The third generation SLR01 project began with known design targets and loads (such as braking force), but also had to conform to UCI rules and existing frame geometry. Conventional methods start with a shape calculation – allowing room for moving parts and so on, then a laminate calculation to decide on carbon materials and layup, and finally comes prototype testing.
BMC’s ACE Technology combines the shape and laminate calculations to simplify the process. It’s a supercomputer-based algorithm, co-developed between BMC and two other companies, one of whom has access to such a computer. BMC had 247 parameters to consider when creating a carbon frame. The second generation SLR01’s ACE Technology design passed through 34,000 iterations before arriving at the final one, adding disc brakes to the mix for the new bike increased that number by another 18,000.
At first glance, the new SLR01’s profile is very similar to the outgoing model. But look closer and the differences emerge, especially on the disc model. Asymmetry is key, with a shallow, almost squared non-drive side chainstay, opposing a taller, slimmer drive side, a wide PF86 bottom bracket shell, asymmetric seat tube and BMC’s customary, but slightly less angular down tube.
The disc fork is all new, and to account for the stress that is created above the front disc caliper, BMC ignored the convention of simply beefing it up with additional material, often around 50-60g, instead, they maintained the same tube thicknesses and altered the individual profiles of each leg, making them quite asymmetric. The fork is optimized for a 160mm rotor, and to avoid unnecessary mounting hardware, BMC created what they call a Direct Frontal Flat Mount for the disc caliper, with the bolts piercing the fork leg from front to rear, with no need for aluminum adaptors. The result is a disc-specific fork that’s only 18g heavier than its rim-braked equivalent, weighing a claimed 355g, including headset compression device.
Following the lead of last year’s Roadmachine, the Teammachine SLR01 has reduced the Crosslock brace inside the top tube and seat tube junction to a buttress. Hidden within is the 'No-Gap' seatpost clamp, which has an internal wedge, and eliminates any gaps between the seatpost and frame with its floating top cap. It’s adjusted from below with an angled 4mm hex bolt. The 195g D-shaped Compliance Post seatpost continues (15mm offset standard; 0mm option available), its flattened rear side allowing it to flex, and the lowered seat clamp extends its active length by 46mm.
Another Roadmachine feature is the ICS (Integrated Cockpit System) stem, which comes fitted to the top three SLR01 Disc models. The stem's lower cover channels the hydraulic hoses and Di2 cables into the frame for a clean look. The cockpit is as adjustable as any other, but sleeker, using proprietary two-part spacers with interlocking halves, allowing front end adjustment without removing hydraulic brake lines. The stem’s open faceplate accepts a slot-in mount for a Garmin and a GoPro or light.
BMC incorporated the Di2 junction box within the upper portion of the down tube, behind the head tube, where its controls and LEDs are easily visible and accessible, and it’s well protected from damage in transit or accidents.
Deciding that the current thru-axle options available were heavy, BMC created its own, which weigh 55g for the pair. They’re a conventional 12mm diameter with 6mm hex required for fitting and removal – one DT Swiss removable hex lever is provided. The racing team’s disc bikes will use an 8mm hex to save a fraction more weight, and because service will always be on hand. The 8mm thru axle socket wasn’t considered appropriate for the consumer market as not every rider carries an 8mm tool.
All that weight saving effort has resulted in a 54cm 2018 model SLR01 disc frame weighing 815g, which compares impressively to the 2017 rim braked SLR01 frame, which weighs 790g in the same size.
BMC’s performance figures show the new bike delivers around 10% more bottom bracket stiffness, and around 10% more vertical compliance, largely thanks to the lowered seat clamp. The torsional stiffness values are said to be the same. All frame sizes from 47cm to 61cm have a unique carbon layup, to give a consistent ride feel that’s well within a +/- 5% tolerance.
The BMC Teammachine SL01 Team Disc model will retail for $11,999 with availability expected in late July.
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Other BMC SLR01 Disc models:
SLR01 Team (Featured): $11,999
SLR01 One: $7,699
SLR01 Two: $5,299
SLR01 Frameset Module: $4,499
- Robin Wilmott
To read the full review, head over to Cycling News