Fox DHX Air 5.0/4.0 Speed Sensitive DamperAdjuster Kit

DHX 5.0/4.0 Air shock conversions to SSD technology

Not available, discontinued.

Replaces the ProPedal Adjuster/Lever with a 15 position low speed compression adjuster or for shocks with the propedal lever, a two position soft-medium or med-hard low speed adjuster lever.
Propedal valve is replaced with a custom valved high speed SSD valve in the existing Fox piggyback housing.
This conversion complements the revalved main piston to completely convert the DHX air to a true speed sensitive damper.

...For Technical Discussion Click Here...

Includes custom revalving and setup for rider, frame and conditions.

Also includes complete rebuild service, new improved seals and dust wiper system, oil, nitrogen charge and typical wear parts* included in price

*The shock must be in good working condition with no scratches or dents on moving parts, if the air can is leaking,
it should also be noted that air side will not be modified in anyway and any air side issues will not be addressed. (Air can rebuild parts not included, self-install from Fox only)
Service interval will remain the same as before the modifications)

**(Typical wear parts: shaft seal, dust scraper, shaft bushing, reducer DU bushings, and o-rings)

Includes Set-Up Chart


Choice of Reservoir Volume Expansion Kit: modified reservoir( included in the cost) or extended volume cap ($49).

The larger the reservoir the less pressure increase during full compression, this pressure effects the midstroke harshness for rising rate linkages.
Also the longer the run the hotter the shock gets, and with small reservoir volumes this could double the pressure in the shock at the beginning of the stroke and make it feel topped out or over preloaded.
Regressive linkages like the "Sunday" only benefit from the bottom-out original unmodified reservoir. Most frames will need more nitrogen volume and will require the modified reservoir.
High rising rate frames and aggressive extended downhill runs on linear and progressive linkages will need the extended reservoir.

Optional Improved IFP:

Improved replacement IFP to prevent premature wear resulting in a blow shock ($29)
Highly recommended for any shock with 100 hrs or more since last service.

Not available as a self install kit.

Damper Modifications apply to all Air versions shown below and similar models not shown:

DHX Air 5.0
DHX Air 4.0
DHX Air 5.0
DHX Air 5.0
DHX Air 5.0
DHX Air 3.0 (available soon)


DHX Air 5.0 with Extended Reservoir


DHX Low Speed Adjuster and SSD High Speed Valve

Fox DHX Air 5.0/4.0

Speed Sensitive Damper (SSD) Adjuster Kit

Shock must be sent in to receive modifications.

Call for availability some items have been discontinued.

Not available, discontinued.

options shown below



Download: Whats been Done and Set-Up Manual (32.6 MB)

Comparison Chart


Order Here and Send Shock for Modifications

not available

Choose the type of riding that you will be doing so we can custom valve it to your specific needs.

Click here for a description of our definitions

Type of Riding

Choose your shock model that the SSD kit will be installed in.

Shock Model

Pick the type of adjuster mechanism your shock has.

Shock Adjuster

Choose rider weight.
Rider weight is without gear, we add 5-7 lbs for DH gear, 7-10 lbs for All-Mtn/Freeride.

Rider Weight

Choose the air pressure you will be using which gives you 30% sag.
We need this number to help set-up your shock rebound damping correctly.

Click here for sag setting Tips

We will help you choose your air pressure if you are unable to.
Service should be performed every 100 hrs, same as Fox recommends. For high leverage frames
or heavier riders requiring sag pressures over 185 psi, you should be aware that the service life of damper oil will be dramatically decreased.

Air Pressure

Choose your rider ability for us to set-up your shock.

Rider Ability

Provide us with Bike info to set-up your shock.




Provide us with any other info to help us set-up your shock.

Set-up Info





Fox DHX Air 5.0/4.0

Shown with Optional Extended Reservoir Cap (available now)


Low speed adjustment - 15 clicks provided now with the existing Blue Propedal knob

2 position with converted Propedal Lever

High speed adjustment - Internal Shim Stack

Revalvable High speed Shims to tune out high speed harshness and dial in bottoming control

Installs directly into the DHX housing, uses exiting Propedal knob or lever as new low speed adjuster, knob shocks are prefered because you will get 13 clicks of tuning vs 2 positions of the lever


DHX Extended Reservoir Cap
shown anodized (gold)








Fox DHX 5.0/4.0

Extended Reservoir Caps

Increases Nitrogen Volume by more than 2.2 times Stock

Eliminates midstroke shock damper stiffness caused by heat affected reservoir pressure build-up

Leak proof needle charging system

Easy to install, can be added later after SSD
modifications if desired

Adds 4.5 mm to length of DHX-5.0 reservoir.

Adds 14 mm to length of DHX-4.0 reservoir.


Add option here

Price $49

Available Now


Optional Reservoir Caps

Price $49






Fox DHX 5.0/4.0

Improved IFP's


Replacement to the left


After 2 or 3 years of riding the Internal Floating Piston
in the Fox DHX reservoirs begins to wear and allows the IFP to tip in the reservoir
and allow air and oil to leak between them.

This replacement IFP has been redesigned with a wider land and tighter tolerances and prevents this from happening. It is also hard coat anodized to prevent wearing out.

We may suggest you replace the stock IFP when we inspect your internals or
replace it now to prevent a blown shock in the future!

Add option here

Price $29.95

Available Now


Improved IFP

Price $29.95






Air Can Rebuild Kit
optional service


Air can and air sleeve
Rebuild and and seal replacement


After 50 hrs of riding the air can seals and air sleeve piston seals need replacing and if not replaced periodically
this allows the internal air pressureto leak between the positive and negative chambers reducing the effectiveness of the air spring system.
The air can seals also become jammed up with dirtand mud which can cause damage to the air piston shaft and create a leak path for the air can pressure.

We may suggest you replace the stock seals when we inspect your internals or
make plans to replace them yourself to prevent these issues!
This does not include damaged or dented air cans or air piston shafts, seals only.

Shocks newer than 50 hours need only be cleaned and reassembled typically.

Add option here

Price $29.95 includes parts and labor


Air Can Rebuild

Price $29.95






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