New RockShox BoXXer Fork Gets 38mm Stanchions and "Coil

RockShox has updated its BoXXer dual-crown fork with a larger 38mm stanchion diameter, with the overall package said to deliver the best possible balance between stiffness, compliance, and comfort for maximum control.

Housed inside those 38mm stanchions is new twin tube DebonAir+ air spring and the Charger 3 RC2 damper offering independent adjustment of high and low speed compression damping. And, both sides benefit from the high-frequency vibration-damping ButterCups implemented previously on RockShox Ultimate level single-crown forks.

Here’s a closer look the 2024 RockShox BoXXer.

The latest BoXXer has to be one of the worst kept secrets in the bike industry this year, what with numerous Downhill World Series athletes having been spotted racing the BlackBox sticker-clad prototypes all season. Two of those athletes are none other than Trek Factory Racing’s Valentina Höll and Loris Vergier, both of whom were involved in the development of the new fork.

Under Vali, the 2024 BoXXer has been piloted to two outstanding victories this season; firstly in Leogang, in her home country of Austria, and secondly on the infamous Black Snake of Val di Sole. Vergier is going well, too, having stood on two podiums this year also.

The BoXXer offers 200mm travel in both 27.5″ and 29″ wheel size models, with updated offset options of 44mm and 48mm for 27.5″, and 48mm and 52mm for 29″. Shorter-travel air springs for 180mm and 190mm are also available aftermarket.

As mentioned, the new fork sees an increased stanchion diameter of 38mm, up from the 35mm boasted by the previous model. Still, that’s 2mm shy of the Fox 40. On this, RockShox says, “We could have made the stiffest fork possible, but we didn’t. Two years of extensive development focusing on the critical blend of bending and torsional stiffness ratios resulted in the all-new 38mm BoXXer chassis”.

Markings are added to the stanchions above the lower crown to allow for easier setup that takes away guesswork, or the need for a measuring tape. The lowers see a new arch design that is, aesthetically at least, more similar to the RockShox Zeb than it is the outgoing BoXXer model.

The new model is subtly different in the offset options available, too. While the previous 29″ model was available in 46mm and 56mm offsets, the 2024 iteration gets offsets of 48mm and 52mm. The brake mount is designed for a 200mm rotor minimum, but can take an adapter to boost that to a maximum of 220mm.

Moving swiftly on, it is the technology inside these chunkier lowers that has the biggest impact on performance. Which brings us to the…

RockShox say their new DebonAir+ air spring is unlike any air spring they’ve produced before, offering a very linear spring curve that gives an action that is “so coil-like, it’s uncanny”. They have achieved that by implementing a twin tube air spring construction wherein the positive and negative air chambers are nested within one another, with the larger 14mm hollow shaft increasing the negative air volume for improved off-the-top small bump sensitivity. The new air spring is also said to give a taller ride height for more confidence when the terrain gets steeper.

We don’t have a cutaway render to show this, unfortunately, but if one materializes, we’ll be sure to share it.

As ever, the DebonAir+ air spring is tuneable with air pressure and bottomless tokens to dial-in end-stroke ramp. Notable also is the addition of a jounce (jolt and bounce) bottom-out bumper for a less harsh experience if and when you do make it to full travel.

Both lower legs see the addition of oil flow ports that encourage continuous lubrication of the bushings by the Maxima Plush Dynamic Suspension Lube. That helps reduce friction in the system, and likely also keeps the foam o-rings underneath the wiper seals moist, too.

RockShox say, “These oil flow ports have an added benefit when the fork is going through its travel on a wicked G-out. This new design evenly distributes air volume above and below the lower bushing, resulting in a consistent spring rate you can trust on the gnarliest drop-ins”.

Finally, the new BoXXer benefits from so-called Lower Leg Plugs, a detailed image of which we don’t have to hand. However, this has an equivalent function to the Pressure Relief Valves implemented on the latest Zeb, Lyrik and Pike forks, allowing a release of air pressure that may have built up in the lowers during riding. It’s possible SRAM switched to the tweaked design in order to circumvent any potential patent infringement.

On the damper side, the 2024 BoXXer is upgraded to the Charger 3 RC2 damper. To allow for fine-tuning from track-to-track, the damper delivers high and low speed compression adjustments over 15 and 5 increments, respectively, as well as rebound adjustment over 18 increments. We are told the Charger 3 RC2 benefits from reduced cross-talk between the HSC and LSC adjustments, as compared to the Charger 2.1 that preceded it.

As seen on the DebonAir+ air spring, the damper too gets the vibration-damping ButterCups, said to remove up to 20% of trail chatter that could otherwise contribute to hand and arm fatigue on long runs.

There are two models of the 2024 RockShox BoXXer; the $1,899 USD // 2,279 €, £ 2,029 BoXXer Ultimate option, and a more basic version simply named, BoXXer. The former is available aftermarket with the choice of two different crown lengths to suit different head tube lengths, while the latter is OEM only.

While the BoXXer Ultimate benefits from all the top-end tech such as the ButterCups and the Charger 3 RC2 damper, the BoXXer goes without the golden-colored vibration-damping devices, and runs the less tuneable Charger 3 RC damper. The latter permits adjustments of Rebound and Compression damping, but lacks independent adjustment of LSC and HSC.

However, those who will go on to purchase a BoXXer-equipped downhill bike will be able to purchase aftermarket upgrades for the both the DebonAir+ air spring and the Charger 3 RC2 damper. Those have an MSRP of $104 USD // 113 € // £101, and $358 USD // 399 € // £356, respectively. The ButterCups themselves are not available separately, so if you want them, you have to buy the upgrades. That said, you don’t have to run a pair of ButterCups in order to benefit from their vibration-damping qualities; you can run a single ButterCup in either side.

There is a subtle difference in weight between BoXXer Ultimate and BoXXer, too. The former is the heavier, weighing a claimed 2,840 grams for the 200mm travel 29″ option with a 48mm offset, while the latter weighs a claimed 2,680 grams in the equivalent spec. Aside from the abovementioned details, and the graphics, the two forks are identical.

A bolt-on fender (not shown), specific to the 2024 BoXXer, is sold with the aftermarket forks, but has to be purchased as an upgrade otherwise.

sram.com/rockshox