2020 Trek Fuel EX 9.8 XT
Size Tested: Medium
Geometry: See Below
Build Overview (9.8 XT Build):
- Drivetrain: Shimano XT 12-speed
- Brakes: Shimano SLX M7120 4-piston
- Fork: Fox Performance 36
- Shock: Fox Performance Float EVOL w/ RE:aktiv tune & Thru Shaft
- Wheels: Bontrager Line Carbon 30
Wheel Size: 29”
Travel: 130 mm rear / 140 mm front
Blister’s Measured Weight (w/o pedals): 29 lbs, 4 oz / 13.27 kg
The Trek Fuel EX first debuted in 2001. While, to some, that original Fuel EX looks like a nightmare by today’s standards, it was a damn good bike for its time. Since then, the American brand has continued to improve the Fuel EX to keep up with the ever-changing mountain bike industry.
Prior to this year, the last major update to the Fuel EX was in 2016, so it was due for some change. For model-year 2020, the Fuel EX underwent a well-needed rework. The EX platform has now been fully upgraded to compete with the new generation of aggressive, shorter-travel Trail bikes, and from the looks of it, Trek’s 2020 Fuel EX has better filled the middle ground between the XC-oriented Top Fuel and longer-travel Remedy and Slash.
We recently got our hands on the 9.8 XT build of the 2020 Fuel EX and so far have only had a handful of rides on it as winter is creeping around the corner. So for now, here is a closer look at the specs of the bike and our initial ride impressions, and then stay tuned for our upcoming full review.
While the old carbon Fuel EX had alloy chainstays, the 2020 Fuel EX now offers a full carbon frame (excluding the rocker link) in the 9.7, 9.8, & 9.9 builds, in addition to fully aluminum frames for the 5, 7, and 8 builds.
The carbon Fuel EX frames include one of my favorite features: an integrated storage compartment located on the downtube.
This is a similar design to the “SWAT Box” seen on Specialized’s Stumpjumper and Enduro models. The Fuel EX’s compartment is accessible through a door that’s connected to the water bottle cage by easily turning a lever. The compartment has enough room to fit a spare tube, CO2 cartridge, and a set of tire levers — all in the included Bontrager BITS tool roll to keep things stable and non-noisy. If I ditch the tools, I could even fit an ultralight rain jacket in the space. Compared to Specialized’s SWAT box, Trek’s take on this is a bit easier and quicker to use thanks to its larger lever. The Fuel EX has also adapted to the 1x standards, losing the option to mount a front derailleur.
Trek outfitted the Fuel EX with the now fairly standard integrated chainstay, seatstay, and downtube protectors, as well as a clean internal cable routing system. The Fuel EX came almost entirely built, and setting up the internal cable routing was extremely easy.
For more frame defense, Trek implemented their Knock Block steering limiter, eliminating the chance of the fork crown hitting the downtube, since they use a straight downtube that would otherwise contact the fork if you tried to turn the bars 360°. Trek says this design creates a stiffer frame (due to the straight, oversized downtube), though it’s a polarizing design and I’m still unsure of how I feel about it. One of the major downfalls to the Knock Block system is that it imposes limitations on the customization of the cockpit. You are limited to stem height as well as changing out the spec’d stem (you have to get a special washer from Trek to use a non-Bontrager stem).
The 2020 Fuel EX frame now can accommodate longer dropper posts — 100 mm on the XS-S sizes, 150 mm on the M and ML, and up to 170 mm on the L-XXL sizes.
Aside from updated frame aspects, the Fuel EX has a beautiful array of matte and gloss color schemes for 2020 (FWIW, the purple / raw carbon frame we have looks pretty dang great).
The Fuel EX’s suspension platform still consists of a classic four-bar linkage, but the 2020 model drops their “Full Floater” design introduced back in 2008. That design attached the lower shock mount to the chainstay, just forward of the main pivot, thereby moving both ends of the rear shock, and thus altering the leverage curve. For 2020, Trek has returned to a fixed lower-shock mount, but carries over the Re:aktiv damper configuration and Thru Shaft rear suspension from the prior model.
What is RE:aktiv? Essentially, it’s Trek’s term for the damper configuration in their proprietary rear shock that was designed with Fox and Formula 1 Penske engineers. In short, it is a way of making the damper regressive — the damping force initially increases with higher shaft speeds, but then actually decreases as the speed further increases. This is accomplished with geometry on the main damper piston that increases the area on which the pressurized oil acts on the compression valve as the valve opens, thereby increasing the force exerted on the compression valve. The idea, as Trek describes it, is to create firmer compression damping at lower-frequency inputs — such as pedaling, or while pumping and popping off of features — while having the damping fall off under sharper inputs, to be more supple under high-speed chatter.
If that last paragraph made your eyes glaze over, that’s okay – we’re talking about a somewhat unconventional damper tune here, but nothing totally off the deep end. And if you want to nerd out on the concept some more, Steve Mathews from Vorsprung Suspension has an excellent video on the damper here (the stuff at the beginning about the air spring is referring to an older version of the shock; the details about the Re:aktiv damper start around 5:38).
The version of the shock spec’d on the EX 9.8 and 9.9 builds is a “Thru Shaft” system. Thru Shaft was created to eliminate what Trek refers to as the “lag” created by the Internal Floating Piston (IFP) as the shock cycles, and the damper shaft (and correspondingly, the IFP) changes direction. Their claim is that the Thru Shaft design allows the shock to respond more quickly while riding over varied terrain. Noah Bodman has a good explanation of this design in his review of the Trek Slash, and was able to compare a Thru Shaft shock back-to-back with a conventional one – check out his review for more detail.
Updated for 2020, all Fuel EX models are now spec’d with a 140 mm fork instead of a 130 mm, and the more expensive 9.8 and 9.9 builds get a burlier Fox 36 instead of the 34 on the lower-end models. In my opinion, this is a good move by Trek since the 36 aids in stability and overall stiffness in the front end through demanding sections of trail, but I would have liked to have seen this fork on some of the lower-end models as well, given the strong downhill performance we’re seeing in Trail bikes these days.
The 2020 Fuel EX is offered in nine* different builds and two frame-only options. The alloy frameset w/ Fox Re:aktiv shock goes for $1,999 and the carbon frameset w/ Fox Factory Re:aktiv & Thru Shaft shock goes for $3,299.
*The full builds consist of the 5, 7, 8, 9.7, 9.8, and 9.9, but Trek also offers the 9.8 and 9.9 builds with different drivetrains. You can get a Fuel EX 9.9 with a Sram X01 Eagle drivetrain, Sram X01 AXS drivetrain, or Shimano XTR drivetrain. And you can get a Fuel EX 9.8 with a Sram GX Eagle drivetrain or Shimano XT drivetrain (the build we’re testing). But apart from the drivetrains and prices, the 9.9 builds are all basically identical, and same story for the two 9.8 builds.
The full builds range from the alloy 5 at $2,099, spec’d with components chosen with value in mind, all the way up to the 9.9 X01 AXS build that features a carbon frame, carbon wheels, carbon bars, top-tier Fox Factory suspension, Sram X01 Eagle AXS 1×12 drivetrain, and Shimano XT brakes for a whopping $8,499-$8,999.99.
The build we are currently testing is the 9.8 XT model, priced right at $5,999. This build comes spec’d with a full carbon frame, carbon wheels and bars from Bontrager, Performance-level Fox suspension, Shimano XT 1×12 drivetrain, and Shimano SLX brakes.
For more info on all of the Fuel EX builds (and the rest of Trek’s lineup), see our Trek Brand Guide.
Initial Thoughts on the Fuel EX 9.8 Build
$5,999 is a considerable chunk of change. If you’re paying such high dollar for a mountain bike, you better get a darn good setup, right?
Well, the Fuel EX 9.8 XT comes with Trek’s top-of-the-line OCLV Mountain carbon frame as well as Bontrager carbon bars and carbon wheels. Fitted on the wheels are a set of Bontrager XR4 Team Issue 29×2.6 tires (tubeless-ready, of course). And if you’re concerned about blowing up your sweet new carbon hoops, it’s worth noting that Trek says they’ll repair or replace the carbon rims for free if you damage them within two years after your purchase.
Apart from the fancy carbon bits, the 9.8 XT comes spec’d with the new Shimano XT M8100 1×12 groupset (shifter, derailleur, crank, cassette, and chain) and after my initial time, I think it’s a nice addition. Although I have only ridden the Fuel EX on a handful of rides so far, the drivetrain performed flawlessly (even after we let Sam Shaheen romp around on it in the muddy creek beds of Moab…).
I was easily impressed when going from the jeep mode (51-tooth, lowest gear) climbing up a steep hill, to dumping the shifter into higher gears with my full weight on the pedals as I drop down over the crest. It was a pleasant escape from the usual horrifying noises I typically get when doing this sort of shifting under load. It will be interesting to see how the groupset holds up over time with rough riding, but knowing Shimano, I have high hopes for the new XT 12-speed.
Another recently revised Shimano product on the Fuel EX 9.8 is this year’s 4-piston Shimano SLX brakes. I’m not sure why Trek decided to spec an XT build with SLX brakes, but the revised SLX model is supposed to offer similar performance as the XT, and it seems that Trek took this as an opportunity to save a bit of money. The Fuel EX 9.8 is fitted with a 180 mm rotor in the front and a 160 mm rotor in the rear, which I’ve found to be a great pairing for a shorter-travel Trail bike like the Fuel EX.
Next up is suspension. The rear shock spec’d for the Fuel EX 9.8 features Trek’s RE:aktiv tune and Thru Shaft design, which we touched on earlier. The shock is essentially a Fox Performance Float EVOL with a 3-position damper (climb, trail, & descend modes) that’s custom-tuned by Trek. This shock loses a few features, such as the 3-position fine-tune adjustment for descend mode and Kashima coat, seen on the Fox Factory Float EVOL offered on the higher-end 9.9 builds.
We can’t really compare (at least on paper) this custom shock to the normal Float EVOL due to the custom nature of the shock on the Fuel EX, but I’ll be discussing how the shock feels while climbing and descending in my on-trail impressions.
The fork on the Fuel EX 9.8 is the Fox Performance 36 with the Float EVOL air spring and GRIP damper. Once again being on the lower end of the spectrum for the Fox suspension line, it still works fairly well and does the job for its intended use on this bike. I ride a 140 mm Performance Elite 34 on my current shorter-travel Trail bike, the 2019 Transition Smuggler, and the stout 36 on the Fuel EX feels notably more stable so far. Compared to the higher-end Factory 36 fork on the 9.9 builds, on the 9.8 you lose the more adjustable GRIP2 damper as well as Kashima coat and options for further tuning (though the Performance 36 has been great so far).
You might be questioning why a $6000 bike comes with lower-tier suspension, and I think that comes down to the fact that the Fuel EX 9.8’s Line Pro 30 carbon wheelset costs nearly $1,300 if you were buying it separately, and the carbon frameset alone would cost you $3,299 (admittedly, with the higher-end Fox Factory shock). So at least on paper, the Fuel EX 9.8’s build / price seems pretty reasonable, though Trek opted to spend a bit more on the wheels and cockpit, whereas some other brands put more money into suspension and stick to cheaper wheels, bars, etc.
Fit and Geometry
Going along with the updated trends of modern Trail bikes in the shorter-travel category, the 2020 Fuel EX has seen a geometry change like most new-gen bikes that can be summed up with the words of longer (reach / wheelbase), slacker (head angle), and steeper (seat tube angle).
The Fuel EX’s head angle has now dropped a degree to 66°, reach has been extended by 10-20 mm depending on frame size, and seat tube angle has gained a degree, now sitting at 75° for a steeper position while climbing. The Fuel EX also has a flip chip “Mino Link” that allows for a half-degree change in HA (66.5° in the high setting and 66° in the low setting) and a few mm change in bottom bracket height.
For reference, here’s the geo chart for the Fuel EX:
For sizing, I opted for a Medium frame. At 5’7”, I thought this was an optimal fit, excluding the spec’d 780mm-wide bars. That’s just a personal preference, but at my size I feel more comfortable riding something closer to 750 mm. But the good news is that you can always cut down bars (and can’t turn a smaller bar into a bigger one), and aside from that, the fit felt spot-on compared to other bikes in this category.
Something to take into consideration about sizing for the 2020 Fuel EX models — they have dropped female-specific bikes this year. They are currently implementing their motto introduced in 2019: “Awesome bikes for everyone.” Instead of having women’s-specific models like they did in previous years, they’re just offering more size options for all builds. Personally, I think this is a pretty cool change since Trek can now offer smaller riders more spec and color options from which to choose. Over all nine builds available for the Fuel EX, there are currently six different available sizes (XS, S, M, ML, L, & XL). The XS is only available with 27.5″ wheels, you can get a size S with 27.5″ or 29″ wheels, and the other sizes all come with 29″ wheels. Interestingly, the carbon versions of the Fuel EX are not currently available in the XXL size, though the aluminum versions are.
At first glance, the Fuel EX 9.8 seems like a shorter-travel Trail bike that’s more suited toward descending than ascending, given its slacker and longer geometry, beefier fork, and wider 2.6” tires. However, I don’t think those specific aspects really hinder the bike’s climbing abilities. The Fuel EX climbs fairly well for this class, and even though it’s not a super efficient ascender, it still gets the job done — especially with help from the pedal-assist lever on the shock (that lever has proven to be more important on the Fuel EX than on my Transition Smuggler).
On longer ascents, the bike felt most efficient with the shock in the middle “trail” setting, which made the bike feel firm when needed without seriously compromising traction, and overall reduced the plush bob off the top of the stroke that I felt when the shock was in the open position. On the majority of my rides, I kept the shock in the middle trail setting, and only on mellow dirt roads did I feel like the shock needed to be fully locked out.
Approaching more committed and technical aspects of trail, I opted to leave the shock in the open position for added grip and traction. This is where the Fuel EX stood out in terms of climbing. The forgiving, plush shock just ate up the rocks and roots, offering little to no tire slip, all without requiring me to make many body-position adjustments to keep the bike on-line. Paired with the buttery smooth 1×12 XT drivetrain, the Fuel EX easily wheeled through punchy, technical climbs. The 29” wheels and 2.6” tires helped tremendously when it came to wheeling over variable terrain, though that wide of a tire also felt a bit sluggish while ascending smoother sections of trail where I would normally be carrying more speed.
While climbing through tight turns, I didn’t notice any steering interference from the Knock Block system, but I could see it possibly giving me some trouble when steering through a true hairpin section.
One thing I do want to point out is that I felt slightly off the back of the bike while seated, which is probably due to the not-extremely-steep 75° seat tube angle and also the positioning of the saddle. I’ll be tinkering more with the saddle and will see if that can alleviate this.
Right off the bat, I felt I was going to enjoy descending on the Fuel EX — everything about it looked like it’d make for a fun Trail bike on the down. I had the Mino Link flip chip in the low setting which put the head angle at 66° and was running my suspension a little on the faster side in terms of rebound, but nothing crazy. According to Trek’s suspension calculator, they recommended me running 30% sag in the rear. I set it up a little under that 30% number, hoping I would gain some support. For the fork, I ran about 65 psi since I like things to be a bit stiffer and was running the GRIP damper a few clicks past the midway point between open and firm (i.e., a bit closer to “firm” than “open”).
The first thing I noticed was how stable the Fuel EX felt during cornering. On flat corners, it was predictable and tracked incredibly well. On more bermed corners, I felt like it was encouraging me to really lean it over and weight the inside, letting me carry speed through the exit without much worry that it was going to slide out on me. In short, the Fuel EX’s predictability made cornering feel easier and it didn’t require me to be perfectly set up / prepared for any awkward transitions. Now with this being said, the combination of super tacky trail conditions and fresh rubber could have been helping, but I feel like that was just a small portion of it. For quick and tight maneuvers, the Fuel EX just handled well.
High-speed rocky sections of trail were where I started to notice the shock’s regressive damper. Similar to climbing with the shock fully open, the bike felt stuck to the ground. The normal chatter and feedback I get from my current trail bike (120mm-travel Transition Smuggler) were not there. This was a smooth and forgiving feeling, almost like a trophy truck’s suspension sucking up all the bumps and its tires maintaining contact with the ground at all times. The Fuel EX feels surprisingly planted and stable for a 130mm-travel bike.
When it came to riding with a looser style and pulling up off obstacles into blind landings, the Fuel EX sucked it up and muted the rough landing, recovering and keeping traction throughout, which was a pleasant surprise.
All that said, the Fuel EX’s plush feel definitely offers something different from my Smuggler, and that’s taken some adjustment on my end. The Fuel EX felt a bit “dead” in the high-speed chattery sections, whereas I’m used to the poppy feel and playfulness of the Smuggler, which lets me hop around or intentionally get kicked from rock to rock. The Fuel EX feels much more planted, and less poppy. I believe that some of this could come from the wider 2.6” tires, and maybe running sag percentage closer to 20% will let me get more pop out of the bike. But at least coming from the Smuggler, the suspension on the Fuel EX felt a bit “off” at first, though I think it’s something that more time and tinkering of the suspension / tire combo will likely solve.
Some Questions / Things We’re Curious About
(1) I’m very eager to play with different sag percentages on the Fuel EX’s Re:aktiv Thru Shaft shock. It will be interesting to see if there is actually a noticeable difference in responsiveness / pop, and more importantly, if it will make the bike feel better or worse. Noah Bodman found that the RE:aktiv shock on the Trek Remedy was very sensitive to air pressure, while the RE:aktiv shock on the Trek Slash was less sensitive, so what about the Fuel EX?
(2) How will the Fuel EX feel with lower-volume tires like a 2.5” Maxxis DHF and 2.3” Maxxis High Roller II?
(3) Is the Fuel EX a viable option for riders looking for a quiver-killer bike that they could use just about anywhere? Or is there any particular area / trail type / riding style for which the Fuel EX is best suited?
(4) How does the 2020 Fuel EX compare to other modern mountain bikes reviewed in the Trail category, such as the Yeti SB130 and Santa Cruz Hightower?
(5) Over long-term use, how will the Bontrager Line Carbon 30 wheelset hold up? And on that note, what about the new Shimano XT 12-speed drivetrain?
Bottom Line (For Now)
The 2020 Trek Fuel EX appears to be a solid revamp from its predecessor, now reflecting trends seen across all modern-day Trail bikes. After my initial time on it, it seems like a very capable, all-round bike. It seems to bring something a bit different to the table than many other shorter-travel Trail bikes, with an emphasis on stability, grip, and plushness over pop and playfulness. We’ll be getting much more saddle time with the Fuel EX to gain a better understanding of where the bike best performs and how capable it really is, so stay tuned for our full review.