For the year 2020 (sounds crazy saying that, right?) Trek have taken what was their 100mm full suspension XC race bike and given it a major overhaul in the name of fun and versatility. The Top Fuel has been competitive ever since it was introduced four years ago, so much so that it's the only bike that many racers take to the start line.
Trek did not forget that the Top Fuel needs to be competitive, fast, and lightweight, but they wanted it to be more capable and fun on the trail, so they added a little more travel. Out back, the bike goes from 100 to 115 millimeters and it gets a 120-millimeter fork up front.
Top Fuel 9.9 Details• Intended use: XC / Trail
• Wheel size: 29"
• Rear-wheel travel: 115mm
• Front-wheel travel: 120mm
• Boost 12x148
• Carbon frame
• Size: S, M, ML, L, XL, XXL
• Weight: 24.3 lbs / 11 kg (9.9, as tested)
• Price: $8,999.99 USD (as tested)
The chassis is longer and slacker. There's more tire clearance and ample room for longer-stroke dropper posts. The swingarm's pivot point has been pushed forward and the shock takes cues from other bikes in Trek's line and is now fixed to the down tube instead of the swingarm's forward end.
All sizes of the bike are designed around 29" wheels and there are a number of build options offered in both aluminum and carbon. The Top Fuel 8 sells for $3,299.99 USD, while the high-end Top Fuel 9.9 AXS burns a hole in your pocket to the tune of $9,999.99 USD. Both the aluminum and carbon Fuels are also available in a frame-only option.
Trek's Top Fuel has gone through several generations. Four years ago, the most recent redesign saw 29" wheels across the board (except size small frames), Trek's Full Floater suspension design, and the ABP (Active Braking Pivot) concentric dropout pivot. Times have progressed, as has the Top Fuel.
Trek have chosen to forego the eddy and jump into the current - joining vanguard brands who have been creating more aggressive XC bikes that are not only quick and nimble, but also fun and not terrifying to ride in technical terrain. The Waterloo, Wisconsin based brand has realized that there are probably more people riding for fun than strictly racing and a more versatile bike is a better option for a lot of people than choosing a strictly race or strictly trail set up. The new Top Fuel slots perfectly into the middle ground - a practical mountain bike for most people - and does a damn fine job of it, I must say.Construction / Features Knock Block and Down tube Guard:
Trek's Knock Block fork stop is one of those things people either love or hate. I'd wager that if you've smashed a frame with your controls then you'll love it, otherwise, you probably aren't a fan. Either way, it does serve a purpose and keeps your fancy bike frame safe.ABP:
Trek's ABP, or Active Braking Pivot system, is a pivot that rotates around the rear axle to keep braking forces from interacting with the suspension.1x Only:
The Top Fuel will nor accept a front derailleur. As a high-end XC bike, there are no ISCG mounts on the frame either, but you can run Trek's top-guide if you feel that you need that extra chain retention.Cable routing:
The Top Fuel uses Trek's 'Control Freak' internal cable routing system. It allows for any combination of cables you want to run, cleanly and quietly through the frame.Mino Link:
Trek's 'Mino Link' is no longer on the seat stays. The flip-chip is now easily accessed on the suspension rocker and allows the geometry to be changed from a low to a high setting. The bike comes stock in the low setting.Frame Options / Build Kits
The Top Fuel is available in five different builds with the most affordable Top Fuel 8 being very similar in spec, but having an aluminum frame. The 9.7 is the first carbon model, with a SRAM NX Eagle drivetrain, RockShox Recon RL fork, Fox Performance Float DPS shock, Bontrager Kovee Comp wheels, and Shimano MT501 brakes.
The Top Fuel 9.8 takes a step up in components, with a SRAM GX Eagle group, and then the 9.9, that I've been testing, has XX1 Eagle, a Fox Factory 34 Step-Cast Fit 4 fork, Factory Float DPS Kashima shock, Bontrager's Kovee Pro 30 carbon wheels (with 108 points of engagement in the hub), 35mm carbon Bontrager handlebars, Bontrager's 13-degree stem, and SRAM Level Ultimate brakes. All models are spec'd with Bontrager dropper posts, XR3 Team Issue tires, saddles, and cockpit components.
Trek offers the new Fuel in a frame/shock only option in both carbon and aluminum. The carbon frame sells for $3,299.99 USD and the aluminum frame sells for $1,999.99 USD.Geometry / Kinematics
The new Top Fuel is designed with more travel, which the team at Trek say makes it a little more balanced than the old bike. The geometry on the new Top Fuel sees the seat tube get a degree steeper, up to 75-degrees from 74. The reach is also a few mm longer, 440 on the size medium in the low setting.
The Top Fuel carries over and continues to use ABP suspension design. The design uses a concentric rear-axle pivot. The idea with this is that it prevents braking forces from affecting the shock. The big difference here is that the shock is now fixed to the frame - it was formerly attached to the forward tip of the swingarm. The swingarm pivot has been moved forward to help the bike pedal better.
The old Full floater system allowed a lot of small bump sensitivity, so to maintain that, Trek now specs a higher volume shock, coupled with the lower leverage ratio. Riders are able to run lower shock spring pressures and there's a wider range of usable air pressures, especially for heavier riders, who easily maxed out the previous shocks.
The fork and shock can be remotely locked out at the handlebars on the go, with a twist style lockout made by RockShox to further stiffen the bike up when the suspension is unnecessary, such as pavement, climbs, or smooth bits of trail.
Also worth noting is that there is more room to run a dropper post. According to Trek's John Riley, "Every bike should have a dropper post at this point." I couldn't agree more. The size-small frame can handle a 100-millimeter post, the medium and up can run a 150, and large and up fit a 170.
I have had the Top Fuel in hand for a couple of weeks now, putting in the miles on it at home in North Carolina. Typically, a more aggressive bike with a little more suspension is optimal for a lot of the riding here, but, I've been feeling right at home with the latest crop of short travel trail and XC bikes, thanks to the more progressive geometry their engineers are incorporating.
Some may consider the Top Fuel to be a little under-gunned on rough terrain at first glance, but it really fits right in on the tight and technical singletrack I often ride and I've been able to pedal it up and down everything from smooth climbs and buff descents to sinewy, root laden ups and chunky downs most people would opt to ride an enduro bike on.
The bike I have been riding is the size medium. I could easily go up to the in-between medium/large size Trek offers, but I have been more than happy on the size I'm on.
Brevard, NC, USAAge:
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I have been spending a lot of time on a few shorter travel XC and trail bikes lately, so I was eager to get on the Top Fuel and see how it handled in the same situations. The Top Fuel is not just an over-forked 100-millimeter bike, as some out there are right now, it's a dedicated 115/120 bike right from the start.
The Top Fuel is competent and composed while climbing. There is the slightest amount of bob in the rear suspension. While it's barely noticeable, if you remember to use the lockout, you can feel things firm up. I really can't say it's at all necessary, except on the smoothest of climbs.
In rooty and technical terrain, I found myself consistently cleaning sections of trail I often find challenging. The bike is quick to get up to speed and acceleration is nearly instantaneous when getting on the gas to get over roots, logs, and whatever else is in the way. The Trek feels easy to ride and the position when pedaling is comfortable for hours on end.
The one quibble I do have is the Knock Block. It does serve a very important purpose in protecting the top tube from levers and the down tube from the fork, however, in ultra-tight sections of trail, it can be annoying and takes a bit of getting used to.Descending
The Top Fuel is damn efficient heading up, but when you hit a downhill the bike rides much more like a lightweight trail bike than a purebred XC race machine, and has no hesitation getting a little rowdy if you're willing to let it. Unless you're charging through a boulder field, the bike is capable of managing some pretty hard hits without losing its composure. The Top Fuel tracks extremely well and there's very little trepidation in rough terrain.
With the little time I have on it thus far, the biggest qualm I've had with this top level XC bike is that it's spec'd with a great set of high-end XC brakes, SRAM Level Ultimates. I've found myself pushing this bike harder than any XC bike I've ridden on descents, and the amount of braking power seems like the weak link. I'm always wanting a little more, which speaks volumes for the capability of this bike. Switching to metallic pads could do the trick, or possible a bigger rear rotor.
The new Top Fuel may not be as much of a purebred racer as its predecessor, but that just means it's a bike you could race one weekend and head out for a big backcountry adventure the next without making too many compromises. And by the looks of things
, there's a good chance Trek has something else in the works for riders looking for a World Cup level XC race bike.