Updated last year, RockShox’s new SID fork still has its eye on the prize with regards to World Cup podiums and Olympic gold medals, but it has also been allowed to stretch its legs into the trail-riding arena, or what’s lately become known as ‘down-country’.  As such there are two versions of the fork; the SL built for racing, and the SID, for low-fat shredding.

>>> Best mountain bike suspension forks 2021

The model tested here is the latter, in Ultimate damper spec, and it’s built burlier than the average XC fork with 35mm diameter upper tubes – just like the RockShox Pike and Lyrik – to keep it tracking precisely during aggressive cornering and other X-rated XC antics. Binding the lower legs together is a 15mm thru-axle bolstered by RockShox’s oversized Torque Cap hub/dropout interface. For comparison, the SL fork uses 32mm upper tubes, gets 10mm of travel and weighs a claimed 1,326g.

Milled out crown saves vital grams. Air cap uses freewheel removal tool and volume can be adjusted with tokens

Material has been carved, scooped and milled from every nook, cranny and crevice to keep the weight down to an impressive 1,508g on our test fork. That’s 150g less than an equivalent Fox 34 Step Cast that we weighed. And that’s despite RockShox moving away from the carbon crown and steerer found on the previous generation SID. However, some of the weight saving measures are much harder to spot. One of the most significant reductions comes from the new Charger Race Day damper. The new bladder unit is incredibly slim, with a much smaller oil volume, and is the best part of 90g lighter than its predecessor.

Deeply recessed rebound adjuster uses removable hex key to tune, which means the key can be used on other parts of your bike. Large dropouts interface with RockShox’s Torque caps for improved stiffness.

All these weight savings mean I didn’t feel too bad about adding 38g back with the integrated mudguard that comes with it, and I definitely enjoyed the improved vision in muddy conditions as a result. It’s not as effective as a guard that extends forward of the brace, but for such a sleek solution it works well enough in all but soaking wet conditions.

Optional damping top cap wires up to RockShox twist grip remote for on-the-fly lockout access.

To reflect the trend for World Cup racers to run 29ers almost universally, the SID is only available to fit 29in wheels, boasts 120mm travel and gets a short, 44mm offset.

New snap-in hose clip is easy to use and secure. Brace has threaded holes to accept a bespoke mudguard.

How it rides

I’ve now spent the best part of a year riding the SID Ultimate fitted to a Mondraker F-Podium, as well as other test bikes including the exceptional Transition Spur and Merida Ninety-Six 8000. During lockdown last year, the Mondraker was my go-to bike for rides from my front door, and as such I used it on a daily basis. It’s been raced and rallied on our normal stomping grounds as well as further afield in the Forest of Dean and the moors of North Yorkshire.

Our Mondraker F-Podium test bike

And on every occasion it has impressed. There’s something really enthralling about thrashing your favourite trails on a bike rocking the bare minimum of weight and travel. OK, so 120mm is still plenty, but as we become more and more accustomed to riding 150, 160 and even 170mm travel bikes, any kind of downsizing brings with it a heightened sense of what’s beneath your wheels. Less inertia, less safety net, more buzz when you get it right. It’s certainly addictive. And the RockShox SID lets you get away with riding stuff that you wouldn’t dream of tackling on any previous XC fork – at least not without the other-worldly skills of Nino Schurter.

Debonair spring keeps dynamic sag high and travel in reserve.

At the forefront of its category-straddling performance is the super supple response. A light touch to the damping is undoubtedly helped by a friction-reduction program that started with the Lyrik and has trickled down to the SID. New SKF seals, Maxima damping fluid, better fork alignment and more accurate bushing sizing all combine to let the new SID glide over even the smallest of bumps. That means more grip at the tyre and more control at the bar. In open mode it feels lively and free, but swing the lockout lever through 180° and the damping firms up to the point that you can wrestle the bars out of the saddle with only the slightest of movement. Great that the spring-loading means it always reverts to open mode, too.

By adding the Debonair spring, but tuning the position of the transfer port, RockShox has ensured that the supple response doesn’t mean a saggy fork that blows through its travel too easily. In fact it’s noticeable how high the SID rides in its stroke, which is really helpful when you don’t have lots of travel and may well be aboard a bike with a steeper head angle. Although you sit closer to top out, it never hits the ceiling with a clang. Yes, you can feel the fork hit the buffers, but it’s not a harsh, metallic bookend and I never found that it impeded overall control.

If you don’t need the remote lockout, this neat switch does the job with minimal fuss and clutter.

There’s an unequivocal feeling of riding on the spring rather than the damper with the SID, which I think suits its application, where I’m more concerned with calming the chatter than saving me from massive craters and square-edge protrusions. For that I expect to rely more on the range of movement of my limbs than a short travel suspension fork.

Given how light the fork is, there’s enough precision to let you get away with railing ruts and slamming it into turns. In back-to-back testing, we’d say it was on par with the Fox 34 Step Cast, yet the SID is 150g lighter. And that weight saving is appreciable too, with a lighter touch to the steering that keeps the front end super agile. Stiffness is a system, of which the SID is only one part, and we have found with certain handlebars and wheels that the front end can become a little less direct than we’d like. As such, take careful note of other pieces of the jigsaw if you ride hard and are thinking of running a SID instead of a burlier trail fork, such as a Pike or even a Fox 34.