In 1990 RockShox hit it big. Ned Overend and Greg Herbold rode RockShox RS-1s to victory in men’s cross-country and downhill at the first UCI World Championships in Durango, Colorado. The game had changed and mountain biking had entered the age of suspension. Skip forward to 1998 and RockShox introduced the SID, a fork that would come to represent the absolute pinnacle of RockShox suspension technology. Through the use of cutting-edge technology and the lightest exotic materials available, the SID suspension fork became the preferred mountain bike fork of World Cup racers and elite cross-country racers worldwide. 

Fourteen years later, the 2012 SID Dual Air XX comes in both 26- and 29-inch models. With travel choices of 80/100/120-millimeter for 26-inch and 80/100-millimeter for 29er’s, the SID Dual Air XX is meant to take on the duties of the modern cross-country mountain bike. It uses hollow forged AL66 crown and aluminum tapered steer tube, low-friction anodized sanction tubes made from 7000-series 32-millimeter straight wall alloy, lowers made of magnesium with RockShox’s Power Bulge and post-mounted disc brake tabs—with options for either 9-millimeter QR or the Maxle Lite 15-millimeter thru-axle.

The internals are comprised of several RockShox technologies. First is the Dual Air spring—a technology SID forks have used since 1999. This is actually two air springs, one for negative travel and one for positive travel. Second is the BlackBox Motion Control which smoothes out the fork’s movements by soaking up small trail bumps, while not soaking up the rider’s energy through pedaling input. It is then combined with Dual Flow that comprises two separate dampening circuits, and allows for the rider to adjust small bump sensitivity on one damping circuit. The second damping circuit is for the factory end stroke setting. The SID Dual Air XX is compatible with RockShox’s new Xloc hydraulic remote fork lock out. The Xloc remote has an adjustable blow off via a barrel adjuster on the remote. It is also compatible with SRAM/RockShox’s Match Maker clamp, thus clamping the Xloc, SRAM shifter pod and brake lever all on one clamp. Translation: this is not that old Mag 21 in the corner of the garage.

We tested the 100-millimeter 29er version of the SID Dual Air XX, complete with 15-millimeter Maxle Lite front axle system and the Xloc remote lockout. Our test mule was a Trek Super Fly 100 29er, thus providing a balanced platform to test the SID Dual Air XX 29er fork. Setup was a breeze due to the recommended rider weight psi chart labeled on the fork’s lowers. It includes both the setting for the negative and positive air springs based upon rider weight. The uppers are labeled with a graduated sag chart and red o-ring, making sag setup easy.

 

SID forks have always balanced rigidity and stiffness with lightweight performance, making for a somewhat willowy ride. But in 2009, RockShox increased the SID stanchion diameter from 28 millimeters to 32 millimeters, making handling a confident, point-and-shoot affair. We liked the ability to lock out the fork with the Xloc for that initial sprint out of the parking lot and up the first climb. And once we got used to the speed with which the Xloc locked out the fork, we started using it when ever possible. The Xloc’s blow off adjustment knob is easily accessible while seated on the bike. 

When set up, the ride on the SID Dual Air XX was almost unnoticeable, meaning the SID Dual Air XX did the job it was designed to do without distracting the rider from the trail. The action was smooth, with no noticeable change over from the small bump damping circuit to the large damping circuit. Even when tuned toward the stiffer cross-county performance, the fork never felt sticky or jerky. The SID Dual Air XX smoothly absorbed the small fast bumps, while soaking up the larger hits and deep g-outs. However, it does not have a seemingly bottomless feel like other forks, but that was never the design intention of SID forks. The SID Dual Air XX retains the hard charging racer feel that SID’s have been known for.

The only drawback we could find is the uncapped fork lowers. Part of the weight savings on the SID is that the lowers are uncapped, meaning riders will have to check the bottom of the forks frequently to make sure no foreign objects or dried mud is stuck up in the uncapped section of the lowers. Also, the 15-millimeter thru Maxle Lite means riders will have to purchase a thru-axle adaptor for their car’s roof rack or a different style bicycle tray. But neither reason affects the performance of the fork. Downloads of the manual with the maintenance schedule are available via the RockShox website, just in case the hard copy gets tossed with the box. 

The SID Dual Air XX 100-millimeter 29er is for the rider looking to upgrade their hard tail or full-suspension racing machine. It brings an elite racing option to the plate at a price well below the world cup model SID. The use of the tapered aluminum steer tube and hollow aluminum crown adds durability to the fork, while keeping the overall weight down. When combined with the Xloc fork remote lock out, this fork would be a significant upgrade to any hard tail or cross-country rig.  

The SID Dual XX is one of six forks in the SID line. All models are available in 26-inch and 29-inch versions with various travel options. The rest of the SID line is made up of the SID XX World Cup, SID RCT3, SID World Cup, SID RLT and SID RL.

Price: $815

Weight: 1,643 grams

More: sram.com/rockshox/