DHX 5.0 air pressure question- Mtbr.com
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  1. #1
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    DHX 5.0 air pressure question

    Just wondering what everyone else does. How often do you check the air pressure? Do you check it every ride? Have you found the air pressure drops between rides-if so, how much does it drop. I'm asking because I've had a lot of bad luck with SPV chambers holding air-yes I know this is not an SPV chamber.

    In addition, I know some of the variation in air pressure is accounted for by the air pump. What I'm asking is how much the air pressure drops between rides and how often you pressure up the chamber. Mine seems to return to 150lbs every time I check it regardless of how much I pressure it up.
    Thanks,
    turtle with new wheels

  2. #2
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    Good questions. Here's another. How can one tell how much pressure drop is due to reengaging and pressurizing the pump and meter?

    The DHX air chamber has a very small volume. Reinstalling the pump prbably sucks up a quarter to half that volume alone. I would guess there is no accurate way of checking the pressure, after one disengages the pump. Even the pumps that have little air loss on dis-engagement still require a fair bit of air to charge.

    I don't have any experience but I would guess it's worth checking once a week, at least until you get a feel for things. I doubt it looses much air even after a month, unless there's a real problem. But for saftey I'll be checking mine weekly.

    But I'm sure our man Tscheezy has the exact measurements in psi and bar
    Faster is better, even when it's not.

  3. #3
    No, that's not phonetic
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    I have only heard of one guy who's DHX may have lost pressure on its own. Mine seems to keep aired up just fine. I recently aquired one of those pumps which does not lose any air when you remove it, so I know exactly what pressure is in there when I take the pump off. Of course it drops when I reattach and teh shock pressurizes the pump, but this is a very predictable drop due to the pump design (Supergo Aeron).

    On a different point, I notice the BV has a much larger effect on suspension movement (bob) than the PP knob does. @100psi BV the bike does exhibit a lot of suspension movement no matter what the PP setting, but @150psi BV it is pretty much solid underfoot. Too much BV (over 150) does not feel so good though.
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  4. #4
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    The position of the bottom out adjustment knob has some effect on the air pressure too. Where do you have yours set?

    I checked mine every ride at first. Never was any air loss, so now only about once a month.
    Nothing to see here.

  5. #5
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    Quote Originally Posted by tscheezy
    ...I recently aquired one of those pumps which does not lose any air when you remove it, so I know exactly what pressure is in there when I take the pump off....this is a very predictable drop due to the pump design (Supergo Aeron).
    I got one of those from Performance.($14) A nice design. I can see how it prevents loss when disconnection.

    Quote Originally Posted by tscheezy
    On a different point, I notice the BV has a much larger effect on suspension movement (bob) than the PP knob does. @100psi BV the bike does exhibit a lot of suspension movement no matter what the PP setting, but @150psi BV it is pretty much solid underfoot. Too much BV (over 150) does not feel so good though.
    This seems to shed some light on what I found in my testing. BV pressure slides the window but apparently not in a linear fashon. At higher pressures BV increments don't seem to increase the platform by as much as it does with the same pressure increase at a lower (middle) starting point.
    Faster is better, even when it's not.

  6. #6
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    Quote Originally Posted by SSINGA
    The position of the bottom out adjustment knob has some effect on the air pressure too. Where do you have yours set?

    I checked mine every ride at first. Never was any air loss, so now only about once a month.
    Good point, and don't forget to redo the pressure whenever you change the BO setting. It changes the air chamber volume thus increases/decreases the BV pressure accrdingly. Also its probably easier to turn the BO knob if you air-down the BV first...just don't cycle the shock until you represureize it.
    Faster is better, even when it's not.

  7. #7
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    Good job! Air Pressure Settings

    Boy, ask a question and get good answers very cool. I keep forgeting about the Supergo air pump-sounds like a great idea-I'll try and pick one up this weekend. Thanks for the tip on the BV settings-there are so many variables when it comes to setting up the DHX-just depnds on how much you want to fiddle.

    I've been fooling with my shock settings for a couple months. Finally, last weekend I jumpped on my bike and it was perfect-have not touched a thing since. I think I backed off the BO adjuster about 3/4 of a turn from fully compressed and run the PP adjuster at 8 clicks. I thijnk there are 2 or 3 threads showing above the spring collar.

    My air pressure settings are pretty consistent-just about everytime I check the pressure, it's right at 150. I think the one week rule is a good guideline. But I'm going to wait two weeks and see how it goes. Like you guys said-once you find the setting you like-you can tell right away if the ride quality changes.

    Thanks for good info.
    turtle

  8. #8
    DGC
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    min to max change

    Quote Originally Posted by Turtle 1
    Boy, ask a question and get good answers very cool. I keep forgeting about the Supergo air pump-sounds like a great idea-I'll try and pick one up this weekend. Thanks for the tip on the BV settings-there are so many variables when it comes to setting up the DHX-just depnds on how much you want to fiddle.

    I've been fooling with my shock settings for a couple months. Finally, last weekend I jumpped on my bike and it was perfect-have not touched a thing since. I think I backed off the BO adjuster about 3/4 of a turn from fully compressed and run the PP adjuster at 8 clicks. I thijnk there are 2 or 3 threads showing above the spring collar.

    My air pressure settings are pretty consistent-just about everytime I check the pressure, it's right at 150. I think the one week rule is a good guideline. But I'm going to wait two weeks and see how it goes. Like you guys said-once you find the setting you like-you can tell right away if the ride quality changes.

    Thanks for good info.
    turtle
    Just a word on what I have found is that the pressure changes 15 psi. when going from one extreme to the other with the BO adjuster, it was mentioned here already that it changes but the number I come up with each time i checked this was 15 psi. difference from say min BO setting to max setting. I checked it both directions too. Keep this in mind when making adjustments on the BO adjuster, It might be worth making a psi. check after doing a BO adjustment of more than 1/4 change of the total adjustment range offered. This is with the BV at 100 psi.
    At 150 psi. in the BV the change in pressure from min to max BO setting will be more. After a bunch of checks at 150 psi., It seems to come to around 25 psi. of a change.
    Last edited by DGC; 02-05-2005 at 11:38 PM.
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  9. #9
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    Quote Originally Posted by DGC
    Just a word on what I have found is that the pressure changes 15 psi. when going from one extreme to the other with the BO adjuster, it was mentioned here already that it changes but the number I come up with each time i checked this was 15 psi. difference from say min BO setting to max setting. I checked it both directions too. Keep this in mind when making adjustments on the BO adjuster, It might be worth making a psi. check after doing a BO adjustment of more than 1/4 change of the total adjustment range offered. This is with the BV at 100 psi.
    At 150 psi. in the BV the change in pressure from min to max BO setting will be more. After a bunch of checks at 150 psi., It seems to come to around 25 psi. of a change.
    Thanks for the tip on the pressure change, I would not have thought of it. From the beginning, I started letting the air out of the chamber before I made any adjustments-that way it was easier to turn the adjuster. Now I'm glad I let the air out of the chamber-I might have blown a seal do to the increase in pressure. whew-that was a close call. Sometimes I do the right things without knowing why.
    thanks,
    turtle

  10. #10

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    Max 125psi

    It is recommended you only adjust the BV when the BO pressure is at a max of 125psi-probably for this pressure increase reason.

  11. #11
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    Quote Originally Posted by Turtle 1
    .... Sometimes I do the right things without knowing why.....
    .................Turtle, why are you dumping the 6 Pack? I thought you liked it so much....


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