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  1. #1
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    06 Reba Team Dual Air 60/60 recommendation?

    I'm trying to dial in the fork on my Flux, and I've read the common settings are 60% of riders weight for positive, and 60% of that for negative. Why is that, when RockShox recommends starting at 100% of the positive for the negative pressure. 60% of the positive pressure in the negative side does not get you the recommended 15% to 25% of sag. So what's with the 60/60 recommendation?






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    I go for around 60% of my riding weight in the positive, but I put the same pressure in the negative too. I weight 165 and I use 105+/108- and I get 24mm of sag. Sometimes I'll drop the neg a few psi if I find the rebound packing up on really fast hits, but usually this is close.

    I find the 60%+/60% of that for negative to give me too little sag. If I go with too little in the negative, then I get annoying top-out.
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  3. #3
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    Thanks, I'll give the 60% of my dressed for riding weight a shot, and do a little experiementing with the negative. I'm wondering if it is necessary to set up the compression and floodgate in order to do the 60/60 method? Wouldn't it be best if I had the compression set to full open until I dialed in the positive and negative perfectly first? Also, are there any internal changes between the 2005 and 2006 Reba Dual Air forks?

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    Good job!

    Quote Originally Posted by royta
    So what's with the 60/60 recommendation?


    Disregard the following comment unless you are CDTofer - Hey, are you happy now?
    In short answer, yes.

    Actually in longer version (since you are very detail oriented) you might like to read these:

    Reba harshness thread
    Reba 'For Dummies' (ie FoShizzle) thread

    Warning this is long - Please explain Floodgate thread

    I got a lot of good info from these threads. As to your questions about floodgate and compression I still need to work on that as well. BUT, I do know they are independant of each other - as in set air pressure for sag and desired 'plushness' and then set compression and floodgate to fine tune the action of the fork. Now having said that, compression and floodgate settings are intertwined. As it is my understanding that Floodgate has more effect as you increase compression. Also I believe you need to set the Floodgate with compression set at full (ie locked)

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    Last edited by CDtofer; 03-17-2006 at 02:38 AM.

  5. #5
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    Thanks, I'll have a look at that last one. I had a Reba and there is some good info out there. Lots of it from Rainman. Lots of it on the 29er forum. I am trying to take that and put it to good use on my Revelation.
    FWIW I am about 190 in full gear and used about 110+/100- on the Reba. Let it break in some and it is a very plush fork with really good structural stiffness. I sold mine to a buddy and he absolutely loves it too.
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    Good info.

    Quote Originally Posted by bikerx40
    I go for around 60% of my riding weight in the positive, but I put the same pressure in the negative too. I weight 165 and I use 105+/108- and I get 24mm of sag. Sometimes I'll drop the neg a few psi if I find the rebound packing up on really fast hits, but usually this is close.

    I find the 60%+/60% of that for negative to give me too little sag. If I go with too little in the negative, then I get annoying top-out.
    That's exactly what I'm dealing with now. Too little sag and an annoying topout. I went w/ the 60/60 rule as well, but I'm going to bump up the negative pressure and see if it fixes the problems.

    I like the fork, but it is a bit harder to setup than my old Vanilla

    Dave

  7. #7
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    Some of the posts on CDTofer's first link just don't make any sense.
    Quote Originally Posted by lanpope
    All this REBA talk has got me thinking about my settings -

    Should I consider lowering my settings even if I am getting full travel. Seems like lower PSI settings may cause me to bottom out more often/harder.

    FWIW I am 155 geared up and I run about 115 pos and 100 neg w/ rebound fully fast and compression wide open. Fork doesn't seem real plush, but it is better than the squisy mess that it was at the recommended settings.

    LP
    Quote Originally Posted by heavyg
    Ianpope-

    Try lower pressure with slower rebound. Worked for me

    First I need to make sure my definition of slower rebound is the same as everybody elses. Doesn't slowing down the rebound (heavyg's post) mean you are increasing the rebound damping, meaning it takes longer for the fork to extend? OK, now that we have that straight, wouldn't a lower positive pressure also make it harder for the fork to extend against a given amount of down pressure (rider's weight)? Then why lower the pressure and and increase rebound damping at the same time? Wouldn't that make it double slow on the rebound?



    Here's another oddball post from him:
    Quote Originally Posted by heavyg
    I had been running 150 pos and 140 neg at my 220#. Lately gone to 132 pos and 80 neg and like it a lot so far (a 60%, 60% rule of thumb). Lower negative pressure definitely seems to have less sag and less "stiffness" or "harshness". Highly recommended.

    Also learning that slower rebound settings do indeed seem to "make up for" lower pressure settings in trems of stiffness and feel.

    Shouldn't a lower negative pressure increase the fork's "stiffness" and "harshness" in it's travel?



    OK, now the following doesn't make any sense at all.
    Quote Originally Posted by JoelM
    ...so, let me see if I've got this right: The manufacturer's instructions on the negative air chamber are completely bass-ackwards? ie, contrary to the owners manual, less negative air pressure makes the fork more compliant to small bumps?
    Lately I've noticed that my Reba feels rather harsh over quick bumpy stuff, so I raised my negative pressure significantly. This thread leads me to believe that perhaps that was the wrong thing to do.
    I've always kept my negative pressure lower than my positive pressure, with both slightly below factory recommendations, but from what I'm reading here, it sounds like i need to drop them both by about 30psi!
    Quote Originally Posted by Rainman
    ...Exactly.. they got it wrong.

    Drop your pressures, use a little less in the negative chamber...try it.


    It works ..


    R.

    This must just magically work with the 60/60 rule. I guess I better give it a try before I start saying these ideas are defying logic.

  8. #8
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    Quote Originally Posted by royta
    First I need to make sure my definition of slower rebound is the same as everybody elses. Doesn't slowing down the rebound (heavyg's post) mean you are increasing the rebound damping, meaning it takes longer for the fork to extend?
    Slower rebound = more rebound damping = longer for fork to extend


    Quote Originally Posted by royta
    wouldn't a lower positive pressure also make it harder for the fork to extend against a given amount of down pressure (rider's weight)?
    You're correct here. Lower positive pressure = less spring force to extend the fork back to full extension.

    Quote Originally Posted by royta
    Then why lower the pressure and and increase rebound damping at the same time? Wouldn't that make it double slow on the rebound?
    Yes. Making both of these changes at once would have a compound effect and make it double slow.

    Quote Originally Posted by royta
    Shouldn't a lower negative pressure increase the fork's "stiffness" and "harshness" in it's travel?
    IMHO, yes. I don't agree with Rainman on this, but I believe his point is that a lower negative pressure will create a flatter spring-rate curve. This flatter curve means that your fork will use more travel over a given bump. The graph below shows that 60+/60 of that in neg. versus 60%+/same psi neg. See how the lower negative pressure creates a lower slope of the line? IMHO, I think that he's feeling the effect of quicker rebound (less packing up; fork can extend fully after each impact before reaching the next impact), which results from lower negative pressures. If you run higher negative pressures, then you need to run faster (less) rebound damping settings.
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  9. #9
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    Why the 60/60 recommendation in the first place then? Why not run 60/100 (100% of positive) and run faster rebound? This gives you more sag, which let's the tire drop better, and probably gives a plusher feel. If it's plusher, than why are people saying it's too harsh? Is this something you just have to try in order to understand?

    edit - I do see your point though. Less sag means the fork travels more over a given bump, which means it is obviously quite plush. I guess I will have to try both styles and see what I like.

  10. #10
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    Roy,
    I gave you the 60/60 rule and pointed out these examples to show that RS had it wrong with the pressures printed on the fork leg. From what you posted it seemed like you should be running the lower of the two pressure ranges since you said you were not getting enough sag (from your OP on Shocks) The 60/60 rule is a good place to start, and in truth I am still working on my settings (its too fockin cold here to dial it in perfectly) but I know that I already like a higher neg setting than the 60/60 rule - I started there but now I am close to the same pressure in both pos and neg chambers.
    (100 pos/90-95 neg.)

    You didnt quote all of Rainmans post. He was talking about dropping pressures in both pos and neg. I think he said he is running 80/80 and he weighs more than you or I do. He has said he likes a very plush fork. His point was he thought it was better to run both pos/neg at nearly the same pressure which I personally would agree with. Just my opinion of course.

    Still, I would like to hear some others chime in and see how they are setting their Rebas and/or Pikes.

    Just for the record:

    My weight: 170 (ish)
    Pos air: 100 lbs (Thinking about dropping another 5lbs)
    Neg air: 90 lbs (gonna bump it up to 95 and then again to 100 and see how it goes)
    Rebound: One full turn from full fast
    Compression: Full open (havent attached pop-lock yet, so I have no choice at the moment)

  11. #11
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    Quote Originally Posted by royta
    Why the 60/60 recommendation in the first place then? Why not run 60/100 (100% of positive) and run faster rebound? This gives you more sag, which let's the tire drop better, and probably gives a plusher feel. If it's plusher, than why are people saying it's too harsh? Is this something you just have to try in order to understand?
    It's just some rule-of-thumb that somebody came up with as a 'solution' to Rock Shox's incorrect/poor air pressure recommendations published in their User Guide. I've tried every combination of pressure & rebound setting that I can think of, and came back to 105/108'ish (1 click of rebound = very fast) every time. For Moab, I was doing more drops and stuff and went up to 120+, but for my local terrain I stick with the lower pressures.

    Bottom Line: Use what works for you, and your local terrain. Positive Psi = more bottom-out resistance. Negative psi = required initial force to get the fork moving at the begining of travel and top-out prevention.
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  12. #12
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    Roy - I'm not sure I agree with BikerX on this issue. I run my negative air pressure about 5 to 10lbs higher than my positive. As I understand the Reba (putting aside the floodgate and compression knob for now), the positive air pressure setting controls your compression rate and sag. The higher the pressure, the more compression resistance and less sag. The negative pressure controls the rate of rebound as a function of resistance against the positive air chamber. The higher the negative pressure the more active the fork will be to bump inputs (i.e. a faster rebound). Running a negative pressure lower than the positive results in a firmer initial platform and a less active ride. If you run a higher negative air pressure you would want to increase the rebound damping somewhat if the fork feels too active or reduce the negative air setting.

    The floodgate and compression dials should only be adjusted after you find your preferred air set up. Floodgate is adjusted with the compression dial in lock mode. Floodgate only controls the threshhold at which the bump input activates the blowoff valve. In full open flood gate, you'll notice the compression knob has very little effect on the fork's resistance to bob and bump inputs. As you increase the floodgate setting, the compression dial becomes more and more effective in resisting rider inputs and trail inputs/compression. Essentially, the FG and Compression dials are a means to finetune the suspension on the fly after you set your air pressures. In full closed FG and full Compression "Lock", you essentially have a locked out fork with a high threshhold blowoff. With both wide open you achieve the maximum plushness/lowset compression damping setting. Just ignore the FG and Compression dials until you find your optimum pos and neg air settings - then fine tune from there depending on trail conditions.

    I found the only way to set your air settings is to start with the recommendations in the manual then fine tune it on the trail, riding over the same sections of trail again and again. Bring a note pad or digital dictophone to record your adjustments and final numbers.
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  13. #13
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    Quote Originally Posted by cutthroat
    Roy - I'm not sure I agree with BikerX on this issue.....the positive air pressure setting controls your compression rate and sag. The higher the pressure, the more compression resistance and less sag. The negative pressure controls the rate of rebound as a function of resistance against the positive air chamber.
    Let's assume that you are running zero pressure in the negative chamber. If the fork was in full compression, then the positive chamber is really small and the pressure is very high. Since there wasn't any pressure in the negative chamber, then there is nothing to resist the fork from rocketing back to full extension. Therefore, the fork rebounds quicker with less pressure in the negative chamber.
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  14. #14
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    These are quotes are out of the Reba manuals ('05 and '06):

    "Negative air pressure effects the amount of force required to initiate suspension travel.
    Negative air pressure works with bump input AGAINST the force of the positive air
    chamber. More negative air pressure results in a suspension set-up that is more active,
    especially to small bump input. Less negative air pressure results in a suspension setup
    does not move or "bob" under rider input or small bumps."

    "Negative Air Pressure: Start with pressure equal to positive pressure, and decrease or increase as desired. More negative pressure = more active initial compression stroke." (i.e. less compression damping with higher neg. pressure)


    "Positive air pressure determines the amount of force required to compress your fork.
    More positive air pressure will result in less suspension sag and higher bottom out
    forces. Less positive air pressure will result in more suspension sag and lower bottom
    out forces."

    I haven't done your hypothetical BikerX about using no negative air, but I think if you ran just the positive air pressure and zero negative and pushed down on the fork it would compress but it would not rebound at all - i.e. it would get stuck down and stay there. I think this was the problem experienced with some of the early Rebas - the seals between the pos and neg chambers were not air tight and riders were getting stuck down forks because the negative air chamber was bleeding out so there was no rebound force. This happened to me in a race last summer. The fork comrpessed down to about 80mm of travel and parked there. I still had some bottoming resistance fortunately, but the negative spring was about at zero. Bottom line - regardless of the theory behind it, we both agree you need to get out there and tweak the thing on the trail.
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  15. #15
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    Quote Originally Posted by cutthroat
    These are quotes are out of the Reba manuals ('05 and '06):

    "Negative air pressure effects the amount of force required to initiate suspension travel.
    Negative air pressure works with bump input AGAINST the force of the positive air
    chamber. More negative air pressure results in a suspension set-up that is more active,
    especially to small bump input. Less negative air pressure results in a suspension setup
    does not move or "bob" under rider input or small bumps."

    "Negative Air Pressure: Start with pressure equal to positive pressure, and decrease or increase as desired. More negative pressure = more active initial compression stroke." (i.e. less compression damping with higher neg. pressure)


    "Positive air pressure determines the amount of force required to compress your fork.
    More positive air pressure will result in less suspension sag and higher bottom out
    forces. Less positive air pressure will result in more suspension sag and lower bottom
    out forces."

    I haven't done your hypothetical BikerX about using no negative air, but I think if you ran just the positive air pressure and zero negative and pushed down on the fork it would compress but it would not rebound at all - i.e. it would get stuck down and stay there. I think this was the problem experienced with some of the early Rebas - the seals between the pos and neg chambers were not air tight and riders were getting stuck down forks because the negative air chamber was bleeding out so there was no rebound force. This happened to me in a race last summer. The fork comrpessed down to about 80mm of travel and parked there. I still had some bottoming resistance fortunately, but the negative spring was about at zero. Bottom line - regardless of the theory behind it, we both agree you need to get out there and tweak the thing on the trail.
    I don't disagree about any of the quotes from the manual. More negative pressure = better small bump compliance. Higher negative pressure = less small bump compliance and more initial force required to get the fork moving. However, both positive and negative pressure affect sag to some degree; the pressures work together to determine sag.

    I believe the issues with the reba seals were causing the positive air to bypass the piston and move into the negative chamber, which stuck the fork into compression. This is the same thing as the Fox Float rear shocks getting stuck down due to positive pressure invading the negative chamber.

    Go try releasing the pressure in your negative chamber and you'll see how fast it rockets back to full extension.
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  16. #16
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    While you guys were typing I was riding the Revelation.
    115+/110- gorgeous (yep, that's the color of the sky right now) weather, and used almost all of my travel.
    Life does not suck.

    I got most out of the DHX-A too. I think I am going to ease off the PP next ride out.
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  17. #17
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    I went for a ride about an hour ago, and used 100/90. As mentioned a few times here or there, I'm about 165 when dressed and watered for riding. It seems fine, but then again, I don't have much experience with today's forks.

    cutthroat - I think that more negative pressure will work against the positive chamber. More negative will allow the fork to compress quicker, and in turn it should also take longer to rebound.

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