TREK FUEL EX 9.9 XX1 REVIEW
THE MAGIC SCHOOL BUS
Words by Drew Rohde
The Fuel EX is Trek’s do-it-all mountain bike and is now in its sixth generation. The new 2023 Trek Fuel EX Gen 6 doesn’t just have a few minor changes either: the bike features a whole host of changes, with a completely new chassis and increased capability for all riders. Read below to find out how we got along with this completely redesigned Trek Fuel EX in this long-term review. We’ll be keeping the lab section a bit brief as we went into the features and details in great depth in our First Ride Report, found here.
• HTA 64.5 (neutral headset cup, low Mino Link)
• STA 77.2 (effective)
• REACH 485mm (Large)
• Adjustable geo & compression rates
Offered in sizes XS through XL, the new Fuel EX gets an extra 10mm of rear wheel travel, bringing it to 140mm, with a 150mm fork up front. The Fuel EX has features found on other Trek mountain bikes, like their Mino Link adjustable geometry, Trek’s Active Braking Pivot (ABP) suspension, and a full-length downtube protector. However, there are plenty of awesome new features that previous generation Fuel EX’s did not have. One of those features is the downtube storage solution, which is probably our favorite and most weather-resistant compartment we’ve seen yet. On the showroom floor, the Fuel EX is a 29er, but it has the ability to run a 27.5” rear wheel when combined with a 160mm front fork. It also has an integrated tool in the stem, size specific stays, an adjustable More/Less progressive suspension chip, and angle adjustable headset cups. The new adjustable headset cup system allows riders to adjust the headset a full degree steep or slacker, From 63.5 up to 65.5. That is huge!
The Fuel EX Gen 6 has a wide range of builds starting from $3,699.99 with two aluminum frame options, before getting into the carbon fiber frames from $4,699.99. The model we have for review, the Trek Fuel EX 9.9 XX1 AXS is the top of the line model, and comes with a price tag of $10,749.99.
With a price tag north of 10k the build better be tip top, and for the most part it is. Up front there’s a Kashima-coated 150mm travel Fox Factory 36 fork, which is paired to a Fox Factory Float X shock to control the 140mm rear travel. Driving and stopping power is delivered courtesy of an oil-slick SRAM Eagle XX1 AXS wireless groupset and SRAM Code RSC 4-piston brakes. These burly Code brakes stopping on the 203 front and 180mm rear rotors could likely be one of the bigger indicators of how capable the new Fuel EX is designed to be. In-house brand Bontrager supplies their top tier Line PRO 30 carbon wheels, which are wrapped in their SE5 tires.
The bar-stem combo is a brutally stiff Bontrager RSL unit, which features a neatly integrated multi-tool. The bar/stem combo weighs in at 250 grams, not including the weight of the multitool. The effective stem is 45mm in length and has a zero degree rise. The handlebar is supplied at a massive 820mm in width, has 27.5mm of rise, 7 degrees of back-sweep, and 6 degrees of up-sweep. Rounding out this build is the RockShox Reverb AXS seat post with 170mm of drop for sizes Large (reviewed) and XL.
The geometry of the Fuel EX was built around the need for a highly capable bike that felt at home in all terrain. The geometry is adjustable both by the Mino Link and the adjustable headset cups as mentioned above. For most of our review period the bike was ridden in the neutral headset setting (64.5°) with the Mino Link constantly being switched between both settings. In the neutral headset and low Mino Link setting, the Fuel EX has a 64.5-degree head angle; 77.2° effective seat tube angle and 38mm bottom bracket drop across the S-XL 29ers. The rear end is size-specific from 435mm to 450mm, with the size Large coming in at 440mm. The reach is 485mm, the stack is 621.3mm, and the wheelbase adds up to 1,250.2 mm on this size large test bike.
Something worth noting is that riders will see different numbers if they mount a 27.5” rear tire and increase fork travel to 160mm, which this bike is approved for. It’s crazy to think where the Trek Fuel EX was ten years ago, to now being a coil-sprung ready mullet with a 160mm fork and DH brakes! Evolution is real and we’re all for it.
Since our Bellingham, WA-based tester Dario introduced what he called a “Pretty perfect all-rounder” in our First Ride Report, the Trek Fuel EX 9.9 has been getting some hammer on the trails around Bend, Oregon. I’ve ridden every generation of Fuel EX and this is the biggest jump in evolution, hands down. Some may feel disappointed that the Fuel EX has transcended that lighter-duty all-around trail bike feel and morphed into a burlier, all-mountain bike, but we’re not mad about it. Trek’s Top Fuel will likely fill that void for riders not wanting or willing to deal with the extra heft, length and aggressive intentions the new Fuel EX has. For everyone else, the Fuel EX is now what so many others have been craving, and it’s aiming to pull riders off their Specialized Stumpjumpers and Santa Cruz Hightowers.
Despite being much more capable on the descents, the Fuel EX is a bike that needs to climb well, as most riders pushing a 140mm bike around will be pedaling to most of their downhills. The geometry, as adjustable as it is, put our riders in a pretty dialed position overall. Some of us felt the bottom bracket was a bit low for very technical, jankier trails where tall rocks, roots or ruts were commonly found. The high position helped, but it’s still something worth noting. From a suspension and efficiency standpoint, the Fuel EX held traction without bobbing deep into the travel, keeping us from feeling the urge to flip the shock lockout for all but the smoothest climbs. The bike is well balanced, and that was apparent from the get-go. It’s not the lightest, but the platform is solid, and as long as we didn’t strike a pedal, we could climb this bike up just about anything. It’s impressive on the way up.
Downhill oriented riders looking for an aggressive trail bike that they can put in big days on, or trail riders looking for a longer travel bike, will be very happy that Trek has ripped the Fuel EX’s envelope wide open. During our review period, the Fuel EX handled copious amounts of chatter and soaked up some fairly big hits, even on shuttle days chasing longer travel bikes. Right out of the gate the acceleration of this bike was quick. It doesn’t feel as sluggish as its bigger sibling, the Trek Slash, though this will likely not come as a surprise. The Fuel EX is the sportier of the two, yet the frame stiffness and body position at speed had us feeling like the Fuel EX wouldn’t be too far behind the Slash if it were a race to the bottom. While there’s no substitute for travel on truly rough terrain, the Fuel EX does well until you realize you’re at speed on terrain that would make a 160mm bike work. The downside to this is a slightly stiffer, or firmer suspension feel than previous generation Fuel EX’s. While we were very happy Trek has finally given an aggressive, progressive feel to the bike, there will no doubt be a lot more riders who will miss the in-the-saddle comfort and cushion of the older designs. With Trek’s adjustable suspension progression chip, you have the ability to give the bike more or less progression and tune the feel a bit, or opt for a coil shock if you’d like, but ultimately the fact remains, the new Fuel EX has a slightly more aggressive feel, for better or worse. It’s nowhere near VPP but closer to how a DW-Link bike feels when hitting square-edge hits at speed.
Along with making the bike feel capable in rougher terrain and at speed, that more progressive and stiffer suspension platform keeps the bike higher in its travel in berms, higher speed corners and big compressions. Flow trail riders will enjoy pushing on the pedals to get a snappy acceleration out of corners or extra hang time off jumps, and it feels as if it’d happily hang in the park from time to time.
While geometry is extremely personal, our testers from 6’3 to 5’11 felt happy overall with the 485mm reach being a pretty great middle-ground. The Medium/Large size has a 470mm reach, which could tempt some riders in that 5’9-5’11” height range, and we think that evaluating your most frequently ridden trails would be a good thing to do as there’s no doubt I would have personally had a bit more fun in some scenarios on the M/L with a 15mm shorter reach. Nevertheless, the Large still suited me fine overall. It’s awesome to see these tight size jumps being offered in the most commonly used sizes as more riders will be likely to find that “just right” fit on the Fuel EX than many alternatives.
The Wolf’s Last Word
There is a lot to talk about when it comes time to review the Trek Fuel EX. From the ground-up redesign to the on-trail performance. Without trying to drag this out, here’s our cut and dry impressions. We don’t like integrated bar/stem combos from any brand, Bontrager’s SE5 tires will likely get replaced if you ride wet rocks or roots but are fine on drier terrain. The new Fuel EX is a bit heavier, burlier and more aggressive than any previous Fuel EX, and while some may not love the changes, a lot of others are going to be going bigger, faster and harder than ever before. We really like the versatility of the bike from wheel size and geometry adjustments to suspension progression settings. We’re sure most riders will set and forget, but at least you’ll be able to set it in the ideal spot for your terrain and style, or switch it up somewhere down the line.
On the trail, we found the Trek Fuel EX to be a blast all around. It’s a stiff, fun, playful and fast machine that does equally well uphill as it does down. For our testers who’ve all spent a lot of time on the Specialized Stumpjumpers, Stumpy Evos and Santa Cruz Hightowers, Trek’s new Fuel EX will absolutely be stealing some riders for more than a couple of reasons.
Frame: Carbon | 140mm
Fork: Fox 36 Factory Float | 150mm
Shock: Fox Factory Float X Performance | 2-pos | 185x55mm
Brakes: SRAM CODE RSC 4-piston | 200/180mm rotors
Bar: Bontrager RSL integrated handlebar/stem | width: 820mm | rise: 27.5mm | Stem: 45mm
Seatpost: RockShox Reverb AXS 34.9mm | XS/S:100mm | M/ML: 150mm | L/XL: 170mm
Saddle: Bontrager Arvada
Wheelset: Bontrager Line PRO 30
Tires: Bontrager SE5 Team Issue 29×2.5”
Cassette: SRAM Eagle XG 1299 | 10-52T | 12spd
Cranks: SRAM XX1 Eagle | 30t | 170mm
Shifter: SRAM Eagle AXS | 12spd
Derailleur: SRAM XX1 Eagle AXS
Fast, confident and ready to rock!
More capable than ever
Great downtube storage solution
Adjustable and versatile geometry options
SE5 Tires in the wet
Some may not like the newer, burlier bike’s transition
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