Avalanche is doing FOX DHX 3/4/5.0 SSD mod/Tune now.

Kntr · Dec 15, 2011

Nice... how much?

92SE-R · Dec 15, 2011

what happened to lsc and hsc adjustment knob?

stumpjump · Dec 16, 2011

Been on the table for about 3 years. Bummer it didnt pan out quicker. I ended up just doing the RC4 mod.

tacubaya · Dec 16, 2011

Bullcrew you need to try one of these badboys out:

Sandwich · Dec 16, 2011

le too late. Sold my sunday and DHX, and I refuse to buy a bike with another DHX unless it's ungodly underpriced.

tacubaya · Dec 16, 2011

Yep, pretty awesome shock.

And the air version feels just as sick

tacubaya · Dec 18, 2011

Just came back from riding some gnarly trails and the Vector HLR fcking blew my mind out.

The best shock I've ever ridden, absolutely amazing.

Ian Collins · Dec 18, 2011

complete opposite of my findings...what the hell are you comparing it to?

tacubaya · Dec 18, 2011

bullcrew said:
That's whats so great about SSD (speed sensative damper) it acts the same when deeper in the travel its consistant. The main reason that fox dhx shocks can feel like the xfusions and the rest now as well as be custom tuned from the start for $199. Cheap for a good upgrade.

Yeah.

The main advantage I can see for the X-Fusion is that it not only has LSC adjuster, but also HSC adjuster and volume adjust for the IFP. Much more tuneable on the trail. But Craig knows his shiat so if anyone is riding a POS DHX they can upgrade for cheap.

tacubaya · Dec 18, 2011

Ian Collins said:
complete opposite of my findings...what the hell are you comparing it to?

I've used DHX, Roco WC, Vivid coil and this Vector HLR

I'd say: Vector > Vivid > Roco WC > DHX

I need to get my hands on a CCDB to compare. Might be the only non tuned shock with similar performance.

Sov · Jan 4, 2012

^^^The reservoir pressure curves are interesting. Realistically though, you will never see 1500psi as the bump stop will never compress down to zero. I don't know how much it will compress down to - say 0.25"? If this is the case, then the resi pressure you'd get at bottom out would be roughly 800 psi, or equivalent to a a 300lb/in spring ramping up to a 350lb/in spring. Pretty subtle I reckon.

staike · Jan 4, 2012

Sov said:
Realistically though, you will never see 1500psi as the bump stop will never compress down to zero.

Oh yes it will. Tried compressing the shock without a spring on before? It's fairly easy to squeeze it out of the way on the DHX.

Sov · Jan 4, 2012

staike said:
Oh yes it will. Tried compressing the shock without a spring on before? It's fairly easy to squeeze it out of the way on the DHX.

Yeah but with a spring around the bump stop, it doesn't really have anywhere to go does it?

I'm a bit of a hack rider and even with an undersprung DHX, I never heard any metal on metal bottom outs so I'm assuming that I never actually achieved full travel.

staike · Jan 4, 2012

I've never thought of that, you're probably right!

tacubaya · Jan 4, 2012

Sov said:
Yeah but with a spring around the bump stop, it doesn't really have anywhere to go does it?

I'm a bit of a hack rider and even with an undersprung DHX, I never heard any metal on metal bottom outs so I'm assuming that I never actually achieved full travel.

Springs are able to compress the same amount (or more) as your shock stroke, else they would bind.

staike · Jan 4, 2012

Yeah what he meant was the rubber bottom out bumper. With the springretainer installed it will never be totally flat. So if you have a 3" stroke shock you will actually never be able to compress it more than i.e. 2,9" before the rubber bumper won't get any flatter. But if you look at the graphs the line stops at ~2,95". So maybe they did the testing with the rubber bumper and spring retainer installed. I have no idea how they tested it though.

Mark · Jan 12, 2012

Does anyone know if the modified and extended reservoir mods are applicable to the Van RC as well as the DHX 4 & 5? I've read the technical info on the Avy site but it doesn't seem all that clear to me regarding the Van RC.

Also, the Avy site states - "VanRC has Modified High Speed Adjuster Valving with wider range 22 click low speed adjuster"

Not sure what "modified high speed adjuster valving" means?

Thank you.

Mark · Jan 14, 2012

Just bumping this up as my post is not showing up as the last post for some odd reason?

Craig Seekins · Jan 14, 2012

Mark said:
Does anyone know if the modified and extended reservoir mods are applicable to the Van RC as well as the DHX 4 & 5? I've read the technical info on the Avy site but it doesn't seem all that clear to me regarding the Van RC.

Also, the Avy site states - "VanRC has Modified High Speed Adjuster Valving with wider range 22 click low speed adjuster"

Not sure what "modified high speed adjuster valving" means?

Thank you.

The VanRC is Fox's redesigned DHX that has the the Propedal valve removed and replaced it with a high speed regressive blow-off style valve with a very limited external low speed adjuster. This makes the VanRC a speed sensitive damper but with emphasis on pedal performance because of the low speed threshold of the Belleville spring valve set-up in the high speed adjuster valve and limited low speed adjuster range. Since the Propedal has been removed, The reservoir now uses a non adjustable fixed charge system and no longer has the need for the Bottom-out adjuster volume reducer feature. The internal volume is now much larger with these features remove and would be similar to the modified DHX 5.0 reservoir volume. The DHX 4.0 volume does not have the Bottom-out features as well so the volume need not be modified, but will except the extended reservoir cap when available.

We have developed a modified version of VanRC valve that uses shimmed high speed valving and a wider range low speed adjuster for more sensitive low speed performance and more progressive high speed feel while still allowing blow-off on square edged bumps. This now allows us to revalve the main piston valving to complement the redesigned adjuster system as we have done with the DHX. The reservoir is charged with fixed nitrogen pressure, but an optional extended reservoir cap will be available soon to minimize pressure ramp-up as we have done with the DHX. Check our website for updates on availability and details on the VanRC and DHX Speed Sensitive Damper (SSD) Avalanche Advantage program develops. We plan on expanding these modifications to all models of the DHX.

missingLink · Jan 15, 2012

Hey Bullcrew, can you offer some more feedback between the x-fusion and chubie? I currently have an avy chubie and really like it but I'm thinking about a vector air hlr to save some weight and have a little more adjustability with the air spring. Does the vector hlr come close to the chubie?
Thanks for any info.

Sandwich · Jan 16, 2012

I have literally three very short runs on my woodie and I am so thrilled to be back on avalanche after the nightmare of a shock the DHX was. I haven't spent a ton of time on cane creeks or elkas, but I'm happy to be a member of the avy cult again....they just work!

Steve M · Jan 17, 2012

This is a really cool mod IMO - the DHX/Van RC are really a very solid chassis but with some weird characteristics, cool to see Avalanche taking advantage of that and reworking the less than perfect parts.

Craig Seekins · Jan 19, 2012

bullcrew said:
So went and looked for the dhx tech page and there's really'intresting data on How the fox ramps up as well as internal pressure of the modded and extended resevoirs and new Internal seals dust wiper and bottom out bumper.

The pressure internally that a stock dhs reaches in the platform (reservoir) at bottom out
A dhx 5.0 with 3" stroke
Stock PS I 1500+
No bottom out 625
Modified 380
Extended resevoir 225

The stock is for regressive, no bottom out and modified is for regresive to linear
Modified is for linear to progressive
And extended reservoir is for progressive to rising rate

We added this to help clear up any questions:

Replaces ProPedal Adjuster with a low speed compression adjuster and custom valved high speed piston system in the existing Fox piggyback housing.
This conversion complements the revalved main piston to completely convert the DHX/VanRC to a true speed sensitive damper.

Technical Discussion
Why change out Propedal valve in the DHX?....The design of the Propedal creates a great position sensitive shock. As the pressure in the shock goes up the propedal valve gets harder to open, this creates more compression damping. The pressure can be increased 3 ways, first my adding more air pressure to the schrader valve, second as the shaft compresses, the displaced oil compresses the reservoir floating piston down, which drives up the pressure in the reservoir, and lastly the chamber compensation bottom out can be dialed in to decrease the reservoir volume and thus cause the pressure to be driven up even faster as the shaft compresses. The Propedal adjuster allows the rider to compensate for the pressure on the valve by applying opposite spring pressure to the valve reducing the force required to overcome this internal pressure and allowing the valve to blow-off more easily.

So this all sounds great but in a real world where courses and terrain are not perfectly smooth and void of square edge holes, this is where the Propedal system fails to allow the valve to blow-off. When the shock hits square edge bumps deep in the stroke the valve becomes harder to blow-off and is actually getting firmer the deeper it gets in the travel (Position sensitive damper).

This is why the Speed Sensitive Damper (SSD) is preferred, as the shaft speed needs to increase the compression adjustment valve needs to blow-off when the bumps become square edged or what we call high speed hits. This creates the need for the conversion and replacement of the propedal system to a shimmed ported valve. Since the shim stiffness is not affected by the build up of pressure in the reservoir, the shims can create damping at low and medium speed compression hits and be valved to blow-off when higher shaft speeds occur thus allowing the damper to smoothly resist the square edged hits. Because the main piston was valved for a very progressive position sensitive Propedal valve we can now revalve the main piston to contribute to the compression circuit and due to the decreased ramp up in the overall spring rate of the damper, the rebound stack can be revalved to be more linear . The main piston can now control it's 70% share of the compression damping giving us many more tuning options for rider set-ups. Rebound can be tuned to be more reactive on small bumps and provide lift where needed while preventing that pogo stick feel. Increased reservoir volume reduces pressure build up deep in the stroke, reducing heat build-up and increased oil and seal life. Optional reservoir volume systems available as shown below:

For a 1/2 inch diameter shaft, 1500 psi equals 294 lbs extra spring force
in other words for a 300 lb/in spring at 3 inches of stroke, the spring rate would increase to 400 lb/in.

What does all this mean? For regressive set-ups it might be good to add a bit more compressive force at the end of the stroke, but this does not come at no cost, as the shock compresses rapidly the reservoir also heats up and causes the nitrogen pressure to even further increase. Even though the propedal valve that was activated by this pressure increase has been removed, the seals, the o-rings and the oil have to deal with much higher pressures then needed. Typical initial nitrogen charge of 160 psi is enough to prevent internal cavitation and allow the shock to have proper damping. So generally for most shock set-ups it is advantageous to keep the pressure as low as needed and prevent the pressure from ramping up as the shock is compressed.

Optimax150 · Feb 9, 2012

That was a very good explanation of the difference between a SSD and a position sensitive dampner, from Craig. So which one would a MX tune by Push be?

Avalanche is doing FOX DHX 3/4/5.0 SSD mod/Tune now.

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