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2021 Trek Slash gets more travel, custom thru-shaft shock, Knock Block 2.0 & hidden storage

2021 Trek Slash, whip!
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With a burly-looking frame, slack steering, 160/170mm’s of travel and 29” wheels, the 2021 Slash is certainly a full-on enduro machine. The Slash was an early player in the long-travel niner department, and for 2021 it’s had quite the design overhaul.

The updated frame boasts new geometry, a revised linkage with more rear travel, and includes Trek’s take on down tube storage. Trek also fit this new frame with a custom shock: The new RockShox Super Deluxe Ultimate Thru-Shaft was designed for the Slash, and offers an adjustable open mode to help control rider inputs.

2021 Trek Slash frame and suspension:

2021 Trek Slash, angle, on trail

The 2021 Slash is offered in a bunch of carbon build options and one aluminum model. The carbon frame’s weight is 2450g/5.39lbs, which Trek claims is almost a pound lighter than ‘the competition’. Including the rear shock the carbon frame weighs 7lbs, and the aluminum frame/shock weighs 9.5lbs.

The Slash has grown in travel and seen its suspension tweaked for 2021. The bike now provides 10mm more squish in both ends, with 160mm of rear travel and 170mm forks (180mm forks are OK if you want ALL the travel).  As for tuning, Trek adjusted the position of the Slash’s main pivot to achieve better pedaling efficiency, and they set it up with a specific new shock…

2021 Trek Slash, rear shock

The Slash’s Super Deluxe Ultimate Thru-Shaft shock was co-developed by RockShox and Trek, who had similar ideas in mind about reducing friction and improving a shock’s ability to control rider inputs. The thru-shaft shock boasts an improved shim damper, an oversized thermal compensator and a tunable open mode with three settings.

The shock’s open mode settings are Plus, Minus, and Zero, and they adjust the low-speed compression. Zero serves as the middle setting, Plus adds a bit of compression for flowy or jump trails, and Minus offers the softest ride for tackling rough terrain. In stock setup the shock has no spacers installed, but both the positive and negative chambers can be tuned by adding them.

2021 Trek Slash, shock in front triangle

Should you wish to swap out the rear shock, the Slash is compatible with several other models of air shocks, and its linkage will work well with a coil shock too. You may have noticed Trek isn’t running a RE:aktiv shock on this year’s Slash: In short, they say they’re happy enough with the Super Deluxe Ultimate Thru-Shaft’s damping.

Knock Block 2.0!

2021 Trek Slash, Knock Block 2.0

Trek has also updated their Knock Block system, and the Slash comes with the Knock Block 2.0. The significant thing to note is that the new Slash frame will not come into contact with your fork crown, so you can remove the Knock Block 2.0 if desired. Trek kept it there because it can save you from ripping out cables/hoses in a crash, something racers would likely appreciate. Since the frame cannot be contacted, the Knock Block 2.0 offers a much wider steering range than the initial version, allowing for 72 degrees of swing instead of 58 degrees.

2021 Trek Slash, down tube storage

Trek has included their version of down tube storage on the new Slash, and they’ve managed to include it on their aluminum frames as well as the carbon models. Bontrager offers a suitable tool roll which has pockets for carrying a tube, tire levers, Co2 canisters and an inflator head. Though Trek shows them in some photos, the tool rolls are an aftermarket accessory and are not included with the bikes.

2021 Trek Slash, Bontrager 34.9 dropper post

The Slash now runs a 34.9mm diameter dropper post (Bontrager’s updated Line Elite 34.9). Trek jumped to the larger diameter as it makes for stronger posts with less side-to-side play and stiction. With an adjustment to the shock position, Trek’s 2021 frames offer 45mm more insertion depth for dropper posts. Mediums come with 150mm, Larges get 170mm, and XL’s get Bontrager’s new 200mm posts. While some brands are putting 170mm’s in medium frames (and it would be nice to see that on this bike) Trek did confirm a 170mm post will fit into a medium.

2021 Trek Slash, derailleur hanger, Boost 148 spacing

Other fitments include Boost 148mm rear spacing, and instead of last year’s press-fit BB, there’s a trusty BSA 73mm threaded BB shell with ISCG mounts. The frame runs a 55mm chainline, and will fit up to a 34t chainring. Trek has also adopted SRAM’s universal derailleur hanger for the new Slash. Tire clearance maxes out at 29×2.5”, and Trek does not intend for people to mullet this bike – It was built to be a niner!

2021 Trek Slash, down tube protector

The Slash features Trek’s Control Freak internal cable routing, and between the port plugs and zip-tie attachments found inside the storage compartment, there’s no need for internally sleeved routing. Other finishing touches include a removable, full length, dual-density downtube protector for shuttling or fending off rock strikes, a chainstay protector, and enough room for a water bottle on all frame sizes.

2021 Slash geometry:

2021 Trek Slash, geo chart

While the carbon and aluminum models were slightly different before, the geometry is now the same between all the 2021 models. The new Slash comes in S/M/ML/L/XL frame sizes. Versus last year’s Slash, the 2021’s head tubes were slackened by one degree, now sitting at 64.1 degrees. The seat masts are also 1-2 degrees steeper, with a new effective seat angle of 75.6 degrees.

Reach was also increased quite a bit with M/L frames now up to 450/469mm. While the front ends got longer, they were stretched out with the Slash’s stubby 35mm stems in mind, so the bikes won’t feel drastically longer than the 2020 versions. Trek has also gone from 51mm offset forks down to a very short 42mm offset.

All frame sizes run 437mm chainstays, which are 2mm’s longer than before to increase the wheelbase and better balance the longer front ends. BB height is now slightly lower, but only by about 1mm.

2021 Trek Slash, Mino Link flip chip

The Slash employs Trek’s Mino Link flip chip, offering Hi and LO positions. All numbers listed above are for the Lo setting – Flipping into Hi position steepens the head tube and seat mast by 0.5 degrees, shortens the chainstays by 2mm, lengthens the reach by 5-6mm, and lifts the BB up 7mm.

2021 Slash model lineup:

There are five different builds for the 2021 carbon Slash, two aluminum models, and carbon or aluminum frameset options. Here are some pics and prices, but with so many models you’ll have to visit Trek’s website for full build specs and color options.2021 Trek Slash 7

Slash 7 (Aluminum) – $3499.99

2021 Trek Slash 8

Slash 8 (Aluminum) – $3999.99

2021 Trek Slash 9.7

Slash 9.7 – $ 4799.99

2021 Trek Slash 9.8 GX

Slash 9.8 GX – $5999.99

2021 Trek Slash 9.8 XT

Slash 9.8 XT – $5999.99

2021 Trek Slash 9.9 X01

Slash 9.9 X01 – $7999.99

2021 Trek Slash 9.9 XTR

Slash 9.9 XTR – $8499.992021 Trek Slash, carbon frameset

Slash carbon frameset – $3999.99

2021 Trek Slash, Aluminum frameset
*Images c. Trek Bikes

Slash AL frameset- $2199.99.

The carbon and aluminum framesets both come with a RockShox Super Deluxe Ultimate Thru-Shaft shock, the bottle cage/storage door, a headset with the Knock Block 2.0 headset cap, and a 35mm Bontrager Line Pro stem.

One final note: Trek’s Project One custom paint option is available for the 9.8 XT, 9.8 GX, 9.9 X01, and 9.9 XTR models. This upgrade will cost you an extra $500. The 2021 Slash is available now online and at Trek dealers (technically… like many bike brands right now, Trek says demand is greater than supply, so you may have to be patient!)


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Ham Jam
Ham Jam
3 years ago

Why is there not a “straight-shot” downtube. I thought it was a better design?

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