Fourstroke

BMC redesigned the Fourstroke platform from the ground up for the 2023 model year, positioning it as a dedicated cross-country and marathon race family. The chassis is built around an updated dual-link suspension layout and a heavily revised frame silhouette that prioritizes real-world racing practicality. Notable updates include guided internal routing that enters through an integrated fork stopper, alongside room for two water bottles inside the front triangle.

The generation splits its intent across two distinct travel brackets. Traditional configurations offer 100mm of front and rear travel for pure XCO racing, while the LT and R variants bump the travel to 120mm for aggressive marathon and light trail use. On the top-tier 01 frames, BMC integrates its proprietary Autodrop system, an automatic dropper post powered by a concealed air tank that lowers the saddle without requiring the rider to sit on it.

Build

Size

Stack	600mm
Reach	477mm
Top tube	623mm
Headtube length	101mm
Standover height	727mm
Seat tube length	470mm

Fit and geometry

The Fourstroke utilizes a highly progressive geometry for a cross-country platform, shaping a ride that is stable at speed but demands an active, forward-biased posture. A steep 76.7-degree seat tube angle places the rider directly over the bottom bracket, optimizing power transfer for steep climbs. This aggressive seated position is highly efficient but may feel abrupt to riders accustomed to more relaxed, rearward trail bike fits.

At the front, a slack 66.5-degree head tube angle provides crucial stability on steep descents. When paired with short 432mm chainstays, the bike maintains quick, responsive steering through tight switchbacks without feeling nervous at high speeds. The defining handling characteristic, however, stems from the bottom bracket drop. At 53mm on the 100mm frames, the exceptionally low center of gravity allows riders to aggressively lean into corners. The tradeoff for this cornering prowess is reduced ground clearance, requiring deliberate line choices and ratcheting techniques to navigate deep ruts and tall roots.

Builds

The Fourstroke lineup spans a massive price range, reflected in the stark contrast between the available builds. The entry point to the premium frame is the 01 THREE, which pairs the 100mm chassis with a RockShox SID SL Select fork and SIDLuxe Select+ shock. It relies on a dependable Shimano SLX mechanical drivetrain, SLX two-piston brakes, and DT Swiss X 1900 alloy wheels. Notably, this build skips the proprietary Autodrop system in favor of a standard X-Fusion Manic dropper post and a conventional alloy cockpit, keeping the price accessible while retaining the core frame kinematics.

At the opposite end of the spectrum, the R 01 ONE is an elite, 120mm-travel configuration built for uncompromising race performance. It features Ohlins RXC34 and TXC2 suspension, a SRAM XX SL Eagle Transmission wireless drivetrain, and SRAM Level Ultimate brakes. Rolling on DT Swiss XRC 1200 carbon wheels, this build fully integrates BMC's Autodrop seatpost and a one-piece carbon cockpit. The R 01 ONE represents the absolute ceiling of the platform's technology, demanding a premium price for electronic shifting, carbon components, and the automatic dropper system.

01 THREE

$4,699

Neon Red

R 01 ONE

$13,499

Carbon / Firestorm

Reviews

Reviewers consistently praise the Fourstroke for its exceptional pedaling dynamics and descending capability. The dual-link suspension is frequently highlighted for its traction on technical climbs, with one tester noting it is "wickedly efficient and grabs the ground under power" (Bike Rumor). On descents, the chassis feels remarkably stable for a short-travel bike, proving "unbelievably fast on rough terrain" (Whatsthebest).

However, this aggressive capability introduces a few distinct tradeoffs. On the 100mm models, multiple reviewers observed that the stock RockShox SID SL fork is "easily outridden by the frame" (Bike Perfect), suggesting aggressive riders might quickly find the limits of the front suspension before the rear end feels overwhelmed. The 120mm LT versions largely resolve this imbalance by pairing the frame with stouter forks.

The proprietary Autodrop seatpost on the 01 models also draws mixed reactions. While racers appreciate the energy saved by not having to squat to lower the saddle, the system requires regular pressurization with a high-pressure pump. Furthermore, its two-position design lacks the infinite adjustment of a standard dropper, which some riders found frustrating on undulating trails. Finally, testers frequently mentioned that the bike's low bottom bracket demands careful pedal timing to avoid strikes on rocky ascents.