Fox VanRc/Performance Rc and Marzocchi Bomber CR
Speed Sensitive Damper Mods

Best AVA option for custom valving for coil compatible progressive/rising rate linkage designs!

What if my frame has a more linear or only a slightly progressive linkage?
You need to consider your bike's travel and intended use.
If it is a all mountain or enduro bike, you are not a big jumper, are mostly trail riding and you want that coil feel:
Are you are able to categorize your riding as trail mostly, only do small drops and
try to avoid high speed g-outs?
Then you could consider replacing your air shock with a coil over shock.
You will need to consider your spring rate carefully and the shock will need a much more aggressive bottom out system.
We can help you determine if your frame is compatible and determine the extent of restraint you will need.

Why is this shock your best choice for a custom valved Fox/Marzocchi shock?

Low initial cost (under $350 new)
Larger midvalve style main piston (27 mm same as 11-6)
Shimable compression adjuster design for tuning high speed harshness out.
Compact light weight design that fits nearly all frames.
Compatible with most aftermarket springs as well as Fox's new SLS springs.
Works with all hardware reducer options and RWC needle bearings.
Available in standard sizes, metric sizes and trunnion mount.
Reconfigurable mix and match parts for eye2eye and stroke changes.($60)
Custom Size eye to eye and stroke($85)
Set it and forget it tuning simplicity.


Custom sized BomberCR 165 x 45mm Trunnion for Evil Following (V2-V3)

Why do I need a compatible linkage that will accept a linear coil shock?
A progressive linkage starts at a much higher leverage which makes the shock feel softer at the top of the stroke,
as the shock compresses the leverage will make the shock spring feel stiffer and the shaft speed will also increase
causing the damper to automatically feel firmer to resist bottoming naturally.
This allows us to valve the shock for a plush, supportive feel with no bottoming.
Matching shocks up with the proper leverage allows them to use all the travel effectively and perform at their best without band-aid solutions,
such as over damping, stiffer springs, larger bumpers and of course position sensitive bottom out devices in the reservoir or air can.

How do I know if my frame has a compatible progressive linkage?
If your bike lists coil options or uses a very large air can system with no volume reduction spacers, more than likely its fairly progressive.
Also if you have maximized the air volume and still can't use all the travel then the rate is very progressive.

List of some of compatible bikes with our coil conversion:

Banshee Prime, Spitfire, Titan V3
Canfield One.2, Canyon Sender, Commencal Meta 4.2, Meta Power Meta TR
Evil Offering, Insurgent, 2019-21 Evil Following 165 x 45(V2/V3)
Forbidden Druid, GT Fury Team, Guerilla Gravity Gnarvana, The Smash
Knolly Fugitive LT/Warden, Nukeproof Mega 275, Oreba Rallon/Rise,
Norco Sight,Revel Rascal, Rocky Mountain Instinct
Santa Cruz V10, Nomad, Megatower, Bronson, Hightower(limited by spring dia)
Specialized Turbo Levo/Kenevo/Stumpjumper
2020/21 Specialized Enduro (with shorter modified reservoir)
Transition Sentinal, Patrol(2019-20 Carbon requires 10 mm shorter reservoir or shorter stroke),
Trek Slash, Rail,
Yeti SB130/140/150/165, Kona Process 29er
YT Tues, YT Decoy/Capra,

Not on the list, Just call or e-mail us!

This modification consists of a revalved main piston and modification of the compression adjuster to convert the VanRC/Bomber CR to a true speed sensitive damper.

Includes custom valving and setup for rider, frame leverage and conditions, and printed set-up chart.

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

Available Sizes

We can recommend a spring rate and shock size and you can order here:

Standard: 7.5x2.0”, 7.7875x2.0”, 7.7875x2.25”, 8.5x2.5”, 8.75x2.75”, 10.5x3.5"(custom size)
Metric: 210x50mm, 210 x52.5(with 2.5 mm spacer), 210x55mm, 230 x 57.5mm(with 7.5mm spacer), 230x60mm, 230x62.5(with 2.5mm spacer), 230x65mm,
250x70mm, 250x75mm (from Marzocchi only)
Trunnion: 165 x 45mm(custom), 185x52.5mm, 185x55mm, 205x60mm, 205, 65mm, 225x75mm (from Marzocchi only)
( For custom sizes please call or e-mail)

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

Includes Set-Up Chart

Low speed adjustment - Modified low Speed Adjuster system with wider range 22 click low speed adjustment.

Midvalve design for supportive low speed compression with plush small bump performance (no need for lock-out lever).

High speed adjustment - Internal Shim Stack tuned to leverage cuvre of linkage and rider needs.

Revalvable high speed shimmed compression adjuster system to tune out high speed harshness and dial in bottoming control

Low speed rebound adjustment - 16 clicks low speed adjustment and revalved high speed shim stack to match rider weight and spring rate.

Suggested spring rate based on rider weight and bike leverage supportive feel and maximized performance




Shape factor bottom-out bumper ($15.95)
Hard coated aluminum IFP with bleed screw ($29.95)
1.50 Hybrid Coil Progressive Conversion Kit (Reduced Friction 1.50 collars and Tapered bumper system bottom out control) ($54.95)
Reduced Stroke (2.5, 5, 7.5mm) spacer additional ($24.95)
We stock light weight Avalanche/Rockshox/NukeProof/MRP springs starting at (59.00)
Rockshox/Fox DU style reducer bushings or Fox Flange style starting at (24.95)

see below to add to mods:

The Van R requires requires a compression adjuster style new upper for mods to be performed.

Damper Modifications apply to:

Performance/Van RC
Bomber CR



BomberCR with 1.5 Coil conversion Kit and tapered bumper system

VanRc Shape Factor Bottom-out Bumper


Fox VanRC

Modified Compression Adjuster System

Fox VanRc/Bomber CR

Speed Sensitive Damper (SSD) Modifications

Shock must be sent in to receive modifications.

Price $249

options shown below

Comparison Chart

options shown below

Order Here and Send Shock for Modifications

Price $249

Do you have a BomberCR/VanRc with the wrong eye2eye and stroke
For an additonal $60 it can be made to what you need!

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

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 spring rate 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

Make sure that this spring gives you 30% sag with 2-3 turns of preload.
We will help you choose your correct spring if you are unable to.

Spring Rate

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





VanRc/Bomber CR Modifications

The VanRC is Fox's redesigned DHX that has the the Propedal valve removed and replaced it with the low speed threshold of the Belleville spring style valve, this setup limits the high speed tuning adjustment of the valve and with a very limited low speed adjuster range it is difficult to find a good setting. We convert the compression adjuster valve to a shimmed system for infinite tuning options and a smooth transition from low speed to high speed without that harsh feel. This makes the VanRC a true speed sensitive damper but with emphasis on pedal performance with our midvalve shim arrangement on the main piston(what we call supportive low speed compression).

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 damping feel while still allowing it to blow-off on square edged bumps. This now allows us to revalve the main piston valving to complement redesigned adjuster system. We also provide a wide range of bottom-out bumpers that match the end stroke needs.

Shape Factor Bottom-Out Bumper

Click here for Technical Description

Basic Budget Shape Factor Bottom-Out Bumper
to be used with stock 1.38 inch diameter
SLS and Steel Fox springs.

Add optional reverse shape factor bumper here:

3 sizes to reduce bottom out with slightly less ramp up than
tapered bumper option generally used with stock fox springs.




Optional Budget Bumper

Price $15.95



Advanced Shape Factor Bottom-Out Bumper
to be used with stock 1.50 inch diameter
Avalanche/Rockshox/NukeProof/MRP springs.


5 tapered sizes that work best with the
1.50 Hybrid Coil Progressive Conversion Kit
(see botton of this page for details)

they also work with 1.38 springs, but not as effective
because of lack of bumper contaiment when compressed.

Price $24.95


Works best with the 1.50 ID Spring Hybrid Coil cupped bottom collar


Optional Tapered Bumper

Price $24.95






Fox VanRc/Marzocchi Bomber CR/Fox DHX

Improved IFP's




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.

The VanRc's IFP are made of plastic and do not provide a bleed screw, these are always recommended to be replaced.

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


Improved IFP






Hybrid Progressive Coil Conversion Kit
(Tapered bumper system)
also used to convert Fox and Marzocchi Shocks
1.50(38 mm)inch Diameter Springs

It includes:
Friction reducing collar for plusher feel
Avalanche style Tapered Shape Factor Bottom-out Bumper System
Cupped spring retaining collar

and when used in combination with a Light weight Linear Coil

Adds ramp up to linear linkages to resist bottoming
Available in many sizes depending on ramp up needed!
Size of the tapered bumper will be determined by stroke and linkage progression.

Improved Bumper Cup Collar replaces the flat spring retainer and constrains
the bumper as it is compressed to create a progressive bottom out resistance system.

Eliminates spring rubbing on damper body

Makes AVA springs and Rockshox's new light weight metric springs fit!


Why not use a progressive spring? Well the progression begins as the coils starts to progress and generally creates too much to soon and affects the midstroke absorption of deep square edged bumps. A bumper system can be used to only affect the end of the stoke thus allowing most of the travel to deal with deep edged bumps while preventing bottoming.

Even if your frame is progressive you can still benefit from a taller tapered shape factor bumper system. We feel the end stroke still benefits from a tapered bumper system because we are trying to make the valving blow off for square edged deep stroke ledge bumps, so we can keep the valving plusher and rely on the bumper system as well.

What most refer to as progressive linkages may not be as progressive as downhill coil like linkages and if it can still accommodate both air and coil it may have a linear or regressive end stroke. We make 4 different tapered bumpers and 3 sizes of the reverse shape factor $16 budget bumpers(more abrupt but provide some protection and less ramp up) that work with the stock spring.
If you want to use the stock 1.38 SLS you can, but we are finding that this spring is very inaccurate at the beginning of the stroke due to the square and grinding tolerance and the very steep helix angle. The 1.5 ID also eliminates the spring from rubbing on the body and provides a friction reducing collar to insure a smooth preloaded feel.

Model Shock




Need your shock stroke shortened?
Custom Shaft spacers

Available in 7.5, 5, 2.5 mm

Under bumper for stock collars, under spring cup collar for 1.5 ID conversion Kits



Stroke reducer spacers