Hands up if you're old enough to remember the original blue RockShox SID. It launched in 1998, when XC racing was arguably at its peak, two years after the first time it was included in the Summer Olympics. The fork might have only had 63mm of travel, but it had a huge impact on the XC scene and has gone on to carve quite a legacy as the benchmark XC race fork, racking up countless race wins from local league to World Cup level.
This latest SID was launched as part of RockShox’s Signature Series line, which also includes the Pike and Lyrik. The fundamental chassis design for the SID hasn’t changed, but the foil graphics are new and there’s now new Maxima Plush damping fluid which is aimed at reducing friction and noise. The air-sprung fork uses a Charger 2 damper with an XC-oriented tune for more support during those out-of-the-saddle uphill sprints.
RockShox SID Ultimate Carbon Details
• Intended use: XC / marathon
• Wheel size: 27.5'' or 29''
• Travel: 100mm only
• Carbon fiber crown and steerer
• 2-position compression adjustment
• Boost thru-axle
• Offset: 42mm (27.5"), 42mm (29"), 51mm (29")
• Weight: 29" - 1,477g (3.18lb) actual weight (uncut steerer)
• Price: $999 USD
SID, by the way, stands for Superlight Integrated Design and this top-level Ultimate Carbon model is a superb expression of that tagline. It’s a 100mm travel fork, no more or less than XC racers really need, with a carbon fiber crown integrated into the carbon steerer tube. More modestly priced versions with aluminum steerers are available, including the SID Ultimate which uses an aluminum steerer tube and crown to save money, and is offered in a 120mm version for riders who want more confidence and comfort on rough tracks. All forks have Boost spacing and a choice of 29 or 27.5" wheel sizes, and 42mm offset on both and an extra 51mm offset option on the 29" version.
The Ultimate Carbon combines the aforementioned carbon fiber steerer tube, tapered from 1.5” to 1 1/8” with an integrated bearing race. The lower legs are made from magnesium with as much material removed as possible to save weight, especially around machined dropouts compatible with SRAM's Torque Cap. I tested the 29" and 42mm offset version, and all forks have 15x110mm Boost width axle spacing. The 32mm diameter stanchions have sag markings neatly printed on them for easier setup.
Weight is critical for XC racers. Less weight obviously means you’ll get to the top of the climb quicker and with less energy expended, but it’s a fine line between being light and stiff, durable and reliable. On the scales, the 29” Boost fork with an uncut steerer tube is 1,477g.Setup
Installing the fork was a breeze. I used a carbon-specific hacksaw to trim the carbon steerer tube to the desired length. A supplied headset compression bung cinches the stem and spacers down onto the frame, and I had no problems getting it all straight and tight.
Setting the air pressure is made easy with sag markings on the legs, plus a recommended air pressure chart on the back of the leg. There's even a handy app so getting up and running with a good setup is made as easy as having a mechanic do the job for you. Further tuning is available with Bottomless Tokens; two are fitted as standard and you get a small bag of spares so you can add more if you need. Adding or indeed removing tokens is simply a case of removing the top cap with a cassette lockring tool. I settled on 70 psi with two tokens.Performance
When you’re racing or riding on the limit you want your XC suspension fork to get on with the business of smoothing the rough while going largely unnoticed, with no excessive bob impacting speed on smooth trails and climbs. The SID delivered all of this, wrapped up in a lightweight and stiff package with easy tunability. It dealt with everything with buttery smoothness and adequate control, and handled all manner of impacts from square-edge ugliness to high-frequency ripples and smaller rocks and roots without any fuss. The damping ensures the fork recovers extremely well from successive big impacts and is ready for the next.
When you’ve got a mere 100mm of travel to play with, the suspension curve needs to work hard, ensuring you have a supple early stroke for dealing with small chitter-chatter that can buzz the handlebars, yet ramp up sufficiently to prevent bottom out over drops and jumps. The SID manages this tricky balance well. There's a smooth progression to full travel with no harsh bottoming out even if you ride like a complete ham-fisted idiot. On-the-fly adjustment is limited to open or locked out, but you can adjust the low-speed compression of the open model so you can tune the fork to suit different courses, say if one is really smooth and another is full of chundery rocks. The range of rebound damping is ample so you can run it quick or slow to suit your preference.
Measuring the stiffness of a fork outside of a rigorous lab test in the real world is a tricky old thing to assess, and there are so many variables, not least rider weight. Weighing in at about 150 lb / 68kg (on a good day) I didn't find the fork to flutter down the harder descents on my local trails or go vague when slamming into tight corners after a bunch of frantic braking to get the speed down low enough to be able to swing around the corner. The all-carbon steerer tube and the crown really aren't just for show and weight loss, it does seem to deliver impressive stiffness ensuring the front wheel goes where you point it, even when you're redlining and puking up your lungs. The steering is precise, it manages heavy braking and it's stout when you're heaving on the bars up a punchy climb.
Talking of climbing, the SID damping is well-suited when you're battling with the cruel mistress that is gravity. Whether you’re spinning a low gear on a smooth fire road or mashing a big gear out of the saddle up a rough boulder-strewn track, the SID fork didn't bob excessively - it just feel composed and stable. The Charger 2 damper prevents unwanted movement giving you maximum efficiency when you're on your limit and trying to extra every ounce of power to keep ahead or alongside your main rival in a race.
You can easily lock out the fork on the move with a flick of the Charger 2 dial. XC racers will probably want the optional OneLoc remote control for adjusting on the fly, but away from races and on fast trail rides where I wasn't against the clock I simply left the fork in the open mode, because it's composed enough that you don't feel at a loss in any situation. It would be nice to have a third 'trail' mode as with the Fox 32, though, for a bit more choice between fully open and locked out. The lockout mode does have a blow-off valve so if you forget to flick the switch before hitting a rough trail you won't blow your wrists to a thousand pieces when you hit the first obstacle.How does it compare?
The obvious comparison to make is with the Fox 32 StepCast
I recently reviewed. Both offer 100mm of travel, but if weight is a major factor in your buying decision, there’s no getting away from the fact that despite its obvious lack of carbon fiber, the Fox is the lighter fork. Granted, only by 34 grams, but grams are grams. When it comes to stiffness, I honestly couldn't detect a substantial difference between the two forks - they both felt solid with precise steering.
Suspension performance is very similar on the two forks too. Each fork can be tuned with volume tokens and there's also low-speed compression adjustment on the top dial so you can make small changes with no tools before a race, or bigger changes back at the pits. The Fox provides a bit more on-the-fly adjustment with three compression modes available from the top dial, while the SID is limited to open and locked. Testing both forks with the same volume tokens (1 per fork) and the same sag produced in the SID a more supportive feeling fork that was less active on the smaller bumps, whilst the Fox was more sensitive and active to smaller impacts. Both displayed good bottom-out resistance with ample progression when you land jumps or hit big holes.
Splitting differences then is tricky. They both offer top-level performance that any racer would be more than happy with. Both are high end forks providing top-level performance and each is offered in cheaper versions if money is a factor. Whichever fork you choose you’re not going to be unhappy.
Controlled, predictable, and smooth damping+
Easy to set up
Not the absolute lightest in this category-
Only 2-way adjustment