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Discussion Starter · #1 ·
so far everything i've seen involving a DHX A and a VPP bike involves lots of switching to a not DHX A and VPP. Seems like nobody likes the combo very much. I've heard of people changing the air can to an RP3 can so that it ramps up faster. It seems like theres nothing fundamentally different about DHX A's and DHX C's when it comes to the damper - they're basically the same. To me, it sounds more like an issue of oil volume, has anybody experimented with this and VPP, such as putting more oil in the can? Similar oil in marzocchi to adjust the progression...

I'd be curious to see this. Also, to see who's running DHX Coils and how they like them. Aside from being slightly more progressive, they should theoretically feel pretty similar if you get the amount of oil in the air shock correct
 

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noMAD man
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I don't know this for a fact, but are you sure the DHXC and DHXA have the same damper design? PUSH will modify the DHX coil all day long, but they won't touch the DHX Air for some reason. As poorly as the DHXA performs, you'd think PUSH would be sitting on a goldmine if they offered DHXA PUSH mods. The fact that they don't gives me the idea that the dampers are a different design. As I said, I have no inside knowledge of the exact damper design comparison between these two shocks.
 

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Discussion Starter · #3 ·
my understanding is hearsay, but Udi over on ridemonkey has had both and has taken them apart several times and posted pictures of the whole damper assembly for both. If he says they're the same, (i think theres something slightly tweaked in the way they mount up inside the shock, but basically the same deal) then i'll believe him. I'd be interested to see the results of a DHX A with oil heights tuned. If anybody has one and is curious to see what they can do, i'll pull up the instructions that he posted!
 

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noMAD man
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OK...I'm still curious that if the damper is the same as the DHX coil, why doesn't PUSH cash in on this potential goldmine? I'm getting the impression from the Udi fellow...sounds like some excelllent work on his part BTW...that the problem lies in the air chamber size and characteristic on the DHX Air. I would think an outfit like PUSH would have no problem in making different volume reducers or similar devices to manipulate the air volume. This comes back to that well discussed issue as to why Fox didn't manufacture for retail sale the well established AVA option on the DHXA. I rode a prototype DHXA with an AVA sleeve on a Yeti ASX at the Fox tent at Interbike in '04.

I still didn't see anyone with the damper apart. Did I miss it? I saw posts suggesting that the shim stack should be manipulated/tuned, but I didn't see anyone who'd done it. I don't know...I'd still like to know if the coil and air DHX shocks are identical dampers, then why PUSH wouldn't jump on the aftermarket service of this shock. Darren...?

Manitou did something fairly unique with their Evolver line of rear air shocks. They have strong mid-stroke, or at least mid-stroke performance that is equal to a coil, as anyone who's tried one can tell you. So it's quite evident that an air shock can be designed and/or manipulated to steer away from the traditionally soft mid-stroke. It's still seems strange that Fox didn't apply something as relatively simple as their AVA sleeve on the DHXA which was already available to them.
 

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I called PUSH about the DHX-A vs. the DHX-C and was told along similar lines the shim stack or lack of is the issue. In the Float series I have an RP23 and RP3 , I feel the RP3performs better - a call to PUSH verified this as the RP3 has a different shim stack style.
 

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Discussion Starter · #8 ·
there should be a cutout view of the DHX A somewhere, lets see if i can dig it up

http://www.ridemonkey.com/forums/showthread.php?t=204317&highlight=air+shocks

anyway, I'm not exactly certain why Push hasn't touched this - seems curious to me as well. The DHX A doesn't seem to have problems with overheating because of the way its setup, and its one of the lightest A shocks on the market. An AVA setup would probably weigh a bit more, and take away one of the big advantages of the DHX A over a DHX C (namely thats its a half lb lighter then a Ti Coil setup), and who needs an AVA when you can just get some oil in there. On paper, this shock is great - it seems bizarre to me that 4 years after it came out, it still has exactly the same problems and almost nobody knows how to fix it, but I would love to see the results of doing this style of tuning and being put on a VPP bike - it would be interesting to find out if its the leverage ratio that F's this shock over, or if its just the DHX A's poor setup that makes it feel like poo
 

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noMAD man
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William, I'd have to differ with you stongly on the AVA. The weight gain would be marginal. I've handled AVA Floats in the past, and the weight difference seems slight to me. The ability to change the spring curve in the air shock when terrain or preference changed would be awesome. The addition or deletion of oil or other volume modifying mediums might be fine for a one-time deal, but having a true and effective trailside tuning element would be better IMO. Also, wouldn't adding oil add weight in itself?...if the lowest possible weight is a major factor?

I don't know, William...that pic of the cutaway doesn't give much comparitive detail. Keen's comment was interesting on the Floats, and I'd almost bet there's some difference in the damper between a DHXC and DHXA...purely speculative, of course.
 

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there is a damping difference between DHXC and DHXA. In the DHX C, the main oil chamber and the reservoir are in line.With the dhxA, to connect the main oil chamber to the reservoir and to use the boost valve, the oil has to pass via the shock shaft. In a classic shock, the hollow shock shaft allows to control low speed compression and rebound. Mid to high speed damping is the work of the shim stack on the main piston. The zero bolt arrangement on push kit closes the shock shaft so that all the damping relies on the main piston shim stack. Doing so on a DHX A would close the connection between the main oil chamber and the reservoir: the boostvalve and the reservoir would be totally useless.

I assume that to use the boost valve correctly, the shock shaft on the DHX A has to remain widely open, reducing the damping action of the main piston shim stack in compression. Here is why the mid to high speed damping feels so light on the DHX A: it has to be considering the particular construction of this shock.
 
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