Rail 9.9 XX1 AXS Gen 4
A 29″ carbon frame full suspension enduro e-bike with ultra high-end components.
Manufacturer Price
$13,799Weight | 52.0 lbs |
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Frame | Carbon |
Suspension | Full, 150 / 160mm |
Fork | RockShox ZEB Ultimate |
Shock | RockShox Super Deluxe |
Wheels | 29″ Carbon |
Drivetrain | 1 × 12 Electronic |
Groupset | XX1 Eagle AXS, X01 Eagle AXS |
Motor | Bosch 250W 85Nm mid-drive |
Battery | Bosch 625Wh |
Brakes | Hydraulic Disc |
Seatpost | Dropper |
For This Bike
Oct 2023
A few years have gone by since the last Rail review. Lots has changed since then. Pete reviews the Trek Rail 9.9 X0 AXS T-Type Gen 4.
Jun 2023 · Alex Evans
Trek’s Rail is claimed to be enduro-descent ready and uses Bosch’s powerful Performance Line CX motor
Great geometry provides stability
Cornering control excellent
Suspension is supple and forgiving with plenty of support
Bosch motor
Tyre compound struggles on anything other than perfectly dry terrain
Harsh feeling ride saps confidence
Jun 2023 · Danny Milner
The last time we rode the Trek Rail we awarded it our 2021 E-Bike of the Year crown in the shop bought category. Since then we haven’t had another chance to ride one, mainly because they’ve been flying off the shop floor. Meanwhile, Trek hasn’t rested on its laurels – the front triangle has been lengthened and the extra space used to stuff in Bosch’s biggest 750Wh battery on all but the smallest frame size. So how does it perform and is it one of the best electric mountain bikes on offer? Need to know: Mino link on the seatstay/rocker interface gives high and low geometry settings – useful if you want to run a 27.5in rear wheel Knock Block steering limiter uses interlocking stem and headset spacers, while steerer tube gets oversize 1.8in taper Top tube System controller and wireless remote are available to buy aftermarket, but they should come as standard M, L, and XL frames get 750Wh battery, while S gets a 625Wh This updated Rail is called the Gen 4, but you can still buy the old Gen 3 model. It gets the smaller 625Wh battery, non-Smart System-compatible electronics and a shorter reach. Although buying the Gen 4 seems like a no-brainer, the new large frame is a really big bike, with a 490mm reach and a yawning 35mm gap to the medium. So some riders may achieve a better fit on the old Gen 3. It’s disappointing that Trek hasn’t fitted the latest Bosch System Controller (as found on the Mondraker) to the top tube. Instead you get a measly blanking plate. To enjoy the improved integration and reduced clutter you’ll have to fork out an extra £1,600 for the next model up, which seems pretty stingy. Suspension Trek claims the Rail delivers 150mm travel, but we only measured 140mm (3mm less than the last Rail we tested). However, we didn’t notice this shortcoming on the trail, mostly because the long wheelbase of the Rail gives it excellent stability at high speeds on rough ground. Where we found it wanting was in terms of grip and sensitivity. It struggled to trace smaller bumps, so not only did it lack some comfort on long rides, but it needed more effort to hold a line on off-cambers, through slow turns, and in the wet. Having said that, there’s plenty of support, so as long as we had the energy, we could ride the Rail like a runaway train. Our bike came with a RockShox Zeb in place of the advertised Domain RC. With 38mm stanchions it perfectly matches the hench proportions of the Rail frame, but it wasn’t the smoothest or most supple fork on test. In that respect there was a symbiosis between the Trek’s front and rear suspension, even if it wasn’t quite the fairytale relationship we’d hoped for. Components Trek proffers two brake specs on the Rail 9.7 – Shimano Deore or SRAM Code R, both in four-piston guise. Given the choice, we’d take the Shimano …Continue reading »
Loves to go fast
Suspension lacks finesse
Feb 2023
Bosch has spent years touting its motor/battery/display array. Now, Trek’s ultra-high-end Rail eMTB gets the signature tech.
Feb 2023
With its updated frame and bigger battery, is this the best electric mountain bike going? Read on for our Trek Rail review.
Incredible suspension performance
Hugely confidence-inspiring ride quality
Powerful & intuitive Bosch Smart System
Big battery offers big range potential
Powerful brakes
Solid wheels & tyres
Battery mount failure
Longer wheelbase has reduced agility
Seat angle could be steeper
Limited size range
May 2022
Trek’s updated 2022 Rail 9.9 represents a significant departure from the outgoing model. Visit The Loam Wolf to read our review of the tech-focused updates.
Bosch Smart System power and control
Loves to go fast
Category blending capability
Technical climbing prowess
Lengthy reach numbers are polarizing, sizing jumps
Firm suspension feel at slower speeds
Limited playfulness in tighter trails
Apr 2022 · BHowell
An excellent e-bike with a lot of electronics.
Well rounded ride
Suspension quality
Powerful Bosch motor
Seat angle could be steeper
Vulnerable Bosch controller and Kiox
Mar 2022 · Guy Kesteven
Trek’s Rail 9.9 eMTB is loaded with carbon fiber and wireless tech. Guy Kesteven explores what the pricey Bosch powered flagship is like to ride on a wet and rocky Lake District demo loop
Lightweight yet super precise full carbon frame
Extended enduro geometry
Superbly controlled suspension performance
Latest big battery Bosch Smart System
Full SRAM AXS and Wiz comms componentry
Mega money
AirWiz feels gimmicky
Frame | OCLV Mountain Carbon main frame, 1.8'' lower head tube, Bosch System Controller-compatible, Removable Integrated Battery (RIB), Knock Block 2.0, guided internal routing, 34.9 mm seat tube, magnesium rocker link, Motor Armour, Mino Link, ABP, Boost148, 12 mm thru-axle, 150 mm travel BB Standard: Bosch, Press Fit Tire Clearance: 2.6" |
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Fork | RockShox ZEB Ultimate, AirWiz, DebonAir spring, Charger 3 RC2 damper, 1.8" oversized tapered steerer, eMTB optimised crown, 44 mm offset, Boost110, 15 mm Maxle Stealth, 160 mm travel Travel: 160mm Spring Type: Air |
Shock | RockShox Super Deluxe Thru Shaft, AirWiz, 230 mm x 57.5 mm Travel: 150mm Spring Type: Air |
Bottom Bracket | Bosch, press-fit |
Stem | Bontrager Line Pro, 35 mm, Blendr-compatible, 0-degree, 45 mm length |
Handlebar | Bontrager Line Pro, OCLV Carbon, 35 mm, 27.5 mm rise, 780 mm width |
Saddle | Bontrager Arvada, austenite rails, 138 mm width |
Seatpost | Size: S, RockShox Reverb AXS, 100 mm travel, wireless, 34.9 mm, 340 mm length; Size: M, RockShox Reverb AXS, 150 mm travel, wireless, 34.9 mm, 440 mm length; Size: L, XL, RockShox Reverb AXS, 170 mm travel, wireless, 34.9 mm, 480 mm length Type: Dropper |
Pedals | VP-536 nylon platform |
Grips | Bontrager XR Trail Elite, nylon lock-on |
Rear Derailleur | SRAM XX1 Eagle AXS |
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Crank | E*thirteen E*spec Race carbon, 165 mm length |
Shifters | Size: S, M, L, XL, SRAM Eagle AXS, wireless, 12-speed; Size: S, M, L, XL, SRAM Eagle AXS, wireless, 12 speed |
Cassette | SRAM Eagle XG-1299, 10-52, 12-speed |
Chain | SRAM XX1 Eagle, 12-speed |
Brakes | SRAM Code RSC 4-piston hydraulic disc Type: Hydraulic Disc |
Rims | Front: Bontrager Line Pro 30, OCLV Mountain Carbon, Tubeless Ready, 6-bolt, Boost110, 15 mm thru-axle, 29", Rear: Bontrager Line Pro 30, OCLV Mountain Carbon, Tubeless Ready, Rapid Drive 108, 6-bolt, SRAM XD driver, Boost148, 12 mm thru-axle, 29" |
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Tires | Size: S, M, L, XL, Bontrager SE5 Team Issue, Tubeless Ready, Core Strength sidewalls, aramid bead, 120 tpi, 29x2.50"; Size: S, M, L, XL, Bontrager SE6 Team Issue, Tubeless Ready, Core Strength sidewalls, aramid bead, 120 tpi, 29x2.50" |
Disc Rotors | Size: S, M, L, XL, SRAM 6-bolt, 200 mm; Size: S, M, L, XL, SRAM HS2, 6-bolt, 220mm |
Motor | Bosch Performance Line CX, smart system, magnesium motor body, 85 Nm |
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Battery | Size: S, Bosch PowerTube 625Wh, smart system; Size: M, L, XL, Bosch PowerTube 750Wh, smart system Recycling Program: ♻️ Call2Recycle |
Charger | Bosch standard 4A, 230V, smart system |
Last updated April 20