The RMU NIGHTTRAIN
At RMU we wanted to match our boutique manufacturing passion with our obsession for Mountain Biking. Our intent was to produce a highly sophisticated small batch (seriously there's not alot of them!) aluminum production for core riders who are dedicated to the mountain lifestyle. So we designed the NIGHTTRAIN in partnership with Dave Weagle using his Orion Dynamics platform and dual idler layout. The NIGHTTRAIN is a full Alloy, no compromise enduro bike that is made for the roughest of terrain to the biggest of jumps, while also being extremely efficient climbing uphill. The bike is designed to pedal very efficiently all while encouraging you to pump, jump and play around on the trail. The NIGHTTRAIN takes from our ski design philosophy at RMU of creating some of the most fun, playful, and versatile skis on the market and brings that to the Bike world.
The RMU NIGHTTRAIN is built for riders who want a true freeride/enduro crossover machine capable of handling everything from bike park laps to aggressive backcountry descents. Designed as a long-travel 29er freeride bike, the NIGHTTRAIN combines 170mm of travel with innovative mid-pivot suspension and Dave Weagle’s Orion suspension platform to deliver exceptional traction, control, and support at speed. Its unique dual idler drivetrain and two-chain drivetrain system help reduce pedal feedback while improving suspension performance through rough terrain. Built from durable aluminum, the NIGHTTRAIN stands apart from traditional alloy mountain bikes by blending playful freeride mountain bike characteristics with the efficiency and capability expected from a modern enduro mountain bike.
TRAVEL FRONT: 170MM
TRAVEL REAR: 170MM
The RMU NIGHTTRAIN 170mm isn’t just a mountain bike; it’s a statement of intent. As part of the ultra-limited production this "Midnight Onyx" edition represents the pinnacle of Rocky Mountain Underground’s engineering and aesthetic philosophy. The NIGHTTRAIN is designed for those who treat the descent as a canvas and the climb as a necessary ritual. The NIGHTTRAIN is a long-travel enduro machine that defies the sluggish stereotypes of its class.
Key Highlights
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Size Specific Geometry and Kinematics: We designed the NIGHTTRAIN with size specific geometry and kinematics. This ensures that whether you're on an S1 or S4, that you are getting a bike tailored for you and the way you ride.
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Elite Pedigree: A bespoke "Midnight Onyx" finish—a deep, stealth-matte aesthetic complemented by premium hardware and understated branding that whispers rather than screams.
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170mm of Pure Confidence: With 170mm of travel, the NIGHTTRAIN is built to swallow rock gardens, huck-to-flats, and steep technical chutes while maintaining a supportive mid-stroke for popping off side hits.
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Precision Geometry: Engineered for high-speed stability without sacrificing the "flickability" RMU is known for. It features a slack head tube angle for the steeps and a steep seat tube angle to keep you centered during grueling transfers.
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Aluminum Mastery: The frame utilizes 6066-T6 aluminum frame, optimized for a perfect strength-to-weight ratio.
About Orion
Dave Weagle's Orion Dynamics is the latest in a long line of his industry defining suspension platforms. The Orion design provides an efficient and stable pedaling response on both smooth terrain and in the rough, and without even a hint of pedal feedback. Exceptional mid-travel square-edged bump compliance creates continuous traction in varied terrain so you're always in control. Optimized for single-chainring big range drivetrains, its two short links work in concert to provide controlled lateral stiffness and keep braking forces in check when the trail gets rough. Seated or standing, climbing or cornering, jumping or hammering rock gardens, Orion does it all and does it well.
RMU worked with Dave Weagle to use Orion as a 6 bar flexstay design. This ensures precise suspension tuning and pedaling support. The design is supple on the small bumps, but when you get into berms and want to pop features on the trail, there’s support to work with, and as soon as you get into the bigger square-edged hits, that support gives way to big bump compliance. The harder you push it, the more it rewards you
Dual Idler
Dave Weagle invented the dual idler as a suspension solution to achieve a mid-pivot vertical chainline location without the efficiency loss drawbacks of a single idler. The dual idler is a thoughtfully engineered dual chain layout that uses large odd numbered tooth primary chainrings coupled with an even number of chain links. This makes for very low chain wear and great chain life, while using 100 year old chain engineering principles to gain extremely efficient power transfer to the secondary drive. The secondary drive chainring is also quite large compared to a single idler, which makes it very efficient. It uses an even tooth narrow wide chainring setup. At the same time the elevated slack side of the chain dramatically reduces pedal feedback and the effect of the rear derailleur clutch on the suspension. So there are suspension gains all over the place with this layout.
Mid Pivot
The 6-bar flex stay Orion suspension is configured in a mid-pivot layout, capitalizing on the best parts of conventional and high pivot suspensions without the drawbacks of either. The result is a bike that maintains traction and momentum through rough terrain while remaining efficient and composed under power, climbing, and braking.
We pushed to maintain shorter static chainstays because of the axle path of the mid pivot suspension design. This bike will be longer at sag than conventional suspension platforms so chainstays will lengthen to support the rearend but in the mid and end stroke it won't expand so long that it feels like a school bus.
Size specific GEO and Kinematics
We designed the NIGHTTRAIN with size specific geometry and kinematics. This ensures that whether you're on an S1 or S4, that you are getting a bike tailored for you and the way you ride.We achieved this size specific geometry and kinematics by changing the layout of the dual idler in relation to the chain line. It not being connected to the bottom bracket center allows the chain length to remain the same across all sizes. The entire linkage system, including the idler moves for our geometry and also us tailors the leverage ratio curves and suspension kinematics per size.
Build Kits
Bike Geo
Chainstay length is much larger under sag then conventional drivetrains. We built a shorter static chainstay to compensate for this growth as to not make the bike feel too long in the mid and end stroke. S2 grows roughly 30mm from static to dynamic.
Engineering
The rear brake mount is routed inside the flex stay and set on the chain stay and remove breaking forces from the flex stay. This makes more precise suspension feel and movement through braking that wont wallow when brakes are applied.
Shock Progression
Were using a 65mm stroke to drive 170mm of travel making a poppy leverage rate for the nimble rider but supplementing that with the mid high pivot design to make sure the bike has all out speed.
DW Orion Suspension
RMU utilized Dave Weagle's Orion suspension kinematics but in a 6 bar flex stay approach to the bike. Utilizing DW's 6 bar approach allows RMU to virtually manipulate the suspension kinematics to create a highly efficient pedaling rig with straight line power and playful handling in the corners.
DW Dual Idler Mid High Pivot
Using Dave Weagles award winning Orion suspension, RMU integrated the orion pivot inside of the unique dual chain ilder. This system increases pedaling efficiency but allows the NIGHTTRAIN to highlight all the benefits of a mid high link bike.
Flex Stay
Dave Weagle designed the NIGHTTRAIN'S suspension with a flex stay to simplify pivot usage and move into the 6bar design vs past 4 bar and 5 bar DW link bikes. This design also allows us to support the midstroke in air shocks, making for much better trail feel through the whole travel of the bike.
Aluminum
RMU wanted to move forward with the lightest space age Aluminum construction possible. Using 6066 aluminum allows us to have full adaptability with CNC and forged parts. Paramount to all of us is our ability to Recycle all RMU Frames making sure no material is wasted from our production.
Seat post insertion
Straight piped and low slung. Tons of room for seat post insertion even on S1!
157mm Rear Hub
This decision was mandatory due to the nature of the dual idler platform, there simply is not enough room. It also allowed us to make the rear end more compliant with the support of stiffer wheels.