Trek Fuel EX 9.8 GX 2021 in review - Trail performance over bling components

The Trek Fuel EX has proven itself as an excellent all-rounder in the past. This year, the American brand enters the race with the € 5,999 Trek Fuel EX 9.8 GX, which combines a high-end frame with a mid-level spec but still features Trek’s own Thru Shaft shock technology. So does it always have to be top-spec? How big is the difference in performance and how does the Fuel EX 9.8 GX fare against its more expensive peers?

For an overview of the test fleet head to the group test: The best mountainbike of 2021 – 22 models in review

**Trek** Fuel EX 9.8 GX | 140/130 mm (f/r)
13.48 kg (size L) | € 5,999 | Manufacturer-website

The Trek Fuel EX 9.8 GX features an elegant carbon frame and makes a very high-quality impression with its semi-translucent red finish with visible carbon fibres. It has 140 mm travel at the front and 130 mm at the rear and comes equipped with a Thru Shaft technology shock, developed specially by RockShox for Trek. The shock uses fewer seals, which is claimed to reduce friction and improve sensitivity. Trek’s proprietary internal storage compartment in the down tube offers enough room to stow a spare inner tube, a CO2 cartridge and a few trail snacks. A long TPU down tube guard protects the carbon frame from impacts and stray rocks. The chainstay protector prevents chain slap and ensures a quiet ride, making the Trek one of the quietest bikes in the test. The integrated Knock Block limits the steering angle and thus prevents the fork crown from damaging the frame or cables from tearing off. You never hit that limit on the trail but it could pose some issues when transporting the bike.

The spec of the Trek Fuel EX proves that affordable bikes can deliver

For this test, Trek didn’t send us the top-of-the-range model we requested but the more affordable Fuel EX 9.8 GX model. This retails at € 5,999 and comes equipped with a 140 mm FOX 36 Performance fork, which uses the worse-performing FIT4 damper rather than the top-end GRIP2 cartridge but still keeps up with the FIT4 forks on the trail. At the rear, a FOX Performance Float Thru Shaft shock controls 130 mm travel. The 12-speed SRAM GX drivetrain with a 10–52 cassette delivers the same gear range and shifting performance as SRAM’s more expensive offerings and only weighs a few grams more. Braking is taken care of by SRAM G2 RS brakes, paired with a 200 mm rotor at the front and a smaller 180 mm disc at the rear: unfortunately, the latter doesn’t do justice to the potential of the Fuel EX, requiring strong fingers and tending to overheat on long descents.

For all other components, Trek rely on in-house Bontrager components. That includes a 170 mm Line Elite dropper post and 780 mm carbon bars. The in-house Line Elite 30 carbon wheelset rolls on wide, puncture-prone 2.6” Bontrager XR4 Team Issue tires. Ironically, the “Issue” designation is rather fitting. To avoid pinch flats and, in the worst case, irreversible damage to the carbon rims, you’ll have to run very high air pressures which only exacerbates the limited grip of the low-profile tread. Add to that the hard compound and the XR4 generates too little traction. We recommend upgrading the standard tires to a narrower 2.4″ or 2.5” model with a more robust casing.The Trek Fuel EX 9.8 GX in size L hits the scales at 13.5 kg.

Uphill, the Fuel EX generates lots of traction and offers a high level of comfort, delivering an impressive performance in all imaginable uphill situations.

**Got everything?**
The cleverly integrated storage compartment offers enough space for snacks and tools and everything is neatly packed in a bag. This prevents your items from disappearing into the depths of your frame.

**Caution: slippery!**
Unfortunately, the standard Bontrager XR4 tires generate little traction and only offer undefined handling – we’re not convinced. That’s a shame because a good set of tires would unlock the full potential of the bike.

**Knock knock who’s there?**
The Knock Block in the headset prevents the fork from damaging the frame and cables from tearing off.

Trek Fuel EX 9.8 GX

€ 5,999

Specifications

Fork FOX 36 Elite 140 mm
Rear Shock FOX DPS Elite EVOL 130 mm
Seatpost Bontrager Line Elite 170 mm
Brakes SRAM G2 RS 200/180 mm
Drivetrain SRAM GX Eagle 1x12
Stem Bontrager Line Pro (35) 45 mm
Handlebar Bontrager Line Pro OCVL 780 mm
Wheelset Bontrager Line Elite 30 29"
Tires Bontrager XR4 Team Issue 2.6

Technical Data

Size XS S M M/L L XL
Weight 13.48 kg

**FOX DPS Elite EVOL RE:aktiv Thru Shaft**
Sounds complicated but it’s not. The shock was specially developed for Trek and is supposed to deliver less friction and a more sensitive response.

**Not only gold glitters**
The FOX 36 Performance Elite fork also offers high performance. While it can’t keep up with its high-end GRIP2 counterpart, it performs better than the FIT4 models in our test.

**Arm pump included**
The standard SRAM G2 RS brakes require strong fingers and tend to overheat due to the small 180 mm rear rotor.

The geometry of the Trek Fuel EX 9.8 GX in detail

The Fuel EX is available in six sizes from XS to XL. For the smallest XS and S frames, Trek have adapted the shape of the top tube to give short riders more freedom of movement. In addition, the smallest XS frame is only available with 27.5” wheels, while the size S is available with both 29” and 27.5” wheels. All other frames roll on big 29” wheels. The intermediate M/L is a real highlight, providing many riders the choice of at least two suitable frames. The reach of our Fuel EX test bike (size L) is 470 mm. Chainstays are 437 mm across all sizes and the geometry of the Fuel EX can be adjusted via a flip-chip in the rocker. We recommend the low setting, which slackens the head angle by 0.5° – this is the setting we used the most in this test!

Size	XS	S	M	M/L	L	XL
Seat tube	356 mm	395 mm	420 mm	435 mm	450 mm	500 mm
Top tube	546 mm	567 mm	577 mm	603 mm	634 mm	663 mm
Head tube	90 mm	100 mm	100 mm	105 mm	105 mm	120 mm
Head angle	66.0°	66.0°	66.0°	66.0°	66.0°	66.0°
Seat angle	75.0°	75.0°	75.0°	75.0°	75.0°	75.0°
Chainstays	437 mm	436 mm	436 mm	437 mm	437 mm	437 mm
BB Drop	21 mm	21 mm	34 mm	34 mm	34 mm	34 mm
Wheelbase	1,120 mm	1,143 mm	1,154 mm	1,179 mm	1,211 mm	1,242mm
Reach	408 mm	428 mm	440 mm	455 mm	470 mm	495 mm
Stack	563 mm	572 mm	609 mm	613 mm	613 mm	627 mm

**Helmet** Giro Manifest Spherical | **Glasses** 100% Glendale | **Jacket** 7Mesh Skypilot
**Pants** Pearl Izumi Summit AmFIB | **Sjoes** Ride Concepts Powerline

More comfort is almost impossible! The Trek Fuel EX 9.8 GX on the trail

As far as riding comfort goes, hardly any bike in our big 2021 group test beats the Trek Fuel EX. The pedalling position is balanced and comfortable and the suspension works efficiently. Even without the climb switch, the Fuel EX climbs willingly while the suspension tracks the ground sensitively, ensuring a high level of comfort and sufficient traction to negotiate technical uphills with ease. While it’s not as nimble as strong climbers like the Yeti SB115, the Fuel EX shines with its comfortable pedalling position, which also makes it an excellent option for long rides. Uphill, it has nothing to begrudge its little brother, the Trek Top Fuel 9.9 X01, while downhill it leaves it behind in a cloud of dust. The Fuel EX strikes a great balance between nimbleness and smoothness, inspiring sufficient confidence on steep descents thanks to its high front.

On steep, rough terrain, the bike inspires confidence and ensures a reasonably smooth ride.

Tuning-tips: narrower tires with a more aggressive tread | heavy riders should run a bigger brake rotor at the rear to unlock the full potential of the bike

On narrow trails and berms, it’s playful and agile. While the rear end lacks end-stroke progression, the suspension still provides sufficient support for active riding maneuvers, generating good traction and remaining composed even on fast and rough trail sections. As a result, the Fuel EX feels most comfortable on flowing trails and singletrack. However, when the trails get too rough and more closely resemble downhill tracks, the rear end reaches its limit – as a result, the Fuel EX struggles to keep up with more capable bikes like the Canyon Spectral. Here, the limiting factor is the rear tire, which offers little puncture protection, has a very shallow profile and has vague handling due to its large surface area. In corners and under braking, the lack of traction costs the Trek a great deal of precision.

Riding Characteristics

Uphill

sluggish
efficient

Agility

cumbersome
playful

Stability

nervous
confident

Handling

demanding
balanced

Suspension

harsh
plush

Fun Factor

planted
poppy

Value for money

terrible
very good

Intended Use

XC

Trail

Enduro

Downhill

Conclusion

Despite the affordable spec, the Trek Fuel EX 9.8 GX convinces with a high level of comfort and good traction on all sorts of climbs. Downhill, it shines with its intuitive and balanced handling on flowing trails and singletracks. The build quality is high and frame details such as the integrated storage compartment are well-thought-out. Unfortunately, the spec isn’t perfect and crucial components such as the tires and brakes limit the riding fun.

Tops

very comfortable uphill
intuitive handling
high-quality frame with integrated storage compartment

Flops

tires are very puncture prone and generate little traction
brakes don't do the bike’s potential justice

Find more information here trekbikes.com

The testfield

Get an overview of the grouptest here: The best mountainbike of 2021 – 22 models in review

This scale indicates how efficiently the bike climbs. It refers to both simple and technical climbs. Along with the suspension, the riding position and the weight of the bike all play a crucial role.↩
How does the bike ride and descend? How spritely is the bike, how agile is it through corners, how much fun is it in tight sections and how quickly can it change direction?↩
Is the bike stable at high speeds? Is it easy to stay in control in demanding terrain? How composed is it on rough trails? Stability is a combination of balanced geometry, good suspension and the right spec.↩
This is all about how balanced the bike is and particularly about how well it corners. Balanced bikes require little physical effort from the rider and are very predictable. If a bike is unbalanced, the rider has to work hard to weight the front wheel to generate enough grip. However, experienced riders can have a lot of fun even with unbalanced bikes.↩
How sensitive is the suspension over small bumps? Can it absorb hard impacts and does it soak up repeated hits? Plush suspension not only provides comfort and makes a bike more capable, but it also generates traction. The rating includes the fork and the rear suspension.↩
This aspect mainly comes down to the suspension. How much pop does it have, does it suck up the rider’s input or is it supportive, and how agile and direct is the bike?↩
We don’t calculate value for money in an excel spreadsheet or based on how high-end a bike is specced. We are more concerned with how a bike performs on the trail and how the bike benefits the rider. What good are the best components if the bike doesn’t perform well on the trail? Expensive bikes with a lower-end spec can offer very good value for money – provided they excel where it matters. Just as supposedly cheap bikes with good components can get a bad rating if they don’t deliver on the trail.↩
No, it’s not about racing, it’s about efficiency. Fast, fleet-footed and efficient – those who want to speed along flowy singletrack and gravel roads need a defined and spritely bike that accelerates with ease and efficiency. Nevertheless, reliable components are important too. We interpret XC more like the Americans do: big back-country rides instead of a marathon or XC World Cup with the ultimate in lightweight construction! Uphill-downhill ratio: 80:30 (not everything has to be 100%!)↩
...also known as mountain biking. Classic singletrack with roots, rocks and ledges – sometimes flowy, sometimes rough. For this, you need a bike with good all-round qualities, whether climbing or descending. Uphill-downhill ratio: 50:50↩
Even more extreme and challenging compared to Trail riding, riddled with every kind of obstacle: jumps, gaps, nasty rock gardens, ruts and roots. For this, you need (race)proven equipment that forgives mistakes and wouldn’t look out of place on a stage of the Enduro World Series. Climbing is just a means to an end. Uphill-downhill ratio: 30:70↩
Strictly speaking, a 200 mm travel downhill bike is the best choice for merciless tracks with big jumps, drops and the roughest terrain. Those would be the black or double-black-diamond tracks in a bike park. But as some of the EWS pros (including Sam Hill) have proven, it’s the riding skills and not the bike that define what you can ride with it. Climbing? On foot or with a shuttle, please! Uphill-downhill ratio: 10:90↩
You can find more info about our rating system in this article: Click here! ↩

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Words: Peter Walker Photos: various

Trek Fuel EX 9.8 GX 2021 in review – Trail performance over bling components