RockShox reveals radical new BoXXer

Updated downhill fork is 29er-compatable, air-spring only and uses “20mm Boost” axle standard

From world cup winners to weekend warriors, the RockShox BoXXer has long been the go-to fork for many downhill and bike-park riders. For 2019, it’s packing some significant updates.

For starters, it’s available in 29in as well as 27.5in wheel size options. Along with Fox’s 29in 40, this makes it among the first commercially available, non-inverted downhill forks on the market.

Throughout the 2017 season, some world cup riders experimented with forks, which used BoXXer uppers and internals with the lowers from a 29er Lyrik, to create a BoXXer-Lyrik (Lyxer?) hybrid that could fit 29in wheels.

More recently, world cup riders have been spotted testing a new 29er BoXXer, with visibly different crowns and lowers. This is that fork.

Lower-profile crowns provide more useable bar-height options. The new RC2 damper offers high- and low-speed compression adjustment
Lower-profile crowns provide more useable bar-height options. The new RC2 damper offers high- and low-speed compression adjustment

The crowns are machined to look like aftermarket moto-fork crowns, while allowing for more bar height adjustability and, in the case of the 29er fork, to compensate for the bigger wheels.

Both wheel sizes use the same upper assembly, but the 29er version uses a different lower to provide the extra wheel clearance, as well as added fork offset. This is the opposite to how offset is adjusted in single-crown forks, where the lower offset remains the same but the sweep of the crown changes.

The 27.5in BoXXer gets 48mm offset like the older fork, while the 29er version has 56mm. The extra offset is intended to compensate for the effects of the larger wheel size by reducing the trail figure, which is otherwise lengthened by the larger wheel-diameter.

It’s not that simple, of course, but increasing offset is intended to quicken the steering which is otherwise made slower by bigger wheels.

A new axle standard?

The new BoXXer uses an axle-hub “standard” previously only whispered about or spotted in world cup pits. It’s called 20mm Boost.

Dear bike industry: really, a 'new' 20x110mm axle standard?!?!

This “standard” uses the same 20x110mm axle as regular 20mm forks. The difference is all to do with the brake mount — it’s 5mm further outboard than regular 20mm forks.

That allows wheels to be laced with the brake-side hub flange 5mm further out, which increases the spoke bracing angle and thereby increases the wheel’s lateral stiffness. Regular 20x110mm wheels can be made to fit with a 5mm rotor spacer, though 20mm Boost wheels won’t fit in regular 20mm forks.

Interestingly, RockShox considered using 15mm Boost axles so that customers could swap wheels between their downhill and enduro bikes. It claimed this wouldn’t necessarily have a detrimental effect on fork stiffness. Ultimately RockShox decided to stick with 20mm Boost, rather than introduce multiple axle sizes within a single discipline.

No coil springs, just coil-like air

The Debonair spring is claimed to more closely match the linear spring curve of a coil spring — softer at the start and firmer in the middle
The Debonair spring is claimed to more closely match the linear spring curve of a coil spring — softer at the start and firmer in the middle

For years, the BoXXer has been available in three price options: the cheaper two would use coil springs (the Team version with its Charger damper and coil spring works brilliantly with the right spring rate), while the most expensive World Cup model used a lighter and more adjustable air spring

Now though, RockShox is only offering air-sprung BoXXers. But as with the latest Lyrik, the air spring has been improved.

The new Debonair spring is claimed to have reduced friction and more negative air-spring volume to increase small-bump and initial-travel sensitivity while adding more mid-stroke support. So, hopefully, it should feel more like a coil anyway.

The new Debonair spring will be available aftermarket for £42 / $42 / €47(plus fitting). It will be available in 180mm, 190mm and 200mm travel.

Fancy a 180mm 29er BoXXer for your enduro bike? Now you could do that. YT has already hinted its Capra is compatible with dual-crown forks. Sounds like an awesome recipe to us.

New dampers

Like the 2019 Lyrik, the BoXXer will be available with the new RC2 damper, offering low- and high-speed compression adjustment.

There’s also a mid-priced Charger RC damper option, which is claimed to provide a more comfortable ride than Motion Control but at a lower price point than Charger RC2.

It uses a self-bleeding damper design with an IFP (internal floating piston) to manage displaced oil, rather than a bladder as with the top-end Charger damper.

Apart from the chassis, axle, spring and damper, what else is new?

Plenty of tyre clearance in the new lowers
Plenty of tyre clearance in the new lowers

Other updates include increased bushing overlap.

By widening the distance between the bushings (the surfaces at which the upper tubes are held and slide within the lowers), the effect of torsional or lateral loads on the fork friction is reduced. This should, in theory, help the fork to slide more smoothly when faced with square-edged hits or bumps when cornering.

Tyre clearance has also been increased to future-proof against inflating tyre sizes. Forks are rated to accept 2.8in tyres with the intended wheel size.

RockShox BoXXer prices and availability

  • BoXXer World Cup (Charger RC2 damper): £1,689 / $1,699 / €1,889
  • BoXXer RC (Charger RC damper): £1,299 / $1,309 / €1,449

Availability is expected in June 2018.

Seb Stott

Technical Writer, UK
Seb is a geeky technical writer for BikeRadar, as well as MBUK and What Mountain Bike magazines. Seb's background in experimental physics allows him to pick apart what's really going on with mountain bike components. Years of racing downhill, cross-country and enduro have honed a fast and aggressive riding style, so he can really put gear to the test on the trails, too.
  • Discipline: Mountain
  • Preferred Terrain: Steep!
  • Current Bikes: Focus Sam 3.0, Kona Process 111, Specialized Enduro 29 Elite
  • Dream Bike: Mondraker Crafty with Boost 29" wheels, a 160mm fork and offset bushings for maximum slackness.
  • Beer of Choice: Buckfast ('Bucky' for short)
  • Location: Bristol, UK

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