Test Marathon-Fully 2023: BMC Fourstroke 01 Two

The cross-country and marathon scene is faced with a dilemma. On the one hand, wider tyres, retractable seat posts and, above all, more suspension travel on current models mean that mountain bike race bikes go downhill faster. On the other hand, the modern development approach inhibits uphill propulsion due to the higher weight. This dichotomy makes the purchase decision difficult for many race bikers.

BMC Fourstroke 01: Trimmed for the descent

But that brand new BMC Fourstroke 01 gave rise to hope after our laboratory check. The key data: BMC combines classic 100 millimetre rear and front travel and an integrated dropper post with a downhill-oriented geometry. Weight: 10.5 kilos in size L - for the simplest equipment variant Fourstroke 01 TWO (8999 euros), mind you. For comparison: In the same price league, the Scott Spark RC with 120 millimetres of travel weighs 470 grams more. The narrower stanchions of the Rockshox SID SL fork alone save 162 grams compared to the more stable 120 mm SID.

But a lightweight mountain bike alone is not enough to bridge the gap between uphill and downhill qualities. The engineers at BMC were aware of this and have completely redeveloped the Fourstroke 01. The obvious first: Compared to its predecessor, the shock is no longer located in the frame triangle, but clamped under the top tube. To optimise the bike for long distances, there are two mounting points for bottle cages on the down tube. In addition, the Swiss have developed the first standard Vario seatpost that lowers automatically at the touch of a button. In terms of geometry, the development team gave the BMC Fourstroke 01 a radical longer/flatter treatment in order to remain competitive downhill even with less suspension travel.

The BMC Fourstroke 01 also climbs steep ramps

So much for the theory. In practice, the test candidate leaves no doubt about the intended area of use. The riding position seems to be made for racing on winding cross-country courses. The steep seat angle and the short stem place the rider in a compact and propulsion-orientated position on the BMC Fourstroke 01 despite the generous reach. There is also sufficient pressure on the front wheel. This allows you to climb steep ramps on the Fourstroke without having to actively fight against a rising front end. The rear suspension of the BMC mountain bike works sensitively under chain tension and generates a lot of traction. In terms of efficiency, too, the suspension doesn't let anything get in its way. Disturbing bobbing? Not a thing. However, if you want to eliminate the last drive influences on tarmac or for sprinting, you can tighten the fork and damper at the same time using the Twistloc twist grip. This leaves nothing to be desired on the climbs.

And what about the downhill performance of the BMC Fourstroke 01?

The 100 millimetre travel requires a little more sensitivity than is the case with MTB race bikes with 120 mm forks. The rear triangle, on the other hand, offers generous suspension travel and responds sensitively to subtle bumps. This makes the rear feel more potent than the 97 millimetres would suggest. Thanks to the long wheelbase and the 67 degree steering angle, the BMC Fourstroke 01 stays on track even at high speeds - more reliably than most of the other 100 millimetre full-sussers on the market. Nevertheless, the BMC race bike is by no means sluggish downhill. Quite the opposite. Thanks to its short chainstays, the newcomer masters quick direction changes and winding trails with ease. The only drawback: the in-house Autodrop seatpost only offers 80 millimetres of travel. Other models offer more freedom of movement here. Otherwise, the downhill performance is also fully convincing.

That would probably solve the dilemma. Cross-country and marathon riders no longer have to choose between low weight and solid downhill performance. They will find a sensible compromise in the development approach of the BMC Fourstroke 01.

Test summary by Max Fuchs, BIKE test editor:

Light, fast and innovative - that sums up the core competences of the BMC Fourstroke 01. The Swiss company has successfully improved the geometry and riding characteristics compared to its predecessor. However, the price of 8999 euros - for the simply equipped entry-level model - is disproportionately high.

Alternative for down-country riders:

For fans of the down-country trend, BMC also offers the Fourstroke in an LT version with 120 millimetres of suspension travel. Prices: 4499 euros to 11999 euros.

BMC Autodrop dropper post in detail

Telescopic seatposts are one of the most ground-breaking inventions in mountain biking. Will BMC succeed in revolutionising the revolution with its automatic function?

Integrated dropper posts are nothing new in BMC bikes. Even in the old BMC Fourstroke, the seat tube and seat post unit could be lowered by 80 millimetres at the touch of a button - just like a normal dropper post, only integrated. In addition, the so-called RAD Tele post used an oval design to prevent twisting, even without an internal guide. At first glance, you would expect the same technology in the new BMC Fourstroke 01. But far from it. What happens on the inside is a world first.

Autodrop - the technology behind the new edition

The name already suggests what the BMC engineers have come up with: The seatpost lowers automatically at the touch of a button. This means that the rider no longer has to take pressure off the pedals to move the seatpost downwards with their own body weight. This is made possible by an air tank in the down tube, which can be filled via a valve above the bottom bracket. Maximum pressure: 14 bar. When the two-stage lever is fully depressed, air escapes from the tank into a reservoir at the lower end of the seatpost. Under this pressure, a spring contracts and the seat post disappears into the seat tube. When the lever is pressed halfway, the air escapes from the reservoir and the spring pushes the seat post back up again. According to our measurements, the tank loses 0.08 bar per stroke. With a minimum pressure of 2.5 bar, the Autodrop in the BMC Fourstroke 01 theoretically allows 144 runs before air has to be refilled.

Pressure drop of the autodrop support in cold weather

But the reality is different. Especially at temperatures below 10 degrees, the pressure drops significantly faster. During our tests on Lake Garda, the system required refuelling after just one day of testing. If the tank has lost all of its air, the support does not engage either at the top or bottom and the Fourstroke becomes unrideable. The function is criticised for the speed at which the support is lowered. In the heat of the moment, mounting and lowering is often faster than the lowering mechanism of the Autodrop. In addition, the support only lowers if the remote lever remains pressed during the process.

Even if the new system still has its weak points, it remains an absolute novelty, inspires technology freaks and still gives BMC bikes a USP over other manufacturers.

Technical data and notes BMC Fourstroke 01 Two

Manufacturer information

• Price: 8999 Euro >> available here
• available from specialised dealers
• Frame material: Carbon
• Frame size: S / M /L (tested size) / XL (48 cm)

Measured values

• Weight without pedals: 10.46 kg
• Frame weight: 2286 g
• Weight of wheels: 4046 g
• Acceleration wheels: 2943 kg x cm²
• Handlebar width: 760 mm
• Frame rigidity (absolute): 40 N/mm

Equipment

• Wheels: DT Swiss XR 1700
• Tyres: Vittoria Mezcal Graphene 2.0 XC-Race 29 x 2.35
• Fork: Rockshox SID Select+ Remote
• Shock: Rockshox SID Luxe Select+
• Spring travel front/rear: 102/97 mm
• Brakes: Sram Level TLM / 180/160 mm
• Gear system: Sram GX Eagle AXS 1 x 12
• Gear ratio / bandwidth: 34; 10-52 / 520 %
• Telescopic post / stroke: BMC Autodrop / 80 mm

Valuation

• Driving behaviour uphill: 27 from 30
• Chassis efficiency: 22.5 out of 25
• Rolling resistance: 11.25 out of 15
• Weight: 20 from 25
• Inertia impellers: 10.5 out of 15
• Bottle cage: 8 out of 10
• Driving behaviour downhill: 27 from 30
• Front suspension: 8 out of 10
• Rear suspension: 12.75 out of 15
• Saddle retractability: 10 out of 10
• Brakes: 7 out of 10
• Tyre grip: 12.75 out of 15
• Driving stability: 2 out of 10

TOTAL UPHILL: 99.25 OUT OF 120

TOTAL DOWNHILL: 79.5 OUT OF 100

• Other: 23.75 out of 30
• Ease of maintenance: good

Bike test rating*: very good - 202.5 out of 250 points

*The BIKE judgement reflects the laboratory measurements and the subjective impression of the test riders. The BIKE judgement is independent of price. BIKE judgements: super (250-205 P.), very good (204.75-170 P.), good (169.75-140 P.), satisfactory (139.75-100 P.), with weaknesses, unsatisfactory.