Trek

Top Fuel9.9 XTR Di2 Gen 4

Claimed weightSize M: 13.10 kg / 28.88 lb (with TLR sealant, no tubes)Complete bike

FrameOCLV Mountain Carbon, int…Size S: RockShox Pike Ultim…

GroupsetShimano XTR Di2 M9250,…Shimano XTR M9200, 12-spe…

WheelsBontrager Line Pro 30,…Bontrager Montrose RSL XT,…

Tire clearance64 mm

The fourth-generation Trek Top Fuel remains firmly rooted in the fast trail category, offering a highly adaptable platform for riders who want cross-country efficiency without sacrificing downhill composure. Rather than a total reinvention, Trek refined the existing chassis to broaden its tuning window and improve daily usability. The core travel target stays at 120 millimeters in the rear paired with a 130-millimeter fork, but the frame now accommodates a much wider configuration envelope.

By integrating a four-position Mino Link, Trek allows riders to adjust both geometry and suspension progression independently. The updated frame also officially supports longer-stroke shocks, longer forks, and mixed-wheel setups. It is a bike designed for those who value a pedaling-focused chassis that can easily morph from a lightweight marathon machine into a capable short-travel trail bike depending on how it is set up.

Trek Top Fuel

Build

Size

$10,500See deal

01 / Buy

Where to get it.

No retailers stocking size M.

Size

0 retailers · Size M

No retailers carrying size M right now.

02 / Specifications

Spec sheet.

Every component shipped with this build.

01Frameset

4 components

FrameOCLV Mountain Carbon, internal storage, tapered head tube, internal guided routing, downtube guard, alloy rocker link, 4-way Mino Link, ABP, Boost148, 120mm travel

ForkSize S: RockShox Pike Ultimate, DebonAir spring, Charger 3.1 RC2 damper, 44mm offset, Boost110, Maxle Stealth, 130mm travel; Size M/ML/L/XL: Fox Factory 36 SL, Float EVOL air spring, GRIP X damper, 44mm offset, Boost110, 15mm Kabolt X axle, 130mm travel

Rear shockFox Factory Float, 2-position damper, 185mm x 50mm

WeightSize M: 13.10 kg / 28.88 lb (with TLR sealant, no tubes)

02Drivetrain & brakes

10 components

Shift leversShimano XTR Di2 M9250, 12-speed

Rear derailleurShimano XTR Di2 M9250, long cage

CassetteShimano XTR M9200, 12-speed, 10-51T

ChainShimano XTR M9100, 12-speed

CranksetE*thirteen Helix Race Carbon, 30T, 55mm chainline, 170mm length

Bottom bracketE*thirteen BB20-P, BSA threaded, 73mm width

Front brakeShimano XTR M9220, 4-piston hydraulic disc

Rear brakeShimano XTR M9220, 4-piston hydraulic disc

Front rotorShimano MT905, 6-bolt, 180mm

Rear rotorShimano MT905, 6-bolt, 180mm

03Wheels & tires

4 components

Front wheelBontrager Line Pro 30, OCLV Mountain Carbon, Tubeless Ready, 6-bolt, Boost110, 15mm thru axle — Size S: 27.5in; Size M/ML/L/XL: 29in

Rear wheelBontrager Line Pro 30, OCLV Mountain Carbon, Tubeless Ready, Rapid Drive 108, 6-bolt, Shimano Micro Spline freehub, Boost148, 12mm thru axle — Size S: 27.5in; Size M/ML/L/XL: 29in

Front tireBontrager Montrose RSL XT, Tubeless Ready, triple compound, aramid bead, 120 tpi — Size M/ML/L/XL: 29x2.40 (Size S front tire not specified)

Rear tireBontrager Gunnison RSL XT, Tubeless Ready, triple compound, aramid bead, 120 tpi — Size S: 27.5x2.40; Size M/ML/L/XL: 29x2.40

04Cockpit & contact

5 components

StemBontrager Line Pro, 35mm clamp, Blendr compatible, 0 degree, 35mm length

HandlebarsBontrager Line Pro, OCLV Carbon, 35mm clamp, 27.5mm rise, 780mm width

SaddleVerse Short Pro, carbon rails, 145mm width

SeatpostFox Transfer NEO, 34.9mm — Size S/M: 150mm travel; Size ML: 175mm travel; Size L/XL: 200mm travel

Grips/TapeTrek Line Elite, lock-on

03 / Geometry

Geometry & fit.

4 sizes published.

The Top Fuel’s geometry strikes a deliberate balance between aggressive pedaling posture and downhill stability. In its stock low setting, the head tube angle sits at a relaxed 65.5 degrees, providing a calm, predictable steering feel that resists twitchiness on fast descents. The effective seat tube angle hovers around 76 degrees, which centers the rider comfortably over the bottom bracket for seated climbing, though some taller riders might prefer an even steeper angle for winching up extreme gradients.

A significant update for this generation is the introduction of size-specific chainstays. Ranging from 434 millimeters on the smallest frames up to 445 millimeters on the extra-large, this approach ensures that fore-aft balance remains consistent regardless of rider height.

The cockpit setup heavily influences the bike's handling character. Carbon models feature Trek’s one-piece Bontrager RSL integrated bar and stem. While this setup delivers highly precise steering input, it is notably stiff and prevents riders from rolling the bars to adjust sweep. The frame also features a shorter seat tube across the size run, allowing for longer-travel dropper posts and giving riders more room to maneuver when the trail points down.

Reach × Stack · size Mmm

Where the handlebar sits relative to the bottom bracket — the single most important fit pair.

01Fit geometry6 values

Stack596 mm

Reach457 mm

Top tube586 mm

Headtube length105 mm

Standover height745 mm

Seat tube length410 mm

02Component geometry5 values

Crank length170 mm

Handlebar width780 mm

Stem length35 mm

Saddle width145 mm

Dropper travel150 mm

03Handling geometry8 values

Headtube angle66.4°

Seat tube angle77.8°

BB height344 mm

BB drop29 mm

Trail115 mm

Offset44 mm

Wheelbase1184 mm

Chainstay length434 mm

Which size should I buy?

Slide your height to see the recommended size. GearWise's fit algorithm works from the published stack, reach, and ETT — the brand's own recommendation may differ.

Your height

5'8"173 cm

5'0"5'5"5'10"6'3"6'7"

Recommended sizeMBased on stack, reach & ETT for your height · score 82/100.

→Calculated from GearWise's own stack / reach / ETT algorithm — the brand's size chart may recommend a different size, and a proper bike fit beats any calculator.

04 / Other builds

The lineup.

6 builds, ranging $4,200 – $10,500.

The Top Fuel lineup spans a wide price spectrum, starting with an aluminum frame option and scaling up to premium carbon builds. The entry-level 8 Gen 4 utilizes an Alpha Platinum Aluminum frame paired with Fox Rhythm suspension and a mixed Shimano XT and SLX drivetrain, offering a functional starting point for riders on a budget.

Moving into the carbon range, the 9.8 GX AXS and 9.8 XT Di2 models represent the sweet spot for value. These builds upgrade to an OCLV Mountain Carbon frame, RockShox Select+ or equivalent suspension, and wireless or electronic shifting. However, they still rely on heavier Bontrager Line Comp 30 alloy wheels, which add rotational weight.

At the top end, the 9.9 X0 AXS and 9.9 XTR Di2 builds introduce carbon wheels and Ultimate-tier suspension. The XTR build is particularly notable for offering significant weight savings over the heavier SRAM Transmission setups. The flagship RSL Gen 4 is a dedicated race-ready build, featuring RockShox Flight Attendant automatic suspension, a SRAM X0 Eagle power meter, and lightweight Pirelli XC tires, catering to riders who want maximum efficiency right out of the box.

— · Currently viewing9.9 XTR Di2 Gen 4

—

$10,500On this page

Closeout (was $9,349.99)

Closeout (was $7,699.99)

05 / Reviews

From the press.

19 reviews from the cycling press.

Critics consistently praise the Top Fuel for its balanced, quiet, and highly capable ride quality. By utilizing an Active Braking Pivot rather than a lighter flex-stay design, Trek created a chassis that tracks smoothly through rough terrain. Testers found the suspension remains active under braking, offering a ride that feels "cohesive" (NSMB) and significantly less jarring than many of its cross-country-derived competitors. On descents, the bike is remarkably stable, tracking "true as an arrow" (Bicycling) at high speeds while remaining agile in tight corners.

Climbing performance is generally viewed as excellent, with the bike maintaining momentum and traction on technical ascents. However, opinions diverge slightly on pedaling efficiency in the open shock position. While many reviewers found the platform calm under power, a taller tester noted that the bike "begs the shock to be in firm mode" (Singletracks) to mitigate pedal bob during hard efforts.

The primary criticism across the board centers on component choices for aggressive descending. Multiple reviewers found the stock SRAM Level brakes underpowered for the speeds the frame encourages. Additionally, the heavy alloy wheels on mid-tier builds were noted to dull the bike's acceleration. Despite these spec gripes, the frame's adjustability is a massive hit. Flipping the Mino Link to the more progressive setting transforms the bike into a "go-fast hooligan" (BikeRadar) that absorbs rubble effectively while maintaining enough support to stay playful.