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RS Revelation Dual air issue

hamplanethamplanet Posts: 8
edited July 2013 in MTB workshop & tech
Hello guys. I've got a problem with my 2009 Revelation (Dual air, motion control with POPloc, 140mm). I'm pretty sure I know what the issue is, but thought I'd throw it out there for suggestions, just in case I have missed something simple! Although the bike is a 2009 model, I bought it last year second hand and it was like new. The previous owner had bought it for a weekend in the lakes and then it had just sat in his house for 3 years unused. I don't ride as often as I would like, so to be honest the fork has had a very easy life so far...

On a recent ride I noticed that the fork was not achieving full travel. It still felt plush through the available travel and appeared to be working reasonably well, however it was only getting about half way through the stroke before stopping. It almost feels like it is bottoming out, not harshly, but it won't go any further. I got the bike home and let all the air out of both the + & - springs to see if this would allow the fork to be compressed fully. But after measuring it, it is only achieving 70mm of travel instead of the full 140mm.

I am pretty competent when it comes to home servicing and would be happy to have a go at the basic stuff like a lower leg service, but I don't want to go as far as full service just in case I mess up and make thing worse! I am reluctant to send off for a service because of the cost, but will do if this is the only option.

My guess is that an o-ring has failed and oil has leaked down into the lowers, causing them to hydrolock. Any other suggestions?

Posts

  • WhipItWhipIt Posts: 52
    edited June 2013
    Removed - total bollocks, shows what I know!
    The volume in the lowers doesn't change when the fork is actuated, so extra oil in the lowers won't matter (and they're big, so it would have to be a lot of oil anyway). Less oil in the damper will, if anything, make it easier to achieve full travel.

    I would guess too much oil in the damper?
  • nicklousenicklouse Posts: 81,520 Lives Here
    and in the Tech FAQs viewtopic.php?f=40073&t=12652233
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • hamplanethamplanet Posts: 8
    Cheers for the input guys. nicklouse that link basically describes exactly what is happening! So off to TF they go! My wife's going to kill me...
  • hamplanethamplanet Posts: 8
    or any other reputable Rockshox service center as they are all great...
  • supersonicsupersonic Posts: 82,708 Lives Here
    get the kit from ebay and have a go - is pretty straight forward!
  • hamplanethamplanet Posts: 8
    I am thinking about it! I enjoy the tinkering side of bikes. I've watched all the vids and that. I just don't get a lot of time and I worry I may make it worse if I do something wrong! I know it would be a lot cheaper and once I've got the extra tools and oil etc I'll be able to do it again in the future.....mmmmmmmmmmm
  • WhipItWhipIt Posts: 52
    I don't get how extra oil in the lowers limits travel - the plunger rod thing is of a fixed length, so the volume of the damping chamber changes but the volume in the lowers stays as is (except for the volume of the stachions as they move down, which is negligible). What am I missing?
  • supersonicsupersonic Posts: 82,708 Lives Here
    It's not negligable - a 32mm wide pipe, closed off at the end has to drop 150mm in total. If too much oil is in the space it can't move!
  • WhipItWhipIt Posts: 52
    I thought the end was open - the plunger that forms the bottom seal of the damping chamber stays in the same position at the end of the damping rod, it doesn't move downwards. Only the outer shell of the stanchions moves down into the lowers, which is the negligible bit.
  • The RookieThe Rookie Posts: 27,747
    Not sure what you are saying...

    The lowers form a cylinder, as the 32mm wide stanchions come down into the cylinder (in bump) like a piston they take up the volume, if the lowers are filled with oil (or anything else!), once the stanchions hit it, they will stop and not go any further (OK a little oil will go up the sides and the piston rod volume doesn't change but I'm keeping it simple here)
  • supersonicsupersonic Posts: 82,708 Lives Here
    The end of the stanchion is plugged, with just the much smaller damper rod passing through, fully sealed.
  • WhipItWhipIt Posts: 52
    GOT IT! Thank you!! Forgot about the plug in the bottom of the stanchions!!!
  • hamplanethamplanet Posts: 8
    A quick update for anyone who might be interested. I ended up emailing Sram tech and discussing my options for service kits. Got a tip off that I could use a basic service kit intended for a 2012 fork. This kit is a seal kit with everything I needed and is only £15. All in I'm only down £32 so far. Stripped my forks last night and found a all of the damper oil in the lower leg as suspected. Other than that, the forks are immaculate. Even the sponge wipers are still in good nick. So glad that I am doing it my self. So far!
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