Trek Rail 9.9 first ride review: fully tech-loaded flagship, long travel, e-MTB

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

Trek Rail 9.9 first ride
(Image: © Guy Kesteven)

BikePerfect Verdict

Trek’s Rail 9.9 is definitely excessive rather than essential in terms of spec but it’s a genuinely outstanding superbike with lightweight and responsive, yet unshakeably confident and controlled, Bosch Smart System boosted performance


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    Lightweight yet super precise full carbon frame

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    Extended enduro geometry

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    Superbly controlled suspension performance

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    Latest big battery Bosch Smart System

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    Full SRAM AXS and Wiz comms componentry


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    Mega money

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    AirWiz feels gimmicky

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Trek’s Rail e-MTB was already one of the best electric mountain bikes available, the 2022 9.9 gets new longer frame geometry based on the excellent Slash Enduro bike.

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It also gets a bigger battery, Bosch’s latest Smart System motor and management suite, and a full set of the latest SRAM wireless AXS componentry including unique wireless tire and suspension monitoring tech. Retailing for $13,799.99/£12,600 it’s a vast amount of money though, so does it all add up on the trail?

Design and geometry

At first glance, the new Rail frame looks the same as last year's bike. Trek’s classic rocker link, rear axle concentric ABP suspension, the RIB (Removable Integrated Battery) side entry battery system in the down tube, geometry tweaking MinoLink eccentric shock chip and Knock Block 58-degree steering lock system are all carried over. The head tube on the full carbon frame is now a massive, oversized 1.8in tube though. Reach numbers are extended significantly with the large stretching from 465mm to 491mm and the XL we tested growing to 521mm. That makes the new Rail even longer than Trek’s Slash Enduro bike and makes room for Bosch’s new 750Wh PowerTube battery on every size but the small, which gets a 625Wh cell. The small 9.9 has no space for a bottle either, but a standard bottle fits on the bigger sizes.

While you can get your Rail with any of Trek’s Project One custom options if you’re prepared to wait, the three stock finishes are all very special anyway. The metal flake Dark Prismatic finish of my sample looked stunning when the sun occasionally shone in the Lakes. 

Trek Rail 9.9 fitted with a Zeb fork

Upfront is RockShox's burly Zeb Ultimate fork (Image credit: Guy Kesteven)

Components and build 

There are two other big upgrades with the Rail 9.9 too. The bigger battery is joined by the latest Smart System bar remote controller and top tube mounted KIOX 300 display. Teamed with the Bosch Flow smartphone app this gives much more customization of modes and displays including biometric wattage and heart rate displays (needs a third party sensor) and servicing/software update prompts. You get one of the best eMTB motors in the form of Bosch’s well-proven Performance Line CX Gen4 motor with 85Nm of torque. This is matched to e*thirteen’s latest Carbon Race cranks with a 34T chainring (the largest the frame will take). Trek also complements the frame finish with the ‘oil’ anodized version of SRAM’s premium XX1 AXS wireless groupset including chain and 10-52T cassette.

Trek Rail 9.9 crankset

e*thirteen cranks transfer pedal input into the Bosch motor (Image credit: Guy Kesteven)

SRAM has also given Trek two exclusives for the 9.9. The Zeb Ultimate fork and already Trek only RE:aktiv Thru Shaft Super Deluxe rear shock are both equipped with AirWiz Bluetooth pressure sensors. These let you calculate and then set your target fork/shock air spring pressures in SRAM’s AXS smartphone app. LEDs on the AirWiz fork top cap and shock top block will then flash green or red depending on whether you’re in the sweet spot. TireWiz 2.0 valve sensors do the same for the tire pressure on both wheels. These versions are also custom-shaped to sync with the Bontrager Line Pro carbon rims.

SRAM also provides the excellent Code RSC brakes with 200/180mm rotors. You should get a RockShox Reverb AXS wireless operated post too but our bike came with a Bontrager cable-operated unit. The rest of the kit is top-line Bontrager (Trek's own brand) too. That includes carbon 780mm bars, a 45mm (same on all sizes) stem, and its SE5 and SE6 Enduro tires in 29 x 2.5in sizes. That brings the whole bike in at just over 22kg which is impressively light for a bike with such a large battery.

Trek Rail 9.9 handlebar setup

Bontrager decks the Rail 9.9 out with its top shelf componentry (Image credit: Guy Kesteven)

Ride, handling and performance

I tested the Trek Rail 9.9 at the Wheelbase Cycles Demo Day so bike time was limited and they only had an XL size when I'd normally ride a large. The test trails were excellent though and riding it alongside four other eMTBs from Mondraker, Whyte and Scott meant I could still learn a lot about this flagship e-MTB.

Firstly, despite the massive reach, larger battery, and 64.6-degree head angle (I ran the geometry in the low mode) I was surprised how responsive the Rail still felt. The healthy surge from the Bosch motor certainly helps, but it consistently felt bright and precisely alive in terms of where it put its tires and responded to my weight shifts. That’s partly due to the very accurately metered mid-stroke movement of the RE:aktiv Thru Shaft shock that I’ve previously put plenty of time into on the Slash enduro bike. Despite the oversized headtube and open side of the downtube where the battery slides in, the frame has a really well-balanced feel too. Definitely decisively locked onto whatever trail target you choose but not in a brutal or bruising way. Add the Zeb Ultimate fork upfront and even the most geologically aggressive situations are smoothed very effectively with minimum speed loss. Only 150mm of rear travel, relatively short 446mm chainstays and the shock character means it’s certainly not a dumb or numb ride experience though. So while the sheer length of the XL and the down tube full of battery took some turning compared to a conventional rig or a shorter e-bike it didn’t stop me popping and playing around with whatever features I spotted. 

Trek Rail 9.9 tire and rim fitted with TireWiz

The updated Bontrager wheels and tires are a great combo and TireWiz further assures the best performance on the trail (Image credit: Guy Kesteven)

The welterweight Bontrager carbon wheels work well with the bike too. The lifetime rim warranty removes some of the worries about charging headlong into sharp and pointy situations. The instant pick-up freehub syncs really well with the half kick power surge of the Bosch motor to hoik the Trek up stepped, scramble climbs, or power wheelie it off drops/through puddles. Neutral ABP pedaling action and very supple top end to the suspension stroke means it charges up technical climbs with real relish too, and I could stay on line up rocky sections even when filming GoPro footage one-handed.

The Bontrager tires have largely benefitted from recent updating too. A softer TW top compound right across the tire means they roll slower and wear quicker than previous versions, but braking and driving grip are noticeably better. They’re really consistent in the grip they offer at all lean angles too, so while I was still drifting through high-speed boggy grass sections on the Rail I wasn’t wiping out in comedy 360 spins like those around me. The extended wheelbase definitely helped in these situations too, and once I’d realized how much the big Trek liked getting sideways, that became my grin guaranteeing mission for the rest of the test ride even on loose rock sweepers.

Trek Rail 9.9 first ride

The handling is still lively despite our larger than prefered test bike (Image credit: Guy Kesteven)

If you want a more trail happy feel as standard on your Rail, it can be set up as a mixed wheel-size mullet bike. The resulting 63.9-degree head, 336mm bottom bracket height geometry would be proper slack and slammed as well. Though the 29er wheels on both ends fitted as standard, definitely help when it comes to smoothing out the trail and keeping speeds higher.

The Rail was one of the Bosch Smart System bikes I rode over the demo weekend and first impressions are very good. There are a lot of buttons on the 3D remote, but they’re reasonably intuitive in terms of placement, and quick glance power setting color swatches are easy to read. The KIOX 300 display is super clean and while the top tube mount means more of a deliberate look down than a bar mount I appreciate the crash-proofing gains. SRAM’s AXS Eagle transmission was as flawless as ever, dramatically reducing hang up or worries when changing gears on the charge. I was nervous about the full carbon cage of the XX1 rear mech when getting loose and sideways in the hills around Staveley though. So while I respect the flagship components flex, I can’t help thinking the semi-metal X01 mech would be a smarter option. As AirWiz is just a pressure communicator, not a tuning guide like the standalone ShokWiz box, it feels more like a gimmick than a genuine gain. Especially as shocks and forks rarely lose air for fun. The TireWiz 2.0 sensors on the other hand give useful quick glance reassurance on a component more likely to lose air though.

Early verdict

Trek already had one of the best-regarded e-MTB platforms around with the Rail and this new frame literally extends its performance even further. Despite the extra reach and full-day ride battery capacity, the handling still feels lively and responsive on top of a rock-solid, surefooted baseline. The carbon frame and carbon component parade mean it’s impressively light too with instant reaction wheels adding extra pop and play. 

While the RE:aktiv Thru Shaft shock adds potential servicing complications, I’ve had nothing but outstanding precision control and smoothness on bikes using it despite several months of combined hard hammering. Bosch motors are generally regarded as the most reliable option and the new Smart System adds a lot of useful functionality and much better rider ergonomics.

While AXS was flawless and the Wiz monitors were fun, I’d certainly suggest that the $9,199.99/£8,900 Rail 9.8 GX (same frame, battery, Smart System and color options) is the sweet spot in terms of performance for the price. Then again Trek UK has already sold through its allotment of 9.9s for this year, so there’s clearly a market, so if you want one you need to start searching dealers as fast as possible.

Tech Specs: Trek Rail 9.9 XX1 AXS

  • Price: $13,799.99/£12,600.00
  • Model name: Trek Rail 9.9 XX1 AXS
  • Discipline: E-enduro
  • Head angle: 64.6-degree
  • Frame material: EW OCLV Mountain Carbon
  • Sizes: M, L, XL(tested)
  • Weight: 22.2kg without pedals
  • Wheel size: 29x2.5in
  • Suspension: RockShox ZEB Ultimate, AirWiz 160mm travel, 44mm offset/RockShox Super Deluxe Thru Shaft, AirWiz 150mm travel
  • Drivetrain:  SRAM XX1 Eagle AXS 10-52T 12 speed rear mech, chain, cassette and shifter
  • Cranks: e*thirteen e*spec Race carbon, 34T chainset
  • Brakes: SRAM CODE RSC brakes with 200/180mm rotors
  • Cockpit: Bontrager Line Pro OCLV Carbon 780 x 35mm bar, 45 x 35 mm stem
  • Wheelset: Bontrager Line Pro 30
  • Tires: Bontrager SE5 Team Issue front and SE6 Team Issue rear 29x2.5in tires T7
  • Seatpost: Bontrager 175mm dropper post (RockShox Reverb AXS as standard)
  • Saddle: Bontrager Arvada saddle
Guy Kesteven

Guy has been working on Bike Perfect since launch in 2019. He started writing and testing for bike mags in 1996. Since then he’s written several million words about several thousand test bikes and a ridiculous amount of riding gear. To make sure he rarely sleeps and to fund his custom tandem habit, he’s also penned a handful of bike-related books and talks to a GoPro for YouTube, too.

Current rides: Cervelo ZFS-5, Specialized Chisel, custom Nicolai enduro tandem, Landescape/Swallow custom gravel tandem

Height: 180cm

Weight: 69kg