Trek Fuel MX 9 X0 AXS Gen 7 review: A modular trail bike with strong climbing credentials

Conclusion by Max Fuchs, BIKE editor

The Fuel MX 9 X0 AXS Gen 7 proves that a heavy aluminium trail bike doesn’t have to be a sluggish climber. At 16.4 kilos, it’s not exactly a treat for weight fanatics. On the trail, however, the Trek conceals its excess weight with surprising skill: the steep effective seat angle positions the rider in a forward-leaning, forward-driving stance, the high front end ensures comfort over long distances, and the rear end remains remarkably smooth even without the shock platform activated.

On the descents, the Fuel MX clearly prioritises safety. The long reach, high top tube and flat head angle ensure an upright, confidence-inspiring riding position, particularly on steep descents and at speed. The small rear wheel keeps the bike manoeuvrable enough in tight bends without turning it into a skittish trail-runner. Overall, smoothness takes precedence over agility.

However, the platform remains the main USP. Thanks to various lever set-ups, flip chips and shock mounts, our Fuel MX test bike could also be set up as a shorter-travel EX trail bike or, in the LX configuration, as a full-throttle enduro bike with 29er wheels. Hardly any other platform covers such a wide range of uses. Whilst the Fuel MX 9 X0 AXS certainly commands a price to reflect this feature, by Trek’s standards it is still surprisingly well-equipped at the current price.

Key facts

Not all mullets are the same

In the MX configuration, there’s a 29er at the front and a 27.5er at the rear. The large front wheel provides stability and roll, whilst the smaller rear wheel allows for greater freedom of movement behind the saddle on steep sections and helps when manoeuvring through tight bends. You can really feel these advantages on our test bike.

Nevertheless, the Fuel doesn’t feel hyperactive. The 440-millimetre chainstays and the overall stable geometry prevent the Trek from becoming twitchy at high speeds or on rough terrain. It is a safe, smooth-riding trail bike that delivers its agility in a controlled manner.

The high front end, long reach and flat steering angle reinforce this impression. The rider sits upright and securely behind the cockpit, which instils a noticeable sense of confidence on steep descents and fast sections. The Fuel MX doesn’t require an acrobatic riding position. It gives the rider space and composure when the trail gets challenging.

Surprisingly strong on the uphill sections

At 16.4 kilograms in size L, it usually feels a bit sluggish when climbing. Nevertheless, the Fuel MX manages its weight well. The steep effective seat angle positions the rider centrally and in a forward-leaning, forward-driving position on the bike. Combined with the moderate chainstay length and the high top tube, this creates a riding position that is comfortable enough for long days, yet sporty enough to tackle steep climbs in a controlled manner.

The rear end is key. Even without the shock platform engaged, the Trek shows remarkably little bobbing whilst pedalling. Even when standing up, the rear end remains stable and doesn’t sag with every crank rotation. This neutral ride character directly contributes to its climbing prowess.

Although the efficient suspension makes riding uphill a pleasure, the higher anti-squat value also results in more pedal kickback when riding downhill off-road, due to the design. This can be annoying on rough, grippy trails. If you’re sensitive to this, we recommend pairing the Trek with an Ochain or Rimpact Spider to reduce pedal feedback.

Chassis, brakes and so on

Otherwise, the four-bar rear suspension offers no surprises. The rear end provides sufficient support when pushing off jumps and when pushing through banked turns, ensuring that active body movement doesn’t go to waste. At the same time, the system responds well, generates plenty of traction and offers sufficient comfort. It’s no revelation, but there’s certainly no cause for criticism either.

The SRAM Maven brakes are in keeping with the bike’s focus on safety. They offer plenty of bite and therefore the necessary reserve when the going gets faster and steeper. The Race Face parts also fit well into the high-quality overall picture. Trek has eschewed decorative touches here and fitted the bike with components that are suited to the intended load. Judged against Trek’s usual price ranges, the overall package offers excellent value for money.

Editorial commentary

The Trek Fuel MX 9 X0 AXS Gen 7 is a success because it credibly combines two things: as standard, it rides as a safe, comfortable and surprisingly capable climbing mullet trail bike with plenty of reserve power for descents. At the same time, the frame allows for conversion into an even more forward-pushing trail bike or a more downhill-focused enduro machine.

With its aluminium frame and a total weight of 16.4 kilos, the Fuel is by no means a lightweight. However, this has less of an impact on riding enjoyment than one might expect, as the riding position, rear suspension and geometry do a good job of masking the weight. On descents, the tall front end provides plenty of confidence, whilst the small rear wheel ensures sufficient manoeuvrability. Only those looking for an extremely playful cornering machine might find the 440 chainstays a little too track-oriented.

The downside of this high efficiency is the noticeable pedal kickback on rough trails. This is not a design flaw, but rather the technical trade-off for the high anti-squat value. All in all, the Fuel MX 9 X0 AXS Gen 7 is a well-designed, powerful all-rounder with plenty of reserves for challenging terrain and enough drive to perform well on touring rides too.

Advantages and disadvantages

Advantages

• Modular frame for technically coordinated EX, MX and LX configurations
• Highly efficient pedalling, even without a damper platform
• A comfortable yet sporty riding position for long rides and steep climbs
• High riding safety thanks to a high front end, long reach and a flat steering angle
• Fox Factory suspension, SRAM X0 AXS and Maven brakes combine to create a powerful overall package

Disadvantages

• 16.4 kilograms in size L – certainly no lightweight
• Noticeable pedal kickback on rough trails
• 440-millimetre chainstays limit agility