RockShox SID – Superlight Integrated Design forks

SID Ultimate forks on Trek mountain bike
Rockshox SID Ultimate on Trek, Top Fuel 9.9 XX1 AXS

Rockshox SID forks - Superlight Integrated Design

Rockshox SID forks are one of the most enduring forks in the world of mountain bikes. These Superlight Integrated Design forks (abbreviated to SID) began production in 1998. 


The SID model range was most recently revamped in late 2020 (The 2021 model forks). Prior to the 2021 model, SID forks were solely 32 mm diameter upper tube design. 


The latest product line completely revamps the Rockshox lineup with the SID now manufactured as a 32 mm, and a 35 mm stanchion. All models now use 44 mm offset for the through axle, wider set rotor tabs for 180 mm discs, and support only 29” wheels.


The 2021 Rockshox lineup names the 100 mm travel, 32 mm Stanchion XC race fork, the SID SL. New to the 2021 Rockshox range is the 120 mm travel, 35 mm stanchion, SID. This completely new fork has captured the limelight. 


SID forks have been an industry leading crowd pleaser for decades. While the history of SID forks continues in the SID SL, the new star on the block is the all new 35 mm SID. This model introduces beefier 35 mm stanchions. The thicker stanchions provide the rigidity to extend the capability of these class leading race forks. The SID is and XC fork bordering on the realm of trail bike enthusiasts.


Both models carry on the award-winning superlight philosophy. The 2021 SID forks are entirely new both inside and out. All models feature all new outers and air springs. Rockshox has also introduced the SIDLuxe rear shock to compliment the SID front end options.


SID models now address two entirely different sectors with their super lightweight 100 / 120 mm travel forks. SID forks are perfect race winners for fast Down-country, Cross-Country and lightweight trail events. 

Rockshox SID forks provide:

  • Excellent Comfort
  • Tuning simplicity
  • Class leading weight reduction
  • Impressive ride stability
  • Fantastic small bump compliance

Rockshox SID Lineup

There are now 4 option of SID forks. All options accept only 29” wheels and all options have 44 mm offset and the latest DebonAir air spring. The different options are:

SID SL Ultimate

  • Gloss blue or gloss black
  • 32 mm stanchions
  • 100 mm travel
  • Race Day Damper
  • 1326g
  • US$1,228 – US$1,335
SID SL Ultimate color options

SID SL Select

  • Black
  • 32 mm stanchions
  • 100 mm travel
  • Charger RL damper
  • 1468g
  • US$921 – US$1,028
SID SL Select color

SID Ultimate

  • Gloss blue or high gloss black
  • 35 mm buted tube stanchion
  • 120 mm travel
  • Race Day Damper
  • 1537g
  • US$1,382 – US$1,489


SID Ultimate color options

SID Select

  • Black
  • 35 mm stanchions
  • 120 mm travel
  • Charger RL damper
  • 1671g
  • US$1,074 – US$1,181
SID Select color

The SID SL Ultimate continues the superlight 32 mm tradition, now shaving even more weight from earlier models. Weighing only 1326 grams, Rockshox claim that this is the lightest fork available.


Rockshox SID SL Ultimate models feature a new machined, lightweight, anodised aluminum crown. The machined crown scraps a few grams off the crowns of the Select models. Apart from the crown, the SID SL Select has the same design as the SID SL Ultimate. Inside, the SID SL Select retains the older Charger RL damper.


Remodelled lowers on SID SL forks introduce weight shaving cutouts. They integrate weight saving into the design wherever an opportunity presents. Rockshox mill inside the magnesium alloy lower casings to shave a further few grams of unnecessary weight.


Rockshox are meticulous. They go to incredible lengths to drill even the smallest nut or nob on SID forks to expel unnecessary metal at every opportunity. Unfortunately, shedding weight at all costs also means that there are no fender mounts on SID SL models.


The lowers have 44 mm offset for the through-axle. The redesigned lowers also feature wider set disc rotor tabs. Gone are the 160 disc rotors of old and in with larger, 180 mm (or 200 mm) rotors for increased stopping power.

Rockshox is doubling down on the superlight chassis in every aspect of SID forks. Like the SID SL, these forks adopt all the same weight saving designs. They maximise function from minimalist ideals.


SID forks provide 120 mm of travel delivering the stiffest fork with minimum weight. Butted aloy upper tubes retain rigidity while shedding weight. (Butting is the use of varying thickness tubing to reduce weight in lower stress sections). 


Rockshox keeps these forks as light as they can be by stripping every non-essential gram that they can find.


The new SID 35 mm stanchion and 120 mm travel transfers the Rockshox SID supelight cross-country race tech to the edge of the trail racer.


True to its brand, the Superlight Integrated Design dictates that this is the lightest fork in the 35mm class. The new SID Ultimate weighs in at 1537 grams.


SID Ultimate forks feature a new lightweight, anodised aluminum crown. The Rochshox SID also has a wider stance than the SID SL. Wider stance and stiffer upper tubes translate to greater control and steering accuracy for the rider. 


Rockshox fit these forks with smooth, low friction SKF seals and Maxima Plush fluid to keep damping consistent. The 2021 fork is far smoother in operation than its predecessors. It is a very comfortable fork, soaking up chatter from rubble and roots.

SID Select models do not have the lighter, machined crown and the SID Select keeps the slightly heavier, but more adjustable Charger RL damper of earlier models.  The SID Select has the same outers, stanchions and DebonAir air spring of the SID Ultimate.


All SID models can be fitted with handlebar remote lockout which bumps up the retail price a little. The difference is that the SID Ultimate is fitted with the latest, 98 gram lighter, Charger Race Day Damper and machined, anodized crown.

Position Sensitive Brain on RockShox SID SL
Brain damper on the SID SL has rebound adjuster on the fork stanchion

The new Race Day damper has been slimmed down to shave 98 grams from the earlier design. This slimmer damper requires less oil than the outgoing edition. The damper body and bladder have been reduced in size and weighs only 88 grams, including oil. 


Not only is the oil bladder and body of the damper thinner and trimmer, Rockshox has paid incredible attention to detail. Every connector, adjuster nut and attachment has been milled to shave extra grams. Every component has been cut, milled, trimmed, or removed to cut mass.


Rockshox have removed the rebound adjuster which now detaches after use. The new Race Day damper adjuster now requires a hex key in order to adjust this setting.


New model Race Day Damper can be retro-fitted into SID forks from as far back as 2014. The older Charger RL damper is still available and performs just as well as the Race Day damper. The difference in dampers is down to weight saving and price.


The lower cost Charger RL dampers are provided on the SID Select models with SID Ultimate forks having the latest bells and whistles as standard.

Rockshox have added another new damper option for SID SL forks. Specialized’s Position Sensitive Brain damper. . This damper has a smart valve that can differentiate between impact from bumps and rider input. 


The Brain operates a valve which opens when forks are jolting over bumps. The Brain allows the damper to function normally while crossing rough terrain. 


On smoother tracks, if the rider pulls on the brakes, or pumps the pedals, the smart valve remains closed, locking the suspension. 


The position sensitive brain prevents the Rockshox SID diving under brakes. The brain also locks the forks when the rider is pedaling. This prevents the damper from sapping rider strength and transfers more pedal power to the ground.


Brain ‘fade’ adjusts the sensitivity of the lockout using an adjuster on top of the fork stanchion. There is also an additional rebound adjuster within the Brain fade unit.


The Position Sensetive brain is featured in SID SL forks on Specialized Epic S-Works mountain bikes.

Rockshox SID forks on Trek eMTB
SID Ultimate are featured on top end racers such as the Trek Top Fuel 9.9 XX1 AXS

Air springs have several advantages over coil spring forks. Most riders favor Airsprings on their mountain bikes as they provide an advantage in more situations. The biggest differentiators of air springs are:

  • Progressive resistance: The increasing resistance as the spring compresses provides more predictability.
  • Fewer Bottom outs: Resistance increases as the coil compresses making the forks (or shock) less likely to bottom on a hard drop.
  • Improved rebound: Assists with bunny hopping obstacles or clearing doubles.
  • Reduced weight. Air shocks are typically half the weight of coil springs. Forks are also substantially lighter.
  • Easier setup: It is easy to add or remove air to adjust resistance. By comparison, coil springs would require a replacement spring.
  • Simple spring progression adjustment: It is simple to add or remove, bottomless tokens to adjust the progression of the fork. A range of replacement springs would be required on a coil fork to obtain the same adjustment.


Coil springs are still preferred by many riders to tackle rough terrain. Riders often feel that coil springs are less reactive or ‘dead’. Dull response forks can provide more control over rough trails. For most other terrain, riders typically prefer air springs.


The 2021 DebonAir spring has been re-engineered to maximize the usable travel of the forks. This is especially useful for relatively short travel shocks like the SID. 


RockShox forks have markers on fork upper tubes which show the amount of travel that occurs on track. Markers are a great guide to understand how efficiently forks are working on the track you are riding. Markers provide valuable information which helps riders tune their suspension for the track conditions.


Stanchion markers also made it very obvious that around 10% of fork travel was lost to support the weight of the bike. Riders could easily see that 120 mm Rockshox SID forks, had functional travel of less than 110 mm.


Rockshox have addressed this concern with their latest DebonAir air shock. To compensate for sag, the 2021 DebonAir ‘spring’ has a longer foot nut. The longer nut pushes the air spring higher in the fork body which compensates for sag. The new DebonAir spring improves the suspension by providing a greater range of travel when operating under load.

The extended foot nut is not the only modification. The seal-head inside the Debonair spring is longer and the seal itself is placed higher. This redesign increases the negative air volume, which changes the characteristics of the air spring. 


The redesigned seal-head lowers initial compression resistance, making the spring more compliant to small ruts and stones. The changed air spring makes better use of damping over the full 120 stroke.


If you wish to retrofit the DebonAir spring, a replacement air spring will cost $42. 


Alternatively, upgrade kits are available. Upgrade kits provide a replacement foot nut and seal-head and can be purchased for $25.


SID forks punch well above their weight for units with 100 / 120 mm travel. On fast, chattery tracks, the smooth operation is impressive and comfortable. The SID SL forks are very controllable and reduce vibration transfer.


2021 forks sit higher and absorb more vibration than earlier generations. The redesigned air spring makes a noticeable improvement to both SID and SID DL models.


The Race Day dampers of the Ultimate option shave a useful 98g from the Charger RL damper of the lower price Select option forks. Both dampers perform well. Apart from weight, the only difference I could tell was the removal of the rebound adjuster nut from the more expensive DebonAir spring.


Rockshox XC mountain bike uphill
Cross Country bikes should be light

Over all, both SID and SID SL are a big step up in performance from previous generations. The new SID forks lineup are all sharper looking, lighter, and better performing than preceding generations.


Pushing the SID Ultimate on fast rocky tracks exceeds the performance design of the fork. The SID Ultimate coped with the challenge, but not as well as a longer travel fork. The Superlight SID began to bounce and lose precision over extreme terrain. 


I guess riders can’t have everything in one package. On the fast, rough stuff, I longed for the precision that the Rockshox Pike would have provided. 


Admittedly, I was testing the limit of the SID beyond its intended use. Even though it was not designed for rough downhill, the SID performed better than I expected. The fork never bottomed, and I did not use any of the bottomless tokens that were included with the forks.

SIDs are very capable forks which emphasize lightness as their primary goal. The SID and SID SL pack an incredible amount of functionality into these ultra light units. Both models are great cross-country forks with the SID certainly able to hold its own against some of its trail centric competitors.

For riders that don’t downhill much, the Rockshox SID SL is fantastic. It smashes fast courses and light downhill tracks.

For cross-country enthusiasts that like to push into rougher country, the Rockshox SID provides a perfect balance.

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