On July 27, 2026, at Crankworx Whistler, a Breckenridge ski company walked into the enduro segment with a 170mm aluminum bike, two chains, two idler pulleys, and a suspension platform nobody had seen on a production frame before. Rocky Mountain Underground, known for handmade skis and mountain-culture soft goods, built its first mountain bike around a new Dave Weagle design called Orion. The Nighttrain is the result, and its geometry and drivetrain make it one of the more unusual enduro bikes to reach production this year.
Weagle is the engineer behind DW-Link, Split Pivot, i-Track, and the Delta System that Evil and others have used for years. When his name is attached to a brand’s very first bike, the suspension is the story. The RMU Nighttrain geometry sits in familiar modern-enduro territory, but the linkage driving those numbers does not.
Why there are two chains
Most riders will notice the drivetrain before anything else. The Nighttrain routes power through two idler pulleys and two separate chains: one from the chainring to an intermediate point, a second carrying drive to the cassette. RMU calls it a dual-idler, two-chain layout, and Weagle’s framing at the launch was blunt. The dual idler is “not a feature, but a solution,” he said, describing it as the cleanest way to put the main chain exactly where the kinematics wanted it.
The goal is the same one high-pivot bikes chase: a rearward axle path that lets the rear wheel move up and back over square-edged hits instead of getting hung up. High-pivot bikes buy that path with a single idler, and they pay for it with pedal feedback and drivetrain drag. Weagle’s answer is what RMU labels a mid-pivot. It captures the rearward-path benefit of a high pivot while, in RMU’s words, delivering “drivetrain efficiency” and reduced pedal feedback “compared to traditional high pivot systems.”
The Orion platform underneath is a 6-bar flex-stay design that Weagle originally developed for motocross before adapting it to bicycles. The 65mm shock stroke drives 170mm of rear travel, and the leverage curve is tuned to feel supple off the top, supportive through the mid-stroke in berms and compressions, and progressive on big hits. “The harder you push it, the more it rewards you, which has been a hallmark of my most successful designs,” Weagle said.
There is a business reason for the platform, too. RMU is a small company, and Orion was engineered so a single linkage can underpin several models. CEO Mike Waesche called the move “a huge step to move the brand into a year round company.” Trail bikes at 140mm and 160mm and an eMTB are already on the roadmap, all planned around the same suspension.
RMU Nighttrain geometry, all four sizes
The numbers are contemporary long-travel 29er, with size-specific chainstays that grow across the range rather than staying fixed. Everything here is the 170/170mm enduro configuration.
| Measurement | S1 | S2 | S3 | S4 |
|---|---|---|---|---|
| Reach (mm) | 440 | 465 | 485 | 510 |
| Stack (mm) | 623 | 632 | 643 | 655 |
| Head tube angle | 63° | 63° | 63° | 63° |
| Seat tube angle | 77.5° | 77.5° | 77.5° | 77.5° |
| Effective top tube (mm) | 557 | 586 | 614 | 632 |
| Seat tube length (mm) | 374 | 387 | 387 | 425 |
| Chainstay (mm) | 426.7 | 430.0 | 434.2 | 437.8 |
| Wheelbase (mm) | 1219 | 1252 | 1282 | 1316 |
| BB drop (mm) | 26.5 | 26.5 | 26.5 | 26.5 |
| BB height (mm) | 348.5 | 348.5 | 348.5 | 348.5 |
A 63-degree head angle is properly slack, on par with dedicated enduro race bikes rather than the do-everything 64.5-degree trail crowd. The 77.5-degree seat tube angle is steep enough to keep a tall rider centered on long climbs without feeling like the saddle is pushing them off the back. Reach spans 440mm to 510mm across four sizes, which is a wide enough ladder that most riders land cleanly on one size rather than straddling two.
The detail that separates the Nighttrain from bikes that simply publish one chainstay number: rear-center grows with the frame. S1 gets a 426.7mm chainstay, S2 sits at 430.0mm, S3 stretches to 434.2mm, and S4 reaches 437.8mm. That 11mm spread keeps the front-center to rear-center balance consistent as reach climbs, so an XL rider is not fighting a stubby back end bolted to a long front. It is the same size-specific thinking Whyte and Norco have pushed, applied here from the first bike out of the gate.
BB height lands at 348.5mm with a 26.5mm drop, which is a middle-of-the-road figure for a 170mm bike. Not so low that pedal strikes dominate technical climbs, not so high that the bike feels perched. Combined with wheelbases from 1219mm to 1316mm, the Nighttrain reads as a stable descender that still has enough rear-center variation to stay maneuverable on tighter sizes.
What the numbers say about the ride
Put the geometry and the linkage together and a picture forms. The slack head angle and long wheelbase point at a bike built to be ridden fast on rough terrain, where stability buys confidence. The rearward axle path from the mid-pivot should make that stability pay off over braking bumps and square edges, the exact places a slack enduro bike wants to track straight.
The dual-idler drivetrain is where RMU is betting it can beat the high-pivot competition on feel. Single-idler high-pivot bikes are fast downhill but can feel dead or draggy on the pedals, and the pedal kickback under power is a known trade-off. If Weagle’s two-chain routing delivers the “chainless feel” the launch coverage described while keeping the rearward path, the Nighttrain would climb and sprint better than most bikes with a comparable axle path. That claim will get tested properly once bikes are in the wild, but the pedigree behind it is hard to dismiss.
The one number nobody should ignore is weight. In size S2, complete builds land between 36 and 40 pounds depending on spec. That is heavy for a modern enduro bike. The 6066-T6 aluminum frame, the Superboost 157mm rear end, and the extra hardware of a two-chain system all add mass. Nobody buys a bike like this to win the climb on the clock; they buy it to hold speed through chaos and let gravity do the work. Still, a rider used to a sub-33-pound carbon enduro sled will feel the difference on every fire-road grind to the top.
How it stacks up against the high-pivot enduro crowd
The Nighttrain’s natural rivals are the idler-equipped high-pivot enduro bikes. The Norco Range built its reputation on a high single pivot and a rearward path, and the Forbidden Dreadnought did the same with its Trifecta high-pivot layout. Both are excellent descenders that ask riders to accept some drivetrain drag as the cost of the axle path.
RMU is arguing you can have the path without the full penalty. On geometry alone the three are close cousins: slack head angles in the 63 to 64-degree range, long wheelbases, steep seat angles. Where the Nighttrain diverges is the mid-pivot and the second chain, plus the fact that it ships in aluminum at a frameset price of $2,499 rather than as a carbon flagship. It is a different value proposition: heavier and more mechanical, but cheaper to buy into and, if the kinematics deliver, easier to live with on the pedals.
For a broader look at where slack head angles and rearward axle paths fit into current design, the mountain bike geometry trends piece covers the shift, and the high-pivot and idler explainer inside the geometry guide unpacks why brands keep chasing that axle path.
Sizing, and a note for tall riders
At 6-foot-4 I ride the top of most size charts, and the Nighttrain’s S4 is genuinely built for it. A 510mm reach and 655mm stack give a roomy, tall front end that does not force a slammed, cramped position, and the 437.8mm chainstay on that size keeps the bike balanced instead of nose-heavy. The 425mm seat tube on S4 is short enough to run a long-travel dropper, which is exactly what a tall rider wants and what older enduro frames rarely allowed.
Riders between sizes should think about intent. The reach jumps are 25mm, 20mm, and 25mm up the range, so sizing down buys a livelier, more playful bike and sizing up buys stability at speed. On a 63-degree, 170mm bike I would size to the descents, not the climbs.
Builds, price, and where this goes next
RMU sells the Nighttrain in four tiers. The frameset with a Fox shock is $2,499. The Shimano Deore complete is $4,999, the Saint DH-oriented build is $6,499, and the range-topping Shimano XT Di2 build is $6,999. The Saint and top builds can be specced toward the gravity end with a 190mm fork and a downhill-leaning drivetrain, which tells you RMU sees this frame doing double duty as a park bike, not just a trail-to-summit enduro rig. Pre-orders opened at launch with shipping projected for July 2026.
The bigger story is that Orion is a platform, not a one-off. RMU has 140mm and 160mm trail bikes and an eMTB planned on the same suspension, so the Nighttrain is the opening argument for an entire lineup. Whether a ski brand can build a bike company around one engineer’s linkage is an open question. But launching with Dave Weagle’s name on the frame, a genuinely novel drivetrain, and geometry this current is a serious way to start. The Nighttrain is not the safe first bike a newcomer usually ships. It is a statement about what RMU thinks an enduro bike should do.