The Trek Slash caused quite a stir when it was launched in 2016 and played a key role in shaping the 29er enduro bike category. Now, Trek have finally presented its successor, the 2021 Trek Slash 9.9 – with more travel, updated geometry and a practical storage compartment. Will this be the new benchmark?

Trek Slash 9.9 X01 | € 8,499 | 170/160 mm | 29”| 14.70 kg | Manufacturer’s website

The most important updates of the 2021 Trek Slash in a nutshell

The new Trek Slash has big shoes to fill! Hardly any bike was as popular in the scene as the 29er preceding it, but it was getting on in years. Trek have increased the travel of the new Slash by 10 mm to 170 mm up front and 160 mm at the rear. The geometry has also been fundamentally revised: the reach is longer, the seat tube angle is almost 2° steeper and the head angle is slacker (now 64.1°). The bottom bracket was lowered by a further 6 mm, despite having more travel, bringing the BB drop to 29 mm. As with the Fuel EX, the American brand have equipped the Slash with a storage compartment in the down tube of both the carbon and aluminium frames.

Looks like a … Trek! There’s no denying the new Slash’s heritage.

There it is! Since the introduction of the new Fuel EX, enduro riders have been waiting eagerly for the storage compartment.
“Flats happen” – true words! Sooner or later you’ll get a flat tire.
All the more convenient to have storage space for a spare tube and tools in the down tube
The new Slash has a longer reach, a slacker head angle and a lower bottom bracket
With the seat tube angle almost 2° steeper, it should climb better too

Trek have also improved many details of the Slash, giving the bike a new Thru Shaft Super Deluxe shock specially made by RockShox, a revised Knock Block that doesn’t limit the steering quite as much, a threaded bottom bracket and bigger frame protectors. On top of that, the new Trek Slash comes with a 34.9 mm dropper post offering up to 200 mm of travel.

The changes made to the 2021 Trek Slash at a glance:

  • longer and slacker geometry with a steeper seat tube angle
  • more travel – 170 mm at the front, 160 mm at the rear
  • convenient storage compartment in the down tube (aluminium and carbon frames)
  • revised Knock Block offering a wider steering angle (72° instead of 58°)
  • Specially developed Super Deluxe shock with Thru Shaft technology
  • bigger frame protectors
  • 34.9 mm dropper post with up to 200 mm travel
Trek always deliver on the finish. The red elements on our test bike shimmer in the sunlight and reveal the carbon fibres underneath – stunning!

The frame of the 2021 Trek Slash in detail

Like its predecessor, the new Trek Slash is available as an aluminium or carbon version. The kinematics and geometry of both versions are identical. Trek are also the first company to integrate the practical storage compartment in the down tube on an aluminium frame – awesome! Like its predecessor, the rear linkage of the new Slash also pivots on the rear axle. As such, the rear suspension should remain active while braking. Trek also continue to rely on their so-called Mino-Link on the new model, allowing you to adjust the geometry by around 0.5° and the bottom bracket height by 6 mm – but we don’t know of anyone who actually uses it. We only ever rode the old and the new Slash in the slack setting.

The Mino-Link is well known and proven. It allows you to adjust the geometry by around 0.5°, but we’ve never used it! During the course of our test, one of the bolts came loose, so we recommend using an extra dab of LOCTITE.
Treks proprietary ABP rear linkage pivots on the rear axle. As a result, the rear suspension should remain fully active when braking.

The Thru Shaft technology on the shock already proved itself on the predecessor, which creates less internal friction thanks to the continuous shaft and the lack of IFP and its seals. For the new model, Trek worked with RockShox to improve on this technology. Instead of using a specially manufactured body, it is now based on the Super Deluxe which allows you to adjust low-speed compression in three stages and thus tune the bike to suit different trails. Flow trails = more compression; steep natural trails = less compression. Another update is that the rebound clicks are now numbered, making it much easier to play with the setup. If you’d prefer using a different shock on the Slash, you can do so without any problems. Most 230 x 62.5 mm Trunnion mount shocks should fit into the rear triangle (e.g. FOX DHX2, FOX X2, RockShox Super Deluxe Coil, FOX DPX2 and MRP Hazard). According to Trek, the Slash is also compatible with coil shocks. The only shock that won’t fit is the classic Super Deluxe air shock because of the position of the lockout lever. Despite having longer travel, Trek have managed to retain the kinematics of the previous Slash, only increasing the overall progression by 2%.

Besides a new frame, Trek also worked with RockShox to develop a new Super Deluxe shock. It features Trek’s proprietary Thru Shaft technology.
At first glance, the Super Deluxe in the Trek Slash looks like any other RockShox shock
However, it doesn’t have an IFP chamber, which would usually pressurise the damping oil. Instead, the damping shaft (seen here in silver) can move through the shock, sticking out of the bottom. Due to the lower pressure in the damping system, the damper should respond more sensitively and work more actively.

Trek have reworked the details too, equipping the Slash with a threaded BSA bottom bracket, which is much easier to replace than a press-fit version. The down tube protector has been lengthened, but it can also be split in two to save weight, though we wouldn’t know who would want to do that. The cables are routed internally and are secured in place at two positions in the storage compartment, negating the need for foam sleeves or dedicated cable channels inside the frame. Trek have also designed the new Slash to accommodate longer dropper posts, speccing a 200 mm travel Bontrager model on the XL bike. Size L comes with a 170 mm version, while sizes ML and M are fitted with 150 mm travel posts. The smallest size S gets a 125 mm model. The travel of the dropper post can be reduced with spacers if need be.

A new feature on the 2021 Slash is the huge down tube protector. If you want, you can split it in half, but we don’t know why you would do that.
The frame accommodates longer dropper posts than before. The Slash now comes with 170 mm dropper on the size L bike and a full 200 mm version on the XL.
The hobby mechanics among us will be happy! The Slash now has a threaded bottom bracket.
The chainstay protector has also been revised. Although the chain runs very close to it, you don’t hear any slapping.

For the rear end, Trek continue to rely on the established 148 mm Boost standard that they introduced. To increase the clearance around the chainring, they choose to fit the latest SRAM or Shimano cranks with a 55 mm chain line. We wrote a separate article explaining why we think the new Super Boost Plus standard makes little sense, so we’re glad that Trek didn’t go down that route.

An analysis of the Slash’s geometry

You can tell the age of the previous Slash by its short reach and the very slack seat tube angle. Trek have updated both of these aspects on the new model. In size L, the new bike has a reach of 486 mm, 33 mm longer than previously. The chainstays have only increased by 2 mm to 437 mm. The seat tube angle has been made 1.9° steeper, but at 75.6° it’s still pretty slack by today’s standards, especially as the effective angle slackens the further the dropper post is extended. The bottom bracket is lower than its predecessor too, but the 29 mm drop isn’t extreme. The intermediate ML size, on the other hand, is an excellent addition as it will make things much easier for all those riders who find themselves between two frame sizes. In general, we like that Trek is offering the Slash in five sizes, thus making an optimal fit available to as many riders as possible.

The geometry at a glance:

Size S M ML L XL
Seat tube 395 mm 420 mm 435 mm 450 mm 500 mm
Top tube 585 mm 610 mm 629 mm 649 mm 684 mm
Head tube 100 mm 100 mm 105 mm 115 mm 140 mm
Head angle 64.1° 64.1° 64.1° 64.1° 64.1°
Seat angle 75.6° 75.6° 75.6° 75.6° 75.6°
Chainstay 437 mm 437 mm 437 mm 437 mm 437 mm
BB Height 345 mm 345 mm 345 mm 345 mm 345 mm
Wheelbase 1197 mm 1222 mm 1243 mm 1264 mm 1305 mm
Reach 425 mm 450 mm 469 mm 486 mm 516 mm
Stack 621 mm 622 mm 626 mm 635 mm 658 mm

An overview of the various Slash models

Trek are offering the new Slash in two aluminium models and three carbon versions. The 9.8 and 9.9 carbon models are further split between versions with a SRAM or a Shimano drivetrain and different colours, including a completely customised paint job thanks to Trek’s Project One concept. Pricing for the new range starts at € 2,999 for the Slash 7. However, the most attractive model for most riders will be the € 3,499 aluminium Slash 8, which leaves little to be desired in terms of its components. The most affordable carbon Slash is the 9.7, retailing for € 4,499. Topping the range is the 9.9 XTR Project One bike for € 9,099. Both the carbon and aluminium frames are available separately for € 3,999 and € 2,499, respectively. Compared to the complete bikes, this doesn’t seem like a very sensible option for most buyers.

A brief introduction of the different models

Trek Slash 7 – your entry into the range – € 2,999

At € 2,999, the Trek Slash 7 is the most affordable model. It comes with a RockShox Yari fork, a Deluxe Select+ shock without a reservoir, an NX Eagle drivetrain, and weak Guide T brakes. Both the suspension and the brakes are compromised and we would recommend paying € 500 more for the Slash 8.

Trek Slash 8 – great value for money – € 3,499

The Slash 8 is available in two colours and is the model offering the best value for money

It sounds almost too good to be true – for just € 500 more, the Slash 8 comes with a RockShox Lyrik RC fork, a Super Deluxe Ultimate shock, a GX-Eagle drivetrain and the powerful SRAM CODE R brakes! Functionally, there is nothing to complain about on this bike. Anyone looking for an attractively priced enduro bike to hit the trails at full speed should take a closer look at this model.

This bike is bound to become a common sight on the trails in 2021: the Slash 8 offers excellent value for money and a practical storage compartment inside the aluminium frame.

Trek Slash 9.7 – your entry into the world of carbon – € 4,499

The Slash 9.7 is the only model in the lineup equipped with FOX suspension. It comes with a 36 Rhythm fork and a DPX2 shock. Shifting is taken care of by SRAM NX and GX components and a pair of SRAM CODE R brakes provide the stopping power. There is nothing to complain about on the bike, but we would personally save ourselves the additional € 1,000 for the carbon frame and spend the money on slight upgrades for the Slash 8 instead.

Trek Slash 9.8 XT or GX – available in Project One on request – from € 5,999

The Slash 9.8 is the most affordable model available in Trek’s Project One range. For a surcharge of € 500 or more, you can get a completely custom paint job. It comes either with a SRAM GX or Shimano XT drivetrain. The SRAM variant is paired with G2 brakes while the Shimano model is specced with a pair of SLX four-piston brakes. We would choose the Shimano option for the brakes. Both models feature Bontrager Line Elite carbon wheels. The suspension is taken care of by a RockShox ZEB Select+ fork and the specially developed Super Deluxe Ultimate shock. In our opinion, if you must have a carbon frame, this is the model to go for.

Trek Slash 9.9 X01 or XTR – also available in Project One on request – from € 8,499

You only want the best? Then you should choose the Trek Slash 9.9. The bike is optionally available with a SRAM X01 or Shimano XTR drivetrain and can be completely customised as part of the Project One concept. The bike’s handlebars, as well as the Bontrager Line Elite wheels, are made of carbon. The suspension consists of a ZEB Ultimate fork and a Super Deluxe Ultimate shock. From a rational point of view, the extra charge compared to the Slash 9.8 simply isn’t worth it – but who of us is rational when buying a bike?

Besides the completely customised Project One, the 9.8 and 9.9 carbon models are available in this third stock colour scheme

Our review of the new 2021 Trek Slash 9.9 X01 enduro bike

More than six weeks before the official launch of the new 2021 Trek Slash, we were lucky enough to do an in-depth review of the flagship 9.9 X01 model in size L. Besides riding the bike on our home trails, as usual, we also took it to the bike park in Innsbruck. As if that wasn’t enough, we included it in our enduro bike group test, which will be published in the next issue, comparing it to the hottest enduro bikes of the year. In total, the new Slash 9.9 XO1 was ridden by five experienced ENDURO test pilots.

We rode the new 2021 Slash on countless trails during the course of this review

At first glance, the new Slash looks a lot like its predecessor. However, the frame is generally beefier. As soon as you climb aboard, you’ll immediately notice a few differences. The bike is longer, the seat tube angle is steeper and the suspension feels plusher. The riding position is comfortable, neither too stretched nor too upright. However, the seat tube angle remains on the slacker side of the spectrum. Long-legged riders or anyone who regularly attempts very steep climbs will have to push the saddle as far forward as possible. By doing so, we were able to find a suitable climbing position. Riding uphill, the rear suspension is as pleasantly efficient as before, as long as you stay seated and pedal in even strokes. If that’s the case, you can leave the shock open without any problems. However, if you have to get up out of the saddle to pedal, we recommend locking out the shock first. Overall, the Slash is a capable climber and will easily get you to the top of every trailhead.

Our smile was definitely bigger on the climbs aboard the new Slash than on its predecessor
The rear end of the Slash is surprisingly efficient and has little tendency to bob when you ride in a relaxed manner
However, the same thing we always said about the old one also applies to the new Slash: the seat tube angle could be steeper. The riding position is more central, but still too far back on steep climbs. Our tip: push the saddle forward!
However, you’ll easily reach the trailhead nonetheless

Let’s be honest – who would buy a Trek Slash for its climbing prowess? If climbing is your thing, you should perhaps take a closer look at the Fuel EX instead. Where the Slash has to deliver is on the descents and once you drop the saddle, you’ll immediately feel that you’re dealing with a completely different beast. While the previous Slash was more reminiscent of a modern, long-travel trail bike with its rather firm suspension and compact geometry, there’s no denying what the new bike was designed for. The suspension responds a lot more sensitively and literally sticks to the ground. The added reach gives you lots of freedom of movement and you’ll feel much more integrated into the 2021 Slash than on the predecessor. When the descents get steep and technical, the bike’s length keeps it very composed, holding its line and generating a lot of traction. Provided that you replace the SE4 rear tire, because it doesn’t do justice to the new Slash in any situation except for its low rolling resistance. On demanding terrain, there is room for improvement with the small 180 mm rear rotor as the SRAM CODE RSC brakes tend to fade quickly. This bike requires at least a 200 mm rotor and is even approved for up to 220 mm versions – excellent!

Just pull up – the Slash easily copes with botched landings!

The chain almost lies on the chainstay protector. The Slash is quiet nonetheless – thumbs up!
The rear suspension is much more sensitive than its predecessor and offers more traction over roots

The rear end of the Slash performs sensitively with just the right amount of progression towards the end-stroke, but we got the impression that it gives up its travel to readily in the medium compression setting, making it wallow slightly in the mid-stroke. The shock offers enough support through compressions, but it’s a little wallowy in general. Installing three volume spacers didn’t do anything to help. We tried different sag settings between 25 and 30%, finding the sweet spot at around 28%. In combination with the long 485 mm reach and the compact 437 mm rear end, the Slash demands a very committed riding style through corners and for quick direction changes. If you don’t get actively involved, you’ll find yourself hanging off the back of the bike and lacking grip on the front wheel. If you set the compression lever on the shock to the plus, the bike offers more support. However, we would only recommend this setting for flow trails as it comes at the expense of small bump sensitivity as soon as you take on more natural trails. We would have liked to be able to fine-tune the shock more. If you’re not sure about the frame size, we recommend sizing down. Looking back, the ML Slash would have been a better option than the L for a rider height of around 180 cm.

You have to actively shift your weight forward in the corners to generate enough traction on the front wheel. Our test riders are 180 cm tall on average and would have preferred the intermediate size ML.
Off to the highline! No problem with the Slash. We recommend fitting different tires if you’re going to ride trails that have a lot of roots.

What else did we notice while testing?

The handling of a bike is key, but there are a few other factors that are important to consider before buying a new bike. One feature that makes the Slash so attractive for many enduro riders is the additional storage compartment in the down tube. You can use it to store a tube, an energy bar, a pump or simply a packet of gummy bears. Specialized were the first brand to offer this feature on their carbon bikes. Compared to the opening on the current Specialized Enduro, that of the Slash is smaller, but the latch is easier and quicker to open.

The most important test criterion: how many packets of gummy bears will fit in the Slash’s storage compartment?
The small opening doesn’t make it easy to fill…
…with all the air let out of the packets, you’ll be able to fit three – enough to be the hero the next time you take a break on a long group ride!

Tuning-Tipps: choose a smaller frame if necessary | larger brake rotor at the rear | Swap tires for a grippier, more robust model

There are a few other things we noticed during our test. Unfortunately, the rubber stopper that allows the thru shaft shock to fully compress came loose. It to be fumbled out of the frame. The shaft had also slightly damaged the housing of the shifter cable – no drama, but annoying. Last but not least, the Bontrager Line Elite carbon rims didn’t survive the test unscathed. While riding, we couldn’t remember encountering any hard impacts and the tires were always inflated to the correct pressure, but the rim wall delaminated from the bed. As a result, the tubeless tire would no longer stay inflated.

A small part, big frustration: the rubber stopper slipped into the frame during our test. To get it out, the crank had to be taken off and the bottom bracket removed.
The cables on our bike were probably too short and therefore pulled on the plug when the suspension compressed. When the rubber stopper disappeared into the frame, the shifter cable housing got damaged.
After we took it out of the frame and put it back correctly, the plug stayed in place for the remainder of our test
Ouch – the carbon rim didn’t survive our test unscathed. As you can see on the rim flange, there’s nothing to hint at an impact. We suspect a manufacturing defect that ultimately led to a failure changing the tire with a tire lever.

Our conclusion on the new 2021 Trek Slash

With a series of updates, Trek aim to put the Slash back on the podium. Thanks to its plush suspension and capable geometry, it’s ready to take on the most demanding trails. The integration of the storage compartment, the comeback of the threaded BSA BB and the longer dropper post are great. However, there’s little innovation and the unsuitable tires, the small brake rotor, the still slack seat tube angle and the lack of adjustability on the rear shock cloud the otherwise positive impression of the 2021 Trek Slash 9.9 X01.


  • plush suspension
  • practical storage compartment in the down tube (also on the aluminium frame)
  • composed handling in rough terrain
  • beautiful paint job
  • additional ML frame size for the perfect fit


  • unbalanced in flat and open corners
  • minimal adjustment options on the rear shock
  • tires and small rear brake rotor don't do the bike justice

More infos on

The new Trek Slash isn’t perfect right out of the box. But if you invest a little time and money in tuning it, you’ll get a very capable enduro bike! Be careful when choosing the size – we recommend downsizing.

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