Joining the new crop of shred-worthy XC race bikes, BMC has just announced their all new Fourstroke 01. Crammed full of all the latest advances that are meant to give their racers an edge, the Fourstroke 01 also has something most of its competitors don’t – an integrated dropper seat post.
However, you’d probably never realize it just by looking at it. Since it’s integrated, the post maintains a continuous profile that looks completely stealth.
It’s only when you realize that the post is actually oval instead of round that you start to realize it’s something special. Called RAD or Race Application Dropper, BMC claims it is the world’s first integrated XC dropper post – it’s definitely not the first integrated dropper so their claim all depends on what you consider XC. Regardless, it’s a very interesting feature – especially when you consider that it wasn’t that long ago that XC racers didn’t want anything to do with a dropper.
Perhaps the decreased weight of the RAD system had something to do with that, however. Thanks to the oval shape which allows for a 30% stronger (claimed) structure with less weight, the overall weight of the dropper is just 345g. To keep things simple, the post is completely mechanical and uses very low pressure (29 psi) which should improve the seal’s durability in the long run.
Limited to two positions (up or down), the post offers 80mm of travel. However, it does limit you to a 90mm saddle height range for any given size which can be adjusted like a conventional post and doesn’t require any cutting. That height range may be a bit of an issue depending on your fit though – I typically ride a medium with a 690mm saddle height. On this bike, the shortest saddle height for the medium is apparently 700mm. The given ranges are 655-745mm for the Small, 700-790mm for the medium, 740-830mm for the Large, and 770-860mm for the Extra Large.
To adjust the post, there is a low clamping mechanism just above the chain guide on the seat tube – this is apparently another benefit of the design since the clamping mechanism is at the bottom of the post, the clamping forces won’t affect the dropper’s performance as often happens with traditional designs.
In order to maximize every gram, the new frame includes fewer parts which should also improve durability. Now you’ll find an integrated headset, a new carbon upper link, optimized suspension hardware, a new super light thru axle at the rear, and a one piece rear triangle for a frame weight of 2180g with shock. Add in the RAD seatpost and hardware and you’re looking at 2525g, with complete bike weights as low as 10kg (22lbs).
Also, thanks to carbon work from BMC’s IMPEC lab, the frame offers 23% more torsional stiffness and 15% more stiffness at the bottom bracket. Combine that with their APS suspension system which has been tuned for XC racing with 100mm of travel, and the Fourstroke should be a rocket ship. The APS system utilizes a metric, trunnion mounted shock.
Elsewhere, you’ll find internal cable routing with a replaceable cable port cover behind the head tube that also doubles as a lightweight fork bumper. The housing has a full guide for the rear derailleur and brake through the frame to the rear swing arm, and there’s a large access window underneath the shock.
Designed for 1x only, the frame includes an integrated chainguide, and the frame includes a chainstay protector, co-molded stainless chain suck plate, and a lower link mud flap. The rear has also been reworked to allow for larger tires, now clearing up to 29 x 58mm (2.28″) rubber.
Other frame details include a PF92 bottom bracket, Boost 148mm spacing, a 44mm offset fork, post mount brakes, and a 38t maximum chainring.
Utilizing BMC’s Big Wheel Concept Race geometry, the Fourstroke moves to more progressive XC geo for more aggressive riding. Combined with a longer front end, you’ll now find a 67.5° head tube angle and a steep 75.5° seat tube angle with 429mm chainstays.
There are three different models to choose from, the Fourstroke 01 One, 01 Two, and 01 Three, or the 01 frameset. We’ll update when we get pricing.
