Review: Trek Top Fuel 9.8 SL

The Top Fuel is Trek’s dual suspension offering for cross-country and marathon racing. The Trek Factory Racing team race the Top Fuel in the UCI MTB World Cup but how does it get along under the steam of an amateur? In short, rather impressively.

The Build

The Top Fuel 9.8 model sits just below the range-topping 9.9 in terms of components and technology with the more affordable Top Fuel 9.7 and 8 offered at lower price point down the range. The Top Fuel 9.8 features an OCLV carbon frame with the exception of the aluminium chainstays and come kitted with the components listed below.

Top Fuel 9.8 SL specifications:

• FrameOCLV Mountain Carbon main frame and seatstay, alloy chainstay, ABP, Full Floater, EVO link, E2 tapered head tube, Mino Link, MicroTruss, Control Freak internal routing, Carbon Armor, PF92, Boost148 and G2 Geometry on 29ers, 100 mm travel
• ForkFox Performance 32 Float, Step Cast, FIT4 2-position damper (with new push-to-unlock remote), E2 tapered steerer, Boost110, G2 Geometry w/51 mm offset on 29ers, 100 mm travel
• ShockFox Performance Float, RE:aktiv XC 2-position damper (with new push-to-unlock remote), tuned by Trek Suspension Lab, 6.5”x1.5”
• WheelsetBontrager Kovee Elite 23, Tubeless Ready, 54T Rapid Drive, Boost110 front, Boost148 rear (15.5˝: 142×12 rear, 21T), tubeless strips included, valves sold separately
• TyresBontrager XR2 Team Issue, Tubeless Ready, 120 tpi, aramid bead, 29×2.20˝
• ShifterSRAM GX Eagle, 12-speed
• Rear DerailleurSRAM GX Eagle, Roller Bearing Clutch
• CranksSRAM Stylo Carbon Eagle, 32T
• Bottom BracketPF92
• Cassette SRAM XG-1275, 10-50, 12-speed
• ChainSRAM GX Eagle
• SaddleBontrager Montrose Elite, hollow titanium rails
• SeatpostBontrager Pro, 31.6 mm, 5 mm offset
• HandlebarBontrager Race X Lite, OCLV Carbon, 31.8 mm, 5 mm rise
• GripsESI Chunky
• StemBontrager Pro, 31.8 mm, 7-degree
• HeadsetFSA IS-2, 1-1/8˝ top, 1.5˝ bottom
• BrakesSRAM Level TLM hydraulic disc
• WeightManufacturer Claimed: 10.93 kg (17.5″) / Review bike: 10.78 (21.5″)
• PriceR 78,999

The Fox 32 SC was pleasantly plush compared to the RockShox SID that I had just ridden at Tankwa Trek. The 32 SC provides good feedback through the travel, giving me a good sense of how it (and I) was handling the terrain. The fork showed little sign of excessive flexibility being able to hold a line through rocks and rougher sections.

The Fox Float RE:aktiv shock works just as Trek explain it, providing an excellent firm pedalling platform but relaxes/ opens when the trail gets bumpy, smoothly moving through the travel. At the end of the day, a 100 mm cross-country tuned shock can only do so much but the RE’aktiv allows it to reach its potential while still being an efficient pedalling bike. I found it most notable on drops where the shock transformed as it opened up to soak up the landing.

I rate the SRAM GX Eagle groupset highly. Despite being SRAM’s entry-level 12-speed drivetrain, it is packed with all the same mechanics of the more expensive XX1 and X01 with a couple hundred grams weight penalty. You can read my full review of the GX Eagle groupset here.

I’m becoming a big fan of the SRAM Level brakes, they pack a big punch, even giving the burlier Guide brakes a run for their money when it comes to feel.

The Bontrager Kovee Elite wheelset performed without fault. Some riders might look for a wider internal diameter than the Kovee’s 22.5 mm but I found the wheels did well to hold their own on the trail coupled with the Bontrager XR2 Team Issue tyres. The rear hub engaged swiftly and the wheelset (and tyres) got up to speed with minimal effort, contributing to the bikes affinity for climbing. The tyres were reliable and predictable. We’ve reviewed these previously here and my experience with the XR2’s is comparable.

As a complete package, the Top Fuel felt refined. Every component seemed to fit in place as intended with the cable routing remaining neat. The bike was built by The Bike Park at Constantia Uitsig (a Trek dealer) who knew exactly how to set up the bike and cabling. All I had to do was simply adjust my saddle height.

I was impressed by the weight of the Top Fuel 9.8, tip the scale at 10.78 kg (excluding pedals, including sealant). That is over a hundred grams lighter than Trek’s claimed weight for the same bike but with a frame two sizes smaller.

On the Trails

When first jumping on the Top Fuel, the size 21.5″ bike felt a bit small and short in the cockpit. On the climbs, I had the sensation of being forward, with most of my weight ahead of the front axle when climbing out of the saddle. I was also a bit cautious on the descents feeling precariously positioned to the front ready to pitch over. Thankfully, after a handful of rides, this sensation quickly passed as I got accustomed to the bike’s feel.

I had been riding a number of bikes with longer, slacker geometry numbers leading up to this review. While these bikes have their advantages on the technical terrain, the nimble feel of the Trek was a breath of fresh air excelling in its own right. That said, I did ride the Trek in the “Low” setting on the Mino Link adjustable geometry.

The Top Fuel is an exhilarating climber. It is in the class of excellent cross-country bikes that encourage you to continually attack the climbs rather than sitting back to simply pedal it out. For what it is worth, I achieved a number of Strava PRs on one of my regular climbing loops during my first outing with the Top Fuel.

It is not just on the gravel roads either, on more technical terrain the Top Fuel thrives, getting up and over obstacles with relative ease. The sharp handling is superb on technical climbs being able to pick your way through tricky rock gardens and around tight switchbacks.

Testing the bike in the Cape Town drought, climbs are dry and dusty, but the Bontrager XR2 tyres did well to keep grip under check. There were times that I opened up the suspension to give the tyres some added traction and the Top Fuel kept on climbing unhindered.

The Trek Top Fuel in action at the 2018 Cape Town Cycle Tour MTB race. Photo: Jetline.

Of course, the characteristics that make a bike fly up the hills do not always make it the best coming down them. The Trek Top Fuel, however, does reasonably well. The Top Fuel is intended for endurance racing where most of the gains are to be made in the endurance elements and while the handling in the rough stuff is not the best, it is a well-balanced compromise.

With a head tube angle of 70-degrees and the bikes forward positioning, it is not the most confidence inspiring bike to throw down the steepest section of the mountain. There are other cross-country bikes that will give you more assistance but there is no doubting that the Top Fuel can hold its own against these bikes, should you possess a moderate degree of bike handling skills.

The full floater suspension does an excellent job. The rear end is not overwhelmed by big knocks while the whole bike works well to absorb those annoying small rocks and roots. The short feeling coupled with the relatively steep head angle did make the bike a little skittish on rougher, steeper descents but, as mentioned, this really played to the bikes advantage on slower trails and technical ascents.

With the Top Fuel being a race bike, I thought it best to get out and ride it with anger. I took part in the Cape Town Cycle Tour MTB race around the Simonsberg trails. It is a race that I have taken part in on a number of occasions and I managed to get my best average speed over the route on the Top Fuel. I felt strong on the climbs and with no real hinderance negotiating the loose, dusty singletrack. The race also featured some open road that the Top Fuel gobbled up, clocking up the miles effortlessly.

In the end

The Trek Top Fuel 9.8 SL is a first-class cross-country marathon race bike. The Top Fuel is an outstanding climber and an efficient eater of kilometres on rolling dirt roads. The sharp handling will hold some riders back in high-speed rowdy descents but it is more than capable on the level of trails regularly faced in marathon races, with excellent dexterity on slower, tighter trails.