RockShox SID SL 2021 Review | The Lightest Fork We’ve Ever Tested

The not-so-minor details


RockShox SID SL Ultimate


$1,299 AUD




- Stupendously low weight
- Supple performance
- Tuneable air spring
- Rigidity is good for such a lightweight fork
- Beautiful machining detail


- Fitment with non-Torque Cap hubs is annoying
- Rebound adjuster is inelegant, albeit functional

Wil Reviews The 2021 RockShox SID SL

Earlier this year, RockShox unveiled a completely re-engineered SID. As the brand’s premium short travel XC fork, the latest version of the SID arrived in March with its sights set on a spectacularly successful year of World Cup and Olympic glory underneath some of the fastest mountain bikers in the world. Of course, 2020 didn’t quite go according to plan. We were lucky to get a few rounds of World Cup action in, along with the World Championships, where we saw SID between the race tape alongside Bec McConnell, Pauline Ferrand-Prévot and Nino Schurter. The tantalising hors d’oeuvre of racing was a brief but welcome distraction from a certain global pandemic, though unfortunately SID, and everyone else, will have to wait just a little longer for the world’s biggest XCO event.

2021 rockshox sid sl ultimate fork
On the left, the 100mm travel SID SL. On the right, the 120mm travel SID. Note the difference in the chassis design between the two.

SID Splits In Two

While the Olympics didn’t eventuate this year, we’re mighty glad that SID did happen, because it’s a significant step up for RockShox. In case you missed our launch feature, the big news here is that SID has split into two very distinct options;

We’ve already spent a load of time on the bigger 120mm travel SID, which blew us away with its supple and progressive suspension performance, as well as its supremely low weight given the big 35mm chassis. You can check out our review of the RockShox SID Ultimate fork here. In this review, we’ll be going into detail about our experience of testing the lighter option of the two – the SID SL.

2021 rockshox sid sl ultimate fork santa cruz blur cc
We’ve been testing the RockShox SID SL for the past few months across a variety of different bikes.

All-New Flesh & Bones

With the SID SL carrying the mantel as the XC race fork in the RockShox lineup, it gets an entirely new chassis that has been optimised to be as light as possible. In order to achieve that goal, options have been pared right back. The SID SL is only available with 100mm of travel, and it’s specifically designed for 29in wheels with Boost front hubs. For those on 27.5in wheels or non-Boost hubs, you’ll have to look further down the RockShox pecking order.

Just like the bigger SID and the new ZEB, the SID SL will only come in a 44mm offset. That matches the 44mm offset option from Fox, and it would appear that the two suspension giants have settled on that number as being the main standard for their 29er forks moving forward.

The SID SL is built around 32mm diameter tapered alloy upper tubes, which plug into a forged alloy crown that is post-machined and anodised on the higher-end Ultimate model. For further weight savings, the one-piece magnesium lowers are completely hollow at the base, and they’re also stepped on the inside face – not unlike the Fox 32 Step-Cast (SC). Even the bolt-up axle is externally machined. The Maxle Stealth weighs a paltry 38g – that’s half the weight of a regular Maxle.

The SID SL gets entirely new guts too, including the latest generation DebonAir spring. The other leg houses the new Charger Race Day damper, which features adjustable rebound damping and a simple two-position lockout. You can get it in a crown-adjust version (as tested) or with a remote lockout for an extra $100 AUD.

2021 rockshox sid sl ultimate
The SID SL chassis has been optimised to remove as many grams as possible. The result? The lightest fork we’ve ever tested.

1,300 grams? Holy Banana!

As per RockShox’ claims, our SID SL Ultimate test fork clocked in at just 1,328g on the scales with an uncut steerer tube. With the steerer cut to 165mm, that weight came down to 1,300g on the nose. To put that into perspective, that’s nearly a 200g reduction over the previous SID Ultimate Carbon fork. Flamin’ Nora that’s light!

The new chassis has, of course, helped to chisel away excess material, but there have been bigger gains with the new Charger Race Day damper, which has taken off 100 whole grams alone. The Charger Race Day damper is essentially a shrunken down version of the Charger 2.1 damper you’d find in a Pike. Given it only has to cover the 100mm SID SL and 120mm SID, the Charger Race Day damper features a smaller bladder, less oil, and smaller valving. Even the damper top cap has been machined within an inch of its life to eliminate as many grams as possible.

2021 rockshox sid sl ultimate fork
Anodised sag gradients on the upper tube make setup a breeze. It’s also easy to see how much travel you’re using too.

How Does That Weight Compare To The Competition?

Very favourably. In fact, it’s the lightest fork we’ve ever tested, lighter even than the previous benchmark – the Fox 32 SC. For a point of reference on that weight figure, here’s how the SID SL Ultimate compares to some of the other big name options on the market;

2021 rockshox sid sl ultimate fork vs fox 32 step-cast factory series
The SID SL is over 100g lighter than the previous title holder – the Fox 32 Step-Cast.

There’s A Cheaper Select Model Too

For those looking to buy a new SID SL aftermarket, there are two options; the Ultimate that we have here, and a cheaper Select model.

The SID SL Select comes with the same core chassis – the lowers, upper tubes and DebonAir spring are identical. The main difference is in the damper. Instead of the Charger Race Day damper, the SID SL Select gets a standard Charger RL damper, and it also misses out on the additional machining and anodising on its alloy crown.

The result is an increase in weight by around 140g. However, with a sticker price of $999 AUD for the crown-adjust version, it’s also $300 cheaper than the Ultimate model.

2021 rockshox sid sl ultimate fork santa cruz blur cc wil

Testing The RockShox SID SL Ultimate

Over the past seven months, I’ve had the chance to ride three different SID SL forks across four different bikes. The main fork I’ve been riding is a blue SID SL Ultimate with a crown-mounted lockout, which was first fitted to my Santa Cruz Blur CC, where it replaced a Fox 32 Step-Cast Factory fork. I’ve also tested that fork on the Orbea Oiz M-Team, and more recently, I’ve been riding a SID SL Ultimate with a remote lockout on our Trek Supercaliber 9.9 test bike.

Torque Cap Hubs Are Great – When You Have Them

All of those bikes have come with standard Boost hubs, which results in an annoying fit with the oversized Torque Cap dropouts on the SID SL fork. Installing the front wheel becomes a more tedious affair since you have to float the front hub between the fork dropouts to just the right spot before the axle slides through. It’s annoying if you need to remove the wheel to throw the bike in the boot of your car, but it’s downright infuriating during a race when you’re trying to repair a puncture.

2021 rockshox sid sl ultimate fork
The SID SL will fit a regular Boost hub, but the smaller end caps float around inside the cavernous dropouts, making axle installation faffier than it needs to be.

This is expected fare for RockShox forks these days, which are compatible with standard Boost hubs and 20mm diameter end caps, but are optimised to be used with Boost hubs with oversized 31mm diameter Torque Cap end caps. When paired together, the result is increased torsional stiffness due to the bigger surface area contact between fork dropout and hub.

It is noticeable too – the Specialized S-Works Epic we tested back in June had a Brain-equipped SID SL fork with a matching Torque Cap front hub, and the improved steering precision was both apparent and welcome. The fit is neater too, and the hub locates quickly and easily. Fundamentally it’s a great design; I just wish we’d see more hubs with those oversized end caps to make use of it.

It’s hard to see in this shot, but the Roval hub comes with the bigger 31mm diameter Torque Cap end caps, resulting in a neater fit, and improved steering precision.

Big Brakes & Big-Ish Tyres

Surprising for such a lightweight fork, the SID SL is officially rated for use with up to a whopping 200mm brake rotor. Otherwise, the post mount tabs are setup to work with a 160mm rotor without an adapter, which is how I’ve had it set up on the Blur. A favourite detail of mine is the non-tooled guide for the brake hose. It’s a snug press-fit, with no cape ties or tiny hex keys required.

With the broader Boost spacing, the SID SL is also rated for use with up to a 60mm (2.36in) wide tyre. Bear in mind that RockShox is a little conservative here, as that maximum width requires a certain amount of clearance around the tyre casing. I’ve had a 2.35in Schwalbe Racing Ray and a 2.35in Maxxis Rekon Race in there without issue, and Nino Schurter has been racing with 2.4in Aspens all season, and he seems to be doing fine. Regardless, it’s always worth checking by depressurising the fork and seeing if the tyre clears at full travel. The last thing you’d want is the front tyre contacting the crown on a hard landing. If you thought 2020 was bad, I can guarantee that it would make things far worse.

Setting Up

With just an air spring and adjustable rebound damping, the SID SL is straightforward to setup. There’s a pressure guide on the back of the fork leg to help get you in the ballpark. I also love that RockShox has anodised sag gradients onto the upper tube, making it easy to eyeball the sag level, while also seeing how close you’ve gotten to full travel during a ride.

For my 68kg riding weight, I started with 100psi in the air spring as recommended, which delivered 25% static sag when standing up on the pedals. While the DebonAir spring is new for this year, the SID SL relies on the same black Bottomless Tokens as the previous SID and Reba forks. From the factory, the SID SL comes with zero Tokens inside, though you can run up to three to increase bottom-out support.

rockshox sid sl bottomless tokens 32mm shock pump cassette tool workshop
The SID SL continues to use the same black 32mm Bottomless Token volume spacers.
2021 rockshox sid sl ultimate fork
DebonAir spring on the left, Charger Race Day damper on the right.

To adjust rebound damping, there’s a minimalist 2.5mm L-handle hex key that plugs into the underside of the fork leg. It’s a little awkward to use, but it’s also very light, and it can be removed to adjust the tooled rebound adjustment on the new SIDLuxe shock. I also found it handy for adjusting the tension on my XTR pedals mid-ride, since most multi-tools don’t actually come with a 2.5mm hex key. As for the rebound setting, I set up my fork on the slower side (7/19 clicks).

With air pressure and rebound set, the Charger Race Day damper gives you a simple two-position lockout. Like the rest of the fork, the lever has been machined within an inch of its life, though it’s nice and positive in use. There are no other external compression adjustments – the damper tune for the open and closed settings is pre-set from the factory. Fiddlers may lament the lack of dials, but I like that RockShox has kept things simple here.

So Smooth, So Light

On the trail, the SID SL shows an immediate improvement in performance over the previous generation SID. The new fork is much smoother, with vastly improved small-bump compliance, resulting in more comfort at the grips, more traction at the tyre contact patch, and more control on bigger impacts. Given there’s just 100mm of travel, it’s an impressively supple fork.

With the old SID, I found I had to load it up with 2-3 Bottomless Tokens so I could run lower pressures and squeeze out more small-bump compliance. It was still never the most freely-sliding fork though, especially compared to the Fox 32 Step-Cast. And for bigger riders who needed even more support, you were also a bit limited with how many Tokens you could fit inside the small air chamber.

2021 rockshox sid sl ultimate fork santa cruz blur cc wil
The new SID SL is impressively sensitive on the trail, with excellent comfort and grip on technical singletrack.

In comparison, the SID SL is nice and slippery right out of the box. The reduced friction no doubt comes down to a variety of factors including the Charger Race Day damper and the addition of SKF-made wiper seals. The new DebonAir spring is also much more refined. It’s noticeably more progressive, even without any Tokens inside.

The SID SL also rides a touch higher, with less travel eaten up by the negative air spring. This is due to a change in the transfer port between the positive and negative chambers, which is now located at the seal head. Aside from helping the fork to sit higher in its travel and better resisting dive under braking, it also means you don’t have to repeatedly compress the fork to equalise pressures when inflating the fork.

On that note, RockShox has rolled out the DebonAir C1 air spring into the latest Pike, Revelation, Lyrik and Yari forks, and it’s also available as an aftermarket upgrade. Check out our standalone review of the new DebonAir spring for more info.

How Does It Compare To Big SID?

Though it is smooth and well supported, the SID SL isn’t quite as plush as its bigger brother, the 120mm travel SID. As you’d expect given the 200g weight increase and bigger 35mm upper tubes, the regular SID does feel more planted on the trail. This becomes noticeable on harder and faster off-camber impacts, where the beefier fork tracks with more precision and less deflection. It also has a more progressive spring curve, to the point where I’ve never once hit full travel.

2021 rockshox sid ultimate fork
The bigger 120mm travel SID uses 35mm upper tubes, giving it a beefier appearance and more planted performance on the trail.

In comparison, I have been able to bottom out the 100mm travel SID SL on similar-sized drops. Bear in mind that we’re talking hard, flat landings that I occasionally encounter on one of my local test loops, which I wouldn’t describe as being typical of an XCO race course. In the spirit of science though, I did try adding a Bottomless Token inside the air spring, which helped to increase support on those harder landings. However, it did come at the expense of small-bump compliance. I’ve since gone back to zero Tokens, while also focussing on riding smoother and taking better lines, and all has been rosy.

On the note of the bigger SID, it’s worth mentioning that some World Cup riders, including Nino Schurter, are actually choosing the SID over the SID SL. Schurter’s Scott Spark race bike is equipped with a 110mm travel SID Ultimate, so clearly there’s enough of an improvement in ride quality to warrant the additional weight. And certainly, for riders on the heavier side, it’d be well worth considering the regular SID, particularly in its 110mm travel guise, assuming your bike can handle it.

RockShox SID SL vs Fox 32 SC

The bigger question though, is how does the SID SL compare to its main rival, the Fox 32 SC?

I’ve had a load of saddle time on both forks – the 32 SC spent about six months on the front of my Blur before it was replaced by the SID SL. To get a more accurate sense of the comparative performance differences though, I conducted an additional back-to-back test session where I swapped the two forks around on the front of an Orbea Oiz, riding several laps of exactly the same test loop with only the fork changing each lap. On top of that, I’ve garnered further on-trail experience of each fork on a variety of other bikes, including the Canyon Exceed and Specialized Epic.

Here’s how the two stack up against each other.

Weight: As mentioned earlier, the new SID SL has turned the tables in terms of weight. It’s now lighter than the Fox 32 SC by over 100g (1,300g vs 1,406g), which is a considerable margin, especially for the more gram-obsessed riders out there.

Chassis: Structurally the two forks are fairly similar, though the SID SL does actually look a little broader and beefier alongside the anaemic 32 SC. Stated tyre clearance is a touch more generous on the SID SL (2.35in vs 2.3in), and the axle-to-crown distance is a hair longer too (506mm vs 503.7mm).

Adjustability: Fox does offer more adjustability with the FIT4 damper in its premium 32 SC Factory Series fork. On the crown-adjust version, you get a blue three-position compression lever with Open, Medium & Firm settings, along with a black low-speed compression dial for tuning the compression damping in the Open mode. Personally, I only ever use the Open or Firm settings, while using the low-speed compression dial to add a little more support. In comparison, the SID SL is much simpler – the lockout is either on or off. When locked out, both forks offer a properly firm platform, though if you do hit something really hard, there’s a built-in threshold to automatically open the fork up and protect the damper internals.

2021 rockshox sid sl ultimate fork fox 32 step-cast factory series
The FIT4 damper on the Fox 32 SC offers more adjustability. Whether that’s useful to you is another matter.

Remote Lockout: Both the SID SL and Fox 32 SC are available in a remote lockout version. You get two remote options with RockShox; there’s a trigger-style remote, and the TwistLoc remote. The TwistLoc is worth mentioning because it offers neater compatibility with under-the-bar dropper post levers. In comparison, Fox just offers the single trigger-style remote lockout. It works well, and if paired to a push-to-unlock damper, it does offer a much lighter feel at the lever.

Performance: On the trail, there is honestly little separating these two forks. While the SID SL looks beefier, I can’t say I honestly noticed a difference in handling precision or chassis flex between the two when setup with the same front wheel. However, the SID SL does move ahead when paired to a Torque Cap hub, so be sure to seek that out if it’s an option for you. These are still lightweight XC race forks though, and there’s always going to be more bending and more twang compared to their burlier siblings. Both are very smooth though, and when ridden on different days, there’s nothing separating them. In back-to-back testing however, I found the SID SL to be just a fraction more sensitive over rubble and square-edge rock strikes. It’s impressively supple for such a weight-focussed fork.

Conclusion: If I was building up a bike from scratch and looking for a new fork, I’d pick the SID SL. It’s a little bit cheaper, and a decent amount lighter, and I like the ease of setup and tuning options. If you already own a Fox 32 SC though, particularly the newer version with the stiffer crown, I wouldn’t be rushing out to sell it to buy a SID SL, unless you desperately wanted to drop some weight from your bike. Both are fabulous performers that are well suited to fast-paced XC riding and racing.


I’m still yet to encounter an issue with our SID SL Ultimate test fork, though it is due for a lower leg service, which RockShox recommends every 50-hours of ride time. Replacement seal kits sell for $29.95 AUD, and any decent bike shop will be well versed in performing this procedure in-house. A full damper and spring service are then recommended for the 200-hour mark, which is more involved but still relatively straightforward, particularly with the nifty external bleed port on the damper top cap.

For anything trickier, there’s always SRAM’s Melbourne-based DSD service centre, which is there to provide backup support both inside and outside of RockShox’ two-year manufacturing warranty. That’s solid peace of mind for sure.

On the note of servicing and spares, it’s worth noting that if you did decide to go for the cheaper Select model, or you’ve purchased a complete bike that comes with one, it is possible to upgrade to the lighter Charger Race Day damper. That’ll set you back $449 AUD. Of course it’d be cheaper to buy the Ultimate model outright, but it’s still nice to see upgrade options.

2021 rockshox sid sl ultimate fork
The SID SL is an impressively well engineered fork, and it shows on both the scales and on the trail.

Flow’s Verdict

In the realm of lightweight XC forks, the new RockShox SID SL takes the mantle as being the best we’ve tested yet. It’s the lightest option by a fair margin, and it brings significantly smoother performance than its predecessor. It’s bristling with neat engineering details, including the beautifully machined crown and trick damper, and it offers excellent steering precision given the stupendously low 1,300g weight.

It might not have all the adjustability of the Fox 32 SC, and performance on the trail is otherwise hair-splittingly similar, but the SID SL impresses with its simple setup and ease of tuning. I’d recommend pairing it to a Torque Cap hub if you can, both to maximise handling accuracy and reduce installation faff.

Fox 32 SC owners don’t need to sweat too much, though if you own an old SID or Reba, this new SID SL is a thoroughly worthwhile upgrade. Not only see you drop a significant amount of weight, it’ll also bring with it more traction, more comfort and more spring support too.

2021 rockshox sid sl ultimate fork santa cruz blur cc wil
Looking for the ultimate XC fork? For those chasing grams, it doesn’t get any better than this.

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