TREK FUEL EXE REVIEW – NOT YOUR AVERAGE LIGHTWEIGHT ELECTRIC MOUNTAIN BIKE
Mid-power that’s anything but ordinary.
There is a joke that one of MBA’s wrecking crew would tell on occasion: “You know a trend is over when Trek gets on board with it.” It’s just a joke, but there is a bit of truth to it or it wouldn’t be funny. Trek is an innovative brand but has historically tended to move slowly and methodically instead of taking big chances. As a result, it rarely makes big mistakes, although early versions of the thru-shaft shock left some permanent stains on our shop floor. Well, that joke might not work anymore, because Trek’s new Fuel EXe mid-level-assist lightweight electric bike is as innovative, progressive and futuristic as they come.
German robotics manufacturer TQ and Trek have partnered to develop the Fuel EXe’s motor. This new motor system features a unique way to transfer its 50 Newton meters of torque and 300 watts of peak power to the drivetrain—a harmonic pin-ring transmission. Other brands’ motors use gears, belts or chains for gear reduction and power transfer. Trek claims that these transmission systems can fail and create noise, making the pin-ring design superior. This motor and transmission are smaller, too, allowing for the battery to be positioned farther down in the frame for a lower center of gravity. The HPR50 drive unit is completely designed and assembled in Germany while the rest of the system is made elsewhere in Europe.
Trek’s engineers spent a lot of time testing for noise output. Trek measured what it calls “tonality” or sound quality, not just total decibels. Some noises are more offensive than others. Trek claims that the Fuel’s EXe tests closer to a traditional MTB than the next quietest electric bike they tested. Trek says that the pin-ring design equals fewer moving parts and a much quieter ride.
Four total modes can be adjusted via the small handlebar remote: Eco, Mid, High and Walk. The three ride modes are tunable in Trek’s Central app. In the app, you can tune max power, assist level and pedal response. The app can also track activity, map rides, suggest or monitor tire and suspension pressure, and get real-time range calculations. A 2-inch display screen located on the top tube shows mode, battery life and other ride metrics at a glance. Trek says the remote and display weigh just 60 grams. The system is also compatible with most Bluetooth or ANT+ cycling computers (like Garmin) in case you want to tie that in as well. Headlights can also be powered off of the main battery via a power splitter that resides in the top tube.
The removable 360Wh battery allows for what Trek claims is two to five hours of real singletrack riding. A 160Wh extender pack that goes in the bottle cage is available as an accessory and offers an additional one to two hours of riding. It is also worth noting that since the battery is removable, you can fly with it, and because the range extender is below some airline’s thresholds of banned capacity, you might be able to fly with the extender in your carry-on. And yes, the bike can be powered with just the extender pack.
With this drive unit system, the bike is about 10 pounds lighter than a comparable full-power electric mountain bike and about 10 pounds heavier than a regular, non-electric version.
At a casual glance, the Fuel EXe’s frame looks like a normal mountain bike frame. That’s because the downtube on the full-carbon Fuel EXe frame is 39-percent smaller than Trek’s Rail eMTB, making it only a little bit bigger than the non-electric-assist Fuel EX’s downtube. Trek claims that the smaller motor allowed for no compromises in frame geometry. As a result, it has normal trail bike-oriented 440mm chainstays, a 65-degree head angle, a 77-degree seat tube angle and a 485mm-long reach in a size large. It’s adjustable, too, via a flip chip in the seatstays. Because of the flip chip, the Fuel EXe is mullet convertible for anyone wanting a more agile bike or more rear-wheel-to-body clearance. A full-size water bottle fits in all frame sizes, except for size small, which only fits a 20-ounce bottle.
There are eight Fuel EXe builds available, starting at $6500 for the 9.5 with a Shimano Deore drivetrain. We tested the highest-end Fuel EXe 9.9 XX1 AXS build, which costs only $14,000. Yes, we are being sarcastic about the “only” part, but this bike comes with top-drawer components, such as a SRAM XX1 Eagle AXS drivetrain wired to the bike’s battery and an AXS Reverb dropper post. Other highlights include e*thirteen e*spec Race carbon cranks; Bontrager Line Pro 30 carbon wheels with SRAM AirWiz for easy tire pressure setup or monitoring; and SRAM Code RSC brakes with thicker, eMTB-friendly, 200mm HS2 rotors. It’s also available in Project One for riders who want to customize their paint and parts.
Trek continues to utilize its excellent ABP rear suspension design to get 140mm of rear wheel travel on the Fuel EXe. This four-bar design puts the rear pivot concentric with the axle as opposed to just in front of it as with a Horst-link FSR design. Our test bike comes with a RockShox Super Deluxe Ultimate with AirWiz. The fork is a 150mm-travel RockShox Lyrik Ultimate that also features AirWiz. Utilizing SRAM’s AirWiz app, riders can easily set and monitor air pressures. According to Trek, the Fuel EXe is also coil-shock compatible.
Ascending on the Fuel EXe is unlike anything we have tried. Its assist power is ultra smooth, and the motor hardly makes any sound at all. It’s so quiet, in fact, that even in High mode it’s hardly audible over the sound of the tires going over the dirt. Vibrations through the pedals are equally muted. In Low mode, it’s like riding with a strong tailwind everywhere. Mid and High modes have some power, but the motor is not blessed with lots of torque. It feels more like a rush of speed than punchy acceleration.
Even with all settings maxed, we found ourselves running out of steam on ultra-steep climbs where other mid-powered bikes made it all the way up the hill. We were forced to put in a fair amount of effort to make the impossible (on a mountain bike) happen. At first, we thought the motor just didn’t have as much punch as others, but after a few rides, we realized that the motor was just reducing power as it got hot. The TQ drive unit has a strong sense of self-preservation. Watching the power output on the display, it would go from putting out around 300 watts at the start of a ride to never going above 200 watts later, no matter how hard we pedaled. Trek says that while riding in the high-power mode, derating can occur under certain circumstances. They say this happens in small steps and only as much as is absolutely necessary to maintain the prescribed maximum surface temperatures of the engine. Trek adds that derating has no influence on the lifetime of the motor.
Suspension performance while climbing is superb. The supple rear suspension lets the rear tire claw at the ground, yet stays neutral under power, resisting excessive movement or bob. And for those who intentionally or unintentionally ride with the motor off, this is one of the best e-bikes we have experienced in terms of motor drag or friction. Compared to other e-bikes, drag is non-existent and closer to that of a gearbox mountain bike than electric assist. Between the lighter eMTB weight and the lack of drag, the Fuel EXe is simply a pleasure to climb on.
The same light weight that makes this bike climb well makes an even bigger impact on the descents. It lays into corners much like a regular bike. You only realize that it’s about 10 pounds heavier when you overcook a corner or start getting in over your head in rough sections. It has a seemingly low center of gravity that keeps the bike light on its feet and makes it feel more like a 36-pound bike than a 41-plus-pound bike. It’s not until you try to hop the rear end up that you really feel the weight, and even then it’s a lighter feeling than full-powered eMTBs. It’s super quiet, too. There are no rattles or other noises to speak of.
Once again, the suspension really impressed the wrecking crew with its composure when pushing hard. There is no need for volume spacers or heavy tweaking to get great action. We set sag, followed Trek’s recommended settings in its app, and rode. Geometry is dialed, too, with solid trail-bike handling in every condition. Even though this is a trail bike, it punches well above its class.
WHAT DID WE LOVE?
Coming off of other eMTBs, the lack of noise and vibration is mind-blowing. It looks very much like a regular mountain bike, too, with its svelte downtube and motor area. The handlebar switch is small yet easy to use. It’s what we wish were on other bikes. The display is bright and easy to see, but best of all it comes with useful information, such as a power countdown timer that reverses when you charge it. Our favorite screen is the power output display that shows your wattage and the motor’s at the same time. Even with the small battery, range is good. We still had battery left after two-hour-long rides with 2000 feet of climbing and the power on High the entire time. With battery management and more effort, we could go much longer.
WHAT DID WE HATE?
As one would expect from a bike costing this much, there is very little we would upgrade. The first two riders who got on the EXe got rear flats in the tread area on their first rides. It’s hard to say if it was a tire durability thing or if the stoke of riding an electric bike this light had us pushing a bit harder than usual. About 2–3 psi more than usual took care of the problem. We might suggest a lightweight tire insert or a heavier tire casing if it were a long-term issue. A few test riders had issues with the integrated Bontrager bar and stem. They didn’t like the rolled-forward feel of the bars. Truthfully, the bars are level, but those riders prefer to have their bars rolled back slightly.
We didn’t love the thermally triggered reduction in power, but it’s not a deal-breaker. Reducing power when you need it most made for a few hike-a-bikes or big efforts where other mid-powered eMTBs made the grade. The good news is that Walk mode works well; the bad news is that the pressure required on the switch to maintain Walk mode on longer hikes made our thumb cramp.
This is truly a game-changing mountain bike. Its silence and overall feel are closer to that of a regular mountain bike than any electric-assist we have tried—and by a pretty wide margin. As incredible as this bike is, it’s not for everybody. Power-drunk riders who rely on high levels of assist on full-power bikes will be disappointed with both the output and range. This is a mountain biker’s electric bike. It’s for those who still want to put in effort, yet want to go longer and steeper than their mountain bike will allow or those who want the lightweight, playful feel that’s missing from full-power bikes. Trek claims that the Fuel EXe removes the divide between MTB and eMTB. This is one of the few times that marketing hype might actually live up to its claim. The Trek Fuel EXe is not just a minor advancement, it’s a quantum leap into the future that sets the bar for all mid-powered electric bikes to come.
WHEEL SIZE: 29″
SUSPENSION: 150mm (front), 140mm (rear)
TREK FUEL EXe 9.9 XX1 AXS
Weight: 24.6 pounds (with bottle cage, no pedals)
Sizes: S, M, L (tested), XL
Frame tested: 140mm travel, carbon
Motor: TQ-HPR50, 300 watt, 50 Nm
Battery: TQ 360 Wh
Controller: Bar switch, TQ LED display with Bluetooth & ANT+ connectivity
Shock: RockShox Super Deluxe Ultimate AirWiz, RCT2 damper
Fork: RockShox Lyrik Ultimate, AirWiz, Charger 3 RC2 damper, 150mm travel
Wheelset: Bontrager Line Pro 30, OCLV Mountain carbon
Tires: Bontrager SE5 Team Issue, 29×2.50’”
Seatpost: RockShox Reverb AXS, 100mm (S), 150mm, (M), 170mm (L, XL)
Saddle: Bontrager Arvada
Handlebar: Bontrager RSL integrated handlebar/stem, OCLV carbon
Grips: Bontrager XR Trail Elite
Brakes: SRAM Code RSC 4-piston
Rotors: SRAM HS2 200mm F/R
Rear derailleur: SRAM XX1 Eagle AXS
Shifters: SRAM Eagle AXS, wireless, 12-speed
Crankset: E*thirteen E*spec Race carbon, 165mm
Cassette: SRAM Eagle XG-1299, 10-52, 12 speed
Chain: SRAM XX1 Eagle, 12 speed
Head tube angle: 65.5-65°
Reach: 490-485mm (19.3–19.1″)
Stack: 623–627mm (24.5–24.7″)
Effective seat tube angle: 77.5–77°
Bottom bracket height: 349–342mm (13.7-13.5″)
Chainstay length: 438–440mm (17.2-17.3″)
Wheelbase: 1,245mm (49″)