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Saucy Size
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Discussion Starter · #1 ·
My setup:

DHX Air 5.0 installed on a 2003 Stinky Deelux. Started it in the "linear" mount position and recently moved it to the "progressive" mount position after repeatedly blowing through all the travel while pedaling down the street and hopping off curbs.

Current pressures are 285# in the main chamber and 170# in the boost valve chamber, with about 6 clicks in on the Propedal thingie.

My loaded (larded!) weight these days is maybe 235# or so. That includes a very full backpack, body armor, FF helmet, etc. (And, yes, it includes a holiday-induced roly-poly tummy).

What I'm wondering is, why is it taking so much air pressure just to achieve the correct basic sag? I'm within 15# of the shock's absolute limit, and I have not yet tried hucking it off anything higher than about 2' to flat. I'm terrified I'm going to blow apart my new $500 toy.

Ditto on the boost valve. If I go with any less pressure, I blow through all my travel on curbs. But if I go with any more, it bucks me off in the hard stuff.

I'm concerned that maybe the boost valve went below its minimum pressure at some time and screwed up the negative chamber. What would I be looking for in the shock's performance to let me know if that's what happened?

I'm also wondering if anyone's experimented with the DHX in both linear and progressive mounts, and which they preferred. As it is now, I'm no longer blowing through the travel but I'm also not getting into the last 1/2" or so of stroke. This strikes me as a good safety margin.

p.
 

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Saucy Size
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4,482 Posts
Discussion Starter · #3 ·
SSINGA said:
Where do you have the Bottom out dial set?
All the way open, for now. Thanks, I forgot about that setting. So the total setup is:

7.875" x 2.25" shock (IIRC)
285# in the main chamber
170# in the boost valve
6 clicks in on Propedal
bottom-out fully out (chamber is as large as it can get)
rebound about halfway in
mounted in "progressive" position on the frame

p.
 

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Elitest thrill junkie
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37,461 Posts
Paul B said:
My setup:

DHX Air 5.0 installed on a 2003 Stinky Deelux. Started it in the "linear" mount position and recently moved it to the "progressive" mount position after repeatedly blowing through all the travel while pedaling down the street and hopping off curbs.

Current pressures are 285# in the main chamber and 170# in the boost valve chamber, with about 6 clicks in on the Propedal thingie.

My loaded (larded!) weight these days is maybe 235# or so. That includes a very full backpack, body armor, FF helmet, etc. (And, yes, it includes a holiday-induced roly-poly tummy).

What I'm wondering is, why is it taking so much air pressure just to achieve the correct basic sag? I'm within 15# of the shock's absolute limit, and I have not yet tried hucking it off anything higher than about 2' to flat. I'm terrified I'm going to blow apart my new $500 toy.

Ditto on the boost valve. If I go with any less pressure, I blow through all my travel on curbs. But if I go with any more, it bucks me off in the hard stuff.

I'm concerned that maybe the boost valve went below its minimum pressure at some time and screwed up the negative chamber. What would I be looking for in the shock's performance to let me know if that's what happened?

I'm also wondering if anyone's experimented with the DHX in both linear and progressive mounts, and which they preferred. As it is now, I'm no longer blowing through the travel but I'm also not getting into the last 1/2" or so of stroke. This strikes me as a good safety margin.

p.
The problem is the leverage ratio of the bike, coupled with 235lbs.

On a bike like the 6pack, it just won't work for someone that heavy, the air pressure required is just too high with the 3:1 leverage ratio. I think your stinky is a bit better with a 2.25" stroke shock for 6" of travel, but that's not much better, so you run into the same problem. Running air shocks on a highly leveraged bike with a heavy rider is just too many negative factors to make it work decently.

You could probably sell the DHX-A for a good amount, and I highly recommend the DHX-C over it for all riding, due to the better mid-stroke support and how it feels more consistant over a wider range of speed and terrain.
 

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not so super...
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Jayem said:
The problem is the leverage ratio of the bike, coupled with 235lbs.

On a bike like the 6pack, it just won't work for someone that heavy, the air pressure required is just too high with the 3:1 leverage ratio. I think your stinky is a bit better with a 2.25" stroke shock for 6" of travel, but that's not much better, so you run into the same problem. Running air shocks on a highly leveraged bike with a heavy rider is just too many negative factors to make it work decently.

You could probably sell the DHX-A for a good amount, and I highly recommend the DHX-C over it for all riding, due to the better mid-stroke support and how it feels more consistent over a wider range of speed and terrain.
Not really Jayem. I hit the scales at 224lbs lately and run the DHX air quite successfully on my Pack. Yes, I am at the extremes of the setup range so I don't have a large set-up range but it does work well.
 

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carpe mañana
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7,297 Posts
When I first got my DHXair on my 5 Spot, it got bottomed out so hard that something got bent inside of it and the metering valve for the oil would not close, essentially rendering the bottomout reservoir useless. I don't think that's the issue in your case, however. What most likely is going on is that some of the positive air pressure escaped into the negative spring, forcing you to really pump up the positive chamber. I would deflate the shock, compress it, while it is on the frame, and unscrew the air sleeve. Take it off, clean it up, make sure the O and Q rings look good, relube and reassemble and try again.

How much travel does your bike get out of the 2.25" stroke?

_MK
 

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carpe mañana
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SSINGA said:
Wasn't the 2003 Stinky a 5" travel bike?
I have no idea. It sounds about right, but I really don't know, and I'm too lazy to check. If that's the case, then the leverage ration on that shock is close to the 5 Spot. This would reinforce my theory, in my mind. ;)

_MK
 

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No, that's not phonetic
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My DHX Air needs considerably higher pressures than my RP3. For drops, with my 180 pound butt I need 270psi in the main air spring (BO half way, BV 140psi). For general dorking around I drop back down to 240psi. That's still a lot. I don't know how 200+ pound people run the DHX Air on 3:1 bikes.
 

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Saucy Size
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4,482 Posts
Discussion Starter · #11 ·
tscheezy said:
My DHX Air needs considerably higher pressures than my RP3. For drops, with my 180 pound butt I need 270psi in the main air spring (BO half way, BV 140psi). For general dorking around I drop back down to 240psi. That's still a lot. I don't know how 200+ pound people run the DHX Air on 3:1 bikes.
Okay, that's reassuring. I've started hearing rumors from other DHX-A users that the air pressures are way, way higher than other air shocks. On my 5.5, I run right around my body weight in pressure to achieve a 30% sag. On my old Super V, it was also body weight.

The frame's travel is 6", so it's a 2.67:1 ratio. Not the highest-ever, but kinda high I guess. I do believe the progressive mount helps a bit.

p.
 

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noMAD man
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Yeah, high pressure.

Paul B said:
Okay, that's reassuring. I've started hearing rumors from other DHX-A users that the air pressures are way, way higher than other air shocks. On my 5.5, I run right around my body weight in pressure to achieve a 30% sag. On my old Super V, it was also body weight.

The frame's travel is 6", so it's a 2.67:1 ratio. Not the highest-ever, but kinda high I guess. I do believe the progressive mount helps a bit.

p.
The other guys have pretty well covered it, but just to add another person with similar results, yes they seem to run noticeably higher pressures. I've tried 2 air shocks on my Bullt before, and none of them required this high a pressure. You asked about what symptom you get if the boost pressure had been too low with the shock stroked. I'm not positive, but I think you'd get some oil in the boost chamber or boost chamber air bled into the damper oil. If either, you'd see a little oil mist when hooking/unhooking your air pump or the air in the damper oil would cause a noticeable loss in rebound control.

High pressure aside, the shock seems to work really well. It's truly a strange shock. I'm curious what PUSH may come up with later on mods for this shock.
 

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tscheezy said:
... 200+ pound people run the DHX Air on 3:1 bikes.
Hey, that's me! 6 Pack frame with 3:1 ratio, 225lbs rider plus gear.

For general trail riding I would have 270-275 psi in main air chamber, 150-160 psi BV and bottom out all the way in. That way I can use almost all the travel for normal trailriding and just bottom the shock on 3' to flat.

For anything bigger, I'm pretty much forced to use 300psi in the main air chamber and possibly add more to the BV for increased bottom out resistance. Or just switch to the DHX-C which is much easier to set up for us heavy people on high leverage ratio bikes.

Another issue with the DHX-Air on high leverage ratio bikes is getting the rebound slow enough. With 270psi in the main air chamber I'm running the rebound as slow as it gets, and it's still not as slow as I'd prefer.
 

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not so super...
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Mr_Slash said:
Hey, that's me! 6 Pack frame with 3:1 ratio, 225lbs rider plus gear.

For general trail riding I would have 270-275 psi in main air chamber, 150-160 psi BV and bottom out all the way in. That way I can use almost all the travel for normal trailriding and just bottom the shock on 3' to flat.
Slash - try increasing you BV psi to 170 to keep it from bottoming. That is what works for me with the bottom out all the way in and 275psi in the main. I run only 4 clicks of propedal and the rebound can go as slow as I want it.
 

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SSINGA said:
Slash - try increasing you BV psi to 170 to keep it from bottoming. That is what works for me with the bottom out all the way in and 275psi in the main. I run only 4 clicks of propedal and the rebound can go as slow as I want it.
Increasing the BV pressure has indeed a great effect on bottom out resistance. I've tried everything from 75 to 200psi, and found that if the pressure is below 140 the shock wallows a lot while seated and it bottoms easily. Around 150-160 is good for general trailrinding. At 170 and above the shock is quite resistance to bottoming, but the ride gets kind of harsh. I feel that I loose some small bump performace, although it's great for hitting the big stuff.
 

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not so super...
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Mr_Slash said:
Increasing the BV pressure has indeed a great effect on bottom out resistance. I've tried everything from 75 to 200psi, and found that if the pressure is below 140 the shock wallows a lot while seated and it bottoms easily. Around 150-160 is good for general trailrinding. At 170 and above the shock is quite resistance to bottoming, but the ride gets kind of harsh. I feel that I loose some small bump performace, although it's great for hitting the big stuff.
If you back off the pro pedal you get the small bump compliance back even while running the "high" BV psi.
 

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No, that's not phonetic
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I can't go above 150psi boost valve without starting to feel the small trail features. My PP knob does not a whole lot. Totally irrespective to BV pressure in my experience too, but ymmv.

You guys can swoon all over your Double Barrels and Chubbies. My next rear shock experiment is going to be a Pearl.
 

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Damn, awesome thread!

I've got only a few rides in with my DHX-air installed on a turner RFX-spot. (5", 2.5:1). The first ride, I tried Push-recomended settings for my weight of 130 in the main, 100 boost. That gave me about an inch of sag on a 2" stroke shock. So then I went up to 165/130, still way too much sag. I'm 175lbs. No hucking that ride!

Last ride I went up to 180/130 and things are better. BO half way in, no PP for singletrack, full PP for fire-roads. Feels pretty good. I think I may need more pressure yet, for wheelie drops and bigger hucks. Kind of scary- I'll need a new shock pump to get these kind of pressures. Last year I ran an RP3 and 170psi felt great. In general I'm not real comfortable with running over 150psi in air shocks, at that point I am questioning fox's design decisions which require such high pressures, seemingly redundant adjustments, and legacy frame modifications. The shock just feels too linear to me. And this is all with 5" rockers- these high pressures are not encouraging me to try 6" mode.

Not too mention, my pushed vanilla RC feels better with less sag and really is not much heavier. also fewer controls, set & forget.

Tuning headaches aside, the DHX-air does feel very good. Jury is still out- at this point I like it, but not enough to keep it. I will definately keep tweaking on it.....any suggestions, let me know.
 
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