The original Trek Top Fuel was a pure-bred race machine, designed for maximum speed at the expense of versatility and comfort. This year, the Trek Top Fuel has had a ground-up makeover, adding more travel, slacker geometry, more clearance, and most importantly a change in attitude from XC-whippet to all-round shredder.

For an overview about the test field click her: The Best Short-Travel Trail Bike – 6 Mountain Bikes in Test

Trek Top Fuel 9.9 | 120/115 mm | 11.4 kg | € 8,999

With 120/115 mm of travel and a full carbon frame, the 11.5 kg Trek Top Fuel 9.9 is the lightest bike in this group test. At € 8,999 it’s also by far the most expensive. Compared to the old model the differences in geometry are startling, with a whopping 2.5° shaved off the head angle and a 1° increase in seat tube angle. Combined with the longer reach, the new Top Fuel 9.8 is a very different beast. Trek’s signature Full Floater suspension has gone, replaced with a fixed lower shock mount to improve frame stiffness and increase clearance to fit a 29×2.4” tire. The top of the line, 9.9 spec tested is dripping with super bling components too. With a Fox 34 Factory SC EVOL fork and Factory DPS shock, 29” Bontrager Kovee Pro 30 carbon wheels and a full SRAM XX1 Eagle drivetrain, there is nothing left to be desired. Premium weight savings continue with SRAM’s featherweight Level Ultimate brakes with 180/160 mm rotors. However, as expected the small 160 mm rotor lacks bite and control. Finished off with a carbon cockpit, this is a dream build, but is such a low weight too much of a compromise?

We love how the Trek Top Fuel darts through corners. However the tangle of cables at the front is less appealing.

Helmet Troy Lee Designs A2 | Glasses Oakley Race Jacket PRIZM | Jersey Troy Lee Designs Checkers SS | Shorts Troy Lee Designs Ruckus

The Trek Top Fuel 9.9 in detail

Fork Fox Factory Float EVOL 34 Step-Cast TwistLoc remote 120 mm
Shock Fox Factory Float DPS damper, TwistLoc remote 115
Brakes SRAM Level Ultimate 180/180 mm
Drivetrain SRAM XX1 Eagle, 12 speed
Seatpost Bontrager Line Elite Dropper
Stem Bontrager Kovee Pro 35 mm
Handlebar Bontrager Line Pro, OCLV Carbon, 35mm
Wheels Bontrager Kovee Pro 30 carbon
Tires Bontrager XR3 Team Issue 2.40″

Birds nest
While the TwistLoc lockout works exceptionally well, it’s only really needed in a race environment and adds a lot of ugly cabling
GripShift activation
The TwistLoc lockout is similar to a grip shift. Simply rotate the shifter to lock out the fork and stiffen the rear suspension, then hit the button to release again.
Knock Block
The ‘Straight Shot’ downtube adds stiffness and a clean aesthetic, but also needs the ‘Knock Block’ steering limiter to stop the forks hitting and potentially damaging the frame.
Sublime suspension
Trek have moved away from the Full Floater suspension design, now attaching the shock to the down tube. The new system is superb, offering maximum support and control.
Rapid acceleration
The 29” Bontrager Kovee Pro 30 carbon wheels move like a scalded cat. Even the smallest pedal inputs propel you forwards.
Seat tube 394 mm 419 mm 470 mm 521 mm 750 mm
Top tube 564 mm 599 mm 632 mm 651 mm 676 mm
Head tube 90 mm 90 mm 100 mm 110 mm 120 mm
Head angle 67.5° 67.5° 67.5° 67.5° 67.5°
Seat angle 75° 75° 75° 75° 75°
Chainstays 435 mm 435 mm 435 mm 435 mm 435 mm
BB-Drop 36 mm 36 mm 36 mm 36 mm 36 mm
Wheelbase 1.117 mm 1.152 mm 1.186 mm 1.207 mm 1.234 mm
Reach 405 mm 440 mm 470 mm 487 mm 510 mm
Stack 594 mm 594 mm 603 mm 612 mm 621 mm

The Trek Top Fuel 9.9 on the trail

So how does it ride? In one word – fast! Pickup in the freehub feels almost instantaneous. Dab the pedals and you’ll enjoy a sharp kick of acceleration from the lightweight wheels. Smash down on the cranks and it leaps forward like a bullet from a gun, both uphill and downhill. A RockShox TwistLoc controller, similar to a grip shift, allows you to lock out the fork and increase compression on the rear shock with a flick of the wrist. While it does work intuitively, we found it of little use for fun trail riding, and the additional front cabling looks a mess. Out of the corners and sprinting up sharp pitches the Trek is unrivalled, but with the lightest wheels and lightest overall build it was always going to score well here.

Tuning tip
For trail riding, we would spend some time wrapping and organising the excess of cables at the front of the bike, or even remove the TwistLoc lockout altogether.

What came as more of a surprise was the Trek’s potency on the descents. Adjustable geometry lets you bias the bike towards up- or downhills but we ran the bike predominantly in the low flip chip position, enjoying the more composed handling. The steering is impeccable precise, allowing you to knife though corners and skip over roots and rocks. Nimble and lively, the Trek’s suspension delivers just enough travel to keep you comfortable without using a single millimeter too many. Even when straying onto very technical trails, the Trek offers superb support, remaining firm without ever feeling harsh. On dry hardpack the small knobs of the Bontrager XR3 Team Issue tires roll incredibly fast but they’re not a versatile option quickly losing grip in the wet. If your rides consist of all-day mountain missions, the Trek Top Fuel is not the most comfortable cruiser and prefers confident riding and a firm hand at the controls. However, if you enjoy the simple pleasure of crushing climbs and making the most of every descent, the Trek Top Fuel is your passport to a world of fun.

With a suspension system that always uses just the right amount of travel without feeling wallowy or lazy and a very balanced geometry, the Trek Top Fuel is a hard-edged but versatile machine. It is more than capable of delivering KOM’s both up- and downhill. The flyweight build kit inevitably increases its cost, but has some definite advantages on the trail.


  • nimble and involving handling
  • happy to step-up to tough terrain


  • lockout is niche and adds complexity
  • SRAM Level brakes prioritise weight over power

Riding Characteristics



  1. sluggish
  2. efficient


  1. cumbersome
  2. playful


  1. nervous
  2. confident


  1. unbalanced
  2. balanced


  1. harsh
  2. plush

Fun Factor

  1. planted
  2. poppy

Value for money

  1. terrible
  2. very good

Technical Data

Top Fuel 9.9

Size: S M L XL XXL
Weight: 11,4 kg
Travel (f/r): 120/115 mm
Wheel Size: 29"
Price: € 8,999

Intended Use

XC 8
Trail 9
Enduro 10
Downhill 11

The test field

For an overview about the test field click her: The Best Short-Travel Trail Bike – 6 Mountain Bikes in Test

All bikes in test: Canyon Neuron CF 8.0 | Merida ONE TWENTY 8000 | Specialized Epic Expert Evo | Whyte S-120C RS | Yeti SB100 C GX

This article is from ENDURO issue #040

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Words & Photos: Trev Worsey

About the author

Trev Worsey

A keen biker since the early 90’s Trev began his professional career as a research scientist and statistician, but it was the lure of the mountains that finally called him. After seven years working as an international Mountain Bike Guide he joined the ENDURO team and now coordinates exciting news, reports, reviews and group tests from the UK office.