Review: Trek's 2023 Fuel EX-e Is Light & Nearly Completely Silent

The EX-e comes in four frame sizes and six built kits, all of which use Trek’s OCLV carbon. Pricing starts at $6,499 USD for the EX-e 9.5 which is built with entry-level RockShox suspension and Shimano Deore drivetrain pieces, while the 9.9 XX1 AXS adorned with all of the electronic fixings from SRAM for a cool $13,999. Matching the component capabilities of the Rail 9.9 XX1 AXS that we tested back in autumn of last year, the Fuel EX-e features Tirewiz and AirWiz that monitor the pressure in the tire and suspension systems, as well as the electronic shifting and dropper post duties that we’ve come to expect from SRAM on these top tier builds.

*Only medium-size frames with 9.8 XT and 9.9 XTR build kits sneak below the 40 lb mark.

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Frame Details

Pretend you could eliminate the electrical components around the cockpit. The Fuel EX-e could easily fool you into being a traditional bike, sans motor. The entire ethos of the bike is “slim”, from the integrated top tube display unit to the downtube that is 39% smaller than the volume of the Rail's (which holds a much bigger batter). Even the charge port is tucked away above the water bottle holder, well above the splash zone.

The bike continues to use the ABP suspension layout and a rocker link housing the Mino Link flip-chip to adjust the geometry a smidge, but an alteration to the seat mast junction optimizes standover height and brings a new look. You'll see that the bike is decked out and comes with the handy BITS steer tube tool and a removable rear axle skewer too.

Trek has also opted to ditch the Knock Block on this frame and it utilizes a standard lower shock mount this time around. They’ve added an effective mudflap above the main pivot and the paint on this frame has been much more durable than that of the Rail I tested. Below the motor area, there are no ISCG tabs, but the bikes will be supplied with a custom skid plate (there were a few items that our early test bike didn’t come with due to supply squeezes) which should save your vitally important chain.

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Motor Details

Remember those circular stencils from pre-school that rotated on geared teeth to create patterns? That’s basically the same movement that the harmonic pin ring motor makes, except it’s driven by a current that flows through copper coils. TQ has used this system before but scaled it down exclusively for Trek to give the EX-e 50Nm of torque through three tunable power assist levels.

What’s special about this motor is that it moves at a much lower RPM which is one of the keys to keeping it deadly quiet. Tonality is described as the harmony of sounds and the unit is measured by comparing the amplitude of the tonal note against the surrounding frequencies. Basically, it’s how annoying the sound is and the Fuel EX-e clocks in at 0.1 on the tonality scale, compared to another competitor’s motor that was almost four times higher.

The small but mighty HPR motor is also compact, and has the same Q-factor as a traditional bike of 135mm. Sitting mostly behind the bottom bracket the motor allows for chainstays that are reasonably short; 440mm on all sizes.

How exactly did Trek and TQ manage to package all of that technology into such a slim figure? For starters, they started from scratch, with TQ borrowing technology and expertise from their other industries, such as aviation and robotics. Once Trek laid out the parameters for the motor capacity and volume, TQ was able to build a motor that is 30% smaller than most competitors.

Not only is the HPR discrete, it has a high torque density and weighs 1,850 grams. All that power in such a small package is highly efficient, and only saps about 3 watts of power when pedalling at a normal 80 RPM. That means you can ride the bike without assistance and it feels very ordinary. I could see this technology evolving to longer travel bikes that could ditch the battery quickly for bike laps or days riding with friends that have traditional bikes.

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Battery Details

Ask and you shall receive; SRAM’s AXS derailleurs can now be powered from the bike’s battery. Not into that idea? Simply remove the cable and install an AXS battery. It’s completely retrofittable. How do you shift when the battery fully drains? Trek and TQ’s engineers left enough power in the tank to complete two hundred shifts.

The main battery slides out of the downtube after unscrewing a few bolts and doesn’t require the motor to be removed first. There’s a nifty handle to carry the 360Wh battery, which only weighs 1,830 grams and can be charged separately from the bike. You can also connect front and rear lights to the system, which is a great idea if you’re covering a lot of road or returning after dark.

Conveniently, the 160Wh range extender battery that straps into the water bottle cage acts as a charger for the main battery and depletes it first. The charge time for both batteries is two hours and the extender adds 900 grams to the system, although a functional one was unavailable at the time of the test. We found that the extender works best with the Bontrager Side Load cage after some wrestling to get it into another aftermarket branded one.

If you’re looking to shed even more weight, the bike can be ridden with only the extender or without any of the batteries, but keep in mind, that you’ll need to install a derailleur battery on the AXS models for that. The shifting doesn’t work with the motor is off when the cable is attached either, which is the tiniest inconvenience when you have to move the derailleur to the lowest gear and pull the rear wheel.

The first time you deplete the battery, which is bound to happen when you’re 8km away and the rain is coming down in sheets, you may lose power at up to 15%. If there’s one thing that Trek and TQ missed with the Fuel EX-e, it would be running the battery through this cycle before it leaves the factory to avoid a customer’s first ride experience, but maybe I’m just jaded. After that, you can fully trust the display to accurately predict the battery life.

Working to preserve the last few battery life bars, which are always presented at the top of the display, is the motor output limiter. Once the battery reaches 10%, the output will be limited to 110W and the display will blink to signify that motor feedback.

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Display, Controls, and App Integration

Displayed in front of you in the top tube is the sleek screen, also made by TQ, that uses one button to toggle between stats, such as RPM, battery life, range, and speed. Together, the remote and the display weighs about only 60 grams. The screen is held in place by a single bolt and the backlight auto-adjusts to any time of day.

Keeping the cockpit clutter-free was the goal here as the entire premise of the bike is meant to be less cumbersome than a full-powered e-bike. Compared to the Bosch remote on the Rail, this sleek controller is worlds apart. There’s also the option to turn off the motor for descending. That means you can toggle between “Off”, “Mid”, and “Boost” power modes with the blip of a button on the handlebars. To engage walk-assist hold the up button, or hold the down button to eliminate any assistance for descending.

During the test period, the app was not available, so we didn't get to play with the motor tuning options or range cloud feature to let you know how far you can travel with the remaining battery life. Connecting to Strava through any of your preferred ANT+ devices is possible, plus the app will display the AirWiz and TireWiz pressure sensors on the 9.9 XX1 AXS model.

TQ has built out an app too, but the Trek version will have all of the same options. Through the app, you can access the TQ diagnostic mode when the physical dongle is connected to the bike to troubleshoot any issues that may occur.

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Geometry & Sizing

Contemporary is a nice way to describe an enduro bike that could have used one degree removed from the head angle, but the Fuel EX-e is not aimed at that style of riding. Instead of focusing soley on the descents, its focus is on making climbs enjoyable and keeping the speed up on the flats with plenty of might in reserve for the downhills.

64.7-degrees is a very acceptable head tube angle for a bike in this category and you could make that slacker by boosting the fork up to 160mm, but then you’d lose a bit of that pleasant climbing position. The seat tube angle lies at 76.7 in the slack setting, which doesn’t throw too much weight over the 440mm chainstays.

That figure remains the same for all four sizes and the reach starts at 427mm for a small, moves up to 452 on the medium that I tested, followed by 482 and 507 on the large and extra-large frames. Limiting the size run to four frames cuts costs, but it does leave a gap in choices, should you stand around the 177cm mark.

The low stack height is another number that tells a tale of where and how the bike is intended to be bike ridden. That’s not exactly leading the charge when it comes to lengthy wheelbase trends, but what it does do well is keep the Fuel EX-e on its toes.

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Suspension Design

Trek’s tried and true Active Braking Pivot (ABP) is a four-bar system that has been in action since 2011. A co-rotating pivot around the rear axle works to isolate braking forces from the suspension. The system delivers 140mm of travel from the Trunnion mounted 230x60mm RockShox Super Deluxe Ultimate Air, but the leverage curve will also work with a coil shock too.

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Our Fuel EX-e 9.9 XX1 AXS shipped before Trek could include a few items, including; the new app, battery range extender, and SRAM's AirWiz and TyreWiz pressure monitors. We did have experience with those features since they were covered in the Rail 9.9 XX1 AXS First Look.

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Test Bike Setup

Beach lovers have been frowning over the wet and mild summer weather, but that’s made the dirt in the middle of the Sea to Sky incredible for riding. It has made the roots unsuspectingly slippery for this time of year and for the most part, I chose to keep the Fuel EX-e’s head above water when it came to trail choice. Sure, it was tested on some slabs and steeps, but I listened to what the bike wanted: dirt ribbon single track.

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Climbing

When I first learned about the new genre of bike, I was confused why Trek didn’t replicate the Rail in a lighter-weight package, and then we hit the trail. Straight out of the door, the motor is the first thing you notice, or at least the boost from the eerily quiet motor. Only until you get to the higher RPMs is any audible hum apparent - those are present in Boost mode around 95-100 RPM, but even then, you can tell that Trek and TQ have done their homework. That tonality number isn’t just pseudo-science. Pedalling the EX-e is so much more pleasant than some other offerings out there.

The power delivery is extremely smooth too. At 50 Nm, it’s slightly trickier to critique compared to a full-powered e-MTB, but we’ll get into how it stacks up against bikes like the Orbea Rise and Specialized Levo SL shortly. Where it really shines is how it manages the torque. I can’t remember spinning out once and having to dab a foot. Even on tech climbs, I felt like the boost mode was never jolting, it was optimal to choose less power when trying to manage pedal stroke timing with rear-wheel traction. Granted, it’s not a large burst like the 85 Nm of the Rail. The important thing to note is that each mode is notably unique and is brought on incredibly smoothly.

This is where there is a temporary problem that cannot be undone by any amount of engineering: you won’t be able to keep up with a full-powered E-bike on lengthy, steep climbs. Ok, so set the assist to Boost. That might keep you in touch for a few minutes, but you’ll be working like a dog. At best, you’re still only getting 50 Nm of torque. Plus, you’ll absolutely rinse the battery dry in about thirty minutes. If you’re conservative, you could run it in Eco mode and chill with your friends on non-assist bikes, but there are still three basic divisions of bikes, so you’ll have to find riding mates with similar style bikes or deal with the moaning of, “Oh. You brought the e-bike today,” or, “You should have bought the full meal deal!” That doesn’t make or break this bike. It simply puts it in a separate category, which is gaining some serious traction.

As for the handling, it likes to be on the move due to more weight being placed on the handlebars. That emphasizes driving your legs long instead of resting on your butt on the saddle and cruising along in a relaxed position. Once I embraced that riding position and learned its advantages the Fuel EX-e turned into a rocketship. Putting the power down on the pedals pulls the bike through corners rather than pushing it through where a slacker head angle might be more prone to understeer.

It’s not a full-attack cross-country race position, but it took a couple of rides to acclimatize to. Being on the upper end of the suggestive height for Trek’s medium frame could be part of this. Another point of view might be that Trek opted to keep the quick handling geometry to make the bike feel daintier and alive at lower speeds, in places where a full-powered e-bike can feel like a handful.

Out of the saddle, there is very little wasted energy. That redesigned RockShox Super Deluxe is brilliant and might fool me for a coil shock if I couldn’t see it. The breakaway is stellar and keeps the rear wheel glued to the ground on the slipperiest, techiest trails. Grasping the lockout isn’t as easy as it has been with the previous Super Deluxe but both the twist-action of the lever and the support of the climb switch are solid.

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Range

This is a major grey zone that varies depending on so many factors. It’s a bit like deciding on how much water to drink on a hot day. You could drain it all quickly, or sip it over the course of your ride. Trek claims that you can get up to 5 hours of riding in Eco mode, but I would imagine that’s on very mellow terrain.

Around Squamish, some of the trails are shared-use with moto trials bikes. You’d often encounter rock slabs that most people would be happy to ride down, not up and punchier climbs. That wasn’t the only kind of riding I did, because singletrack is what the Fuel EX-e loves. I was able to commute to the trailhead to cover between 20 and 30km while climbing between 650 and 800m using a variety of modes; primarily the Mid power mode and Boost for some of the steep road grades, but I could also milk the battery on Eco mode when the juice dipped to one third.

On a few of those rides longer than 90 minutes, I drained the battery completely and still pedalled home without thinking much about the drag from the motor. I’d compare it to riding a trail bike on the flat asphalt with downhill tires versus a standard trail casing.

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Descending

Edgey like a knife, not a hammer, the Fuel EX-e doesn’t shy away from chunder, but it shouldn’t be jumped blindly over rises into piles of rocks. Not that it can't handle that - it’s a mighty 140mm of travel. You just shouldn’t expect it to get away with the same exact moves you'd perform on an enduro bike.

Moving through low-angle terrain is where the Fuel EX-e excels. The extra weight never felt like a burden to pick up and pump the ground or when transitioning into a turn. That suspension has a solid platform to push against and generate speed from corners without diving or wallowing about.

I’d actually forget that I was riding a bike with a motor. Fighting to slow the bike and initiate the lean into a corner makes me shy away from full-powered e-bikes. That’s not the case with the Fuel EX-e. Tipping the bike side to side through consecutive corners happens quickly and naturally.

On those heinous steep sections and rough bits of track there are two friends backing you up; Code RSC brakes with dual 200mm rotors and that fantastic Super Deluxe Ultimate. The new RockShox forks with the ButterCups offer some of the most active fork suspension I’ve ridden. They work their magic to take the edge off of those roots and stutter bumps too. For the first time in a while, I found myself turning the damping down to dial in the composure of the front wheel - it’s very reactive if you like that kind of ride. All three of those components do an impeccable job to keep you grounded when you need the tires to hook up the most.

Even a keen ear would struggle to hear any noises from the motor, battery, or cables on the descents, which is definitely not the case with some e-MTBs. Not one rattle or backlash from the motor was heard. There’s a full chainstay protection wrap right up to the chainguide which keeps that racket to a minimum.

One thing I often bring up is the need for a bash guard, and although it's an option, I’d like to see it mounted right away. This bike is loaded with the latest and greatest tech, so why not protect those crucial pieces of the drivetrain?

I’d also prefer if the steertube was left another 10mm higher, just to play with that option of raising the front end, especially considering how you can’t simply change the handlebar for a higher rise option. Stacking headset spacers on top of your one-piece bar and stem detract from the clean aesthetics, but trimming down the steertube isn’t a huge job either.

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Technical Report

TQ HPR50 Motor: You know Trek and TQ are onto something special when you watch someone with high standards and low expectations jump on this bike and come back in awe of just how damn quiet the motor is. Hats off to the two teams who built this bike. It's a well-oiled machine and hasn't missed a beat, even in torrential downpours and plenty of bike washing with no precautions taken. You know exactly what to expect when you stand on the pedals or let off for that matter. That tiny harmonic pin ring drive unit is the golden goose of e-bike motors.

Bontrager SE5 Team Issue Tires: Holding back the stellar singletrack mind of the Fuel EX-e are the Bontrager SE5 tires though. They work decently in dry dirt, but through the rain-soaked summer we’ve had in Squamish they quickly spun out on polished roots and glistening rock. Their round profile on the Line 30mm wide rims meant that leaning on the side lugs commitment and time to reach. I swapped them early on for something with more tackiness to unlock what the bike was really capable of.

Bontrager Raceshop SLR bars: I dig the unibrow look of the one-piece bar and stem - thankfully there are no integrated cables. The 6 and 7-degree up and backsweep might not be the most common, but I got along well with the straighter backwards bend. Although, I did notice a little more pressure on my palms than normal. Most bars tend to have a 5-degree upsweep and can be rolled in the stem clamping surface to your liking. Initially, I chalked up the hand fatigue to the low front end, but it might be worth thinking about slip-on grips if you start to feel discomfort here. I also trimmed the width down from a whopping 820mm to 770 and never felt like they were too stiff.

RockShox Super Deluxe: This shock in combination with the suspension kinematics is phenomenal. There's plenty of range to twist the dials and it's not overly complicated. No matter the size of the impact, the shock ate it all with forgiveness and support when needed, only ever using the perfect amount of travel. I'd go far enough to say that, aside from the motor, it's the standout component on the bike.


How Does It Compare?

To be fair, there aren't a lot of other bikes in this lightweight e-MTB category, at least from mainstream brands. The two main players before the Fuel EX-e arrived on the scene were the Orbea Rise and the Specialized Turbo Levo SL. The Rise uses Shimano's full-size EP8 motor, but it has been de-tuned in terms of power and runs off of a smaller battery, while the Levo SL uses a different motor than its full-powered e-MTB siblings from the big "S". All three competitors come in carbon-framed offerings and hover around the 18-19 kilogram mark.

Where they are drastically different are the power delivery, output, and noise levels. The Shimano motor in the Rise has plenty of jam, but it is the least refined and the gears rattle considerably on the descents. The Rise frame geometry also has a more conservative feel with a steeper 65.5-degree head angle. On the other hand, the Levo SL doesn't have extreme geometry and the minimal motor output emits a higher pitch whine than the Rise. Its power delivery is smoother than the Rise, although all three bikes can be tuned via apps.

Then there's also the cost factor. Yes, this top-spec Fuel EX-e 9.9 XX1 AXS has all of the bells and carbon whistles, but compared to the equivalent Specialized S-Works Turbo Levo SL, it comes in under the $14K mark. They are both well-finished bikes that are very sleek, but the extra power and minimal noise of the Fuel EX-e wins out by a mile. Looking back at the Orbea, the price is reasonable, but the motor trades a boost in power for a less polished experience.

Simply put, nothing comes close to the Fuel EX-e when you paint the picture of the mountain bike experience as a whole. Up and down the hill, the TQ motor rides along under the yellow carbon carpet in such a hush manner that you'd barely know it's there. You also have to factor in the torque density and packaging. Look at it - it's tiny and powerful.

The only way I could see it improving would be to revert the AXS derailleur back its own battery pack and use a similar size remote on the motor assist controller for zero wires. I know that goes against the grain of tying all those servos to a central power bank, but I'd prefer to eliminate those tiny wires before they get eliminated on the trail.

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Pinkbike's Take

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Reviews and Tech eMTB Reviews Trek Fuel Ex E