Dirt Rag Magazine

Review: Trek Top Fuel 9.9 SL

Tester: Mike Cushionbury | Age: 45 | Height: 5’10″ | Weight: 155 lbs. | Inseam: 32”

Trek discontinued its 26-inch-wheeled Top Fuel cross-country line a few years back in favor of the successful Gary Fisher 29er Superfly FS. Now, as the Superfly grows long in the tooth, the Top Fuel is reborn for 2016. And it’s as modern and high-tech as a cross-country bike can be.

Trek Top Fuel -1

The frame is entirely carbon and, like the longer-travel Fuel EX, the 100 mm travel Top Fuel uses an EVO rocker link and Full Floater suspension design, which attaches the shock to two moving points. It also has Active Braking Pivot and the geometry-adjusting Mino Link. This changes head-tube angle by half a degree and raises or lowers the bottom bracket by 8 mm, going from a 70-degree head angle and 12.9- inch bottom bracket in low to 70.9 degrees and 13.4 inches in high. This brings the short-stravel bike in line with the technology Trek has been using for its long-travel bikes, raising the expectations of what a cross country bike is capable of.

The Top Fuel has Boost 148/110 hub spacing, Smart Wheel Size and Control Freak cable management. Boost, which was developed in part by Trek last year for its trail and all-mountain bikes, creates a stronger 29er wheel and frame. Boost also provides more tire clearance and gives Trek the opportunity to shorten the chainstays by 17 mm compared to the Superfly. With 148—which is as wide as you can go without affecting Q factor—width and bottom-bracket junction stiffness is maximized without making the bike wider at the cranks. By going 110 on the fork, the front end is equal to the rear in terms of strength, stability and the ability to run a bigger tire.

Trek Top Fuel -3

Trek believes that for cross-country applications a 29er wheel is absolutely the fastest, so you won’t be seeing multiple options; it’s 29 only, save for the 15.5-inch frame. Smart Wheel Sizing dictates that for this small of a frame, 27.5 is the answer to keep the bike fitting correctly, lower the front end and achieve no wheel/toe overlap. Frame sizes 17.5 inches and larger utilize 29-inch wheels.

Believe it or not, with all the various drivetrain, suspension and dropper-post options, there are 54 different ways to route cables, according to Trek. To make sure any and all work, Trek developed a very flexible system called Control Freak cable management that works with any combination of cables and electronic wires, including internally routed dropper posts. There are also small guides along the down tube and top tube to cleanly run your rear brake or dropper post externally if you choose.

Trek Top Fuel -2

Interestingly, Trek didn’t include a specific bottom-bracket or seat-tube internal option for a Shimano Di2 electronic battery; it’s meant to run sidesaddle to the water-bottle cage or for you to use a cable cinch in the down tube, meaning you’d have to take the fork out of the head tube and then lower the battery into the down tube from there. Also, the bottom bracket access port for internal cable installation is on the small side compared to other brands, making access a bit more challenging.

At a price of nine grand, the line-leading Top Fuel 9.9 SL has a complete package of top-shelf parts, albeit some surprising yet sound choices that stray from what you might expect. Shifting is handled by
the flawless Shimano XTR cable system, yet rather than a traditional Shimano double ring, the 9.9 SL goes 1×11 with Race Face’s ultralight Next carbon crank and direct-mount 32T chainring. And while accessories like the handlebar, seatpost, stem and saddle are all feathery Bontrager XXX carbon fiber, Trek felt that stiff, yet light, DT Swiss XMC 1200 carbon wheels were the best choice to match up with its Boost spacing. Suspension is controlled by a RockShox RS-1 Solo Air fork and Monarch XX shock with an XLoc Full Sprint hydraulic remote lockout that controls both the shock and fork.

All this adds up to a 29er full-suspension race bike that weighs less than 22 pounds. Trek claims a 17.5 inch frame with shock and all hardware weighs only 4.3 pounds.

Trek Top Fuel -4

I kept the bike at the lower geometry setting to get the slackest head angle possible, in line with what most modern-day cross-country bikes are using. This, along with the added efficiency and stability
from the wider Boost spacing, makes the Top Fuel an extremely capable cross-country racer as well as an exceptional do-it-all endurance machine within the realm of 100 mm travel. It’s fast, it’s light and it handles like a dream.

Besides handling and climbing prowess, the wider stance, along with the EVO rocker link and Full Floater suspension, makes you forget, more often than not, that it has only 100 mm of travel. Oddly, within the first week of riding, the RockShox Full Sprint hydraulic remote button fell off, nullifying the ability to lock out the rear shock (the fork lockout remained operational), and I never missed it. Trek’s suspension design produced efficient pedaling even on the smoothest of climbs. If given an option, I’d easily choose a manual lockout for the shock rather than the hydraulic combination controlling both the shock and fork, since I didn’t necessarily need one for the shock.

Another surprise? While the stock Bontrager XR1 Team Issue tires looked questionable for rough, rocky conditions, set up tubeless they performed exceptionally well, providing great traction in all conditions (I could successfully run less than 20 psi when it was wet and slick). They have also proven to be very durable.

With Boost spacing, a PF92 bottom bracket and hydraulic linked suspension, there’s very little part swapping to be had with the Trek Top Fuel 9.9 SL. When you consider the quality of all those parts, there’s nothing I’d change besides having the option for a manual-lockout shock.

The Top Fuel is one of the most high-tech, potent and fun short travel 29ers I’ve ever ridden; it’s also one of the lightest. It’s a full-on racer as well as a full-on fun-to-ride bike. There is one other thing I’d change, though: adding my own dropper seatpost. This little addition would help make the Top Fuel an even more aggressively awesome bike on the descents.

  • Wheelbase: 43.7″, 53.6
  • Top Tube: 23.8″
  • Head Angle: 70°, 70.9°
  • Seat-Tube Angle: 74º, 74.9
  • Bottom Bracket: 12.9″, 13.4″
  • Rear Center: 17″
  • Weight: 21.3 lbs. w/o pedals
  • Price: $9,000
  • Sizes: 15.5″, 17.5″ (tested), 18.5″, 19.5″, 21.5″ (specs based on size tested)
  • Online: trekbikes.com



First Impression: Trek Fuel EX 29 9.9

Few bikes have such a storied lineage as the Fuel EX. Trek introduced a refreshed version of its 27.5-wheeled version last year with the incorporation of the Fox Re:aktiv shock technology. This year the 29er model gets the same treatment, with a host of the same features plus some new ones.


While still built around a 120 mm travel, full-floating, ABP (active breaking pivot) suspension design, the new Re:aktiv shock was designed with input from auto racing powerhouse Penske Racing shocks, a company that is normally designing products for Formula 1 cars. The idea is that it can detect the difference between different inputs (pedaling forces versus impacting a root at speed) and adjust on the fly. The speed that the shaft moves is what dictates how the damping reacts. It’s a rather complex technology that is found on only some of the top models, starting with the Fuel EX 8.


Unique to the 29er model is the introduction of Boost spacing front and rear. The 12×148 mm thru axle out back and 15×110 mm on the fork push the hubs’ flange spacing out and allow for a stronger, stiffer wheel. Trek says it makes the 29er wheel as stiff as a 27.5 wheel, and while I can’t say I can tell a major difference in the DT Swiss wheels, I have no reason to doubt their claims.


The 9.9 build we’re riding is the flagship model in the new Fuel EX range, with a full OCLV carbon frame, chainstays, seatstays and rocker link. Geometry is adjustable with the small Mino Link, an eccentric pivot where the seatstays meet the rocker link that alters the head tube angle, bottom bracket height and chainstay length a small amount.


Some key geometry numbers in the Low and High settings:

  • Head tube angle: 68.8 / 69.4 degrees
  • Effective seat tube angle: 73.6 / 74.6 degrees
  • Chainstay length: 436 / 434 mm
  • Bottom bracket height: 13.15 / 13.46 inches

trek-fuel-ex-29-first-impression-14 trek-fuel-ex-29-first-impression-4

The frame also features internal cable routing that integrates nicely with the Control Freak ports. There are also attachments to run the rear brake cable externally, if that’s more your style.


Hanging on is a 120 mm Fox 34 fork with the new and drastically improved FIT4 damper, a 1×11 Shimano XTR kit powered through a carbon Race Face Next crank. The RockShox Reverb Stealth sits up top and the carbon DT Swiss XMC1200 wheels put the power to the ground.

This is a spare-no-expense build ($8,400 to be specific) but Trek knows us media slimeballs are hard to please. (OK, that’s not the reason at all, actually. Brands want to show off the best of what they can do and what their employees work so hard to create, something I can hardly blame them for.) I’ll admit it is a little intimidating knowing that it retails for twice what I paid for my pickup truck.


My first ride on the Fuel EX 29 9.9 was on some dedicated gravity trails where it felt right at home. The only thing holding it back was the 720 mm carbon Bontrager handlebar the stock Bontrager XR3 front tire, which was begging for something more aggressive. (Update: Trek informed me that some early bikes shipped with a 720 mm bar, while the stock bikes ship with a 750 mm Bontrager Rhythm Pro bar.) You’ll see in the photos I swapped in a 750 mm Truvativ Jerome Clementz BlackBox handlebar cut specifically for the new WTB Padloc grips, which I’m also testing. Plus a bell. Ding!


I also had a packaging issue with the Reverb remote conflicting with the XTR Trail brake, leaving it skewed at a less-than awesome angle. Usually it’s mounted below the bars on the left side, but this bike shipped with the right/bottom, left/top remote.


Aside from a few spec hiccups, the Fuel EX has really impressed me with its ability as an all-around performer. This is a bike I wouldn’t hesitate to line up for an XC race or toss on a chairlift for some bike park runs. I have very high expectations for this bike and have no doubt it has the ability to reach or exceed them. I’m looking forward to our time together! Keep an eye out for my full-length review in an upcoming issue of Dirt Rag.

Update: Some folks have asked about converting the Fuel EX 29 to 27plus. While a 27×3.0 tire easily fits in the Boost-spaced fork, it rubs on the chainstays on the frame. A few tweaks to the rear end might make it possible, so will we see something like that in the future? We’ll have to wait and see. Trek has been committed to the 29plus platform, so a whole new bike is just as likely.


Inside Line: RockShox and SRAM introduce Boost components

The new product news continues to roll in, with SRAM and RockShox releasing a pile of new parts related to the new Boost axle standards.


Boost 110

Both the 27.5 and 29-inch versions of the Pike, Reba and SID are being made available with a new 110×15 axle standard. The wider forks will allow for the ever-growing tires that riders are using on ever-widening rims, and will make the wheels stiffer due to the spoke bracing angle.


For those readers clamoring for 27plus news, RockShox says the new 29er Boost forks will fit a 27.5×3.0 tire, but to confuse things even further, the Pike fork will also be available in a “standard” 27.5 Boost version as well. All the traditional 15×100 forks will still be available, of course.


The hubs at the heart of the new forks are designed around the Torque Cap, a RockShox/SRAM exclusive technology that uses a larger axle endcap interface between the hub and fork. It is not to be confused with the Torque Tube Axle from the RS-1 fork (though we don’t blame you if it is). It isn’t clear yet if these new forks will work with non-Torque Cap hubs, or if Torque Cap hubs will work with other manufacturer’s  110×15 forks. So much Torque! We reached out to SRAM to clarify and we’ll update when we hear back. It is also not clear if hubs are cross-compatible with the new 15×110 Fox forks announced last week.


If you’re wondering if you can space out a 15×100 hub with custom end caps to work with the Boost forks, the answer is probably not because the brake caliper won’t line up with the rotor. You could possibly create an adapter to move the caliper inboard, but once you go down that rabbit hole who knows what is possible.

Boost 148

The Boost 148 standard was introduced last year on the new Trek Remedy and Fuel EX as a way to increase the stiffness and strength of a 29er wheel, improve clearance for chainring and suspension pivots and increase tire clearance, all without changing the bottom bracket or Q-factor.


This is accomplished by spreading the hub flanges 3 mm each, and widening the axle by 6 mm. This pushes out the chainline an additional 3 mm, which is easily handled with a offset chainring for the SRAM modular crank system. RockShox says a 29er wheel built on a Boost 148 hub is as stiff as a 27.5 wheel built on a 142 hub.


If you’re wondering why not just go with a 150mm downhill hub, it’s because those hubs actually measure 157mm with the flanges, and were deemed too wide to work with a standard 73mm bottom bracket spacing.

sram-boost-cranks sram-boost-cranksets-1

We’ll see Boost 148 cranks at the XX1 and X1 level, along with Rise 40 wheelsets (with matching 110×15 front hub) in 27.5 and 29. Two levels of hubs will be ready this summer: XO or MTH 700, which uses the same internals as an X9 hub. Both hubs have the option of an XD driver or 8/9/10 speed Shimano splined cassette body.


What’s next

SRAM was quick to support the fat bike market with drivetrain parts and the Bluto fork, and seem to be lined up the same way for the 27plus movement. While the new Boost products were not designed specifically for the mid-fat wheels, they certainly make it easier to work with them. But what bike(s) will they go on? Chances are we will find out soon.

And will Shimano come on board with parts to support the Boost standard? With the launch of the 2016 XT group at Sea Otter we should have an answer soon.


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