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Trek Top Fuel 8 review

Can Trek’s new aluminium 120mm speedster top the downcountry charts for 2022?

Our rating 
4.5 out of 5 star rating 4.5
GBP £3,850.00 RRP | USD $3,830.00 | EUR €4,099.00 | AUD $5,300.00
Pack shot of the Trek Top Fuel 2022 full suspension mountain bike

Our review

Impressively playful characteristics, progressive geometry and solid build, despite lacking the outright pace of XC-derived competitors
Pros: Effective suspension gives suppleness and support; confidence-inspiring geometry beyond XC-derived counterparts; a riotous blend of capability and playfulness
Cons: The robust frame means it’s heavier than its rivals; a flexy fork is the only weak spot in a bullet-proof build
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Trek’s 2022 Top Fuel 8 shifts the model further from the cross-country race thoroughbred released in 2005 and continues the trend of the previous 2019 incarnation, with longer travel and a heavier-duty frame.

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“The downcountry/XC-trail category is evolving,” says Trek, and the new 2022 Top Fuel is built to respond: a pure downcountry shredder with 120mm travel, slacker angles and all-day capabilities.

Trek Top Fuel 8 frame and suspension details

Trek says the new Top Fuel is “for riders who enjoy pedalling up as much as they enjoy going down.” So, if you want to ride all day on longer loops, downcountry bikes such as the Top Fuel are for you.

New for 2022

The new Top Fuel is designed to “keep the pedalling efficiency but make it way more capable, not limited like a traditional XC bike.” To achieve this, Trek has taken the pivot position from the previous Top Fuel and moved it forwards, tuning the anti-squat curve to make it flatter and keep characteristics more consistent throughout the travel.

Trek’s ABP pivot remains, which it claims helps the rear suspension respond under braking, preventing brake-jack and keeping the wheel in contact with the ground. The chunky rocker link promotes stiffness, but is made from magnesium to save weight.

In-frame storage

One of the most obvious changes is Trek’s in-frame storage; its answer to Specialized’s SWAT box. Trek says that it “adds weight but it’s important for bikes in this category”. These stash areas give riders the ability to store items previously carried on their body, in the bike.

The Trek Top Fuel 8 2022 full suspension mountain bike has a stash box in the downtube
A neoprene bag in the stash box keeps everything organised and quiet.
Steve Behr / Immediate Media

This is claimed to increase stability of the bike and rider, lowering their centre of gravity. Trek has gone to great lengths to bring this feature to all bikes in the range, including the aluminium models as well as the carbon bikes.

New Knock Block

Trek’s contentious Knock Block steering-lock limiter allowed equipped bikes to have a straight down tube to enhance stiffness, and prevented damage from fork top caps on the down tube or low-slung brake levers on the top tube. But some riders found the 58-degree angle irksome and disliked the compatibility issue this caused if choosing to remove the device.

The 2022 Top Fuel features Knock Block 2.0, which has been redesigned to be less extreme and allow an increased steering angle from 58 to 72 degrees. Top Fuel frames have been designed with more down tube clearance for fork top caps, doing away with the previously straight, stiffness-promoting down tube found on Knock Block 1.0 bikes.

The Trek Top Fuel 8 2022 full suspension mountain bike is equipped with a KnockBlock 2.0
Trek’s Knock Block 2.0 is unobtrusive and doesn’t hamper the bike on slow-speed turns.
Steve Behr / Immediate Media

Presumably, this makes the bike less stiff, so Trek must feel it is a sacrifice worth making. If both fork top caps clear the down tube and brake levers clear the top tube, Trek says it’s possible for riders to remove the Knock Block 2.0 completely with minimal fuss.

Wheel size is 29in except for the XS, which comes with 27.5in wheels (and in the 9.8 spec only). All complete bikes come with 2.4in-wide Bontrager tyres, but the frames will take up to a 2.5in, so mud clearance should be ample for UK riding.

Maintenance and durability

Trek hasn’t forgotten the mechanics out there, who will be ecstatic to hear that although the Top Fuel has internally routed cables, Trek has fitted full-length internal sheathing throughout the bike. That’s right, no fishing around with bent spokes and magnets when it’s time to refresh the outer cables.

Interestingly, Trek has chosen to rid itself of press-fit bottom bracket (BB) issues for this bike and return to the venerable old 73mm-width threaded shell. While Trek hasn’t commented on the reason for this shift, many feel that the threaded BB is less prone to creaking, and it is hard to argue with the ease of replacing a threaded BB when compared to its push-fit cousin.

The Trek Top Fuel 8 2022 full suspension mountain bike has a stash box in the downtube
The integrated stash area hides under the bottle cage.
Steve Behr / Immediate Media

The seat-tube diameter has expanded to the new 34.9mm standard, allowing the next generation of longer dropper posts to be fitted.

The reasoning behind yet another new standard is actually pretty sound. Its girthier chassis boosts stiffness and spreads side-loading more effectively, meaning modern, longer posts retain stiffness when extended, are stronger and experience reduced wear. According to Trek, the related stiffness improvement in the frame itself (because of the larger-diameter tube and increased surface area at junctions) is “slight”.

Trek is also pleased to extol the burlier nature of the new Top Fuel, by extending warranty coverage to include the fitment of a longer 130mm-travel fork. Fitting one would slacken the head angle and seat tube angle by 0.5 degrees and raise the BB by 3mm.

Trek Top Fuel 8 geometry

The new Top Fuel has more progressive geometry when compared to previous versions, boasting a 76-degree seat tube angle, 1.5 degrees steeper than the previous model.

Mirroring the seat tube angle, the head angle has been slackened by 1.5 degrees to 66 degrees to improve stability when descending. These changes alone would decrease cockpit room for the rider, so to reduce these effects Trek has increased the reach by 10mm in each size, with the large measuring 480mm.

Male cyclist in gret top riding over rough ground through woodland
The Top Fuel 8 has geometry that makes you feel comfortable on even the most technical terrain.
Steve Behr / Immediate Media

Chainstays remain the same length across the sizes at 435mm, which keeps the 2019 bike’s playful nature and should make lifting the front wheel a breeze.

The bike is available in six sizes: XS (9.8 only), S, M, ML, L, XL and XXL.

Trek’s trusty Mino Link is found on the Top Fuel, albeit moved to the lower shock mount (allowing a trunnion-mount shock to be used). By removing just one bolt, the chip can be flipped to steepen head and seat angles by 0.5 degrees and raise the bottom-bracket height by 7mm.

Trek Top Fuel 8 geometry in LOW setting

SMMLLXLXXL
Seat angle (degrees)707070707070
Head angle (degrees)666666666666
Chainstay (mm)435435435435435435
Seat tube (mm)39542043.5450500540
Top tube (mm)568598615631654676
Head tube (mm)101010.51112.513.5
Fork offset (mm)444444444444
Trail (mm)118118118118118118
Bottom bracket drop (mm)363636363636
Bottom bracket height (mm)338338338338338338
Wheelbase (mm)115111811198121512411265
Standover (mm)715735740745755765
Stack (mm)595595600605618627
Reach (mm)420450465480500520
Seatpost travel (mm)100150150170170170
Crank length (mm)170170170170175175

Trek Top Fuel 8 specifications

The 8 is the highest-spec aluminium Top Fuel (above the 5 and 7), with RockShox’s 35mm SID Select fork and Deluxe Ultimate shock. The 8 gets Bontrager Line Comp 30 wheels shod in 2.4in wide Bontrager XR4 tubeless tyres, the latest Shimano 12-speed XT derailleur and shifter, SLX cranks, cassette and chain.

It has a 780mm Bontrager Line 35 bar (which measures a whopping 800mm with lock-on grips attached) and uses a 35mm OD to clamp into a 45mm-long Bontrager Line stem above Trek’s Knock Block 2.0. Brakes are Shimano SM6120 four-pots with small 180mm/160mm six-bolt rotors.

The Trek Top Fuel 8 2022 full suspension mountain bike is equipped with Shimano M6000 levers & M6120 four-pot caliper brakes with 180/160mm rotors
The tiny 160mm rear rotor heats up too quickly on the descents and robs power from the multi-piston brakes
Steve Behr / Immediate Media

The Trans-X long-travel dropper sits in the oversize 34.9mm seat tube.

Trek Top Fuel 8 ride impressions

Over the past months, I’ve thrown this bike around trail centres, up and down every bikepark trail I can find, and even hit some big jumps.

Setting it up for my preference was as easy as swapping out some spacers from below the stem and adding air to the suspension. I ran 100psi in the fork and 200psi in the shock.

The Trek Top Fuel 8 2022 full suspension mountain bike is equipped with a Rockshox Super Deluxe Ultimate shock
The RockShox Super Deluxe Ultimate shock provides good low-speed support when riding jumps and berms.
Steve Behr / Immediate Media

I weigh 65kg and am an aggressive rider who likes big jumps and rough tracks. If I had the bike for longer, I would like to play with the volume spacers (tokens), but as standard they felt supportive enough – although I was still using all the travel.

Trek Top Fuel 8 climbing performance

Stab the lever that raises the unremarkable Trans-X dropper, chunk yourself precisely (thanks Shimano) into the biggest cog on the SLX cassette and the Top Fuel climbs like a sticky mountain goat.

The steep seat angle for a short-travel bike is helpful, positioning your seated mass further forward and centred over the bottom bracket, helping to keep the front wheel planted and pedalling efficient. When combined with the low 30x51t gearing, you can comfortably climb almost anything (traction permitting).

The Trek Top Fuel 8 2022 full suspension mountain bike is equipped with Shimano XT/SLX 12 speed groupset
Shimano’s XT/SLX 12-speed groupset is quiet, reliable, precise and reassuringly well made.
Steve Behr / Immediate Media

The Bontrager XR4s are a little slick for off-piste conditions, with a rounded profile and shallow tread blocks tending to skate over the surface rather than dig in.

The trade-off is they roll fast and are communicative on the limit, letting go predictably. They provide acceptable grip on surfaced trails and leaf mulch.

The shock lockout lever on the Super Deluxe has an uncomfortable-to-operate indexed notch, which snaps open unpredictably, making it feel agricultural to use (especially with cold fingers). However, it does provide a severe but effective platform when climbing. In contrast, the SID Select fork lockout is a rather spongy affair.

Male cyclist in gret top riding over rough ground through woodland
Jumps are no problem for the Top Fuel 8.
Steve Behr / Immediate Media

Overall, the geometry and crisp Shimano shifting mean it’s a doddle to winch your way up to the top of a peak.

It does lack the taut eagerness of XC-derived downcountry rigs such as the Scott Spark, which strain at the leash to attack every climb, whereas the Top Fuel prefers to lope comfortably along.

As downcountry bikes go, the Top Fuel’s forward pivot position, placid anti-squat curve and overall build are swayed toward delivering incredible overall performance and stable, low-effort climbing rather than scintillating polka-dot-jersey-esque uphill sprints.

Male cyclist in gret top riding over rough ground through woodland
This bike copes with terrain that would feel awkward or unwieldy on other downcountry rigs.
Steve Behr / Immediate Media

Trek Top Fuel 8 descending performance

Point it downhill and the flickable chassis is easy to manoeuvre: if you’ve felt over-biked and sluggish on a 140mm trail bike, this is the answer.

Whereas some downcountry bikes are XC race rigs on steroids: devastatingly efficient on trail-centre loops, but unwieldy descenders, the Top Fuel feels like Trek has tautened and lightened its Remedy trail bike.

While it lacks athletic fervour, it feels exuberant and cheeky, goading you into manuals and riding the trail playfully .

Male cyclist in gret top riding over rough ground through woodland
The Top Fuel 8 is confidence-inspiring in corners.
Steve Behr / Immediate Media

With predictable cornering manners and progressive-feeling rear-suspension kinematics, thanks to its forward pivot point, this bike is devastating on the descents.

But whereas the XC DNA of many downcountry rigs means they seem as if they’re processing bumps for you, insulating you from the trail, the Top Fuel feels like a bike that works with you, involving the rider in the glory of a corner well hit or an obstacle correctly anticipated. It flatters your moments of brilliance but buffers any mistakes stoically.

Male cyclist in gret top riding over rough ground through woodland
The Top Fuel 8 copes incredibly well and isn’t out of its depth until the roughest black runs.
Steve Behr / Immediate Media

Indeed, the level of grip and confidence is so high that it’s not until you get onto rougher black trails or find yourself offline that you need to brace for impact, and remember this isn’t an enduro bike.

This means it’s easy to inadvertently throw the Top Fuel way out of its depth and get carried away with the fun you’re having on the descent.

When you push the Top Fuel beyond its depth, the RockShox SID begins to feel exactly like what it is – a beefed-up XC fork. I would love to try a more robust 130mm fork (which is approved within Trek’s warranty) and spend more time with the TF8.

Male cyclist in gret top riding over rough ground through woodland
More manoeuvrable than a trail bike, the Top Fuel 8 shines when the trail gets technical.
Steve Behr / Immediate Media

Even on the tightest turns, I never felt limited by the 72-degree steering angle of the Knock Block 2.0, the way I occasionally did with the original 58-degree Knock Block.

The Shimano drivetrain and Bontrager wheels feel taught and reassuring, but the four-pot brakes, though progressive, lack ultimate power, as they struggled for leverage on the miniscule rotors.

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Trek Top Fuel 8 bottom line

While lacking the ruthless outright pace of XC-derived competitors, the Top Fuel’s playful characteristics flatter your riding skills, progressive geometry takes care of tough terrain and a confidence-inspiring build makes this one of the most entertaining all-rounders you can buy.

Product Specifications

Product

Price AUD $5300.00EUR €4099.00GBP £3850.00USD $3830.00
Weight 14.41kg (L) – without pedals
Year 2022
Brand Trek

Features

Available sizes S, M, ML, L, XL, XXL
Headset Bontrager
Tyres Bontrager XR4 Team Issue 29x2.40in 120tpi Aramid tubeless
Shifter Shimano XT M8100 12s
Seatpost Trans-X 34.9x170mm dropper
Saddle Bontrager Arvada 138mm steel
Rear Shocks Rockshox Deluxe Ultimate RCT, Trunnion mount, 185x50mm
Rear derailleur Shimano XT M8100 12s
Handlebar Bontrager Line 35 27.5x780mm
Bottom bracket Shimano SM-BB52 73mm
Grips/Tape Bontrager XR Trail Comp lock-on
Frame Alpha Aluminium alloy, 120mm (4.7in) travel, in-frame storage
Fork Rockshox SID Rush RL Debonair 120mm (4.7in), 44mm offset, tapered, boost
Cranks Shimano SLX 7100 55mm 12s
Chain Shimano SLX 12s
Cassette Shimano SLX 7100 10-51t
Brakes Shimano M6000 levers & M6120 four-pot caliper, 180/160mm
Wheels Bontrager Line Comp 30 (tubeless ready)