The Trek Fuel EXe was launched just a few months ago, arriving to much fanfare thanks to its unique TQ-HPR50 motor and clean aesthetics. We were totally captivated by the smooth and quiet motor performance, while the low weight, balanced geometry and supportive suspension gave it an impressively playful and agile character on the trail.

We’ve since spent a load more time aboard our test bike, and have made a few key changes and upgrades along the way. For those who are curious about this lightweight e-MTB, or for those who already own one and are looking to delve a bit deeper into its capabilities, here’s a look at what we’ve learned from our long-term review of the Trek Fuel EXe.

There’s an app for that

The release of the Fuel EXe has been accompanied by a new app called Trek Central.

Designed specifically for the Fuel EXe, the app incorporates a number of features including ride tracking, navigation and range estimation. It allows you to tune the performance of the TQ HPR50 motor, and it provides recommendations on suspension and tyre setup. You can pair the app with a heart rate monitor, and it’ll even talk to SRAM TyreWiz and AirWiz modules to provide live pressure readouts.

It’s easy to tune the TQ-HPR50 motor

The most interesting component of the Trek Central app is the Perfect Tune function. This lets you adjust the motor’s power output and assistance behaviour across each of the Eco, Mid and High assist modes. Within each mode you can adjust the Maximum Power, Assist Factor and Pedal Response using a simple sliding scale.

Our main interest here was to see if we could give the TQ motor a little more punch for shorter rides. Although the High mode already comes with the Maximum Power set to the full 300W, it is possible to increase both the Assist Factor and Pedal Response settings, which is exactly what we did.

With both settings maxed out, the Fuel EXe accelerates faster and requires less pedal input to deliver maximum power. It still requires plenty of input, and it isn’t as gutsy as a full-powered motor like a Bosch Performance Line CX or Shimano EP8, but it is noticeably quicker compared to the stock settings.

Of course the downside is reduced range, and it’s possible to rinse that 360Wh battery pretty quickly, especially for heavier riders. It works well for an hour-of-power session after work, but for longer rides you’ll want to make use of the Eco and Mid settings, and consider dialling down the Assist Factor. This will encourage you to pedal harder to receive maximum motor support, while only relying on the High setting when you really need it.

It still has some lag

In our initial review, we mentioned that the TQ-HPR50 motor didn’t always provide support when we wanted, exhibiting some lag in certain circumstances.

Now we aren’t referring to the mechanical pickup of the motor. That is near-instantaneous, with very little free-play in the cranks before they engage the drive system. Rather we mean the delay between when you input a pedalling force, to the point that the motor starts delivering power output.

Even with the Pedal Response set to the maximum level, this delay can still sometimes occur. If you’re climbing in a higher gear at a slower cadence, pausing to freewheel over an obstacle won’t be met with instant power delivery once you get back on the gas. Similarly, if you’re cruising along at speed and need to pause on the pedals, there is some lag in the motor’s pickup when you begin pedalling again.

To avoid this, we’ve found the TQ-HPR50 motor to provide better support at higher cadences. Make use of the lower gears, spin at a higher RPM, and the motor will respond faster and more willingly.

Generally speaking though, this is a motor that is here to give you a subtle helping hand rather than feeling like you have a rocket booster strapped to the bike. The soft and smooth power delivery is what contributes to its discreet and energy-efficient performance, allowing the Fuel EXe to be built with such a small and lightweight battery in the first place.

The wide Q-factor may be a bother

Despite spending another couple of months on the Trek Fuel EXe, I’ve not gotten used to its wide stance at the pedals.

To clarify, the TQ-HPR50 is one of, if not the smallest mid-drive motors on the market, and its bottom bracket axle is narrow at 135mm. The issue is with the carbon e*13 crank arms that come on the Fuel EXe 9.8 and 9.9 models. These bulky cranks add significant width to the overall Q-factor, pushing the pedals further away from the bike.

According to my measurements the Q-factor is nearly 195mm. That is very wide, and it’s caused me some knee pain on longer rides.

I visited a local Trek dealer and compared the Q-factor with the alloy e*13 cranks that come on the cheaper Fuel EXe 9.7 and 9.5 models. The difference is almost 20mm, with the alloy crank arms being considerably slimmer and coming much closer to a crankset on a regular mountain bike.

Many riders won’t be fussed by a wide Q-factor, and indeed the broader stance can improve overall stability on the bike. But for riders with sensitive knees, it is something to consider. Indeed if the Fuel EXe were my bike, I’d be looking at changing out the crank arms.

But it’s oh so quiet

Since reviewing the Trek Fuel EXe, I’ve been riding a whole bunch of other e-MTBs including the Canyon Spectral:ON, the Scott Patron and the Cube Stereo Hybrid 160. Those all make use of full-powered motors that have their various strengths and weaknesses, but one of the most noticeable differences is the amount of noise out on the trail.

The TQ-HPR50 motor is remarkably quiet, even in the highest assist mode with all of the settings maxed out. The pitch and overall volume are so discreet, that every time I jump onto a full-powered e-MTB, it feels like I’m riding a vacuum cleaner.

It’s also unnoticeable on the descents, with none of the freewheel clacking that has plagued the Shimano EP8 and Bosch Performance CX drive units. Along with its smooth and surge-free power delivery, I’ve been really impressed with the experience that the stealthy TQ motor brings to riding the Fuel EXe, which feels closer to a regular mountain bike than a full-powered e-MTB.

The RockShox suspension is performing beautifully

Both the Trek Fuel EXe 9.8 XT and the top-end 9.9 models come fitted with the new 2023 RockShox forks and shocks as standard. Featuring an all-new construction with updated internals, the Lyrik is equipped with the new Charger 3 damper, and the Super Deluxe shock features the RC2 damper.

In our initial review, we found the Fuel EXe’s suspension to be incredibly supportive, but not the most compliant over smaller bumps. That was particularly the case up front with the Lyrik, which even felt harsh in some situations.

I’m happy to report that the suspension has bedded in a lot since new, though I’ve since been riding the Fuel EXe with a different Lyrik Ultimate. This Lyrik had been freshly serviced by SRAM, and it has bedded in beautifully over the last few weeks of riding. Compared to the original fork it is significantly smoother and plusher, especially across smaller rubble. The support is still there, it’s just vastly more comfortable and reactive.

This experience has turned around my earlier feelings on the Lyrik, which I wasn’t overly impressed with. Aside from the different colour, the only difference between these two forks is the fact that the green one had been serviced. It isn’t uncommon to encounter varying levels of assembly grease and oil with mass-produced suspension products, though perhaps the new RockShox forks are more sensitive to it.

My advice to anyone out there with a 2023 RockShox fork that is feeling harsh? Have your local bike shop check the lowers for the proper lubrication levels. It could make all the difference, as it has done on our Fuel EXe.

It’s brilliant with a 160mm travel fork

While the Trek Fuel EXe comes standard with a 150mm travel fork, the frame is rated for use with up to a 160mm fork. And so alongside the green Lyrik Ultimate, I’ve also been testing a Fox 36 GRIP2, both set at 160mm of travel.

The extra 10mm of travel does lift up the BB slightly, and it also slackens the angles a touch. With the longer fork fitted, I needed to nose the saddle down slightly, and I dropped the stem down one spacer to bring the grips down to the same level as before.

On the trail the longer fork feels fantastic. There may be a touch more front wheel wander on the climbs, but having lowered the stem to get more weight over the front, it’s pretty minimal. And the added ground clearance has actually improved the Fuel EXe’s technical climbing abilities, allowing me to keep pedalling over chunky sections with less fear of pedal strikes.

It’s on the descents where the extra 10mm of travel has been most welcome though, delivering increased grip and control when things get rough and rowdy. The whole bike feels more planted, and it’s plusher overall.

I was worried the bigger fork might feel mismatched with the 140mm of rear travel, but that hasn’t been the case. The Fuel EXe is a mighty capable bike, and its rear suspension is nice and progressive with plenty of end-stroke support thanks to the Hydraulic Bottom Out feature in the new Super Deluxe shock. Because it uses its travel in such a controlled manner, it actually feels more balanced with the bigger fork up front.

With that in mind, I can highly recommend experimenting with a longer fork on your Fuel EXe. The good news is that this a relatively cheap upgrade, as you only need to buy a 160mm air shaft to extend the RockShox Lyrik and Fox 36.

Mullet compatibility

A lesser known fact about the Trek Fuel EXe is that it can be run as a mullet. While the bike comes standard with 29in wheels and the Mino Link set in the Low position, Trek says flipping the chip into the High position will help counter the drop in BB height if you decide to fit a 27.5in rear wheel.

That’s true to an extent, though the difference in BB height between the High and Low positions is only 7mm. In our experience with trying out mullet conversions on other bikes, that difference isn’t quite enough. If we were to mullet the Fuel EXe, we’d recommend pairing that setup with a 160mm travel fork to help lift the BB up again to roughly the same spot as the stock setup.

The downside of fitting a 27.5in rear wheel? The TQ’s speed sensor can’t be recalibrated for a different wheel circumference, so the system will still assume you have a 29in wheel fitted. This will affect the speed readout on the top tube display, changing the motor’s behaviour slightly and resulting in a lower actual cutoff speed.

If you’re prepared to put in more effort at the pedals however, the mullet setup will be an effective way to add further agility into the Fuel EXe while increasing bum clearance for shorter riders. See our recent Specialized Stumpjumper mullet review if you’re keen to know more about the advantages and disadvantages.

Burlier tyres are a great upgrade

While the stock Bontrager SE5 tyres on the Trek Fuel EXe are decent all-rounders, we did find ourselves wishing for more bite up front. As well as wanting a stickier and more aggressive set of tyres, we were also curious to try out a slightly narrower width to improve handling precision.

Since reviewing the bike in its stock form, I’ve been riding the Fuel EXe with a set of Continental Kryptotal tyres. This combination features a front and rear specific tread pattern, and I elected for the burlier Enduro casing option that features the Soft rubber compound.

We’ll have a separate feature coming on the Continental tyre range, but so far I’ve been really impressed with this setup on the Fuel EXe. The 2.4in width suits the bike well, and the sturdy casings offer a really nice balance of stability and damping. Along with the soft rubber compound, the level of grip is outstanding, inspiring more confidence and control compared to the stock SE5s. Along with the 160mm fork up front, I’ve been able to push the Fuel EXe harder and faster on the descents, while enjoying a more responsive attitude through twisty singletrack.

Dialling in the contact points

As with the tyres, I’ve also been trying out some different contact points on our Trek Fuel EXe test bike. The stock Bontrager saddle and grips will be fine for most riders, but there’s always room for personalising these touch points to improve comfort and control.

I swapped the Bontrager Arvada with an Ergon SM E-Mountain Pro saddle, which features a pronounced kick-tail profile. This elevated ramp at the end of the saddle is particularly beneficial on an e-MTB, as it helps to anchor your sit bones while you’re pedalling in the saddle on a steep climb. The ramp is subtle enough that it doesn’t feel weird on the flats though, and combined with the broad platform, relief channel and OthoCell inserts, this has quickly become my favourite e-MTB saddle.

Along with the saddle I’ve fitted a set of Ergon GD-1 grips. These utilise Ergon’s high-end Factory rubber compound, which is incredibly tacky while being quite durable. Along with the tapered profile and one-way traction grooves, the GD-1s provide a more tactile feel and much improved damping over the stock grips. A small but meaningful upgrade, which doesn’t cost a lot either.

Flow’s Verdict

We continue to be impressed by the Trek Fuel EXe, which stands as one of the most agile and enjoyable electric mountain bikes we’ve ever ridden. The discreet TQ motor allows for elegant packaging, while offering quiet and subtle power delivery on the trail. And the option to tune the motor via the Trek Central app means you can customise its performance to suit your range requirements.

It’s also been great fun trying out different upgrades on our long-term test bike. The 160mm travel fork is a winner, offering a plusher and more controlled ride quality that allows you to capitalise on the Fuel EXe’s descending capabilities. Similarly, switching the stock tyres out for burlier casings and stickier rubber has levelled up traction and control. If you’re a Fuel EXe owner and you’re looking to broaden its performance window, we can highly recommend those upgrades.

Keen to know more about the tech and development behind the new bike, as well as prices and specs for the full range? Read on for our Trek Fuel EXe review.

Watch our Trek Fuel EXe video review here: