Frame Geometry & Wheel Configuration
The RMU Nighttrain chassis accommodates mixed-wheel setups while offering options to fine-tune handling characteristics back to engineered specifications. Although it is optimized for full 29" wheels.
Mullet Wheel Compatibility
The frame supports a mixed-wheel configuration consisting of a 29-inch front wheel paired with a 27.5-inch rear wheel.
Geometric Modifications
Utilizing a mullet configuration will cause a slight reduction in Bottom Bracket (BB) height and result in a slacker Head Tube angle of 62 degrees and a slacker Seatube angle of 76.5 degrees.
Correction Recommendation
To adjust the handling dynamics back toward the stock standard geometry of 63 degrees, the installation of a +1 degree angleset headset is highly recommended.
Suspension & Shock Hardware Specifications
The rear suspension layout supports multiple stroke lengths to vary total rear wheel travel, requiring precise spacing hardware for setup.
Front Fork Compatibility
| Travel | Offset |
|---|---|
| 170mm | 44mm offset |
| 160mm | 44mm offset |
| 190mm Dual Crown | 48-52 offset |
| 200-203mm Dual Crown | 52 offset |
Known Rear Shock Compatibility
- FOX: Float X2, Float X, DHX2
- Marzocchi: Bomber Air, Bomber CR
- Rockshox: Vivid, Vivid Coil (Super Deluxe NOT COMPATIBLE)
- EXT: Vecta, Storia V3-V4, Arma v4, Aria V1-V2
- Cane Creek: Kitsuma Air, Kitsuma Coil, Tigon
- Ohlins: TTX2 Air, TTX22m.2, TTX1 Air
Rear Shock Sizing Options
- 230mm x 65mm (for 170mm travel)
- 230mm x 60mm (for 160mm travel)
Shock Mounting Spacing
- 10mm x 40mm lower hardware spacing
- 10mm x 35.2mm upper hardware spacing with 40mm bushing and additional 19mm Outer Diameter RMU Spacers
- RMU also has custom spacing kits. For EXT/ Shocks that do not use IGUS bushings these are 19mm Outer Diameter X 11.2mm width for the 10mm bushing. For Fox shocks and ones that use the IGUS bushings these are 19mm Outer diameter X 9.3mm width for the 10mm bushing.
Bushing Kit Requirements
40mm bushing required in conjunction with 33.53mm and RMU spacers or 35mm spacers (for upper shock mount).
Drivetrain & Interface Compatibility
Component choices must align with the layout of the bottom bracket shell and proprietary frame clearances to ensure an ideal chainline.
Bottom Bracket (BB)
73mm BSA threaded bottom bracket shell standard.
Crank Spindle Length
Optimized for 130-136mm Boost standard cranksets and 55mm chainline parameters.
Chainring Interfaces
Fully compatible with RMU-specific direct-mount chainrings (including RaceFace CINCH and SRAM 8-bolt patterns). Pivot 3-bolt direct-mount chainrings are also compatible with an accompanying crankset.
Integrated Crank Systems
Hope cranksets along with Hope (Pivot-compatible) chainrings are certified as fully compatible with this frame interface.
Idler Chain Length
Is set at 38 links including the quick link.
Main Drive Suggested Chain Lengths for 12spd Drivetrains
| Drivetrain | S1-S2 | S3-S4 |
|---|---|---|
| Shimano/TRP | 106-108 links | 108-110 links |
| SRAM T-type | 106-108 links | 108-110 links |
Cable Management & Chassis Dimensions
The frame integrates clean management pathways to simplify routing while dampening physical vibrations.
Rear Brake Routing
Configurable via internal routing lines using an internal foam sleeve, or through a clean external routing layout (Moto configuration also available).
Control Cables (Dropper & Derailleur)
Utilizes full internal cable routing pathways. It is recommended to install internal foam sleeves over the housing to eliminate cable rattle inside the tubes.
Seatpost Diameter
31.6mm
Seatpost Collar
34.9mm
Rear Hub Thru-Axle Dimensions
Stock rear axle spacing is designated at 188-190mm width by 12mm diameter, with a 1.0 thread pitch.
Rear Hub Spacing
12x157mm Superboost standard rear hub.
Dual Idler Chain Setup
Setup Procedure
- For optimal idler alignment the Bottom bracket is recommended with a 2mm spacer on the inner side of the driveside BB.
- Once BB is installed. Install a 2.5mm spacer on the driveside of the crankset and a 1mm spacer on the non-drive side.
- Check that the 27t chainring is aligned with the inner dual idler ring as shown below.
- Once you have confirmed alignment of the inner dual idler ring and the 27t chainring. Torque the crankset to the manufacturers specifications.
- Torque the 17mm bolt on the idler to 20nm using a socket wrench holding the non-drive side with a 10mm allen wrench.
- Use a 10mm allen wrench or 17mm socket wrench to hold the idler and Loosen non-drive side of the idler pivot bolt 1 full turn with a 10mm allen wrench.
- Assemble the idler 38-link (including quick link) This chain should be a 12spd chain (any will work).
- Install chain onto the 17t inner dual idler ring and the chainring by rotating the cranks to seat the chain.
- For proper chain tensioning start with the eccentric axle at the bottom and rotate it clockwise by using a 10mm allen wrench. Proper tension should be between 180° and 360°.
- Rotate the cranks and confirm that the inner chain cannot be derailed. The chain should have about 1-2mm of slack when fully tensioned.
- Use a 10mm allen key int to hold the dual idler and then torque the non drive side of the idler pivot bolt to 20nm.
- Install outer chain over the outer 20t chainring.
