Four years ago, we test-rode the TREK Top Fuel Generation 3 and loved it. In fact, we rated it among the top five bikes we had ever ridden at that time. So, we were keen to see what the Generation 4 model would offer. We spent a few weeks on the TREK Top Fuel 9.8 GX AXS and here’s what we discovered.
THE BIKE
First of all, let’s orientate the Trek Top Fuel model. It slots between the XC-orientated Supercaliber and the Enduro/Trail-orientated Fuel EX. In other words, the ideal bike for a large segment of the South African market who enjoy participating in marathons and stage races and riding local trails.
The model we tested, the 9.8 GX AXS has a carbon fibre frame that’s been completely redesigned. Although it doesn’t immediately look too different from its predecessor, the tubing is a little thinner, making it apparently 160g lighter than Gen 3; the rocker is a two-piece aluminium one (replacing the one-piece magnesium one); there’s now a storage compartment in the downtube and the suspension is increased from 120mm to 130mm up front. There’s also no more Knock Block, so the bars have unlimited range of movement.
Still present is the 120mm travel on the rear and the linkage-driven single-pivot ABP design, which incorporates a cartridge-bearing Trunnion mounted shock. What’s important to know here is that this is a traditional suspension design and not a flex-stay design used by many brands on their shorter-travel models, including the TREK Supercaliber, in the pursuit of lighter weight. So, while the frame overall is lighter than its predecessor, the total frame weight of 2.6kg (with shock) isn’t on the lightest side in this segment. But, as we have always maintained, light weight doesn’t necessarily translate to a better ride.
The shock is the RockShox Deluxe Ultimate with 120mm of travel and the fork is the new RockShox Pike Ultimate with 130mm of travel, adding 10mm of travel up front over its predecessor. The wheels are Bontrager’s Line Comp 30 with 30mm inner width alloy rims – focussed more on durability than light weight. The front comes with Bontrager’s new Gunnison RSL XT 2.4 tyre and the rear with Bontrager’s new Montrose RSL XT 2.4 tyre.
The drivetrain is SRAM GX Eagle AXS 1×12 and the brakeset is SRAM Level Silver 4-piston. The cockpit comprises a Bontrager RSL integrated bar and stem, Bontrager Line dropper post and a Bontrager Verse saddle.
Our test bike was size Medium. What stood out for us initially was the integrated carbon bar-stem combo. Partly because it’s seemed a bit unusual on a non-XC race bike and partly because of the bar width. The bars are 820mm wide! Obviously they can be cut down to suit the owner of the bike, but we don’t make any permanent adjustments on test bikes, so prepared ourselves for some ‘wide rides’…
The look is very understated, with a mostly Matte Black colour and just a pop of blood red at the base of the downtube where the TREK branding is. The SRAM AXS drivetrain with the new T-Type derailleur and the Bontrager Gunnison and Montrose tyres also caught our attention, mainly because they’re 2.4 width tyres, but look a lot narrower.
Also noticeable is the 4-Position Mino Link at the base of the shock, which allows you to adjust the geometry, suspension and even rear wheel size. In other words, a highly adjustable bike! The Mino Link offers a High/Low geometry setting that changes the headtube angle by 0.5 degrees and the BB height by 6mm.
It can also be flipped forward and backwards to adjust the suspension leverage rate. It comes in the forward position (14% progression) and flipping it offers 19% progression with more ramp up at the end of the stroke.
You can, if you want to, set it up to incorporate a rear shock with 130mm of travel, which in turn allows you to increase the fork to 140mm and run a 27.5-inch wheel at the rear. We kept it in the standard setting for the duration of the test for the sake of familiarity and consistency. We did however adjust the suspension rebound and compression for each test rider.
THE RIDE
We got to ride this bike on a range of trails in Gauteng and also took it to Summerplace Game Reserve in Limpopo to test it on the Enduro lines. Three mountain bikers test rode it to give a broader perspective. We rode it in summer before the significant rains arrived, so conditions were largely dry and loose.
CLIMBING
There’s a switch on the rear shock that firms it up almost completely. We never used this, not even on long, smooth climbs. The ABP suspension design on this bike is impressive and it enables the TREK Top Fuel to be a formidable climber! Long and steady or short and steep, it conquers ascents with absolute assurance. Two test riders recorded several climbing segment PRs on this bike. The steepish seattube angle combined with the design of the seattube positions you a little more in front of the BB than most other short-travel bikes. It feels very responsive and our test riders all reported feeling really comfortable on ascents. The rear shock sits quite high in its travel and the anti-squat characteristics offer a firm platform when standing occasionally to add power or to unweight on a technical climb.
DESCENDING
You’d expect a bike that climbs with so much composure to show some weakness on descending. However, on the Gauteng trails, it was solid. One test rider secured a PR on the Flow Line at Asidlale on this bike, beating his times on an enduro-specific bike. On the longer, more rugged descents at Summerplace Game Reserve, it was tested fully though. The new Pike fork, with Charger damper, is a great choice for this bike and while we used its full 130mm of travel, it never felt like it was out of its depth. The bike was highly capable, but the SRAM Level 4 brakes felt a little inadequate at times. For most South African mountain bikers, these brakes are fine though.
The new TREK Top Fuel was smooth and responsive on descents, displaying great allrounder capabilities on both rocky and smooth trails.
CORNERING
The reach on modern short-travel bikes is relatively short (usually 440-470mm on a Medium frame). On this bike, it’s more generous – 599mm on a size Medium frame. Our testers liked how it felt through corners, requiring just a small amount of forward body movement to secure full front-wheel traction on flat turns. We also found the new Bontrager tyres to be rather grippy, which no doubt also contributed to the bike’s predictable and stable cornering. We prefer carbon rims to aluminium rims for a more planted feel in corners, especially banked turns/berms, but the Bontrager Line Comp 30s weren’t bad at all. If you want the Top Fuel Gen 4 with carbon rims, you have to fork out R230K for the 9.9 XO AXS model. Or you could just buy this model and upgrade to carbon rims…
HANDLING
The female tester, for whom this frame size is suited, said she found the very wide bars compromised her natural control a little, but the male testers, although initially a bit out of sorts, adapted to the width. This would be the first thing we would change though if we bought this bike. The one-piece carbon bar/stem combo is also quite stiff and took a bit of rider adjustment. As mentioned earlier, the ABP suspension design sees the bike sit quite high in the shock travel. Combined with excellent small-and-medium bump management, there were no pedal strikes, which is a nice change as most short-travel bikes we have ridden recently have delivered some unexpected pedal strikes, which can be unsettling.
SUMMARY
The new TREK Top Fuel 9.8 GX AXS Generation 4 is an incredibly versatile mountain bike. It’s a little heavier than most of its short-travel rivals, but man it climbs superbly, descends with confidence and handles with great clarity. You don’t feel the weight, you feel the efficiency and control. Kudos to TREK for sticking with the ABP suspension design – it’s undoubtedly a huge asset.
The fact that you can adjust the frame with the Mino Link to four different configurations adds to its versatility. The frame storage works well, but is quite limited in what you can carry by the fairly bulky neoprene holder. We also like that TREK removed the Knock Block, which obviously has some benefits in terms of protecting the top tube from potential lever damage, but we feel this doesn’t outweigh the feeling of fully free steering.
We loved the previous generation model, but feel that with this version, TREK has refined it further. The previous model was responsive, but felt quite firm, whereas the Generation 4 Top Fuel feels smoother but retains its responsiveness.
At R125 000, this model offers good value for money when you compare it to the Top Fuel XT Gen 4 – essentially, the same bike but with the Shimano XT groupset (including brakeset and hubs), which has mechanical shifting, at R150 000. As mentioned, the only adjustments we would make would be a bar trim – or even a switch to traditional alloy bars and stem for a touch more comfort; and replace the alloy rims with carbon rims.
One key issue with this bike is the single bottle cage. In hot weather or on long rides, you either need to ride with a hydration pack, or you need to plan regular stops for refills. It will affect some more than others and it could even be a deal-breaker for some riders. For those riders, consider the TREK Supercaliber which sacrifices a classic suspension design for space for a second bottle cage.
Four years have passed since we last rode a TREK Top Fuel. We can confirm, we’re still in love with this bike…
Sizes: S, M (tested), M/L, L, XL (note the Small comes with 27.5-inch wheels)
Price: R125 000
See the full specs and features on the TREK website here.
