The title to this article is a bit deceiving because obviously front suspension is not restricted to mountain biking alone. There’s been an explosion in different types of bikes in the last decade, blurring the lines between different disciplines, and adding new ones to the mix every year or so.
The most obvious example is gravel cycling, adventure riding, and/or bikepacking, all revolving around road bike type bicycles adequate for increasingly rough terrain.
Manufacturers of MTB front suspension have branched out in every conceivable cycling discipline. This of itself has created just as many different forks and accompanying technologies. In this article I’m going over all technologies from the biggest brand names, and what problem exactly they are trying to solve.
The article is meant to do away with proprietary jargon and fancy naming, and provide a reference for those of you either interested in purchasing an entire bike with a certain front suspension, or the fork itself.
Besides the frame, front suspension is probably the most expensive single bicycle component, and also the most complex one. Let’s demystify it.
GRIP2 sealed cartridge damper
The GRIP2 damper is a compression-damping technology that offers the most adjustability of any front suspension as of this writing.
Instead of the FIT4 3 settings, you have a 16-click dial for low-speed compression adjustment, within a 9-click dial for high-speed compression adjustment.
The GRIP2 damper also features an independently adjustable high- and low-speed rebound adjustment at the bottom of the damper.
Besides increased adjustability options over the FIT4, the GRIP2 damper does not use an expanding bladder, which is a more durable construction offering a lower risk of stiction and smoother fork action.
It also has more oil volume using a spring-backed floating piston to control oil flow. All things combined it means it’s the plushest fork in Fox’ catalog.
FIT4 sealed cartridge damper
The FIT4 damper is a compression-damping technology within a sealed closed cartridge system (FIT = Fox Isolated Technology), which offers a 3-position lever with on-the-fly settings equating Open (no damping), Medium, and Firm damping (high-speed compression) configurations. The settings can be configured with a single dial.
Inside the big lever sits a smaller knob offering 22-click low-speed compression adjustment, to stiffen the fork and provide more support of the top of the stroke (available in the Open setting).
The FIT4 damper offers a 10-click rebound adjuster knob at the bottom of the damper, which means you cannot independently adjust high- and low-speed rebound. This improves ease of setup at the cost of adjustability.
GRIP sealed cartridge damper (3-position)
The FIT GRIP damper is a compression-damping technology that offers 3 on-the-fly settings equating Open (no damping), and Firm damping configurations with infinite adjustment in between 3 detents. The settings can be configured with a single dial.
The GRIP damper offers a 10-click rebound adjuster knob at the bottom of the damper, which means you cannot independently adjust high- and low-speed rebound. This improves ease of setup at the cost of adjustability.
GRIP sealed cartridge damper (2-position)
The FIT GRIP damper with the black dial is the same as the blue version, but operates without detents and instead uses friction with infinite adjustment between Open and Firm.
Taper-cast refers to the shape of the lower legs in Fox’ lineup of front suspension. The newest technology is available for Fox’ lightest suspension meant for gravel cycling. It’s a weight-saving technology.
Step-cast refers to the shape of the lower legs in Fox’ lineup of front suspension. As they say themselves “its narrow stance and stepped design saves weight, decreases frontal area, and provides clearance for the spokes and brake rotor.” The technology is found on their most expensive forks since it increases the complexity of the build.
The Kashima coating is a third party coating from Japanese firm Miyaki whereby the microscopic porous coating of the anodization film of the fork legs is filled up with molybdenum disulfide through electrolysis. In turn, it creates a smoother, harder, longer-lasting coating with a characteristic bronze color.
FLOAT EVOL air spring
The FLOAT EVOL (Extra Volume) air spring has a larger negative air chamber, besides the standard positive one. Aside from supporting your weight in a neutral position, the air spring offers a more linear spring curve that’s supple off the top on small bumps yet still has the support to resist bottoming out on those big hits.
The size of the positive air chamber can still be reduced as you’re used to with air volume spacers, without affecting the functionality of the negative chamber.
By reducing the air volume of the positive air chamber you make the fork act more progressive, resisting bottoming out more for those of you who like to ride hard and aggressive.
Lower leg bypass channels
By integrating bypass channels into the lower leg, the air volume of the negative air chamber is increased, reducing unintended pressure ramping.
The side-benefit of this technology is that there’s an increased lubrication of both foam rings and bushings.
Lower leg bleeders
As you use the fork, pressure can build up into the lower legs, thereby reducing its performance by lowering the maximum amount of travel you could potentially achieve, as well as diminishing small bump sensitivity and responsiveness.
Lower leg bleeders allow you to maintain the optimum performance level of your front suspension by releasing this atmospheric pressure buildup.
Kabolt X axle
The Kabolt X axle is a bolt-on floating axle tightened down with a single-sided pinch bolt, adding characteristics of both stiffness and lightweight to the thru axle setup.
RockShox’ BRAIN damper adds Specialized Inertia Valve with Position-Sensitive technology into the mix.
Initially introduced by Specialized on rear shocks, it has since been applied to front suspension as well. It allows the forks to differentiate compression types from the below and the top, which would correspond with normal impact compression and added weight on the handlebars when moving out of the saddle.
So it’s basically an auto-lockout function, which reduces power loss, control, stability, and overall ride quality because of unwanted compression. The bike becomes more rigid when you need it, for instance when climbing, and compresses when the trail demands it.
It also features something called position-sensitive BRAIN. It’s an initial 15mm amount of travel where the fork operates without the BRAIN technology, enabling super-efficient small-bump sensitivity assuming you’ll always be in the saddle for those portions of the ride. Beyond this initial travel the platform is hit where the BRAIN technology activates.
The large dial on top of the damper is called the BRAIN Fade which changes the sensitivity of the inertia-valve from fully open to closed (firm setting) with detents in between.
The red dial sitting on top of the BRAIN Fade is a rebound adjuster knob. Instead of sitting at the bottom, it makes it just that bit easier to adjust the fork.
Charger 3 damper
The Charger 3 damper is a compression-damping technology offering a 15-click dial for low-speed compression adjustment, within a 5-click dial for high-speed compression adjustment.
This pretty extensive low- and high speed adjustment can be achieved without introducing additional harshness and loss of control.
The Charger 3 offers a 18-click rebound adjuster knob at the bottom of the damper, which means you cannot independently adjust high- and low-speed rebound. This improves ease of setup at the cost of adjustability.
The damper does not use an expanding bladder, which is a more durable construction offering a lower risk of stiction and smoother fork action.
It also has more oil volume using a spring-backed floating piston to control oil flow, making it the plushest fork in RockShox’ catalog.
Charger 2 damper
The Charger 2 damper is a compression-damping technology using bladder technology for the displacement of oil upon compression.
The Charger 2 damper features a 17-click dial for low-speed compression adjustment, within a 4-click dial for high-speed compression adjustment.
It offers a piston design with a low-friction glide ring for increased small-bump sensitivity and an overall less harsher ride.
The damper also offers low-speed rebound adjustment.
Charger RL damper
Charger Race Day damper
The Charger Race Day damper is an XC-oriented lightweight, non-adjustable damper. It’s as straightforward as a damper can get, with an easy-to-setup lockout mechanism providing maximum power retention for both climbing and sprinting.
Everything has been done to keep the weight incredibly low, so unlike traditional dampers, rebound adjustment is done with a 2.5mm hex key.
Motion Control damper
The RockShox Motion Control damper is a budget-friendly option with minimal adjustability, offering an incredibly easy setup. It’s the oldest and most simple damping technology in RockShox lineup, with more complex variations either no longer available or being replaced by newer compression damping-technology.
The damper offers a single dial for open and closed low-speed compression damping. A full lockout can be enabled and completely closes the compression oil ports.
The damper offers a neat failsafe mechanism, which opens the compression valve cover on a locked out fork during a big hit, preventing possible damage to the internals and enabling fork travel again. It allows for a single big hit before a spring closes the valve cover again.
DebonAir+ air spring
An air spring is made up of a shaft on which in this case a floating piston is installed, sitting between two seals. The Debonair+ air spring improves upon earlier models, by swapping out the plastic shaft for an aluminum one.
Larger volume negative air chambers for all three iterations is achieved by hollowing out the top hat of the piston.
Just as with Fox’s Float EVOL air spring, the larger negative air chamber offers a more linear spring curve and a reduced risk of bottoming out.
SoloAir air spring
The SoloAir air spring simplifies suspension setup by being able to inflate both positive and negative air chambers using a single schrader valve. It means you always run the same pressure in both chambers.
Although it is easier to set up, the fact that there’s no independent configuration of both air chambers does away with customisation of the initial travel characteristics, which translates to fine tuning small-bump sensitivity.
Since both chambers run the same pressure, it’s not possible to run a higher pressure in the negative air chamber, which is used for the downward stroke since it sits at the bottom of the air spring. This reduces the small-bump sensitivity obtainable with this type of air spring.
ButterCups is a front suspension technology to reduce high-frequency vibrations otherwise known as “trail chatter”. This is the result of a fork not being responsive enough to handle small rocks and roots, directly translating the impacts to your body, causing fatigue, hand numbness, and even neck and shoulder issues on longer rides. Both damper and air spring feature these cups.
The buttercup on the damper side essentially holds two elastomers looking like small rubber pucks between a metal plate sitting within an aluminum housing, at the end of each shaft.
The air spring side only has one of those pucks, with an o-ring sitting on the upper side. That’s because the air spring is much more effective on compression (downward stroke) not on the rebound (upward stroke).
They function as a suspension within a suspension, offering about 4mm of vertical compliance, taking out the smallest of trail irregularities, before the more advanced suspension technology is activated and reducing roughly 20% of trail chatter.
SKF wiper seals
Wiper seals are meant to keep accumulated dirt sitting on the stanchions from contaminating the oil in your lower legs, possibly damaging its bushings or the coating of the stanchions.
RockShox has outsourced its seal manufacturing process to SKF, which specializes, among other things, in the creation of these parts. The result of this collaboration is supposed to provide the lowest friction wiper seals possible without sacrificing their protective nature.
Pressure relief valves
RockShox also features pressure relief valves on some of their forks. They offer the same functionality as those that sit on front suspension from Fox.
The TTX sealed-cartridge damper offers 13 clicks of low-speed compression adjustment, with35 clicks for high-speed compression adjustment.
A lever enables the quick 3-way setup of high speed compression to support you maintaining stability and power from downhill to climbing. With a fourth setting serving as a lockout removing unwanted suspension travel.
Furthermore the fork offers 15 clicks of rebound adjustment.
The damper offers a twin-tube design for two-way oil flow
The latest iteration of the damper is said to be significantly lighter, reducing a whopping 27 percent optimizing it for shorter travel forks sitting in XC and downcountry mountain bikes.
Although not easy, you can adjust the amount of travel. However it involves a full service and replacement of internals.
Öhlins decided the damper should be operated left-handed. Although counter-intuitive, it means you can operate the shifter with the other hand, making it easier to maintain stability while renewing your damper configuration.
RXF air spring
The RXF air spring, both for EVO and M.2 forks, is a cartridge which offers a rather different three-chamber design. With a self-regulating positive and negative air chamber besides a third one for bottom-out-control, which can be independently set up.
With up to 6 air volume spacers the rider can increase the progressive nature of the fork to ensure a more lively character and further improve control and stability on rougher terrain.
RXF36 m.2 coil spring
I could write an entire article on the benefits of coil springs over air springs, and probably should. Suffice to say for now is that Öhlins offers a convenient transition to coil springs or an out-of-the-box version of their RXF36 fork.
The biggest thing of a coil fork is that the spring has a linear compression rate versus a progressive one. So as the force increases it doesn’t become harder to achieve a downward stroke, creating a much more floaty feel than a traditional air fork.
Because there isn’t a progressive compression rate, you can brake harder without activating the suspension, or at least not as much as with an air fork. In turn it creates a more effective usage of fork travel, without leaving any of it unavailable.
The preload adjustment is incredibly easy to finetune with a dial instead of a tool. The overall build is simple, durable, and easier to maintain than an air fork, becoming less of a drain on your wallet through the years.
Coil forks take about twice as long before they need servicing, and wear and tear is reduced because of less heat buildup in seals which don’t need as much tightening as in a traditional air fork since they don’t need to prevent air from leaking out.
Less breakaway force is needed to move a coil fork, increasing the small-bump sensitivity. It increases the bouncy feel of the fork, yet significantly reduces trail-chatter, and is easier on hands, neck, and back.
You can even argue that the increased small-bump sensitivity helps the bike maintain its traction better while cornering.
Öhlins offers a floating axle design, which greatly enhances lower leg alignment , and improves suspension performance and consistency.
A correct alignment of the lower legs prevents premature wear on fork internals, stanchions, and lower leg bushings.
The thru axle is tightened with an allen key, and further held into place with a single pinch bolt.
The TPC+ (Twin Piston Chamber) damper is a velocity and position dependent damping circuit that maintains light damping through small bumps when the fork is high in its travel.
The secondary TPC+ circuit controls damping force for deep travel movement caused by jumps, big drops, and the like. As the fork compresses deeper in the travel the IFP (Independent Floating Piston) engages and increases the damping force for added support and bottom-out prevention.
The TPC+ damper offers both a whopping 16 clicks of high-speed compression adjustment and 16 clicks of TPC+ deep travel compression adjustment.
Furthermore the fork also offers 18 clicks of rebound adjustment.
Additionally, an independent Hydraulic Bottom-out (HBO) circuit further increases the damping force in the final 30mm of travel to soften deep travel events and prevent hard bottom out.
The Multi Compression Control (MC2) damper provides an independently adjustable high-speed compression circuit which combines with an independently adjustable low-speed circuit to offer an externally adjustable, on the fly high-speed blowoff threshold and tuning range.
The MC² damper offers 10 clicks of low-speed compression adjustment, and 4 clicks of high-speed compression adjustment.
Furthermore the fork has a 10-click rebound adjuster. And all MC2 dampers include the hydraulic bottom out (HBO) system, which kicks in the final millimeters of travel.
VTT Pro damper
When developing the VTT Pro (Variable Terrain Tune) damper the goal was to maintain a rock-solid lockout without compromising the open and mid settings.
The downside to many dampers with firm lock-out modes is that in any other position than lock-out you will reach some critical shaft velocity that choke off the low-speed flow path.
When this happens the damper peaks at nearly the same lock-out force as the locked-out position. This translates to harsh force in the hands and possibly lack of control.
The goal with VTT is to eliminate that high-speed spike while maintaining the lock-out force demanded by most XC users. This allows the fork to have less progressive high-speed response while maintaining some low-speed support.
This is achieved through independent shim stacks (one for lockout, one for the other two positions). By controlling the shim stack through which the oil flow is diverted you can manipulate the characteristic of the damper to be lock-out, digressive, or progressive to meet the demands of rider and the terrain.
The VTT-6P (Variable Terrain Tune) damper adapts to any terrain with the turn of a single knob. VTT adjusts both high-speed and low-speed circuits in three factory set tunes for maximum versatility with minimum rider input.
The VTT-6P damper adjusts both high- and low-speed damping characteristics with the same 6-click dial (hence the name), providing quick configurability and ease-of-use.
Furthermore the VTT-6P damper has 10-clicks of rebound adjustment.
The Absolute+ damper, also known as ABS+, offers independent high- and low speed damping characteristics.
The externally adjustable low-speed damper is a tapered needle-based damper offering 8 clicks of low-speed compression.
ABS+ is the compression damping portion of TPC. It’s a shimable high speed compression circuit using a special piston design that allows us to create platform force by preloading the shims.
The high-speed compression circuit can be tuned using different shim stacks to suit your specific needs, which makes for an easy yet great DIY tuning platform.
Depending on how much preload the shim stack receives, the force required to blow-off the platform can be tuned.
IRT air spring
The IRT (Infinite Rate Tune) air spring allows for advanced spring tuning by independently adjusting air pressures in the beginning and end stroke.
IRT technology creates a secondary positive air spring that affects only the middle to end stroke of the fork. This allows the main air spring to be set to lower pressures for improved small bump sensitivity while maintaining mid-stroke support and moderate to aggressive end-stroke ramp-up.
The Air Spring system contains a unique balancing valve that equalizes the positive and negative air chambers during the air fill process resulting in a consistent feel without any flat or dead spots. It also allows easy travel adjustability without the need for any spare parts.
Dorado Air w/IVA air spring
The Dorade Air with the IVA air system offers similar air spring functionality as the one used.
The unique feature of this air spring is the IVA technology, offering similar functionality as air volume spacers without actually using air volume spacers.
What this does is enable you to increase the progressive nature of the fork by reducing the amount of volume, without opening it up. Reducing air volume resists bottoming out the fork and provides more compression power for aggressive trail riding.
The GRIP damper offers general continuous or infinite compression adjustability with (no detents) with a two position dial. The compression alters both high- and low-speed compression.
By circulating oil through the entire lower legs continuous lubrication, longer lifespan, and lower risk of wear is guaranteed. It also enhances the length of operability before your next service iteration.
Lack of dual compression adjustment is always a risk for proper mid-stroke support without negatively impacting low-speed compression.
Furthermore the GRIP damper offers 13 clicks of rebound adjustment.
In terms of technology its the same damper as the one from Fox, which is Marzocchi’s parent company
The RAIL damper offers the same type of adjustability as the GRIP damper, and offers 16 clicks of rebound adjustment.
The RAIL damper aims to simplify its damper technology by separating the compression and rebound pistons. There’s no damper shaft connecting the two within a container. Rather the compression piston can be found underneath the top cap while the rebound shim-stack assembly is located at the bottom and kept into place with the foot nut.
With no need to bleed the damper, serviceability is simplified. While normally you’d need to bleed the damper, now you can simply drain the column of damping oil and fill the stanchion back up again, before putting back the internals.
FLOAT air spring
Similar to the Fox Float EVOL air spring.
Bomber Z1 coil spring
Ranging from soft, and medium, to firm, and extra firm, Marzocchi offers 4 different types of coil springs to finetune your preferred riding style.
Made from light-weight tempered silicon-chromium steel spring. The steel-tempering process involves heating the metal just below its critical point temperature before air-cooling to strengthen the structure.
Preload adjustability is enabled using an external dial.
To prevent bottoming out the coil spring its oil to add a progressive nature to the otherwise lineair spring curve, while at the same time performing the function of lubricating the lower legs.
Johan van Seijen
Johan van Seijen is the founder of restoration.bike. His passion for cycling in general, and restoring older bikes turned into a website to share his knowledge with a broader audience. Starting out on his father’s road bike and riding classics as the Amstel Gold Race and Liege Bastogne Liege he has shifted his attention to trail, XC, and gravel riding since. No matter how much he loves writing about everything related to cycling, nothing beats actually using his ever-expanding bicycle collection.
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