Review: The 2019 BMC Fourstroke 01 One is a Purebred XC Race Rocket

You have a choice of three models priced from $6,500 to $11,000 USD for the range-topping model on test here that's decked out with a plethora of race-ready, gram-saving components like a Fox 32 Step Cast fork, SRAM X01 Eagle groupset, Level Ultimate brakes, and DT Swiss XRC 1200 Carbon wheels. There's also a frameset option if you want to keep your sponsors happy and deck it out with the right equipment.



Contents

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Construction and Features

Clean, sharp, and fast. Those are the words that spring to my mind when looking at the Fourstroke. It’s all huge oversized tubes with sharp creases and an air of purposefulness. I like it a lot. It has been totally redesigned, unrecognizable from the previous bike, and the result is that it has all the hallmarks of an absolute speed machine with looks that I have to agree are very satisfying. Enough about the looks, the Fourstroke has 29” wheels (naturally; find me an XC race bike that doesn’t) with 100mm of suspension travel front and rear and an integrated dropper post that provides 80mm of saddle height adjustment.

Weight will always be a top priority with a bike like this, and BMC has really counted every gram. The frame weighs a claimed 2,575g. To achieve this low weight it has used fewer parts, with the added bonus of also improving durability (fewer parts to go wrong) and has refined the suspension to shed 51g, used carbon fibre for the upper linkage saving another 40g, and developed superlight thru-axles in its Impec Lab to shed another 9g compared to the old bike.



More on the rad RAD dropper post, aka the Race Application Dropper to give it its full name. The overall weight is 345g, which the company claims is 100g lighter than any other rivals (a KS Lev Carbon is 419g with 65mm of travel). It’s cleanly integrated into the seat tube and provides 80mm of drop with two-position adjustment via a handlebar lever. The ovalized shape of the post is intended to both reduce weight and improve its resistance to unwanted flex. Saddle height can be adjusted via a small bolt near the bottom bracket, and you’re looking at 90mm of height adjustment so no cutting of the post should be required.

There are some smart details from the cleanly routed internal cable routing that is guided inside the front triangle, lower link and swingwarm for easier cable replacements, to a choice of two bottle cage mounts in the main frame and a mud protector cover over the link to protect the bearings from mud and water. Protecting the carbon chainstays is a small alloy plate, and there’s a chain guide for extra reassurance against dropped chains.

Crashes can and do happen at the top level, and because BMC wanted a straight down tube for maximum stiffness, it has integrated a fork stopper into the lower bearing race and downtube to prevent the fork crown from smashing into the frame. It does the same job as Trek’s Knock Block but is arguably a neater solution to the same problem. Other key details include a PF92 bottom bracket, 12x148mm thru-axle, and a 1x focused frame design.

Geometry & Sizing



Progressive is the keyword here. It won’t have escaped you that XC bikes have been evolving in recent years, driven by increasingly challenging courses (for the most part) and riders pushing their equipment to the limits. Bike brands have responded to the point where some of the latest machines are hugely impressive, not only between the tape but when you venture deeper into the backcountry.

As a result, the Fourstroke has the sort of numbers that might not look out of place on a mid-travel trail bike. The size large tested here has a 67.5-degree head angle, 75.6-degree seat angle, 465mm reach, and 1,180mm wheelbase with a 44mm offset fork.

The company’s BWC (Big Wheel Concept) has been designed to make the most of the 29'' wheels to provide “more control, more comfort, more confidence, and a whole lot more speed” to quote BMC. It’s about optimizing everything from the chainstay length (429mm across the size range) to the short stem lengths, slacker head angle and long top tube.

There are just four sizes to choose from, S through to XL, with 423 and 485mm reach respectively and the same head, seat tube angles and chainstay length. There’s the same 720mm handlebar on each size but stem length varies, from 50mm on the small to 60mm on the medium and large, and 70mm on the XL.

Suspension Design

Climbing

Make no mistake, if there’s a hill climbing competition in your local woods you’re going to be right in the mix on this Fourstoke. Holy smokes, this bike ascends quickly! That’s to be expected given how damn light it is, but if you do enjoy the climbs as much as the descents (yes it is possible to enjoy both), then a lightweight XC race bike is hard to beat.

There’s more to its climbing and general XC trail talents than just weighing bugger all on the scales. The suspension is on your side, too, with good small bump sensitivity to find traction on tricky climbs and let you keep on pedaling across the top of rutted dirt paths when hardtail pals are being bounced about. It’s a very efficient design, and it noticeably leans towards being quite progressive. That ensures there’s very little pedal bob, even when thrashing the pedals, and even if you leave it in open mode all of the time which you can do for regular trail riding, avoiding the need for constant lever fiddling.

For general riding, not racing, I preferred the open setting as you get all the benefit all of the time with no downsides. The handlebar remote lever does ensure it’s very to firm up the shock on-the-fly. But does it make any difference when climbing? To find out I did a couple of timed runs on different tracks and on the smoother ones, there was nothing in it. On rough tracks, I was quicker with the shock open, which was really no surprise as the rear wheel is better able to track the ground. And because it’s very progressive, there’s enough control that you don’t feel like you’re wallowing into the stroke.

For racers, the remote lever is going to be useful for those smoother trails where it just limits the suspension movement when you're really cranking on the gas, and it’s easy enough to change that you’re at no disadvantage. The difference between the two modes isn’t the night and day difference that some open and platform modes can sometimes be - it's very subtle.

The lever also operates the Fox 32 Step-Cast fork at the same time, but I got rebellious and disconnected it so I could leave it in the open model permanently. I never used the full lockout mode other than to check it worked - I can see it being useful if you have to ride pavement or maybe for the start of an XC race, which is usually a drag race to the first corner.

The geometry works in your favor too. While the long and slack approach obviously benefits you on the descents as we’ll discuss later, it’s an advantage on climbs, too. The position is very comfortable on long rides and climbs because you don’t feel cramped at all; you’ve got room to breathe, it’s well balanced, and the seat angle puts you in a good place over the bottom bracket, The handlebar is comfortably shaped, giving a very commanding feel over the bike and when you're pulling hard on them when climbing steep gradients.

You won't be surprised to learn that the massive down tube ensures the Fourstroke is extremely stiff when going flat out. No watts are wasted when you’re mashing the pedals up a climb or sprinting to get into a tasty bit of singletrack descent ahead of your rivals/mates/dog.

Descending

True, old-fashioned XC race bikes were terrifying on the descents, especially with a big side order of roots and rocks, but that's not the case anymore with bikes like the Fourstroke. It’s the most fun I’ve had on a bike with this little travel in probably ever! I can’t recall a bike that combines the stunning speed to let you boss the climbs so easily, yet be so incredibly capable on the descents no matter how gnarly the roots and rocks or the gradient might get.

The Fourstroke is a long way from the nervous and skittish descending abilities of classic XC race bikes which were fast going up and rubbish going down. Despite its low weight and skinny forks and tires, the BMC never felt nervous or fragile when really hammering it down a trail. Yes, you’re always aware of the fact you’re on a very lightweight bike with all the skinny weight saving accouterments, but the Fourstroke surprises and impresses with how well it masks that and just lets you actually enjoy the descents and have fun.

The head angle, wheelbase, and low bottom bracket height contribute to how planted the bike feels in corners. Sink the bike fast and hard into a bermed corner and once the tires have done their job of scrabbling for grip, the Fourstroke is so assured and certain that you’re left in no doubt that maybe you could carry a bit more speed into this turn on the next lap. There’s adequate nimbleness for tucking the BMC around very tight corners though, it's not lazy at all, and it’s easy to pop the front wheel for getting over bigger obstacles, stepped roots, and drainage channels. Changes of direction happen almost telepathically. It flows from corner to corner, the stiffness of the front keeping everything tracking in the same direction and resisting twanging twisting forces when you load it up into corners.

I found the Fourstroke manageable on every trail I rode it. You do have to choose your lines more carefully, but that’s true of most bikes but more critically with this small amount of suspension. If you want to be able to just plow headfirst into chundery terrain and expect the bike to sort out the mess for you, well, this probably isn’t the bike for you. Just go watch any video of Nino Schurter and watch the way he’s floating over the trail choosing the fastest and smoothest line where possible.




We're all sold on dropper posts, right? Well, except XC purists who argue against the weight and the fact they feel they don't need them, but in the real world, they're bloody useful. The RAD integrated dropper post is a revelation. It's super easy to operate with a light action and the 80mm drop is plenty adequate to give you a bit more room to throw shapes down descents and carve the corners with higher speeds. It transforms the Fourstroke from a pure XC race bike into a rad little trail bike for blitzing local trails. I’ve ridden this bike through a British winter and it’s been abused a ton, but yet it’s still working perfectly with no sealing issues.

The suspension travel isn’t much on paper and be in no doubt that on chunkier trails or dropping off drops, you’re reminded that 100mm travel isn’t a lot - you can't just send it into a rocky trail and expect the suspension to look after you. You've got to dial up the skill level, choose the right line, and work with the bike to get through rough sections fast. The available suspension is well controlled, though, with a high progression that means it ramps up very well to handle any big impacts. As for the Fox 32 fork, I was surprised with how relatively stiff and controlled this fork felt in even the rowdier trails, with any deflection very hard to detect. That said, I swapped to the new stiffer 32 during the review, which beefed up front-end steering and braking control a touch - review on that coming soon.

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How does it compare?

One of the best comparisons and a bike I’ve ridden is the Intense Sniper XC Elite, which matches the BMC with an all-carbon frame and 100mm of suspension, and both bikes have similar geometry numbers. The BMC is more impressive from a design and innovation standpoint, and also feels stiffer and more direct in its handling and power transfer.

A bike I’ve not ridden but which can be added to the consideration list is the Santa Cruz Blur that has also been redesigned with modern geometry, 100mm travel, and a lightweight all-carbon fibre frame. The Blur is quite a bit steeper and a little shorter than the BMC, which would likely limit is ability on technical descents, and a dropper post is an after-sales upgrade not integrated into the frame design.

Technical Report

SRAM XX1 Eagle Groupset: Simply flawless. The XX1 Eagle groupset was consistently reliable and has been hammered through the worst British winter conditions and just keeps on working sweetly. There’s all the range needed for taming steep tracks and hooning down fast descents, and the 34t chainring choice was never in doubt thanks to the wide-range cassette bringing the 50t sprocket into use in the steepest grinds.

Fox Suspension: Matching Fox suspension with Kashima coating gives the BMC a very premium feel and the damping quality is first class. The 32 SC fork impressed with a relatively high level of stiffness and little detectable deflection when pushed hard, and the Kabolt thru-axles save weight and look clean, though you’ll need to carry a multitool to remove them.

DT Swiss XRC 1200 Carbon wheels: Lightweight, just 1,411g thanks to an all-carbon rim with a 22.5mm internal width, and laced to DT 240s hubs with 28 straight pull spokes, the wheels felt really good. Obviously, the low weight helped get the bike up to speed but there’s just a hint of flex that prevents the wheels from feeling overly stiff and jarring in a way some carbon wheels can be. Hugely reliable hubs, too, and easy tubeless with different brands of tires.

RAD dropper: I’ve been really impressed with this dropper post. Its light action makes it easy to drop the saddle and the 80mm drop is adequate, more than enough for providing a bit more space for throwing shapes on the descents. Initial concerns about the reliability ebbed away over the months of testing, and now a good six months of riding through all sorts of crappy weather, the post is still working smoothly with no wag in the saddle. It can be easily serviced by lifting the dust wiper, wiping away any muck and adding a bit of fresh grease. This is something BMC recommends you do every 25 hours of riding. A more thorough seatpost cleaning should be conducted after 50 hours, which involves removing the post from the frame to grease the shaft.

Vittoria Barzo TR tyres: The Vittoria tires sure look smart with the tan sidewalls, and out the trail they provided low rolling resistance from the low profile tread pattern and good levels of grip in the dry. In the wet, I found the tires less willing to grip to damp roots and shiny rocks, and it really knocked my trust in them so I experimented with some other XC race tires during the test period.

Is this the bike for you?

If you’re an XC or marathon racer and seeking one of the fastest, most modern and well designed full-suspension bikes, there are few that reach such impressive heights as the new BMC Fourstroke. Away from XC racing, it’s a very capable and comfortable bike for general trail riding if your preference is for carrying speed everywhere with a lightweight package. It’s been designed to meet the expanding technicality of modern XC world cup courses but it’s right at home as a fast short travel trail bike.

Pinkbike's Take

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Posted In:
Reviews and Tech Reviews XC Bikes Bmc Bmc Fourstroke