FIRST RIDE: RockShox BoXXer Ultimate 15

We get our hands on RockShox's all-new fork for two days of bike park smashing in Whistler

Downhill racing has elevated to a level that is more abusive on components and riders than ever before. The increase in speed and impact being put through bikes led RockShox to focus on better handling those forces so a rider's hands won’t have to. Seen in the past two seasons of World Cup downhill under a variety of SRAM BlackBox athletes, the all-new Boxxer wasn’t much of a secret, but the finer details within certainly were. We spent two days in Whistler getting to know the new fork to see how these changes all stack up. 

Photos: Anthony Smith


RockShox BoXXer Highlights

  • 38mm chassis 
  • DebonAir+ twin tube air spring
  • Signature Electric Red colorway
  • RockShox fender compatibility
  • Lightweight machined and anodized crown
  • Crown height gradient for a visual guide to simplify setup
  • Charger 3 RC2 damper featuring High-Speed Compression, Low-Speed Compression, and a revamped Low-Speed Rebound
  • ButterCups
  • Short and tall crown options available to accommodate different head tube lengths 
  • Ultra-low-friction SKF wiper seals 
  • Maxima Plush Dynamic suspension lube
Vital's BoXXer test bike
Vital's BoXXer test bike

What's New with BoXXer - Technical Info

The big talk with the new Boxxer is the switch to a larger 38mm stanchion diameter from the previous 35mm model. What’s even bigger is the all-new cartridge air spring paired with a proven Charger 3 damper. RockShox took the approach of using travel more effectively by creating a more linear spring curve. The fork ramps more naturally with the new air spring rather than using volume tokens. The new design uses a hollow 14mm air spring shaft to create a larger negative volume and improve the off-the-top sensitivity over the 10mm shaft found within the rest of their lineup.


Because the air cartridge is housed within the upper tube rather than running along the inner diameter of the upper tube and sealed off at the bottom, pressure built in the lower legs is dissipated along the length of the entire upper tube, creating a larger internal volume RockShox could better control. Utilizing this lower leg pressure, the upper tubes feature two ports that force oil toward the upper bushings to keep things running as smoothly as possible. Another beneficial feature found on the upper tubes is using gradient lines to set upper and lower crown heights for the correct axle-to-crown setup, ensuring enough clamping area for the upper crown.


With the larger upper tubes come new lower legs with a built-in fender mount, and a larger arch with a more robust shoulder around dust wipers. There is a new air bleeder system that will be a retroactive change to all existing models, too. Rather than the spring-loaded button with recesses to release pressure, the new bleeders are dials with a recess built into the threads. In our experience the pressure release is much easier, only requiring about a quarter turn to bleed off. This design also keeps oil from seeping out thanks to an O-ring below the head of the valve and the ability to torque them closed. The popular Buttercups technology is found at the bottom of the lower legs tied to the lower foot nut to improve vibration damping. All new crowns hold everything together with a higher torque spec across all bolts, clamps now face away from the rider, and the machined portion of the crowns has a much thinner profile than the previous generation to shave as much weight as possible while maintaining rigidity and creating a slightly wider stance. 



Using the RockShox Trail Head app to find our recommended pressure, setup was very straightforward. The app recommended a spring pressure of 196psi and 6 clicks from closed on rebound. After some parking lot testing this was bumped up to 202psi to achieve a better front-to-rear balance on our Canyon Sender test bike. First laps on the fork were spent in Whistler over the course of two rainy bike park days. We picked an easy setup lap linking Angry Pirate into Samurai Pizza Cat, Afternoon Delight, and then Heart of Darkness which provided an excellent foundation for finding a good starting point for air pressure and damper settings. We then headed up to the top of the gondola for some heavier hits after the initial setup.


On Trail

Right off the bat, squaring off roots and rapid compressions was met with incredibly active movement out of the fork which kept the front wheel on-line. Without knowing much about the internal workings of the fork and spending a lot of time on a Zeb Ultimate, our initial thoughts were that it felt nothing like the Zeb. The Boxxer nearly feels like it has a coil spring by comparison and remains consistent in every part of its travel. How active the fork remained through larger successive hits was warmly welcomed. The more we expanded into gnarlier trails throughout the day revealed how much easier it felt to ride aggressive terrain. There was a heightened sense of confidence pointing the front wheel into roots and rocks knowing the front wheel was going to maintain consistent traction. Under heavy braking, I experienced a bit of dive but was able to correct it with a few clicks of low-speed compression damping; coincidentally matching our Zeb setup of High-Speed Compression set in the middle with Low-Speed Compression at +2.


As trail speed got faster and the velocity of compressions increased, the fork was getting deeper into the travel and an additional 10psi was added bringing to the fork up to 212psi. We slowed rebound by 1 click to see if riding higher in the travel would keep things in balance better. After one run and a lot more feedback than the runs before, pressure was dropped 5psi, settling on 207psi, and we lost the click of rebound added. The fork felt perfect for the terrain and settings remained there for the rest of the trip.

Aside from the incredibly active bump absorption, the bottom-out support from the fork at the end of big rock rolls was equally impressive. The feeling could be described similarly to the hydraulic bottom-out support used in the Super Deluxe rear shock. While there is no hydraulic bottom-out control inside the Boxxer, it ramps up similarly to the rear shock, making heavy G-Outs significantly easier to manage. High-speed impacts have a similar level of support, slowing things down nicely before reaching full bottom. When full bottom was achieved, it wasn't accompanied by any clacking noise thanks to the new shaft-mounted bottom-out bumper. 


What’s the Bottom Line?

Overall, the new Boxxer is a premium-level offering for downhill applications with a lot of end-user convenience in mind. While the majority of tuning is made possible by the air spring without the use of volume spacers, RockShox has eliminated many factors that can be confusing or result in a setup that is uncomfortable. The comprehensive compression dials and effective damping of the Charger 3 damper make for easy and effective changes on trail that remove the guesswork of how many clicks in or out a rider may be. The fork is comfortable to ride all day thanks to a highly active air spring. Two days is not a lot of time to try every possible setup with the fork, but with the diversity of Whistler as the testing ground, our setup felt great in just about every situation we encountered. If downhill racing is your thing, or if you frequent the bike park and want a dual crown solution for your bike, the new Boxxer may be the best option on the market today.


About The Tester

Jonathon Simonetti - Age: 29 // Years Riding MTB: 20 // Height: 6’4” (1.93m) // Weight: 215-pounds (97.5kg)

Jonny started mountain biking in 2003 after a trip to Northstar showed him how much more could be ridden on 26” wheels than on a BMX bike. He began racing downhill in 2004 and raced for 12 years until ultimately deciding having fun on a bike was more important than race results. After working as a mechanic in the industry for a few years and developing a deeper understanding of bikes inside and out, he has an aptitude for pairing his riding ability with the analysis of bikes and breaking down what makes them work well. He spends most of his time between trail rides and skatepark sessions, with occasional days on the downhill bike. 


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