Trek Releases New Top Fat MTB. Here are our First Ride Impressions

Words and photos: Mike Blewitt

The Top Fuel has been the marquee model in the Trek mountain bike range for several decades.

Reintroduced in 2015, Top Fuel was a World Cup racing weapon, tested by the likes of Dan McConnell from the Trek Factory Racing team. For 2019 the Top Fuel got a major rethink, as Trek changed the bike's 100mm travel 29er XC bike to a 120/115mm travel 29er platform that's better suited to everyday touring.

Trek has just released the fourth generation of its popular Top Fuel mountain bike. Reborn in 2015 as a World Cup racer, Top Fuel entered a shorter travel bike in 2019, with further refinements in 2022 until we see the latest iteration just released in 2025.

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Suspension in Top Fuel

The latest Top Fuel has a travel mix of 130/120mm front to rear, but the stiffened frame can be upgraded to a 140mm fork, and the longer rear shock can deliver 130mm of rear travel. Borrowing from the Trek Fuel EX, the lower shock mount allows the rider to run a standard forward or progressive setting to allow for better support on big hits or at high speeds. Trek also has their MinoLink settings in this area, with four positions available between a high and a low setting, with more or less continuity.

The Top Fuel has slightly better anti-squat as well, so it gets better out of the saddle when accelerating through trail features or attacking a small climb. The same ABP rear pivot is used in the frame design.

Features of the frame

First and foremost, we like that Trek kept the headset in place with nothing but earphone bearings. The outer cable and tubes frame the rear of the head tube, allowing for less maintenance in the long run, and more freedom of movement when packing your Top Fuel on a mountain bike trip.

The frame's storage has undergone minor changes, but overall it's much smaller than something like the SWAT storage on Specialized's Epic 8 EVO – another 130/120mm 29er made for a party.

The Trek has an accessory mount under the top tube, single bottle cage placement, multiple stances, and the ability to use the frame as a mullet (MX) suspension with a 27.5” rear wheel – if you store the bike in the top position. .

Geometry

There are no major changes in terms of geometry, with a 65.5 degree head angle and a 76 degree seat. Reach on our big test bike is 477mm, and chainstay is 440mm. What's new is that Trek offers a specific seat size for the Top Fuel with three lengths between the mini size and the XL frame. This is a good move, as it helps to maintain the same handling – regardless of your size.

Build kits

Trek has aluminum and carbon Top Fuel models, and we have a 9.8 GX Transmission model on test. With a SRAM GX Transmission groupset, a RockShox Pike Select+ fork and a Deluxe Ultimate RCT shock, it's got some great gear. Bontrager offers Line Comp 30 wheels, Gunnison and Montrose tires, a nice RSL one-piece cockpit, a 34.9mm dropper post and a plastic dropper lever. It's good to see Trek sending their bikes out to be tubeless, valved and with a bottle of sealant that goes with the bike. It couldn't be easier to roll!

Our test bike came in at 13.31kg before the pedals were installed.

Maximum Fuel Range:

Top 8 oil $5499.99
Top Fuel 9.8 GX AXS $8999.99
Top Fuel 9.8 XT $10599.99
Top Fuel 9.9 XO AXS $15499.99
Top Fuel 9.9 XX AXS $18499.99

First ride response

Considering the last Top Fuel I rode was a 2015 model on my Buck weekend – I didn't expect anything to feel the same way. I really enjoyed the Specialized Epic 8 EVO I tested earlier this year, which I expected Top Fuel to show on the track.

But I couldn't have been more wrong.

While the Epic EVO is a souped-up XC bike with burlier suspension and tackier tires on the same frame ridden in the World Cup, the fourth-generation Top Fuel matches it as a short-travel bike design. When I built the bike I was skeptical about the wheels, as they are some of Bontrager's newer models that don't seem to have the heft I was expecting. With the silver/grey design of the bike it reminded me a lot of the Norco Optic I tested in Autumn 2020. And a lot has changed since then.

Along the way, all this changed. I found the Top Fuel to be the best ride for the bike, and I tightened up the shock on smooth fire road climbs. But it was going down and going fast when the bike told me it was a trail bike, not a long distance XC bike. It feels very balanced in the rockier terrain, or in the inevitable double terrain that I seem to put test bikes on. Visually, the rear end looks a lot stiffer and has more wheel clearance than something like the Epic EVO as well.

As I built the bike the night before and parked it in the parking lot, I was more impressed than I thought. I still have a lot to do before I can complete the review, but I think Trek has made sure that the Top Fuel is a good fit between the latest Supercaliber and the Fuel EX – and I think it may even be suitable for those who miss the previous generation. The Fuel EX is, by all accounts a true mountain bike.