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  1. #1
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    Sag for 150mm Revelation fork for low-weight rider

    I weigh 130 lbs with gear and have a 2010 RS Revelation 150mm U-turn fork on my Mojo. I am running 30% sag in back, and some MTBR posters have suggested that I should have a similar percentage of sag up front, even though the RS manual talks about 15-25% sag. Do you agree, even for a 150mm fork? (Am I supposed to have the same percentage sag, or just the same number of mm of sag?)

    So assuming that I want 30% sag, that's 45mm. In order to get that, MTBR posts have said that I start with the negative pressure at zero, and increase positive pressure until I get the right amount of sag. I then add negative pressure until it causes the fork to start sagging when I'm off the bike.

    Following those instructions, I have found that I get 30% sag if I have 50 psi positive and about 22 psi negative. Those numbers are much lower than RS recommendations of 90-115 psi. However, my fork feels fine on rides.

    Do my numbers make sense?

    Can I damage the fork if I have too low pressure?

    I have tried higher numbers such as 70 positive and 50 negative, but I find that while I can get 30% sag, the fork tends to sag a lot even when I'm off the bike.

    Also, I was trying to find a way to get the negative pressure close to the positive pressure so that I can have more small bump compliance, but couldn't find a winning combination.

    Thanks!
    Mark

  2. #2
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    Reputation: doismellbacon's Avatar
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    I haven't run this exact fork, but I've always done it like this on RS forks w/ adjustable air neg. spring....
    Start with the mfr's recommended settings for both + & - springs, and light comp & rebound damping, and don't worry much about sag at this point (it's good to check it and know what's happening, but don't stress about it), instead, just ride the snot out of the fork and adjust your pos spring so that you get full travel, or at least real close. THEN take a good look at your sag and see what's happening there. Being a light weight person, and therefore running relatively lighter pressures to get full travel, you'll probably find that you're sagging deep and can lower the psi in the neg spring to get a higher ride height, and have more available pos travel when at sag. Play with the neg spring pressure up and down to try out different sag/ ride height. Generally a higher neg pressure will produce more plushness in the initial to mid stroke, but you don't want so much neg pressure that you're sagging 50%, then the fork is ramping up abruptly after that...and it shouldn't be sagging when you're not on the bike.
    There's a lot more to learn about fine tuning...we haven't even talked about damping adjstments.. .but keep it simple and try to be disciplined about adjusting one thing at a time and then riding it so that you learn how that change translates on the trail......
    IMHO
    Last edited by doismellbacon; 11-01-2009 at 06:08 PM.

  3. #3
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    Reputation: merlin's Avatar
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    I'm in the process of putting together a build for MOJO SL and am leaning towards the same shock, because I want a remote lock out, and the fork weights less then the Fox. I have test ridden the Fox and it is a nice fork. I have not tested the RS and do not see a lot of them on the MOJO in this thread. So, I was wondering what you and others think of the fork??
    Ride to eat, Eat to ride.

  4. #4
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    I like the RS Revelation 150mm U-Turn, but don't have much to compare it to--my last fork was a 100mm Recon. One thing that I noticed is that the fork raised the handlebar height, and I understand that the Fox raises it less.

    I chose the 2010 Revelation over the Talas because of this review--
    2010 Fork Shootout: Fox 32 vs. RS Revelation (long) which concludes:

    We both agreed that the Revelation feels much more like an “all mountain” fork while the Fox feels more like a long-travel cross country fork. The usable travel and stiffness issues are a deal breaker. Additionally, the Revelation is cheaper, has a better warranty, and performs nearly as well (if not better) than the Fox in nearly every situation.

  5. #5
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    I find that air pressures are more of a guide. Having said that the general idea with sag is to measure the rear with rider on saddle and arms dangling down and the fork whilst in the so called attack position. Having sag differences front and rear is not bad per se but you need to understand that that will change the dynamic geometry of the bike. So 30%rear 20% front will slacken the bike a touch and vice versa. The revelations are a nice fork and are easy to service ( at home) to keep them running super sweet.

    Given most manufacturers aim for an average weight rider of 11 stone approx then it is fair to assume that you may need some adjustment to damping if you are over or under this figure. This may be the case in your situation. And remember unless you are bottoming the fork a lot you should worry too much about air pressure. Its not like a Curnut/Avalanche etc where you need a minimum in a platform chamber

  6. #6
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    How is your fork holding up? I put this on my new Mojo SL also. Unfortunately it failed on my first ride.

  7. #7
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    Quote Originally Posted by sawbonz
    How is your fork holding up? I put this on my new Mojo SL also. Unfortunately it failed on my first ride.
    No problems in the few months that I've had it.

  8. #8
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    Did you ever get your forked dialed? 2 years later?

  9. #9
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    my RS revelation 150 sits at about 135mm when I am not on the bike. If I put more air in the positive chamber and less in the negative i can get it to 150mm but then the fork is too stiff. At 120lbs I run about 75psi in the positive and slightly more in negative because I like a plush ride. I also run about 30% sag on my mojo. I dont really see the point of having a bunch of travel if you are not going to use it. I have never bottomed out my mojo or my fork. The uturn on my revelation doesnt work however which is annoying. it's stuck at full travel. This is another reason i dont mind only getting 135mm out of it. I like the ability to change the travel for climbing and right now I cant.

  10. #10
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    Quote Originally Posted by fishercat
    my RS revelation 150 sits at about 135mm when I am not on the bike. If I put more air in the positive chamber and less in the negative i can get it to 150mm but then the fork is too stiff. At 120lbs I run about 75psi in the positive and slightly more in negative because I like a plush ride. I also run about 30% sag on my mojo. I dont really see the point of having a bunch of travel if you are not going to use it. I have never bottomed out my mojo or my fork. The uturn on my revelation doesnt work however which is annoying. it's stuck at full travel. This is another reason i dont mind only getting 135mm out of it. I like the ability to change the travel for climbing and right now I cant.
    If you pull on your fork to full extend it, can you get it to 150mm?

  11. #11
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    yes.

  12. #12
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    Remember there's an approx 60:40 weight bias towards the rear. So 30% sag at the back will mean 20-25 up front. I find if you go 30:30 then the forks get too soft in certain situations such as steep slow tech sections where you weight gets pushed forward and you are braking a lot

  13. #13
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    check this thread 2010 150mm Rockshox Revelation Settings Thread

    Also more air in the negative leads to better small bump compliance. I am 175 lbs geared up and run 85 positive and 90 negative. I also have the compression 1 click from lock out. This setup allows good small bump compliance and keeps the fork high in its travel during turns, breaking, or low speed compression events.

    Make sure to have the low speed compression set full open when you set the sag.

  14. #14
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    I run 80psi negative and 75 positive. That gets me 20% sag. When I'm not on the bike, there is about 10mm sag. I sometimes find that the sag off the bike is more, and then I remove the air from the negative chamber and pump it back to 80.

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