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BMC’s Fourstroke has proved itself the be one of the best full-suspension mountain bikes when piloted by the likes of Absolute Absalon-BMC team riders Pauline Ferrand-Prevot and Jordan Sarrou who won the 2020 XCO World Championships followed by Tom Pidcock who dominated at the men's cross-country Olympic gold in Tokyo aboard an off-sponsor unbranded Fourstroke.
Part of this success is down to the fact that the Fourstroke is one of the more radical cross-country mountain bikes. So what happens when you bolster its trail capabilities with a downcountry spec, slacken it out, and top it up with an extra 20mm of travel.
Design and aesthetics
The frame itself has a very aggressive and purposefully low-slung shape. The shapes have a bit of a brutalist nature to them with their angular shapes and monochrome color palette. The twin-link suspension uses compact rockers connecting the front and rear of the frame and delivering 120mm of travel.
As the frame architecture has simply been lifted and tweaked from the XC race version, much of the geometry numbers are shared between the two bikes. It's still got a low stack and short chainstays, however, the additional extra travel has had some influence. The Fourstroke LT is a degree slacker for a progressive 66.5 and less progressive 74.8 degrees for the head-angle and seat angle respectively. The effective top tube stays the same at 607mm (medium) but the slackening has cut 5mm off the reach, luckily the Fourstroke was already generously measured here so it still has 440mm (medium) of reach. The medium LT version does lose an additional 10mm from the stem length too as it's specced with a 50mm, rather than a 60mm stem. Finally, the bottom bracket gets a bit of a hike up with the Fourstroke 01 LT featuring a bottom bracket drop of 35mm, still within the realms of acceptability.
The frame features an integrated fork stopper to stop the bars from spinning and causing damage in a crash and the cable routing feeds into the underside of the downtube rather than the headtube for simplicity. There are built-in chainstay and lower link protectors, although no downtube protector which I think is as equally important to protect from rock strikes.
In a move more akin to road framesets, BMC has integrated the seatpost into the frame. The RAD integrated seatpost has the internals located within the frame and uses an oval shape post. The result is a very clean look but it does mean you can’t spec your own choice of dropper. Saddle height is still adjustable, using a bolt low on the seat tube and is no more complicated than a regular seatpost. It only has 80mm of extension which on an XC bike would be enough however on a 120mm ‘downcountry’ bike with a 66.5-degree head angle it seems a little short. It would have been nice to see at least 125mm for that little extra clearance.
There is more to the integrated seatpost than meets the eye too, BMC has included compatibility for its Autodrop dropper system, a design that uses compressed air to drop the saddle without the rider needing to manually push it down by sitting. Autodrop is not currently commercially available but has been tested on the World Cup circuit since 2019.
The Fourstroke 01 LT comes in two build options, one or two. Our test bike came equipped with a mechanical groupset, however, for 2022 the Fourstroke 01 LT One will come equipped with SRAM’s GX Eagle AXS Drivetrain. The newer spec will also come equipped with a DT Swiss XR 1700 Wheelset, rather than the Mavic Crossmax Carbone XLR here. The bike rolls on Maxxis Rekon 2.4in EXO tire and slowing down is handled by SRAM’s Level TLM brakes with 160mm rotors (160/160 S-M, 180/160 L-XL rotors), I'm not sure why BMC hasn't just specced 180mm rotors on all the sizes though. A neat 50mm BMC stem and 760mm carbon bar takes care of the cockpit and a Fizik Antares R7 offers a perch on the climbs.
Suspension is from Fox, upfront there is a Fox Float 34 SC Performance Elite fork and a Fox Float DPS Performance Elite rear shock. Both suspension units can be controlled at the same time using a handlebar-mounted lever, switching between open, climbing, and full lockout. While I like the manual suspension control at the flick of a switch, I hate that it's mounted on top of the handlebars. Handlebar space is at a premium these days, but it's really worth integrating it below the bars, like Scott’s Twin Loc system, out the way of damaging itself or the rider.
On the trail, the Fourstroke 01 LT’s geometry feels excellent and plenty capable with sure-footed confidence on descents. We dropped into legitimate EWS trails in an attempt to shake its position yet it attained its composure superbly. The front triangle feels stout and precise and the rear tows the line as you punch the bike through rock gardens and through berms. In fact, the only real restriction was the 80mm dropper post which really limited our ability to be dynamic on the bike and get the weight back on technical jumps and fly-offs, that said we were pushing the bike way beyond its remit and on regular trails, it wasn’t as much of an issue. Considering the push for capability in the downcountry sector, and the limiting fact that the post is integrated, it would have been nice to see a more drop as there is no possibility of upgrading at a later date.
Despite setting the bike up in accordance with the sag gauge on the frame, the rear suspension feels reluctant to offer up travel and it never gave us much in the way of small bump plushness. While some riders may prefer a bike that feels more supple and trail bike-esque, the Fourstrokes rides like a bike that’s going up a weight class, it feels like you are under-biked but without the shortcomings of actually bringing a knife to a gunfight.
Leveraging the suspension's tautness to enhance the fast race bike characteristic is one of the really addictive elements of the Fourstroke. Providing a rigid feeling under pedaling load explodes the bike forwards and makes the bike feel poppy and alive when sprinting, cornering or hopping.
Combine the suspension characteristic with a 34mm legged fork, large 2.4-inch Rekon tires, and a stubbier cockpit to produce a bike that really rewards hard and fast riding. Tackling root-strewn trails and chatter sections become smoother the more blurry the trail is below you as the bike's stiffer suspension setup refuses to get sucked into holes. As long as the trail isn't so steep that the saddle interferes, the Fourstroke is a precision tool when it comes to brave mid-trail maneuvers too, using speed to gap technical sections without a second thought rather than brake and navigate. The result is the faster you ride, the more speed you carry, and repeat. This gives the Fourstroke LT a one-upmanship style where even on casual rides you are hitting warp speeds and vying for personal records on every trail you point it down.
There is a limit though, encouraged into rowdy riding, the fork can be pushed beyond its comfort zone. On higher force impacts we did notice a couple of occasions the fork could flex causing it to stick or bind. This is a shame as we found the rear suspension felt better the harder you push.
Climbing is impressively efficient although less of a spectacular affair. The downcountry-fication of the Fourstroke format and slackening of the seat tube doesn’t seem to have hampered the climbing grunt as we cleared a number of really technical climbs that up until the Fourstroke were an e-MTB only affair. The weight is impressive at 11.3kg (medium) and paired with the taught suspension really gives the Fourstroke 01 LT an explosive feel when pedaling.
The Fourstroke is a tricky one to decipher. It certainly benefits from its cross-country roots, the Fourstroke 01 LT hasn’t forgotten any of the snap and efficiency that makes sorted cross-country bikes really great to ride. It bolsters a whole bunch more capability with the slacker geometry but keeps the lightweight and playful character. The suspension enthusiasm for hard riding will suit riders who like to push the envelope when it comes to descending too.
The cross-country make-over certainly missed some bits and Fourstroke 01 LT can sometimes feel like a bike that wasn’t ready to go up a weight class. The biggest weak point is the dropper, while it wasn’t a problem all the time there was always a constant fear on steep stuff or on technical features that it would interfere with body position or suddenly give you a hunt out the front. It seems like a real oversight by BMC too, considering it has control to design a longer post that would take full advantage of the low-slung frame. The 35mm bottom bracket drop never felt tall, but it did leave me wondering how much better the bike would be if it was 10mm lower, the same can be said for the 74.8-degree seat tube.
The BMC Fourstroke raises an interesting point about the direction that downcountry bikes are going to go. While some brands are going downcountry specific, BMC isn't the only one dressing its XC bike in trail clothing, we found Specialized’s Epic Evo also successfully applies its XC frame to rowdier riding although Canyons Lux Trail tried the same thing with less success. I love the feel of a punch above its weight class XC bike and the Fourstroke 01 LT really delivers this but at the same time, it's hard to ignore the XC artifacts that are leftover in the evolutionary process.
Tech Specs: BMC Fourstroke 01 LT One
- Price: $8999 / £TBC / € 8,499
- Model name: BMC Fourstroke 01 LT One
- Discipline: XC/downcountry
- Head angle: 66.5-degree
- Frame material: BMC 01 Premium Carbon
- Size: S, M (tested), L, XL
- Weight: 11.3kg
- Wheel size: 29in x 2.4in
- Suspension (front/rear): Fox Float 34 SC – Performance Elite FIT4, 120mm/Fox Float DPS – Performance Elite, 120mm travel
- Drivetrain: SRAM X01 Eagle 10-52T 12-speed rear mech and SRAM GX shifter
- Cranks: SRAM X1 Carbon 34T chainset
- Brakes: SRAM Level TLM with 160mm rotors
- Cockpit: BMC MFB01 Carbon 760mm, BMC MSM01 50mm stem
- Wheelset: Mavic CROSSMAX CARBON XLR 30mm wheels
- Tires: Maxxis Rekon 2.4in WT, TR, EXO tires
- Seatpost: BMC RAD 80mm dropper post
- Saddle: Fizik Antares R7 saddle