ABOUT THE GEN 4 TREK TOP FUEL
FRAME AND FEATURES | At one point in time, the Trek Top Fuel was built for cross country racing. Now on its 4th generation, we have seen a major departure from those roots, but it still stays pays homage to its pedal-focused ancestors when it comes to getting up the hill.
In the stock configuration, the Top Fuel comes with 120mm of rear travel, with a 130mm fork. The rear can be bumped up to 130mm by removing the travel reducer in the shock, and the frame is rated up to a 140mm fork to give you a bit more squish for heavy hitting terrain. Additionally, the Gen 4 Top Fuel is compatible with a 27.5” rear wheel, thanks to a flip chip on the lower shock mount. Depending on the spec level selected there is either an OCLV Mountain Carbon Fiber or Alpha Platinum Aluminum frame. Lastly, this new frame also has in-frame storage, and a quite large cavern at that.
SUSPENSION | The Top Fuel uses Trek’s classic ABP system. This system places the rear suspension pivot concentrically around the rear axle, isolating braking forces from suspension movement in a bid to provide more traction under braking.
The Top Fuel also features Trek’s Mino Link. In this case, it’s a four-position flip chip in the lower shock mount. This not only changes the geometry between Low and High settings, but also offers a progression change for the shock. The high position increases the headtube angle by .4º and raises the BB by 6mm. When changing from the linear to more progressive setting, the frames leverage rate goes from 14% to 19%. This change in leverage rate is a noticeable feel out on the trail, and in the more progressive setting you could run a coil shock. I spent all but my first ride on the bike in Low and Progressive with the stock Fox Float DPS air shock.
GEOMETRY | At 6’1” (187cm), I opted to test the size large. Trek states the Large is for riders between 5’10” and 6’2”, which I found to be pretty accurate. The 477mm reach netted the upright climbing posture I was after, and with my 35mm rise bars installed I never felt cramped climbing or descending. The 612mm stack is lower than I typically like, but with this being essentially a long-travel XC bike, it makes sense. This was remedied by going to the 35mm rise bar, putting me closer to the 640mm figure I like. Out back, the 440mm chainstays felt balanced for the bikes use and overall size. And of course, making use of the Mino Link to fine the bike to your terrain and riding style is a great bonus.
BUILD SPECS | Our Top Fuel 9 is the highest spec aluminum-framed offering, retailing for $5,249. The most entry level spec lands at $2,899, while the top-spec will make you pull out $9,999. Upgrading to a carbon frame with the 9.8 model will cost $6,499. In this upgrade you do change from Sram Drivetrain and Brakes to Shimano’s new wireless XT derailleur and updated XT brakes.
The Top Fuel 9 we tested had a solid spec, with the Fox Rhythm 34 fork featuring the GRIP damper paired to a Fox Performance DPS rear shock. SRAM provides a GX T-Type Transmission drivetrain and Level Bronze brakes with 180mm rotors – our biggest complaint with the bike.
Bontrager provides the rest of the kit, with their Line alloy cockpit; Line Comp 30 alloy wheelset wrapped in the Gunnison Pro XR tires, and finally their Line 170mm dropper topped with the Verse Short saddle. At 31.7lbs for the size medium, it’s no featherweight in this space, but in a happy spot as a versatile short travel trail bike.
THE DIRT
SETUP | Getting settled on the Trek Top Fuel 9 was quite simple and required little fuss, something that was a pleasant surprise. I landed on 28% sag in the shock at 176psi with the stock tokens (I never did open the shock to see what the stock set up was, as it felt great). One thing I did run into was that the rebound tune felt quite fast. Even with the dial fully closed it was still on the fast end of the spectrum. In the Fox 34 up front I ended up running 86psi – about 10psi more than the recommendations on the leg for my weight – with two volume reducers. Rebound was set to my preference and the compression dial on the GRIP damper roughly 2/3rd’s from closed. I was left impressed with the damper on this bike, more on that later. On my first ride I noticed a few more bottom out events in the rear that I would have liked, so for my second ride I swapped the Mino Link into the more progressive setting, which really helped keep me from pinging off the end of the stroke. For the remainder of my riding the bike was left in the progressive setting. I experimented with the high and low geometry options, but ultimately liked the low. Overall, I was easily able to find a balance of small bump sensitivity and ramp. This is something I am very particular about and usually faff with quite a bit to get the feeling I am after, but it was not required with the Top Fuel.
For the tires, I was surprised by the ability to run lower pressures, something I was not expecting to do with the trail casing. I ran 23psi front and 26psi rear, giving me great grip with enough sidewall support. We do not have many sharp rocks in my zone, helping to make these pressures manageable. In more abusive zones, I’d encourage going a little higher.
CLIMBING | Being one of the lighter bikes I have been on recently, of course the Trek Top Fuel was easy to climb. Even though this is not the lightest model Trek offers, it still is much lighter than typical longer legged trail or enduro bikes. Sure, weight weenies from the Lycra world will say it is heavy, but with my gravity-focused riding preference, it felt amazing. The Top Fuel’s overall weight was noticeably low, but the Gunnison Pro tires both front and rear really aided in the rolling speed when getting to the top of the hill. At just 875 grams, they are around 400G lighter than typical enduro casing tires. The trail casing makes perfect sense for a bike like this and is very noticeable when it comes to longer days in the saddle.
Pedaling up and out of the saddle provided minimal suspension movement and the balance of support and grip was spot on. There are many sections at my home trails I very much do not look forward to climbing, and the Top Fuel helped to lower that climb anxiety. I often chose the shortest possible route on steep service roads instead of the more moderate climb trails, simply because I could make them stick on the Trek.
The seat tube angle was just about steep enough but still left some room for improvement for my long legs. Another degree steeper would be awesome, however I did not get any lower back pain on longer rides, so it was not the biggest issue. I swapped the 170mm travel dropper for a 220mm, allowing me to get the saddle down and out of the way. Sizes M. L and XL all come with the same 170mm travel post, and it would be great to see the L and XL come with at least a 200mm variant.
The ease of climbing on the Top Fuel made it an easy choice for long days and normal shreddy group rides alike. I found myself going into much harder gears and holding a higher average speed on our climb route. Consistently I was going about 2 minutes faster over an 18-minute climb, with perceivably less energy spent. I had my friend Kyle ride the bike for a few weeks and he said, “I did not realize climbing could actually be enjoyable”.
DESCENDING | Of course, the bike is going to climb great, it’s a 120mm cousin to an XC race bike. In fact, the Trek Factory team did run this frame in a shorter travel configuration at one of the XC World Cups, so technically it still is a XC race bike. With that said, the Trek Top Fuel is an absolute gem of a bike going down. It is hard to explain how impressively smooth the rear end was on rough sections of trail. I was shocked at how composed it stayed, even with a basic monotube shock. I am generally fussy about small bump feedback to my feet and there was as close to zero chatter as a 120mm bike could have when riding well beyond its normal scope of trails.
At the start of one of my favorite setup trails is a high-speed uphill rock garden with rocks embedded into the soil anywhere from 5” to 10” tall. This is a great short section to feel if the suspension wants to hang up on square edge hits. Even with just 120mm travel, I was able to come in at speed and float through that section, which genuinely caught me by surprise. In the progressive setting on the Mino Link, I found that there was enough support at the end of the stroke to allow for a generous 30% of sag without harsh bottom outs or demanding extra volume reducers. I rode it on trails that the bike was not intended to be on, and the only thing that had me on edge was getting slowed down with the Level Bronze brakes. I understand why they were spec’d, but I have yet to ever have a good experience with them. I would happily take a few extra grams in exchange for a more consistent and powerful brake set up. With that said, the bike continued to impress me the more time I spent on it.
On more mellow blue tech and flow, the Top Fuel was truly at home. Pumping rollers, pedaling out of berms and gaining speed from any undulating section of trail was all second nature. This type of terrain is where the bike really liked to be pushed. The fast-rolling nature of the bike on the climbs directly transferred to the smooth single track, and the small bump sensitivity on back country terrain provided a comfortable and fun experience.
The Gunnison Pro tires seriously impressed both me and Kyle. For how light and fast rolling they are on the climbs, the traction and sidewall support was great. The tread does like to pack up a bit in stickier conditions, but was acceptable given the other more positive tradeoffs. I was quite surprised that 26psi out back was enough, I usually land around 29psi in EXO+ tires for reference. There were no flats or rim dents in my test period, and only a few burps when running laps at the local jumps. There is a left hander with unreal support there, and any tire burps when slammed into the corner, so it’s no surprise.
The bike did become a bit overwhelmed when encountering larger repetitive compressions. Things like back-to-back 4’ drops, for example. But with that said I think this was more of a component spec issue – that little inline shock can only move so much oil at a time, after all. When really giving her the beans, the 34 did have some flex under higher loads, but this is to be expected. I am very curious how the bike would feel with the new 36SL and a Float X or even X2 shock out back in the longer travel option. Would you lose that peppy feeling that makes the bike so enjoyable on climbs and moderate descents? Or would it push it into the lower end of the “trailduro” bike holy grail category? Sure, these upgrades won’t make the geo more aggressive, but I don’t think it needs to be.
FINISH AND VALUE | Not once did I have a bolt come loose, which is a product of Trek’s long history of making quality bikes. No weird creaks or sounds developed either. I did not have any paint chips or heel rub though the paint on the chainstay, which is something I commonly run into. Overall, the bike has a very put together feel when out on the trail.
Value is a tough one. At just over $5k for an aluminum frame with lower spec suspension and brakes, it is a bit tough to swallow. Trek has never been the best value on paper for your dollar, but you do get several dedicated support networks and a solid warranty with lifetime frame support and two years on the linkage bearings and alloy wheels. At this price point, I would like to see higher level suspension and a better brake spec. With that said, you can opt for the frame-only option and build it to your liking with spare or used parts on a budget. The real value is in the Top Fuel 8, which at just under $4k gives you a perfectly good riding bike you can upgrade over time.
COMPONENT REPORT | There was nothing wild to note here, I did not have any failures or issues during the testing period. As mentioned earlier I would have liked to see a 200mm dropper offered on the size large. The brakes never failed me, but left me wishing for more power, especially on the steeper sustained descents I enjoy most.
HOW DOES IT COMPARE?
The closest bike I could compare the Top Fuel to is the Gen 3 Norco Optic. Another short travel trail bike, but with more of a focus on the descents given its slacker head angle and high pivot suspension layout. Dare I say the Top Fuel was smoother through the rough stuff? Yes, surprisingly I do. The Optic had your back when it came to the geo and getting outside the bike’s comfort zone, but that price was paid with a heavier overall bike weight and more energy expended on the climbs. The A1 Optic is a better value though, with Factory level suspension at just $250 more.
The Wolf’s Last Word
The Gen 4 Top Fuel always left me with a smile on my face and energy in the tank for another lap. Trek have done an excellent job producing a bike that rips the climbs and still has legs for a rowdy descent. It’s a bike that riders of all skill levels and disciplines can hop on and feel at home. 
Price: $5,249
Weight: 31.7 lbs
Website: Trekbikes.com
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ABOUT THE WOLF
Cole’s den is in Spokane WA, where he relocated a few years back. Growing up in the lush, loamy playgrounds of the PNW, his soul is forever tied to steep, rooty descents and that unmistakable squish of perfect dirt. After 19 years of shredding, Cole’s been on every kind of rig out there. Once a die-hard fan of big travel bikes, he’s now on a quest for the mythical short-travel do-it-all machine. And yes, skids may be for kids, but this middle-aged manchild is here to prove they’re also for anyone who loves having a damn good time.
Rank: Professional Amateur
Size: 6’1” / 185cm | 170lbs / 77kg
Social: @adventuresbycole
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