Trek Slash 9.9 XO1 Review


Review and Photos by Max Rhulen

Last year Trek gave their Slash the longer, lower, slacker treatment. This was an important update to keep Trek’s long-legged enduro race machine relevant and competitive. The previous version of the Slash was blurring the line between trail and enduro, but with these new updates there is no question that the Slash falls in the enduro mountain bike category. We’ve been putting the Slash 9.9 XO1 through its paces for quite some time, and it’s clear that these changes have improved the descending capabilities considerably, but not without compromise. In this review, we will put the Trek Slash 9.9 to the test to better understand its new performance capabilities and where it excels.


Trek’s Slash is a 29” wheeled, 160mm travel enduro machine designed around a 170mm fork. It continues to use Trek’s classic linkage-driven single pivot suspension design, with a magnesium rocker link driving the shock, and their Active Braking Pivot (ABP) which adds a pivot around the rear axle to control the braking influence. The rear end is controlled by Trek’s exclusive RockShox Super Deluxe ThruShaft rear shock, which does away with the IFP typically found in a rear shock to deliver a shock that is claimed to “respond to changes in terrain faster than any other shock on the market”.


• 160mm Linkage Driven Single Pivot with ABP Suspension
• HTA 64.1 (Slack setting)
• STA 75.6 (effective)
• REACH 486 (Large)

Price: $3,829 /£3,200 /€3,399 (Slash 7) – $12,549 /£11,600 /€13,099 (Slash 9.9 XX1 AXS Flight Attendant)

The Trek Slash 9.9 XO1 is offered in a choice of alloy or carbon fiber frames depending on the spec level selected, with the lower price Slash 7 and 8 featuring the Alpha Platinum aluminum frame, and the 9.7, 9.8 and 9.9 models using their lighter weight OCLV Mountain carbon fiber frame. Regardless of the material selected, the frames feature the same full-length downtube guard; Knock Block headset; internal frame storage and threaded bottom bracket.

Trek Slash 9.9 XO1 Profile Shot

In previous years Trek has introduced new standards and features that would change the industry for better or worse. The previous model of Slash, with its straight shot down tube, introduced Knock Block, a system integrated into the headset that keeps the handlebars from swinging all of the way around should a rider crash. This prevents the fork crown and shifter lever from damaging the frame and the cables from becoming damaged, which could be the difference between a quick spill on a race run and an unrideable bike. The updated Slash has gotten rid of the straight downtube but has kept the knock block and increased the range of rotation by about 30 degrees. However, if this is a feature that you really can’t stand, it is removable.

Trek has moved the Slash to a 34.9 mm seat tube diameter and has updated their Line Elite Dropper to accompany the bike. As Trek describes, “The post’s larger diameter allows for an increase in structure strength, and provides better performance with less stiction, less sideplay, and better durability.” An upgrade that was nice to see across a few Trek models was downtube storage. The downtube storage is even available on the cheaper alloy-framed models – great news for riders on a budget. The Slash comes with a little bag that nicely holds a tube, tire iron, co2, and inflator head. It’s always nice to get a little weight off of your back.

Trek Slash 9.9 XO1 Downtube Storage

Trek offers the Slash in a choice of five sizes from Small to XL to suit riders from 5’0”-6’5” (153-196cm). In the low/slack position of the Mino Link geometry adjustment, reach in the size Large (19.5) tested is 486mm, which is paired with a 635mm stack height. The effective seat tube angle is 75.6 degrees, and the head angle is 64.1 degrees, with a 29mm bottom bracket drop. The rear end length at 437mm gives a total wheelbase of 1264mm.

The Trek Slash 9.9 XO1 tested came equipped with 29-inch Bontrager Line Elite 30 carbon wheels, XO1 drivetrain and more, with a price tag of $8,549.99. The 12-speed eagle drivetrain with 10-52 tooth range covers gearing for any and all terrain. The cockpit is made up of Bontrager parts as you would expect on a Trek. A 35mm stem is clamped to an 820mm carbon Bontrager bar with 27.5mm of rise. This build kit is no longer available, but Trek continues to offer similar builds ranging in price all the way from $3,829.99 to $12,549.99 to cater for varying budgets and preferences.

Trek Slash 9.9 XO1 Review


Setting up the suspension on the Slash was fairly easy. All the knobs and settings are easy to reach, and Trek even provides an online guide to help you get started. This was my first time riding a bike with a 170mm RockShox Zeb fork so that was a bit of a learning curve for me on setup. In my previous RockShox 160mm Lyrik I was running 73 psi with 4 volume tokens for my 155lbs mass. I started out with 50 psi and 3 tokens in the Zeb, and it was way too stiff. The front wheel was not tracking well, and the bike was too harsh. After some experimentation, I dialed in my settings at 48 psi and only one volume token, after which things were in a good place. The RockShox Super Deluxe Trek Thru Shaft shock feels great. I found that 155psi, my body weight, was the right amount of pressure on the Slash. More pressure than that felt very harsh and stiff. At 165 psi I wouldn’t use all the travel on drops and compressions that should use all of the stroke.

My first few rides on the Slash were on chunky, square edged, technical climbing with steep, loose descending. I got to know the Slash quite well just on the first ride because the bike was not well suited for the climbing and the descending is exactly what it was made for. This bike has since seen fast alpine, rough and rocky, flowy, and even some days at the Mt Bachelor and Trestle Bike Park.

Starting off with one gripe of the build on the Slash, is that it is spec’d with a 30-tooth front chainring. This gearing ratio left me wanting more on the descents, and if you come to a climb where you want that 30 tooth ring, chances are it’s too steep for the Slash anyways, which I will expand on below. Personally, I would opt for a 32 tooth chainring, and some stronger riders might even prefer to have a 34 tooth ring with the 10-52 tooth cassette. It gives you more gear for the way down, which is where it matters on this long travel race machine.

Trek Slash 9.9 XO1 Review

I left the shock fully open the whole time, preferring to focus on the trail ahead than reaching down for a lockout lever, and didn’t notice too much pedal bob when seated. Certainly not enough to convince me to make the effort to reach down – the Slash pedals very efficiently for a bike of this size. When out of the saddle and cranking hard there is a bit of movement in that rear end, but when you have 170/160mm of travel that is to be expected, and it helps the bike to track and find traction when pedaling through rough terrain on the way down the hill.

The 35mm stem, long wheelbase, and slack head angle made navigating technical climbs a bit trickier than the previous generation Slash. When encountering obstacles during the climb it was necessary to stand or lower my center of gravity more than normal to get some weight over the front wheel. In addition to fighting the wheelbase, as the trail increased in grade, I found myself scooting forward on the saddle to fight the front wheel coming up. As I scooted forward on steep climbs the rear wheel would lose traction easily. This made for a tough balance of weight over the front, but traction for the rear tire. When I hit those punchy 15 degree or more climbs, I found myself walking more than I’d have liked. However, as I got used to these mannerisms and how to manage them, it made less of an impact on my riding experience. If technical climbing is your idea of a good time, you may be served better by an alternative machine. That said, the Slash has gone from more of a trail/enduro bike hybrid to being a full on enduro, long travel rig, as it should be. As we know with these long travel bikes, they are never going to take home the win on the climb. Thankfully the descending prowess makes up for it, and then some.

Unlike the climbing, the descending capabilities of this bike beg for rougher and steeper. The 64.1-degree head angle paired with the 170mm RockShox Zeb provides the stiff front end to plow through all terrain with ease. The length and stiffness of the bike inspire confidence while the somewhat playful nature of the suspension design lets you slash (no pun intended) and jump your way down the trail. While the bike can be playful and it jumps well, it is clear that the main focus is speed, which it maintains incredibly well. When on straighter sections of trail I found myself gaining on other capable riders on comparable bikes time and time again, while feeling composed and controlled. On undulating sections of trail the Slash carried copious amounts of speed up and over rises asking for less exertion, which over the course of a enduro race could add up to shaved seconds. Cornering the bike, it feels responsive with a firm platform to push into and generate speed. The weighting feels well distributed and the traction is plentiful. Only on occasion did I have the front end start to slide when going through flat, loose corners, but the way the bike wanted to break traction in these instances was very manageable. Tight switchbacks were a crux, but aren’t they always…

Trek Slash 9.9 XO1 Review

There is not much to complain about when it comes to the Sram XO1 drivetrain and Code RSC brakes spec’d on this bike. The performance of the bigger dropper post was noticeable on the first ride, giving a definite upgrade over the previous with no issues during the testing period. In the past the notably slack seat tube angle present on the Slash has led to premature wear and stickiness with dropper posts, so it was great to avoid these issues on the new model.

With RockShox’s new Zeb fork up front the bike feels very stable and it tracks through rough terrain very well. The 38mm stanchions are noticeably stiffer and more responsive than the 35mm stanchions on the Lyrik that was spec’d on the previous generation Slash, and it pays dividends when charging hard. The Zeb comes with a little more than a pound increase over Lyrik, but it’s weight worth taking in my eyes. This bike as a whole is about 2lbs heavier than the previous generation coming in at 31.14 lbs with no pedals, which is still a competitive weight in its class, but certainly detracts from its overall efficiency and pedal-friendliness.  At 155psi in the rear end with the stock volume spacers I never felt the bottom and the shock felt very smooth. Due to the Thru shaft technology you need to order specific volume reducers, which is far from the end of the world but still something that needs to be considered. I ran 3 clicks of rebound even though it can be set much higher. All the other settings felt very, very fast. There is no full lockout on the shock but there is “lock” and open setting as well as three clicks of compression.

One new design feature that does not function as well as the engineers may have planned is the drain tube directly below the rear shock. The frame creates a little bowl just under the rear shock where water and mud would pool on wet days. In theory the drain tube was a good idea to route pooled water down around your bottom bracket and out through a hole in the bottom of the frame. However, when I first received the bike, I noticed that this rubber tube was loose and rattling around in the frame. In order to put the tube back into place I had to pull out the crankset, remove the bottom bracket (which is threaded, score!), and remove the shock. When placed correctly the tube sits nicely, but the seal does not seem to be overly snug, letting a small amount of water creep under the rubber and into the frame on those really wet days or when washing the bike. I would prefer that there was no drain, and a little bit of water would pool there since it would bounce out when riding. Otherwise, the Slash proved to be a well-considered and high-quality bike all round.

Santa Cruz Bronson V4 CC Action

The Wolf’s Last Word

So, what is our final takeaway of the updated Trek Slash reviewed here? As much as I’d like to complain about how this new generation Slash is more of a burden on the climb than the previous generation, the descending is oh so worth it. Even on some of our smooth, winding singletrack here in Bend, Oregon the Slash is an enjoyable bike. Fast, playful, and confidence inspiring is how I would describe the new Trek Slash after its longer, lower, slacker treatment. This is not your high mileage, high vert, epic ride kind of bike. You could do it, you just have to be stronger than your riding partners! This bike shines on the steeps, excels in the rough, and is fun on the jumps. The perfect rig for some enduro racing, time in the bike park, and cruising on your local trails.

Price: $8,549 /£8,250 /€8,999
Weight: 31.14lbs (14.1kg)


Frame: OCLV Mountain Carbon | 160mm

Fork: RockShox ZEB Ultimate, Boost Charger 2.1 | 170mm
Shock: RockShox Super Deluxe Ultimate Thru Shaft, 3-position damper

Brakes: SRAM Code RSC | 200F/180R Centreline rotors

Handlebar: Bontrager Line Pro Carbon 35mm| 820mm| 27.5mm Rise
Stem: Bontrager Line Pro 35mm | 35mm Length
Headset: Knock Block 2.0 integrated, 72 degree turning radius
Seatpost: Bontrager Line Elite dropper 34.9mm,
Dropper Travel: S: 100mm; M, ML: 150mm; L: 170mm; XL: 200mm
Saddle: Bontrager Arvada

Hubs: Bontrager Rapid Drive 108T, Boost

Rims: Bontrager Line Elite30, TLR
Front tire: Bontrager SE5 Team Issue, TLR, Core Strength Sidewall, 29×2.60”
Rear tire: Bontrager SE4 Team Issue, TLR, Core Strength Sidewall, 29×2.40”

Bottom Bracket: SRAM DUB Threaded

Cassette: SRAM XG 1275; 10-52T
Cranks: SRAM XO1 Eagle, Boost, DUB, 30T, 170mm
Shifter: SRAM XO1 Eagle; 12s
Derailleur: SRAM XO1 Eagle; 12s

Santa Cruz Bronson V4 CC Rear Forward Link

We Dig

Steep terrain crusher
Rough terrain performance
Fun jumper

We Don’t

Not the best climber
Ineffective drain tube


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