Review | Testing the 2025 Trek Top Fuel as a 140/130mm travel trail bike


Wil reviews the 2025 Top Fuel in ‘Long Travel’ mode

Earlier this year Trek unveiled the 4th generation Top Fuel. Admittedly it doesn’t look all that different to its predecessor, and indeed it shares the same amount of travel and features similar geometry. However, as I found out in our Trek Top Fuel review, it’s a better riding bike thanks to its newly slimmed-down frame. It also possesses some clever tricks up its sleeve including a unique 4-position Mino Link and the ability to extend its travel by 10mm at each end.

While I’ve throughly enjoyed riding our Top Fuel 9.8 GX AXS test bike in its stock trim, I was curious to see what it would be like with a little extra squish. I got in touch with SRAM Australia about modifying the RockShox Pike fork and Deluxe shock, and since then I’ve been riding the Top Fuel in its long travel configuration. Along with several other key changes, the end result is one of the best trail bikes I’ve ever tested.

2025 trek top fuel 9.8 gx axs
Following on from our review of the Trek Top Fuel, Wil’s been experimenting with the long travel configuration.

Increasing travel on the 2025 Trek Top Fuel

The 2025 Trek Top Fuel comes standard with a 130mm travel fork, though the frame is designed to handle anywhere from 120-140mm. In the case of the RockShox Pike it’s a pretty simple process to increase the travel. You can purchase a 140mm air shaft for $77 AUD, and fitment is straightforward provided that you know how to perform a basic lower leg and air spring service. Alternatively you can send your fork into SRAM and have the air spring fitted as part of a 200-hour rebuild, which will cost $220 AUD plus parts.

As for the rear suspension Trek specs a 185x50mm shock to deliver 120mm of travel. However, it is possible to extend the shock stroke to 55mm, which will boost rear travel to 130mm.

Doing so with a Fox Float is relatively easy since no special tools are required to remove the 5mm internal travel reducer. It’s a bit more complicated with the Deluxe shock as it requires you to disassemble the main damper shaft in order to access and remove the travel reducer and open up the stroke to 55mm.

2025 trek top fuel 9.8 gx axs
A 5mm travel reducer can be removed from the RockShox Deluxe shock to increase the stroke to 55mm.

Thankfully SRAM Australia was able to do this for me as part of a $220 AUD shock rebuild. While the techs were at it, they replaced the damper body ($90 AUD) to ensure I had the correct anodised sag gradients to match up with the new 55mm stroke. This part isn’t necessary, but it is nice to have when setting sag and evaluating travel usage.

Unless you’re able to do all this suspension work yourself, you’re looking at around $600 AUD in total to extend the Top Fuel’s travel. It’s not an inexpensive upgrade, but it’s still a heckuva lot cheaper than buying a whole new fork and shock.

2025 trek top fuel 9.8 gx axs rockshox pike ultimate
With an air spring swap the RockShox Pike can be run at 120, 130 or 140mm of travel.

Does it affect the suspension setup?

The longer stroke increases the air volume inside the shock, which does require less pressure. To maintain 30% sag I dropped down from 137psi to 128psi.

Even with the Mino Link positioned in the more progressive setting I did find I was bottoming out more regularly, likely because I was also pushing the bike harder. I added a single Bottomless Token into the Deluxe air can, which provided the necessary ramp-up. I also slowed down the rebound one click (now 6/10 clicks) to help steady the ship on harder landings.

Likewise with the fork, the increase in travel creates a larger air volume that benefits from running less pressure. I dropped down from 70psi to 65psi, but kept the single Bottomless Token inside. I also left the rebound damping (12/20 clicks) and continued to ride with the compression adjusters in their neutral positions.

2025 trek top fuel 9.8 gx axs
With a 140mm fork up front, the head angle slackens out to 65.1º.

Any changes to the geometry?

Not a huge amount. With 10mm of extra fork travel, the head angle kicks back to 65.1º with the Mino Link in the Low position. The seat angle also slackens out slightly, which I measured at around 76.6º at my saddle height.

Because the shock’s eye-to-eye length remains the same, the difference at the back end is minor. The BB isn’t that much higher, coming in at 339mm off the floor according to my measurements. However, the longer shock stroke does provide more sag at the rear wheel, so the dynamic ride height is pretty similar.

2025 trek top fuel 9.8 gx axs
Despite the added travel, the Trek Top Fuel retains its sporty character.

How does the 140/130mm travel feel on the trail?

Absolutely superb! I was already impressed with the stock RockShox suspension setup, but the added travel kicks things up a notch.

With an additional 10mm at each end the Top Fuel affords a more forgiving and floatier ride quality. It feels more confident to pilot on the descents thanks to the slightly taller front end, and having a little extra squish in reserve for soaking up hard landings encourages you to push just that bit harder. It is remarkably capable, and I’m yet to be overwhelmed on any of my regular test trails.

The longer stroke shock gives the suspension a more open and fluid feel, with the lower starting pressure improving small-bump sensitivity. Combined with the trunnion bearing mount and active suspension design, the rear wheel is able to follow the terrain smoothly, providing excellent all-round grip.

2025 trek top fuel 9.8 gx axs
10mm of extra travel at each end doesn’t sound like much, but it makes a surprisingly big difference when you’re pummelling through big rock gardens.

It further cements the advantage the Top Fuel has over competitors that use a single-pivot flex-stay platform, like the Scott Spark and Specialized Epic EVO. In comparison the Top Fuel does a far better job of impersonating a proper trail bike, and that’s especially the case in this long travel configuration. The suspension is smoother, more reactive, and better at rounding off rough edges.

Despite the improved ride quality from the extra travel, I was pleased that the Top Fuel retained much of its sprightly character. This differs to other modern trail bikes like the Trek Fuel EX, Giant Trance X, Canyon Spectral and Specialized Stumpjumper 15, all of which have gotten bigger and heavier as they’ve grown in travel. In contrast, the Top Fuel remains peppy and efficient. It’s able to skip and hop its way down challenging trails with greater enthusiasm, and it’s an absolutely brilliant technical climber.

2025 trek top fuel 9.8 gx axs
Climbing performance is still excellent, with a great seated position and plenty of rear wheel grip.

Leveling up the brakes

With the long travel Top Fuel encouraging me to descend faster, I’ve found myself wishing for more better braking.

The SRAM Level brakes didn’t impress out of the box, with a soft lever feel and not a whole lot of grab. Massaging and lubricating the pistons helped a lot with sharpening up the bite point, but they were still lacking some oomph.

Rather than fitting an entirely new brake, I got myself a set of thicker SRAM HS2 rotors in the same 180mm diameter along with some metallic compound pads. Following the bed-in procedure the difference on the trail was immediately apparent.

2025 trek top fuel 9.8 gx axs
Upgrading the SRAM Level brakes with thicker HS2 rotors and metal pads made a significant improvement to power and feel.

Firstly, there’s less dead stroke at the lever thanks to the thicker rotors (2.0mm vs 1.85mm). This does reduce pad clearance slightly, but the HS2 rotors are stiffer to begin with so I find that they exhibit less rub.

There’s quite a lot more initial bite with the metallic pads, reducing the amount of force you need when pulling on the levers. Overall power is noticeably improved and they’re far better at sustaining that power on long descents. It honestly feels like a different set of brakes.

Aside from a bit of added weight from the HS2 rotors, the only downside is a bit more noise during soft braking before they heat up. Otherwise this is an upgrade I can recommend for anyone who owns a set of Level brakes and is finding themselves wanting for power.

bontrager brevard rsl xt tyre tire
Wil’s been testing out the new Bontrager Brevard XT tyres on the Top Fuel.

Chunkier tyres

I’ve had few complaints from the stock Bontrager Montrose and Gunnison tyres that come on the Top Fuel. They’re fast rolling, have a nice supple casing and provide good traction on the dry and dusty trails I’ve been riding of late.

Still, I was looking to see how far I could push the long travel Top Fuel on more technical trails. Keen to try out some meatier rubber, I got a pair of the new Bontrager Brevard XT tyres.

These effectively replace the old SE5 and they feature much the same tread pattern. A new casing construction and Trail Triple Compound rubber makes them quite a bit heavier though, coming in at a confirmed weight of 1,123g for the 29×2.5in size.

With an extra 275g of rotational weight, the Brevard XT tyres have added notable stability and momentum at speed. Traction is excellent on loose and rocky terrain, and the burlier construction has inspired more confidence to really open up the Top Fuel on the descents. You can get more info in our Bontrager Brevard tyre review.

race face turbine wheelset
The Race Face Turbine wheelset has dropped a good amount of rotational weight over the stock wheels.

Lighter wheels

More recently I got my hands on a Race Face Turbine wheelset to test out. These have replaced the stock Bontrager Line Comp 30 wheels, which do ride nicely and have been totally hassle-free throughout testing. They are on the porky side though at 2,094g for the pair (with TLR rim strips and valves), making them a tempting component to upgrade on the Top Fuel.

Having already reviewed the Race Face Era carbon wheelset earlier this year, I’ve been interested to try out the alloy version; the Turbine. Built with the same Vault hubs and butted straight-pull spokes, the Turbine wheels feature 6069 alloy rims with a shallow profile that’s unique front and rear. They weigh in at 1,914g (with tape and valves), making for a near-200g reduction. Combined with the buzzy 3° engagement, they feel swift and compliant on the trail.

First impressions are good so far, but I’ll have a proper review of the Race Face Turbine wheelset coming in the future once I’ve spent some more time bashing them about.

2025 trek top fuel 9.8 gx axs
With a strong focus on compliance, the Race Face Turbine handlebar is far more comfortable than the stock Bontrager RSL carbon cockpit.

Any other changes?

Our pals at Race Face have also hooked us up with a Turbine bar and stem as well as set of Chester grips. While the Bontrager RSL cockpit is very lightweight at just 259g thanks to its snazzy one-piece carbon construction, having trimmed the bar down from 820mm to 760mm, I was finding them to be far too stiff.

I was able to get a Turbine handlebar in a dedicated 760mm width, which offers vastly better compliance that transmits less trail buzz. Along with the soft compound Chester grips, front-end comfort has improved significantly.

A less noticeable change to our Trek Top Fuel has been a change from a 30T to a 32T chainring. I didn’t do this from a gearing perspective, but rather to reduce drivetrain feedback. Going to the larger 32T chainring drops the effective anti-squat, which means that pedalling performance isn’t quite as snappy. However, the reduced chain growth has resulted in a smoother ride quality, especially when traversing across rocky sections of trail.

In the same vein, I also added the STFU chain damping modules. Comprised of two plastic guides for the chain to pass through, they can be a little tricky to get aligned properly depending on your bike’s suspension design and chainstay protector. Once in place they limit the range of movement for the chain when you’re bouncing down a trail, helping to minimise noise while also reducing how much the chain tugs on the chainring during harder compressions. The result is less feedback and a quieter ride, making it a great upgrade for what is a relatively low-cost item relative to an Ochain or a Rimpact Chain Damper.

2025 trek top fuel 9.8 gx axs
Sizing up to a 32T chainring and fitting the STFU damping modules has helped to smoothen drivetrain feedback.

Trek Top Fuel weight

With all of the latest changes my Trek Top Fuel now weighs in at 13.65kg (tubeless, without pedals). That’s about half a kilo heavier than the stock build.

I should point out that extending the travel to 140/130mm doesn’t actually add any real weight. The reason my Top Fuel has gotten heavier is due to the spec changes, with the burlier tyres, alloy cockpit and thicker HS2 rotors being the main culprits.

That said, all of these changes have been worth it in terms of the overall ride quality. It’s made the bike smoother and grippier, inspiring more confidence for tackling technical trails on steeper terrain.

2025 trek top fuel 9.8 gx axs
Extending the travel to 140/130mm doesn’t add any significant weight to the Trek Top Fuel, though Wil’s component changes have.

“You’ve just made an older Fuel EX!”

A lot of folks shared that opinion in the comment section of the YouTube video. I can see why, as it’s true that the older Gen 5 Fuel EX shares the same 140/130mm of travel and a similar-looking frame design. I spent a lot of time on the previous Fuel EX, and there are some notable differences worth mentioning.

For a start, that bike came with a bigger Fox 36 fork and Trek’s proprietary RE:aktiv shock with the Thru Shaft damper. It also had fatter 2.6in tyres, a Knock Block headset, a steeper head angle and a slacker seat angle. The carbon frame was quite burly and stiff, which made it responsive but also translated more feedback on choppier trails.

trek fuel ex
The previous Gen 5 Fuel EX also features 140/130mm of travel, but the execution and ride quality is quite different to the Top Fuel.

In comparison, the Top Fuel is a lot springier and livelier overall. Pedalling performance is snappier, acceleration is quicker, and along with the steeper seat angle, it’s a better and more comfortable climber. It’s also more adaptable in terms of the suspension, and you can set it up as a 120/120mm travel XC bike, which isn’t really possible with the previous Fuel EX.

From a practical standpoint, I like the conventional headset and the fact that Trek has moved away from proprietary suspension. The RockShox Deluxe is beautifully tuned for this bike and it’s easy to experiment with the 4-position Mino Link.

How does the Trek Top Fuel compare to the latest Gen 6 Fuel EX?

The differences mentioned above are even more pronounced with the latest Gen 6 Fuel EX, which has beefed up a fair bit. It’s got more travel (150/140mm) and it comes with a Fox 36, a piggyback shock, chunkier tyres and slacker geometry. Realistically it’s much closer to an enduro bike now, which is both good and bad.

trek fuel ex
Riders who are after a sturdier and more DH-capable trail bike will be better served by the Gen 6 Fuel EX.

I’ve only spent time on the carbon frame, which for its category is quite heavy at 3,400g, including the Float X. Along with a stocky build kit, the Fuel EX 9.8 GX AXS is claimed to weigh 14.53kg.

It certainly has a sturdy feel to it, making it great for high-load scenarios where you’re really pressing it hard. There’s great support from the suspension when hitting bigger drops and jumps, making it well-suited to getting buck-wild on modern flow trails. Indeed it’s a great option for those who want a daily driver that still has the necessary downhill chops to handle several trips a year to their favourite bikepark.

The downside of the stiffer frame is some harshness on rockier trails, and the extra mass also makes it a bit sluggish up the climbs. Those attributes aren’t exactly unique to Trek however, with the Fuel EX being part of a wider industry trend that’s seen modern trail bikes get a bit heavier each year. As a lighter rider, often those trail bikes end up being just a little too thicc for my personal preference.

2025 trek top fuel 9.8 gx axs
Compared to its bigger brother the Trek Top Fuel is lighter and peppier.

The beauty about this long travel Top Fuel is that it still has a relatively lightweight frame and build, along with suspension kinematics that make it a perky pedaler. The slender tubes give it more compliance and grip on natural trails, which means I’m not exactly desperate for more travel.

Given the last couple of months of (excellent) riding, I wish there were more lightweight trail bikes in this 130-140mm travel bracket. I would love to see Trek offer a Top Fuel LT model (or dare I say, Top Fuel EVO?), but from a commercial standpoint I can understand why it wouldn’t. The US brand already makes a boatload of bikes, and the stock Top Fuel does slot in quite neatly between the Supercaliber and Fuel EX. Of course owners do have the option to extend the travel if they want, and having done so myself it’s something I can highly recommend.

2025 trek top fuel 9.8 gx axs
Given how well the Trek Top Fuel rides with 140/130mm of travel, it’s a wonder why it isn’t offered in this configuration to begin with.
2025 trek top fuel 9.8 gx axs
We’re currently testing the 2025 RockShox Pike and Fox 34 on the front of the Top Fuel – stay tuned for a head-to-head review coming soon!

What’s next for the Top Fuel?

Next up for our Trek Top Fuel test bike is a head-to-head review between the latest RockShox Pike and the Fox 34 GRIP X. Following that is an abrupt about-turn, with the plan to set it up in XC race mode with 120/120mm of travel. I’ll be stripping it down to get a confirmed weight on the frame, then I’ve got a bunch of parts to rebuild it as a lightweight race machine.

I’ve been wanting to do this since we first received our test bike, and even more so having seen the Trek Factory Race team use the Top Fuel at the final 2024 World Cup round in Mont-Sainte-Anne. I won’t have the fancy Flight Attendant suspension, but it’ll still be a cool build and an interesting experiment to see just how versatile the one bike can be.

2025 trek top fuel 9.8 gx axs
It looks pretty good with the longer fork and chunkier tyres eh?

Wil’s custom 2025 Trek Top Fuel


See our video review of the 2025 Trek Top Fuel 9.8 GX AXS here:

2025 trek top fuel 9.8 gx axs
One of the best mountain bikes launched this year? Wil certainly thinks so – the Trek Top Fuel is a ripper!

ABOUT THE REVIEWER - Wil Barrett

Hometown

Bendigo, Victoria

Height

175cm

Weight65kg

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