Trek Slash Review | A totally one-of-a-kind custom bike build

The not-so-minor details

Product

Trek Slash 8

Contact

Trek Bicycles Australia

https://www.trekbikes.com

Price

$3,312 AUD (frame only)

Weight

15.75kg

Last year saw Trek pull the wrappers off of its all-new Slash enduro bike. Featuring a redesigned chassis with in-built downtube storage, the 2021 Trek Slash received a whole suite of updates, including a brand new rear shock that was codeveloped alongside RockShox. Our two testers, Ben & Dan, were thoroughly impressed with the supple suspension and the bike’s ability to monster-truck its way through horrendously rocky and technical terrain. However, it was the Slash’s agility that was the real surprise, giving it an approachable and easy-to-manage demeanour on less gnarly singletrack. Despite its EWS-level capabilities, the Slash is a proper all-rounder.

The bike we tested prior to the official launch was the top-end Slash 9.9 X01. However, Trek offers three other models beneath it, with the Slash 7 being the cheapest option at $4,999 AUD. For those who want to build something a little different, there’s also the option to buy the Slash frameset.

And that’s exactly what Ben decided to do.

2021 trek slash 9.8 x01 holden commodore ss ute
Trek launched the new generation Slash last year, and we were thoroughly impressed with the 9.9 model we tested.
2021 trek slash 8 alloy
Trek also offers the Slash in an alloy frame. It’s heavier, but also a whole lot cheaper.

Going Off-Script With The Trek Slash

But first, allow us to introduce you to our fellow Flow Frother.

Ben is a full-time bike shop guru, a skilled mechanic, and an appreciator of very robust IIPAs. With some three decades of riding and bike industry experience behind him, he’s also a talented and discerning rider, with an infectious enthusiasm for geeking out on new bike tech, while simultaneously being a connoisseur of fine retro collectables. Notable highlights in the shed include a Klein Mantra, Shimano Airlines groupset and a Manitou X-Vert Carbon. Not that Mick is jealous or anything.

After being thoroughly impressed with the Slash 9.9 X01, Ben heard through the grapevine that Trek Australia would be bringing in a very limited number of Slash framesets into the country. One impulse-purchase later, and a Slash 8 frame was on order.

To assemble his custom Slash, Ben’s chosen an eclectic build kit that is comprised of a variety of components that he’s been testing for Flow, along with a few parts that were purchased specifically for this bike. The build hasn’t stayed still either – a number of components have already been swapped around in search of the perfect setup, and there are a few upgrades planned for the future too.

Without further ado, let’s get stuck into the build and Ben’s impressions of this one-of-a-kind Trek Slash and some of the parts strapped to it.

2021 trek slash 8 alloy
Bike guru Ben decided to snag a Slash 8 frameset to build up a one-of-a-kind enduro bike.

The heart of any bike is the frame, so let’s start there Ben. Why did you go for the Slash?

Well I had been hankering after a big bike for a while after many years of riding XC and trail bikes. I used to ride and race a lot of DH in my younger days and have never quite been able to let it go! The Slash just had this great mix of playfulness and agility, whilst also being able to just steamroll through techy sections and feel very planted and confidence inspiring. It’s super fun to ride.

I opted for a frame only option as by the time I had decided to order one, only a few days after the official release, the complete bikes had already been snapped up! Lead times on the second shipment of complete bikes was far too long for my impatient nature so I sourced a frame before they all disappeared.

2021 trek slash 8 alloy
Ben’s been testing a range of components for Flow, while the rest of the build kit is made up of both new and second-hand parts.

Did you choose the alloy frame specifically over the carbon option?

I never really considered the carbon option as I wanted a bike that I could be less delicate with and worry less about when tackling the extremely rocky local trails we have here. The added weight didn’t phase me, I have other bikes that are light and fast uphill, and that’s not what I bought the Slash for. The alloy Slash 8 frame (and complete bike) are perhaps the sweet spot in the Slash line up as it shares the same Rockshox Super Deluxe Ultimate Thru Shaft shock that you’ll find on the more posh carbon 9.8 and 9.9 models. This shock is a big part of why the Slash handles as well as it does, so it’s cool to see it offered on the alloy frame as quite often alloy models receive a more basic shock.

The alloy frame sells for nearly half of the carbon frame option with the same shock.

As with the carbon frames, the alloy Slash still gets the new downtube storage accessed by a trapdoor under the bottle cage, adjustable geometry via the Mino Link and generous downtube protection. Price was also a consideration. I already own a… ahem…not insignificant amount of expensive bikes so there wasn’t much scope for a full on enduro dream machine. The alloy frame sells for nearly half of the carbon frame option with the same shock. I’m never going to be at the pointy end of an enduro race so the alloy option was a bit of a no brainer.

2021 trek slash 8 alloy
A big plus for the Slash 8 is the fact that it gets the same Super Deluxe Ultimate shock as the carbon models. No downgrades here.

That Trust fork is absolutely bonkers! Why the heck is that on there?

Ah, yes, the elephant in the room! The Shout is the second fork from the now COVID coma-induced Trust Performance. Trust was founded by three industry veterans, most notably the hugely influential Dave Weagle. Both Trust fork models, the 130mm Message and the 178mm Shout are linkage driven forks made almost entirely of carbon fibre and feature an air spring in each leg and a three-position damper unit in one leg.

Linkage driven forks are nothing new but these are perhaps the first to really benefit from the engineering flexibility of modern carbon fibre, while adding in intricately adjustable dampers and air springs.

I really feel the Trust forks are one of those products that, whilst not perfect, has perhaps paved the way for others to try something different.

I actually didn’t intend on building the Slash with the Trust Shout fork to begin with. I had a perfectly nice set of Lyrik Ultimates ready to go but the Trust came up for sale on the second hand market just as I was finishing the build, and I couldn’t say no! I have the shorter travel Trust Message fork on another bike and love it, so I was really keen to see how the 178mm Shout fork would feel.

I’m drawn to the more outlandish bicycle and component designs as these are what can push the envelope of what we currently ride and the way we think about bike and component design. I think that’s one of the reasons I have such a love for vintage mountain bikes. There was so much experimentation back in the day and lack of concern about what company shareholders would think. Don’t get me wrong, there were a lot of mis-steps but they have all in some way shaped the pretty amazing mountain bike and parts we ride now. I really feel the Trust forks are one of those products that, whilst not perfect, has perhaps paved the way for others to try something different.

2021 trek slash 8 alloy
Technical climbing is not the Shout’s forte.

You’ve since fitted a more conventional telescopic fork. How’s the performance in comparison?

Yeah I’ve now fitted a 170mm 2020 Lyrik Ultimate upgraded with the new C1 Debonair spring. It has really changed the way the bike behaves in a number of ways.

Instantly noticeable was the improvement in small bump sensitivity, particularly on very rocky, slower sections of trail, both uphill and downhill. The main weakness of the Trust fork was its climbing performance, admittedly not the designers’ biggest concern when making the fork but worth mentioning. The Trust fork tends to sit really high in its travel, raising the front of the bike and making slow, technical, rock-strewn climbs particularly tough going. The Lyrik is much plusher off the top, which naturally tends to lower the front end as you shift your weight forward. The initial suppleness also does a better job of soaking up momentum robbing rocks that can be the difference between cleaning a tech climb or not.

2021 trek slash 8 alloy
The Slash has since gone back to a more conventional Lyrik Ultimate fork.

The difference between the forks when the terrain points down is interesting. I felt the Trust shines on high speed flow trails, where the stiffness and lateral rigidity of the huge carbon legs allows you to corner and carry speed in a way that makes you feel as though you could give Greg Minnaar a run for his money! The Lyrik still feels great in comparison on this type of descent but doesn’t quite give you the confidence to really let go on the corners like the Trust does.

When the descents become more technical and rocky the Trust does not feel as composed as the Lyrik, there is definitely a lot more feedback through the bars. The Lyrik does a better job of smoothing out the trail but the Trust feels faster and as though it carries more momentum. The rearward axle path of the Trust’s initial stroke has a lot to do with this as the wheel can more quickly move out of the way of an incoming rock, minimising its effect on your forward motion. It will be interesting to go back to the Trust after some time on the Lyrik to see if it highlights any other differences.

2021 trek slash 8 alloy
On high-speed flow trails, the linkage design comes into its own.

Let’s talk about the Crank Brothers Synthesis Alloy wheels; how have those held up?

Yeah, I’ve been testing out the entry level Crank Brothers Synthesis Alloy Enduro wheels, which sell for a reasonable $945 AUD and weigh in at 2,130g for the pair. Like the carbon versions, these wheels are designed and built differently front and rear to provide different ride qualities.

The front rim is 31.5mm internally compared to 29.5mm for the rear, the front also has 28 spokes where the rear has 32. Crank Brothers reckons the wider rim profile better supports a wider front tyre for cornering stability whilst also rounding the tyre’s profile, which again can help in the corners. The lower spoke count theoretically reduces front wheel stiffness a touch, potentially allowing a touch more compliance through choppy corners where an overly stiff front wheel can ping off rocks and ruts and leave you feeling sketchy.

The narrower rear rim is meant to better match up with a narrower, faster rolling rear tyre. The 32 spokes provide a laterally stiffer wheel, allowing more precise tracking through the corners.

It’s especially noticeable on technical climbs, I found myself second guessing every pedal stroke when trying to pick a line over rocky climbs.

The wheels have held up pretty well, suffering only a minor ding to the rear rim. This is no slight on the rims though, our trails are very rocky and I’m sure any alloy rim would have sustained some damage. Overall the wheels felt fine, not too flexy, not too stiff. This could be down to the difference in stiffness Crank Brothers reckon it has designed into the wheels, but this is hard to quantify.

The major issue for me with these wheels is the sluggish engagement of the rear hub. It’s 17 degrees, which is very slow, and I reckon for a nearly a $1000 wheelset these days is unforgivable. It’s especially noticeable on technical climbs, I found myself second guessing every pedal stroke when trying to pick a line over rocky climbs.

2021 trek slash 8 alloy
Those wheels haven’t exactly had the easiest time.

On the plus side the wheels are built with readily available J-bend spokes, external nipples and easily sourced cartridge bearings meaning they will be easy to maintain and live with. However, replacement rims aren’t particularly cheap at $195 AUD each. This is definitely worth factoring in if you are a frequent rim muncher.

My overall verdict on the Synthesis Enduro alloy is that they could really benefit from a higher-engaging freehub to be competitive with other wheels out there at this price point, or they need to come down in price. Whilst the differing ride qualities built into the front and rear is a nice concept, I personally haven’t found the benefits noticeable enough on the trail to justify the price or overcome the drawbacks of the rear hub.

Now you’re on the carbon Bontrager Line Pro 30 wheels. How do they compare?

After riding the Synthesis wheels, I then fitted a set of Bontrager Line Pro 30s. These sell for considerably more at $1,999 AUD, but they’re also lighter at 1,881g for the set, including rim strips and valves (you can get the full tech rundown on these wheels in our separate tech feature here).

When I swapped wheels, I kept the same tyres and overall setup for the whole bike, in order to isolate the performance differences as accurately as possible. And in comparison, they feel great, lighter and more direct on the trail. They are 250 grams lighter than the Crank Brothers wheels, which doesn’t sound like a lot but it is definitely noticeable. The carbon rims add to the feeling of directness, without feeling harsh or chattery like some carbon wheels can (like previous generation Bontrager carbon wheels).

2021 trek slash 8 alloy
Ben’s gone from the alloy Synthesis wheels, to a set of carbon Bontrager hoops.

The rear hub features the Rapid Drive 108 freehub mechanism, which offers 3.3 degrees of engagement. This is super fast, especially when compared to the 17 degrees on offer from the Crank Brothers wheels.

Bontrager claims that the rims found on the new Line Pro 30s are the strongest it has ever tested. We’ll have to take this with a grain of salt as testing is obviously done in house. Bontrager does back all of its carbon wheels with a lifetime warranty and a 2 year “no questions asked” crash replacement policy though. Damage your carbon wheels within a 2 year period and Bontrager will replace them. This is increasingly common in the carbon wheel market these days but still pretty cool to have that peace of mind when purchasing.

Would you recommend either wheelset over the other?

I prefer the Bontrager wheels over the Crank Brothers but they are twice the price, so it’s not a fair comparison. I personally love the direct and lively feel of a stiff carbon wheelset. These qualities worked well with the Slash’s super supple rear suspension as the wheels could handle the speed I found myself entering with into chunky rock gardens and off-camber sections.

By comparison the Crank Brothers wheels didn’t feel as positive or stiff. This could actually be a good thing though, particularly for lighter riders or those on hardtails who are looking for a bit more compliance from their wheels. I’d personally like to see a quicker-engaging freehub, but if you’re not so bothered by that, they’re a solid set of hoops for under a grand.

It’s worth mentioning the Bontrager wheelset that sits below the Line Pro 30, the Line Elite 30. These wheels are $1,499 AUD and feature the same Rapid Drive 108 hub internals and the same warranty support, but are built with slightly heavier carbon rims and J-Bend spokes. The Line Elite wheels are only 130 grams heavier, and in my mind would be worth considering when looking for an off-the-shelf wheelset.

2021 trek slash 8 alloy
A 2.4in Maxxis Dissector on the back. It’s not as heavy duty as you might expect given the EXO+ casing though.

What tyres are you currently using?

I’ve been running a Maxxis Minion DHF EXO 2.5in up front and a Maxxis Dissector EXO+ 2.4in on the rear, both with the 3C Maxx Terra rubber compound. The Minion DHF weighs in at 1,065 grams, but while the Dissector is meant to have a heavier duty EXO+ casing, it’s actually quite a bit lighter at 925 grams.

The Minion DHF, as we all know, is superb and provides a ton of confidence up front. The Dissector certainly rolls well for an aggressive tyre but hasn’t given me the confidence that the Minion did. The Dissector did also suffer a ride-ending pinch-flat after sustaining a big hole on the bead and through the top of the casing. I’m not hard on tyres so this was a bit disappointing. If you’re a certified tyre shredder then consider the tougher Double Down casing, particularly on the rear tyre. That’s exactly what I’ll be ordering shortly!

2021 trek slash 8 alloy maxxis minion dhf
The ever-dependable Minion DHF.
2021 trek slash 8 alloy
Spot the problem(s).

You’ve been testing the Shimano Deore 1×12 drivetrain too. Give us the lowdown on your experience so far.

Listen up bike snobs (myself included) – Shimano Deore 12 speed is bloody amazing, seriously impressive! The shift quality is superb, particularly when shifting into harder gears as it uses the same HG+ cassette design as SLX, XT and XTR 12 speed groupsets. I ride the XTR 12 speed groupset on my XC bike and honestly the difference between this and the Deore groupset is so small. The shifter feels a touch softer and a little less positive than XTR but the actual difference in shift quality is negligible.

I do miss the multiple upshift offered by XT and XTR shifters but if you’ve never ridden with this it won’t be an issue. It has not given me a mis-shift or any cause for concern since it’s been fitted to the Slash, its performance is outstanding, especially considering the cost of the entire groupset is less than the cost of a cassette from a top-tier groupset from either Shimano or SRAM.

I think in the long term I would consider upgrading the cranks and the cassette as these components are pretty heavy. Changing to XT cranks and cassette for example would save nearly 300 grams without sacrificing any strength or durability (for confirmed weights and a closer look at the full Deore M6100 groupset, check out our detailed tech feature here).

2021 trek slash 8 alloy shimano deore 1x12 M6100
You could buy a single high-end XTR or XX1 cassette, or an entire Deore 1×12 drivetrain.
2021 trek slash 8 alloy
Even the Deore brakes mimic the function, ergonomics and feel of the higher-end XTR groupset.

What about the Deore M6120 brakes?

The Deore four-piston brakes have been impressive with good power and modulation. Fitting and set up is simple and straightforward, and the bleed process is the same as all current Shimano models. I’ve paired them with Shimano XT Ice Tech 180mm rotors front and rear.

Modulation on Shimano’s four-piston brakes is improved over their less powerful two-piston models, and there’s a really nice power progression as you move through the lever stroke. The lever feel was consistent throughout the test, with none of the wandering bite point that some Shimano models have had a problem with.

I will say that the stock resin pads didn’t quite give the bite that and power that I was used to from sintered metal pads though. Unfortunately I couldn’t find anywhere that had stock of sintered Shimano pads to suit these Deore callipers, and it’s worth noting that the finned pads for the four-piston XT and SLX brakes are not compatible with these Deore callipers.

One of our main suppliers at the shop had just started doing Galfer pads and rotors so I’ve since fitted a pair of the standard compound pads, which made a big difference to braking power and firmed up the lever feel at the bite point. For anyone with Shimano brakes who’s looking for more power over the stock resin brake pads, I can highly recommend upgrading to some sintered or semi-metallic pads.

2021 trek slash 8 alloy shimano deore m6120
OneUp carbon handlebars provide a noticeable improvement to vibration damping over most other 35mm diameter carbon bars.

Tell us about the rest of your bike’s cockpit setup.

I’m running a 45mm long Bontrager stem, which clamps a 35mm One Up carbon bar with 20mm of rise. I’ve cut these down from 800mm to 780mm. Currently I’m riding the ODI Elite Flow grips and a 180mm travel OneUp dropper, which is paired to the Shimano dropper lever.

The OneUp bar is super comfortable due to its flattened, oval shape that allows some vertical flex whilst still retaining fore and aft stiffness. They are a huge improvement over the PRO Tharsis carbon bars I initially built the bike with, those things are really stiff, and I found them to be quite harsh.

The dropper has also been top-notch, though I’m not in love with the Shimano lever. It works fine, and the textured paddle is nice, though the return spring requires more thumb force every time you press the paddle, and the physical position of the paddle is too close to the grips. Some further adjustability, or just a bit more clearance between the paddle and the grip would be nice.

2021 trek slash 8 alloy oneup v2 dropper
Ben’s fitted a 180mm travel OneUp dropper, though he’s looking to upgrade to a 200mm post in the future.
2021 trek slash 8 alloy shimano deore
The Shimano dropper lever is fine, but it’d be nice if the paddle sat a little further off the bar.

What do you love most about it?

As I mentioned before, the bike’s ability to feel lively, and chuckable whilst still feeling planted and stable when needed, is a great quality. The rear shock and shock tune is superb as well, really smooth and supple at the top off the top, supportive in the mid stroke and ramps up nicely at the end of the travel.

I also really like the Knock Block steering limiter, which has been essential in previous generations to stop the fork crown slamming into the downtube. With the new Slash, this is no longer needed but it still prevents brakes and shifters whacking your top tube in a crash. This also allows you to run nice tidy cables and brake hoses without worrying about them getting damaged in a crash when the bars try to fully rotate. The turning radius on the Knock Block has been increased over the previous generation, it also comes with a replacement chip to allow for complete removal, if you feel like trying to channel your inner Brandon Semenuk!

2021 trek slash 8 alloy
While it can totally monster-truck its way through the chunder, it’s the Slash’s agility that makes it such a good all-rounder.

Any other changes on the horizon?

I’d like to try and squeeze a 200-210mm travel dropper post in there if possible, just to get the saddle more out of the way on some of the really steep sections. To help minimise rock strikes I’ll probably switch to 170mm crank arms. Only the 175mm arms were available at the time of launch, and while they haven’t been a huge issue, any reduction in your pedals smacking into rocks is a plus. I’ll probably switch to a Wolf Tooth dropper remote at some stage too.

In the longer term I’d love to give the Vorsprung Secus a go on the Lyrik Ultimate. The Secus is essentially an enlarged negative air spring that actually sits outside of the fork at the base of the lower leg. It’s supposed to give your air fork a “coil like feel” in the top 2/3rd of the travel whilst providing a more gentle ramp up at the end of the travel.

The only other more immediate change will be an Absolute Black oval chainring, as I bloody love those things. I’ve used them for years now on almost every bike I own, I find they really help smooth out power delivery on steep, loose pinches, which helps prevent a loss of traction at a critical moment. I’ve ridden them for so long that normal round rings feel a bit weird!

2021 trek slash 8 alloy
Ben’s custom Slash 8 as of right now, though being the bike nerd he is, there are plenty of tweaks and upgrades on the horizon.

Ben’s Custom Trek Slash 8 Specs

trek slash 8 trust shout linkage fork
It certainly gets plenty of looks on the trail!
2021 trek slash 8 alloy
Yieeeewwwww!

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