Mid-Term Review | 6 Weeks Aboard Our 2020 Trek Fuel EX 9.8 Long Term Test Bike

The not-so-minor details


2020 Trek Fuel EX 9.8


Trek Bicycles Australia





12.74kg (in current spec configuration)


- Stupendously plush rear suspension
- The Fox 36 has really stepped up the EX's appetite for gnar
- New geometry brings masses of high-speed stability


- Rattling from the downtube trapdoor
- Knock Block system works but creates practical annoyances
- The 35mm carbon bars are overly stiff

Since receiving the 2020 Trek Fuel EX 9.8 test bike back in September, this muscly trail brawler has joined me on many a ride across the countryside. From my hometown of Bendigo in the Goldfields region, over to Beechworth in the Victorian High Country, the Fuel EX and I have so far enjoyed a few hundred kms of singletrack slashing, with plenty of saddle time to get to know one another. My early verdict of this long term test bike? It’s rapid. Very rapid.

2020 trek fuel ex 9.8 beechworth car thule velospace xt 3 rack
On the road to Beechworth yieeewww!

But while the Fuel EX is absolutely humming now, it did take a bit of fine-tuning to get it all dialled in to how I like. And in recent weeks, I’ve also swapped out a few key components, including the drivetrain, brakes, wheelset and tyre combo, to see how the bike would handle with a different setup, while also providing the opportunity to review those parts separately.

Here we’re going to take a look at the current bike setup, with some detail on what settings I’ve settled on, and the changes we’ve made so far. If you’re after a more detailed look at exactly what’s new with this 130mm travel trail ripper, make sure you check out Mick’s story on the 2020 Trek Fuel EX from the launch, which includes a broader overview of the six-model Fuel EX lineup.

2020 trek fuel ex 9.8 vs 2019 ex 8
2020 Fuel EX meets the 2019 model.

Suspension Tweaking

Having ridden many examples of the previous generation Fuel EX, I was initially surprised to find the suspension on the new bike to feel firmer than I was expecting. Previous versions have been plusher than a penthouse suite, particularly with the recent addition of the Thru-Shaft damper design in the Fuel EX’s rear shock, but the new bike didn’t feel quite as active.

2020 trek fuel ex 9.8 thru-shaft re:aktiv shock
There’s 130mm of rear wheel travel controlled by a Trek-specific rear shock made by Fox. It took a few rides for the shock on our test bike to bed in.
2020 trek fuel ex 9.8 fox 36 rhythm fork 140mm
The 9.8 and 9.9 models are equipped with a 140mm travel Fox 36, which is an absolute beast of a fork.

So over the course of a couple of rides, I lowered both the fork and shock pressures, while also removing some volume spacers to help open up the end of the travel.

The Fox 36 Rhythm fork comes with four volume spacers inside the EVOL air spring as stock. I brought that down to two, and then to one single spacer. This improved the fork action for my 70kg riding weight, and I was able to access full travel more easily. The fork has bedded in quite a bit and become more supple over the last few weeks, so I’ve since added a 2nd volume spacer to regain some mid-stroke support.

With 68psi in the air spring, the rebound dial set 10 clicks off the slowest setting, and the compression lever set partway between Open and Medium, the fork is now spot-on. I really like the 36 Rhythm, even though it’s meant to be the ‘budget’ fork in the Fox line. At 2065g (confirmed) it is heavier than a comparable 34, but it gives the EX a really stout feel. Along with the robust carbon frame and slacker geometry, the new generation Fuel EX has quite the mini-Slash vibe about it.

2020 trek fuel ex 9.8 quarq shockwiz fox 36 rhythm
I’ve gone from 4 to 2 volume spacers inside the fork, which has helped open up the end of the travel. It’s absolutely humming now!

I also tried a smaller 0.2³ volume spacer inside the rear shock, which did help to reduce the initial firmness I experienced. The shock felt smoother, but it was bottoming out too much on hefty landings, so I reinstalled the stock 0.4³ volume spacer. Compared to when the bike was fresh out of the box, the shock feels like it’s bedded in a lot, and it’s now exhibiting the buttery-plush performance I was first expecting.

And holy crap is this thing plush!

Trek recommends setting the rear shock between 25-33% sag, so I’ve got 150psi inside the air spring to put me around the 30% marker. Rebound is set just faster than halfway, at nine clicks from the slowest setting. With the shock settings dialled in, I’ve been thoroughly enjoying how responsive the back end is on the Fuel EX, and how it keeps the rear tyre glued to the ground. It’s reactivity to incoming obstacles, no matter how rapid-fire the hits are, is really quite something for a bike with just 130mm of travel.

2020 trek fuel ex 9.8 thru-shaft re:aktiv shock
The RE:aktiv damper means the the Medium and Firm settings on the shock are much more usable on the trail, providing improved pedal efficiency when you need it.

With the Penske-Trek designed RE:aktiv damper inside, the blue compression switch alters between Open, Medium and Firm settings. The regressive damper design means that you can achieve a pretty firm platform in the Medium and Firm positions, with a super fast breakaway when enough pressure builds behind the valve to crack it open as you encounter a bump. In principle, it aims to achieve the same goal as the Specialized Brain damper. In practice, it isn’t as firm as a Brain shock, but it is much smoother and faster in its transition. And in my experience, it makes the Medium and Firm settings a whole lot more effective.

Whereas I’d only use a shock’s compression switch for riding on the road or on a really smooth fireroad climb, I’ve been able to utilise the Medium setting for technical singletrack climbs, where the increased platform helps to improve efficiency while also lifting the bike up a touch for more ground clearance. If the climb isn’t littered with ledgy rocks and roots, the Firm setting goes one step further. I generally prefer to leave my suspension wide open when I’m riding off-road, but the compression settings on the Fuel EX’s shock offer such distinct ride experiences that it’s worth utilising them to get the most out of the bike.

2020 trek fuel ex 9.8 thru-shaft re:aktiv shock
The back end of the Fuel EX is supremely supple and very active for a bike with ‘only’ 130mm of travel.

Groupset Change

The Fuel EX 9.8 comes stock in Australia with a SRAM GX Eagle groupset, which has thrown up zero surprises so far. However, we recently got our hands on the new Shimano SLX M7100 groupset, including a set of the new 4-piston brakes. While much of the media hype has centred around XT and XTR, we reckon the new 12-speed SLX groupset is more exciting, particularly as it comes in at a third of the price of XTR!

With the SLX groupset looking for a home, I removed the GX Eagle setup from the Fuel EX so I could fit the new SLX test components. So far the performance has been excellent – shifting under load is particularly impressive. The 4-pot brakes are also superb, with more power than Shimano’s 2-piston callipers, but noticeable better modulation to control that power.

shimano slx m7100 brakes
I’ve fitted the new Shimano SLX M7100 groupset to our Fuel EX test bike, which includes the new 4-piston ‘Enduro’ brakes.
shimano slx m7120 4-piston brake rotor mt800
4-pistons of powaaaar!

Pricing is pretty similar between Shimano SLX and SRAM GX Eagle, but there are some key performance differences. Stay tuned for a separate in-depth comparison feature, and feel free to ask any questions you might have in the meantime.

It’s worth noting that you’ll need a Micro Spline freehub body to fit the new Shimano 12-speed cassettes. Depending on the wheelset you’ve got, that might be easier said than done. Bontrager is licensed to produce Micro Spline freehub bodies though, so it’s a question of popping into your local Trek dealer to purchase one. In my case, I had another set of test wheels with a DT Swiss 350 rear hub, so that was also an easy swap, as Micro Spline freehub bodies have been available from DT Swiss for well over a year now.

2020 trek fuel ex 9.8 shimano slx m7100 crankset
The new SLX crankset uses a direct-mount chainring to create a modular system that looks dead clean too.
2020 trek fuel ex 9.8 shimano slx m7100 12-speed 1x12 cassette 10-51t
The 10-51T Shimano cassette offers impressive shifting under load.
2020 trek fuel ex 9.8 shimano slx m7100 10-51t 12-speed cassette 1x12
You’ll need a Micro Spline freehub body to fit the new Shimano 12-speed cassette though.

Lighter Wheels, Faster Tyres

Speaking of wheels, the Fuel EX 9.8 comes fitted with a set of Bontrager Line Carbon 30s as stock. These feature deep section carbon fibre rims with a 29mm inner width, and Bontrager TLR rim strips come fitted to create a reliably airtight seal.

During the initial build process, I was surprised to find that there were no tubes inside the tyres – these wheels are legit tubeless ready from the factory. Two bottles of Bontrager TLR sealant are supplied with the bike, so all you need to do is remove the valve cores, squeeze a bottle into each wheel, and you’re ready to roll. Nice!

It’s also worth pointing out that Bontrager now offers a 2-year crash replacement scheme with its carbon wheels, which is nice peace of mind. The Line Carbon 30s have been solid so far, though at 1908g on my scales, they’re not the lightest hoops out there.

curve cycling dirt hoops wider 40 carbon rims
Chunky carbon wheels from Melbourne-based Curve Cycling. These have a 40mm external width!
curve cycling dirt hoops wider 40 carbon rims pirelli scorpion m 29x2.2 mtb tyre tire
The Dirt Hoops are surprisingly light though – less than 1700g for our test set.
dt swiss 350 straightpull hub
Tidy straight-pull DT Swiss 350 hubs and Sapim CX-Ray spokes.

Looking to inject a bit more speed into the Fuel EX, I decided to fit a set of Dirt Hoops from Melbourne-based brand, Curve Cycling. This is the ‘Wider 40’ model, which features carbon rims that measure 40mm externally and 30mm internally. With DT Swiss 350 hubs, Sapim CX-Ray spokes and a confirmed weight of just 1637g, they’ve helped to boost the bike’s acceleration and rolling speed noticeably. The only downside is the use of 18T ratchet plates in the rear hub, which feels comically slow compared to the 54 points of engagement in the Bontrager wheelset. I might look at popping in a 36T or 54T upgrade kit in the rear hub soon. For more info on the Dirt Hoops, take a gander at the detailed first look story here.

As for rubber, I’ve been consistently impressed with Bontrager’s latest XR4 tread pattern over the past couple of years. In its big 2.6in guise here, it’s supremely grippy and you can run them at quite low pressures – 18psi on the front and 20psi on the rear has worked well for me. The XR4 is a really versatile tyre, transcending dry to wet riding conditions, from loose to hardpack trail surfaces. For more aggressive riders though, I’d consider putting an XR5 up front though for more hold on loose and steep enduro-style trails.

2020 trek fuel ex 9.8 fox 36 rhythm grip pirelli scorpion 2.4 curve dirt hoops wider 40
We’ve set our test bike up with a pair of faster-rolling Pirelli Scorpion tyres.

Given their huge volume, the XR4s are a decent weight for a burly trail tyre, clocking in at around 920g each. They do put more rubber on the ground though, so they’re noticeably draggier than the 2.4in tyres that came as stock equipment on pre-2020 Fuel EX models. Along with the active suspension and the stock bike’s generous 13.2kg weight, the big volume tyres give the Fuel EX a robust and grounded demeanour on hectic, technical descents. On the flip side, it also contributes to a slightly lethargic feel on the climbs – at least compared to more slender and trail bikes in this travel bracket anyway.

If you’re after more rolling speed, a tyre change is a good way to do it. I fitted a pair of 2.4in wide Pirelli Scorpion tyres – a Scorpion M (Mixed) for the front, and a Scorpion R (Rear) for the back wheel. These are actually a very similar weight to the stock Bonty tyres, but they have a significantly faster rolling tread pattern. They’re also well suited to my local dry and dusty trails, including the Harcourt MTB Park and You Yangs, where the Pirellis manage the sandy soil composition mighty well.

pirelli scorpion m 2.4 tyre
There’s a 2.4in Scorpion M tyre on the front, which has been surprisingly grippy on sandy and loose rocky trails.
2020 trek fuel ex 9.8 pirelli scorpion r 2.4 tyre
The Scorpion R uses a rear-specific tread pattern for stability under braking.

Handlebar Switcheroo

In the search of more compliance, I’ve also recently switched up the Fuel EX’s cockpit. The stock Bontrager Line Pro bars are made from OCLV carbon fibre and feature a 35mm clamp diameter for the stem. Being very stiff, I’ve found them to be somewhat unforgiving on my hands and upper body – something I’ve experienced with a lot of 35mm bars. In my eyes, it remains as one of the most annoying standards to have permeated the mountain bike industry. Anywho…

So I recently fitted a set of Syncros Hixon iC 1.0 Rise handlebars that I’ve previously tested. These are one of the most compliant full-width bars I’ve ridden, and they’ve already made a noticeable difference in vibration damping on the front of the Fuel EX. Using a one-piece carbon fibre construction that integrates the steerer tube clamp into the centre of the bars, they’re also stupendously light at 273g. Remember, that’s the bar and the stem in one. Width is 800mm and you can get them with a ‘virtual’ stem length of 40mm or 50mm.

2020 trek fuel ex 9.8 syncros hixon ic rise 1.0 handlebar
Looking for more compliance out of the front end, I’ve fitted a Syncros Hixon iC 1.0 Rise carbon handlebar.
2020 trek fuel ex 9.8 syncros hixon ic 1.0 rise handlebar
The handlebar integrates the steerer clamp into the one carbon structure. It’s lighter, simpler and there are a few less bolts to worry about. It isn’t perfect though.

I’ve got the shorter option, which I think is a touch too short for the Fuel EX. The Medium frame has a 440mm reach, which I’ve found ideal for my 175cm height. It isn’t super long by today’s standards though, and the grips now feel a little too close. I’ll look at going back to a 50mm stem length with a different bar/stem combo at some point down the line.

On the note of the cockpit change, if you decide to fit a non-Bontrager stem to your Fuel EX, you will need an adapter so you can ditch the keyed Knock Block headset spacers. This adapter is a simple locking that bolts to the steerer tube directly above the headset, and you can get this small piece of alloy through a Trek dealer for $30.

2020 trek fuel ex 9.8
Here’s what it looks like with the original spec.

For those wondering how our long term test bike has evolved, here are the finer details of what’s changed so far;

2020 Trek Fuel EX 9.8 Current Build Specs

2020 trek fuel ex 9.8 cable freak internal routing
The internal cabling pops out for a brief gasp of air before popping back into the chainstays.

Any Problems So Far?

Nothing major. I did have a tricky time routing a new hydraulic line through the frame when I fitted the SLX 4-piston rear brake. The bolt-on Cable Freak ports are snug and pretty user-friendly, but there’s a very tight section just behind the main pivot where the rear brake line and derailleur cable exit the mainframe and then re-enter the chainstays. A Park Tool IR-1.2 cable routing kit ensured things didn’t get too sweary for me. I will admit that the routing does look very clean on the Fuel EX, but I’m still a bigger fan of externally-routed cabling.

2020 trek fuel ex 9.8 storage integrated
The carbon frames get integrated downtube storage underneath the bottle cage.

The only other issue that’s popped up is a rattling noise that’s emanating from the trapdoor underneath the bottle cage. On our test bike, the fit isn’t quite 100% and there’s enough lateral movement where the locating stub at the base of the trapdoor clips into the frame that it causes a rattle when you have a bottle on board. It isn’t particularly loud, but when the rest of the bike is so stealthy quiet, it’s a right old pain in the arse.

I’ll note that this wasn’t a problem that Mick encountered with his test bike during the launch back in July. To see if this was an isolated issue with production models, I went to my local Trek dealer and found that out of the six bikes there with integrated downtube storage (including two Domane gravel bikes), only one frame had a properly tight fit between the frame and the trapdoor. After swapping around trapdoors, I’ve come to the conclusion that the sloppy fit on our test bike is partially from the door itself and partially in the frame component.

I really like the concept of integrated frame storage, but it absolutely needs to be perfect – especially on a $7K bike, and especially when Trek has copied the idea from one of its main rivals. We’re awaiting an official response from Trek, so we’ll keep you updated once we have a solution.

2020 trek fuel ex 9.8 storage integrated
The fit on our trapdoor isn’t totally snug though, and the whole assembly rattles around while riding. Not good on such a premium bike.

What’s Next?

Lots! With plenty of new riding destinations to explore this summer, I’m frothing to see how far I can take the Fuel EX.

One thing I’d like to investigate further is the option of fitting a longer travel fork (or a longer air shaft in the current fork), as I suspect the beefy carbon frame will handle it. A slightly longer fork combined with tougher tyre casings would open up the option of racing enduro – such is the capability of this bike. Speaking of endoooro, we’ve also got some fancy DT Swiss wheels that will no doubt end up on the Fuel EX shortly.

I also intend to flick the Mino Link into the high-and-steep position, since it comes set to low-and-slack out of the box. A little extra pedal clearance wouldn’t go astray, so I’ll be trying that out soon. I’m also keen to upgrade the shifter to an XT I-Spec EV model so I can remove one clamp from the bars, while also getting the double-upshift function that the SLX shifter misses out on.

shimano slx m7100 brake shifter
There’ll hopefully just be a single clamp here next time you see this bike.
2020 trek fuel ex 9.8
The Fuel EX is capable of some outrageous speeds. This is a trail bike that sits closer to an All Mountain bike in terms of its plush suspension performance and high-speed poise.

Right, so that’s where we’re at with the 2020 Trek Fuel EX 9.8 long term test bike. What do you folks think? Have you got any questions for us about the new Fuel EX? Any parts you’d like to see us test on there? Be sure to let us know in the comments below!

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