up, it looks just like that.

    So yes, it is normal.
  • 06-15-2014
    shupack
    cool, thanks! seems strange though
  • 06-15-2014
    trailbildr
    Lump it on! If you don't, it might leak. It happens.

    Embrace the grease.

    mk
  • 06-15-2014
    shupack
    Quote:

    Originally Posted by trailbildr View Post
    Lump it on! If you don't, it might leak. It happens.

    sounds like a design flaw to me.


    We'll see, I put a light coating on, as directed.... If I start losing air I'll open it up again.

    Thanks for the advice!
  • 06-16-2014
    vicrider222
    Quote:

    Originally Posted by shupack View Post
    sounds like a design flaw to me.


    I put a light coating on, as directed....

    Thanks for the advice!

    Huh? What instructions are you following?

    From the SRAM service pdf for the Revs:

    "Apply a liberal amount of grease to the inside of the upper tube, from the end of the tube to approximately 60 mm into the tube."

    If you follow these instructions, you'll pretty much end up with what you have in the photo. I'm no suspension expert but I think the idea is that the grease gets thrown around as the fork shakes during the ride, so the walls are always lubed. If you go with a thin coat, the grease will get pushed to the top and stay there and your piston will run dry in the stanchion tube.
  • 06-16-2014
    shupack
    well ****... I read that twice and saw "light" instead of "liberal" both times... would that be considered a brain-fart? or a freudian slip?

    Either way, I read what I expected, not what I actually saw. Thanks for noticing my mistake. It's not tough to tear it down, I'll add some grease tonight.
  • 06-16-2014
    trailbildr
    You can add grease from the top. Just remove the air spring top cap. Quick work.

    mk
  • 06-16-2014
    shupack
    Quote:

    Originally Posted by trailbildr View Post
    You can add grease from the top. Just remove the air spring top cap. Quick work.

    mk

    I was just about to ask that. Thanks!
  • 06-16-2014
    freeclimbmtb
    When I called SRAM about upgrade options, they tech said the same thing.. "When you rebuild the air side, coat the seals, the inside of the tube, and put a big glob on top. Whenever the fork cycles, the positive chamber pressure will force the grease down into the sealing area to maintain the air seal and keep the pressure from creeping between the chambers." He also said while any heavy weight grease will work, PM600 Military grease is what they use and recommend for the air spring seals. The last one of these I did I used Belray waterproof motorcycle grease and it worked fine with no issues.
  • 06-16-2014
    trailbildr
    I use boring-old Slick Honey...

    mk
  • 06-17-2014
    freeclimbmtb
    Quote:

    Originally Posted by trailbildr View Post
    I use boring-old Slick Honey...

    mk

    So do I on everything but the air seals (also per SRAMs advice.) So Slick Honey on the dust wipers, everything on the damper side, and the top cap and shaft guide O-rings on the air side, and the PM600 on the positive and negative air piston seals. As I said, I used Bel-Ray waterproof grease on everything on the first rebuild I did and it worked just fine. As long as it's a smooth oil soluble grease I don't think it makes a whole lot of difference.
  • 06-17-2014
    shupack
    Quote:

    Originally Posted by freeclimbmtb View Post
    As long as it's a smooth oil soluble grease I don't think it makes a whole lot of difference.

    sooooo, wheel bearing grease from NAPA is a no? [/sarcasm]
  • 06-17-2014
    ktm520
    I've always used slick honey on RS air seals as well. Really, for the air seals, you can use just about any "general purpose" grease. Where you have to be careful with type of grease is anything that comes in contact with the damper oil. If you want something similar to the RS "PM600", look for a grease labeled "tacky". I have a tube of Lucas Oil "Red Tacky" that I use for various suspension parts, mostly coil springs. Think I bought it at Menards.

    I don't agree with the notion that the thick tacky grease gets pushed around by air pressure. When it heats up, it may flow a bit, but once the piston scrapes it off the wall, there it sits. Slick honey on the other hand will flow (not from pressure though) as the viscosity is much lower.
  • 06-17-2014
    freeclimbmtb
    Quote:

    Originally Posted by ktm520 View Post
    I've always used slick honey on RS air seals as well. Really, for the air seals, you can use just about any "general purpose" grease. Where you have to be careful with type of grease is anything that comes in contact with the damper oil. If you want something similar to the RS "PM600", look for a grease labeled "tacky". I have a tube of Lucas Oil "Red Tacky" that I use for various suspension parts, mostly coil springs. Think I bought it at Menards.

    I don't agree with the notion that the thick tacky grease gets pushed around by air pressure. When it heats up, it may flow a bit, but once the piston scrapes it off the wall, there it sits. Slick honey on the other hand will flow (not from pressure though) as the viscosity is much lower.

    I agree for the most part. I went with the PM600 because thats what the SRAM tech recommended. As for the piston scraping the grease off the walls, that's the intent behind the blob on top of the piston, that as the piston moves, it will drag the blob against the tube walls and help keep it coated. He actually recommended against using slick honey on the air seals BECAUSE it's such a thin grease. Im sure it works just fine, but like I said...I'm just parroting what they told me.
  • 06-17-2014
    ktm520
    Quote:

    Originally Posted by freeclimbmtb View Post
    As for the piston scraping the grease off the walls, that's the intent behind the blob on top of the piston, that as the piston moves, it will drag the blob against the tube walls and help keep it coated.

    That may happen for few cycles, but eventually it just sits like the big blob it is. It's an easy test. Leave off the top cap, smear in some fresh grease, cycle away, and see for yourself. You eventually end up with a blob on the piston and a ring around the top of the cyclinder just taking up volume.
  • 06-17-2014
    jps
    oil on top of air piston?
    Quote:

    Originally Posted by ktm520 View Post
    That may happen for few cycles, but eventually it just sits like the big blob it is. It's an easy test. Leave off the top cap, smear in some fresh grease, cycle away, and see for yourself. You eventually end up with a blob on the piston and a ring around the top of the cyclinder just taking up volume.

    Myself and a friend have been having issues with our 2014 SID 120mm RCT3 solo airs.............he has torn down, rebuilt, used the red grease per SRAM specs, even sent it back to SRAM where they rebuilt it, but his still has a lot of stiction, etc. I took my top air cap off my fork after some air leakage and noticed the big glob of red grease on top of the piston. I cycled it many times and did notice it just builds up on top of the piston. Would it be a bad idea to add a few ml's of red rum oil on top of the air piston? I know my Fox forks used oil on top of the piston to help keep it sealed, why did RS use grease? Thanks a lot! I have been following any threads on the newer RS's and their problems with stiction, air leaks, setting sag, etc.
  • 06-17-2014
    shupack
    I just glopped a bunch in (about 2 tablespoons) I'll pull the cap after the next ride and see what it looks like.

    I have noticed it's a SERIOUS PITA to set sag. I can check it 10 times without touching pressure, and get 10 different readings. I try to use the same method. Bounce on hands, bounce on feet, bounce hands, rock back/forth a bit to settle in. set the oring then lean back to get off and check. I'm at 85psi +&- chamber, I get anywhere from 30 to 45mm sag, with a 37mm target. The average of the readings is 37, so I'll go with that for a few rides...
  • 06-17-2014
    marpilli
    First Rebuild (RS Revelation), big glob of grease..???
    I use a heavy synthetic gear oil (90w) on top of the positive air piston.
  • 06-17-2014
    ktm520
    Oil will not stay on top of the RS piston like Fox, which uses a cup seal vice an oring. It quickly ends up in the neg chamber and eventually the lower.
  • 06-18-2014
    freeclimbmtb
    Quote:

    Originally Posted by ktm520 View Post
    Oil will not stay on top of the RS piston like Fox, which uses a cup seal vice an oring. It quickly ends up in the neg chamber and eventually the lower.

    Agree. O-rings are used in hydraulic applications all the time, but they are usually static (union joint as opposed to a sliding seal). Seals on things like hydraulic rams or accumulators usually use either cup seals like ktm said, or quad rings, or if they do use O-rings, there are usually several of them, and they are larger cross section rings with tighter tolerance on the piston/walls. (keep in mind your air pistons are plastic)
  • 06-18-2014
    marpilli
    First Rebuild (RS Revelation), big glob of grease..???
    Quote:

    Originally Posted by ktm520 View Post
    Oil will not stay on top of the RS piston like Fox, which uses a cup seal vice an oring. It quickly ends up in the neg chamber and eventually the lower.

    In my multiple SID overhauls, I haven't had any issue with the gear oil migrating into the negative chamber. If you want, I can provide links to RockShox/SRAM rebuild guide stating you should "Pour 3-5cc of RedRum into the top of the upper tube on top of the air piston. This will ensure long o-ring life, smooth stroke and less friction."
  • 06-18-2014
    ktm520
    Quote:

    Originally Posted by marpilli View Post
    In my multiple SID overhauls, I haven't had any issue with the gear oil migrating into the negative chamber. If you want, I can provide links to RockShox/SRAM rebuild guide stating you should "Pour 3-5cc of RedRum into the top of the upper tube on top of the air piston. This will ensure long o-ring life, smooth stroke and less friction."

    When you service the air side, there is still 5cc of oil on top of the piston after 30+ hrs??? You must have a freak of nature. I don't care what the RS service guides say. I haven't seen that recommendation for Redrum in awhile anyway, and the latest Solo Air guide definitely doesn't saying anything about oil. The solo air version is even worst than the dual air because of the negative transfer port. And, it has been well documented that the dual airs won't hold oil either. It's simple physics. An oring with light tolerance under pressure in dynamic conditions will not stop fluid from migrating. I've done multiple tests on DA forks and at best 5cc would last for 5hrs of use before it disappeared. It doesn't hurt anything, but it just doesn't have much of a useful life.

    The real issue is when it gets into the lower leg, which is effectively another low volume air spring. It doesn't take much change in volume or pressure in the lower leg to start causing problems.
  • 06-18-2014
    marpilli
    First Rebuild (RS Revelation), big glob of grease..???
    I have two SID forks left. At the next service I'll measure the fluid on top of the positive piston and provide an update.

    I certainly won't say it was a great design. Just simply sharing my experiences which seem to differ greatly from yours...
  • 06-18-2014
    ktm520
    I assume they are dual air springs?
  • 06-18-2014
    marpilli
    First Rebuild (RS Revelation), big glob of grease..???
    Yep. 2004'ish...

    One Team and one Race.

    edit: I also have a 2012 Reba (DA). But, I've had no reason to open the air spring, yet.
  • 06-19-2014
    honns
    I am pretty sure that when they changed to the new solo air (not the old style with the valve), they moved away from oil and suggest the glob of grease that has been mentioned above. I would be interested to hear if anyone who uses the slick honey finds any migration to the lower. You would ideally want some thinner grease so that it didn't blob up and leave the o-ring un-greased after a while but I could see migration issues happening.
  • 06-20-2014
    trailbildr
    I've tried the oil as a last resort when trying to run a problem to ground and it does stay put on top of the air spring piston.

    If you have trouble setting sag on your newer RS forks, remember that the new solo air system has a negative spring so you have to air up the fork, cycle it a few times to equalize the + and - air chambers then check sag. You can also air up fork, cycle it, re-check pressure, bleed some off if needed, then check sag. More of a PITA but this should help.

    mk
  • 06-20-2014
    shupack
    Quote:

    Originally Posted by trailbildr View Post
    I've tried the oil as a last resort when trying to run a problem to ground and it does stay put on top of the air spring piston.

    If you have trouble setting sag on your newer RS forks, remember that the new solo air system has a negative spring so you have to air up the fork, cycle it a few times to equalize the + and - air chambers then check sag. You can also air up fork, cycle it, re-check pressure, bleed some off if needed, then check sag. More of a PITA but this should help.

    mk

    Thanks,

    Mine is a dual-air, 2011 Revelation RLT Ti. 150mm (new old stock, installed in January).

    Should sag be read with the negative chamber pressurized or not? I've seen recommendations for both, the manual isn't clear, but looks like it should be pressurized.

    The manual states ideal sag is between 10 and 40%, that's a wide range for an "ideal" setting. Turner 5-spot, 140mm rear travel. suggestions on the turner forum are for 25% rear, 30% front sag for this bike. I've been running about 85psi to get 30% sag, but it never felt "right", not bad, but not in the sweet-spot.

    reading the other suggestions here I went with the chart on the legs, put it at 120psi (130 negative for a little more plush on the small stuff) WAY better feeling. More controlled, significantly less brake dive and I was much faster down, and uphill last ride. Havn't bothered measuring sag. I used about 3/4 of the travel, but I wasn't doing anything big, as it was wet/slippery.

    So, I'm still not sure if I'm setting it up right, but I'm getting closer to not noticing it/thinking about it during a ride.

    Now to true my damn rotors so I can forget about them too....
  • 06-25-2014
    shupack
    Update, after a few rides I opened it up and the grease was well mixed, but I think it may have been too much. In another thread I read a suggestion to add grease to get more of a ramp-up and prevent bottoming. Last ride I only got about 60% travel, kept lowering the pressure and nothing changed.... SO I scooped out a bunch of grease, I'm guessing it's about the ammt that was there when I opened it up the first time. How do I tune this thing? Most threads I've found just say "there's not a lot of info on tuning the revelation...."

    With 30% sag I'm at 85psi, which gives me terrible brake dive and feels very wallowy, not in control at all. per the chart on the fork my starting point is 120psi +/-, what do I do with the rest?

    Rebound, I think I have a handle on that.

    Compression/lockout - I've been using it like the fox CTD settings, correct or hands off?

    floodgate - more open = plusher, but does that contribute to brake dive at the lower pressure?

    I've put everything at the mid-point with 120psi +/- what do I adjust and which direction on next ride? I'm looking for a good mid point- all around performance, not XC race stiff, not free-ride big-hit soft. I guess that's a decent way to describe it.
  • 06-25-2014
    ktm520
    shupack, the short answer is run more air, less sag. Dive is countered more by spring force than damping force. Tune it for the support and small bump you seek. It will be a compromise. Don't worry so much about travel usage. There is a ton of info here on setting up dual air springs.
  • 06-25-2014
    shupack
    Quote:

    Originally Posted by ktm520 View Post
    shupack, the short answer is run more air, less sag. Dive is countered more by spring force than damping force. ....


    That's what I needed to know! Thank you!
  • 06-25-2014
    ktm520
  • 06-25-2014
    shupack
    DUDE! that's exactly what I needed. 95+/80- was perfect tonight. Great ride, bike felt like it was on rails. one click faster rebound and didn't think about it again.

    thank you!