This article originally published on BikeRadar
While team riders Thor Hushovd, Taylor Phinney, and George Hincapie will use the additional comfort and handling stability over the cobbles, the new bike will likely prove well suited for just about any rider looking to cover lots of distance quickly, but without beating themselves up.
Key features on the GF01 include use of BMC's Tuned Compliance Concept, as well as a new concept called 'angle compliance'. As on the TeamMachine SLR01, the new GF01 features specially shaped tube sections to promote directional flex over bumps. This is most notable in the seat stays, which are dramatically flattened from end to end.
BMC frame designers also acknowledge that from a purely geometrical point of view, merely flattening particular tube sections isn't as effective as it could be — after all, a triangle with one straight side that's thinner than the others still doesn't want to compress. Therefore, BMC have built in additional kinks at the top of the seat stays, just ahead of the rear dropouts, and just above the fork tips to act as pseudo-pivots that flex under load.
Moreover, the rear dropouts are intentionally offset rearward — creating a short moment arm — that further promotes flex when hitting bumps.
The giant chain stays transmit more road buzz but that's apparently what the BMC team wanted — a stiffer feel in normal conditions but a softer ride when the going gets really, really tough
TCC and 'angle compliance' are built into the 27.2mm-diameter carbon seat post, too, which will be available in three setbacks — the standard 18mm plus 3mm and 30mm options – each with its own specific lay-up schedule and flex pattern. Taken in total, BMC claims a 40-percent improvement in comfort for the GF01 over the SLR01 — a bike already we found to already be unusually comfortable for a race bike.
Engineering types may view the built-in flex points as areas of focused stress, but when asked by BikeRadar BMC frame engineer, Jonas Müller, insisted it's not a concern, saying GF01 frames have exceeded all industry standards and in-house tests, and moreover, there is no rider weight limit. BMC also offer a five-year warranty on the frame and fork with an optional crash replacement program for top-end models as well.
More comfortable, stiffer, but with tweaked geometry
BMC of course claims that there is no effect on overall frame torsional rigidity or drivetrain efficiency, either. In fact, BMC says internal testing shows the GF01 to actually be about 20-percent stiffer than the SLR01 at the bottom bracket and more than 30-stiffer in full torsion thanks in part to the BB86 press-fit bottom bracket, the larger 1.5in lower diameter on the tapered steerer tube (the SLR01 is 1.125in), and the correspondingly bigger down tube and seat tube profiles and more widely spaced chain stays.
Claimed frame weight for the GF01 is still less than 1,000g for a 54cm size — a penalty of less than 100g compared to the SLR01.
As is typical for this genre of bike, BMC has slightly tweaked the frame geometry for additional stability and slightly more relaxed handling. Changes relative to the SLR01 include a slightly slacker head tube angle (by about half a degree), extended head tubes by a modest 7-12mm, longer front and rear centers, and 2mm of additional bottom bracket drop though that's essentially offset by the bigger tires (more on that later).
Keeping in mind the cumulative effect of all the changes — the fork axle-to-crown length is longer, too — the effect on stack and reach are a little more significant with 8-16mm decreases in reach, and 14-19mm boosts in stack depending on size. As a result, the GF01 will offer slightly more relaxed handling but also a modestly shorter and more upright fit than BMC's more race-oriented options.
T's crossed, I’s dotted: DTi, chain watcher, and tire clearance
BMC continues the so-called 'gran turismo' theme with the ancillary features and even the standard component spec. The new DTi (Dual Transmission Integration) routing setup is designed for easily maintained external cable routing but the stops are removable (cosmetic covers will be included at production) for use with internally run Shimano Di2 or Campagnolo EPS wires. At least in the case of Di2, the battery is fixed to a dedicated mount beneath the chain stay.
The bottom bracket sports a rigidly mounted integrated chain catcher with interchangeable bits that will work with standard or compact double cranksets as well as triple setups.
One of the most impressive features on the GF01 is clearance for up to 28mm-wide tires, which will come as standard equipment on complete bikes, while still using standard-reach brake calipers. BMC raised the brake mounting holes relative to the rim as is typical for this sort of design goal but they're also cleverly angled, too.
The rest of the spec is similarly well thought out, such as tubeless-compatible Easton EA90 RT rims with 22mm-wide profiles, wider and more generously padded fi'zi:k Aliante saddles, and compact-bend Easton handlebars.
Total claimed weight for a complete GranFondo GF01 with Shimano Ultegra Di2 is just 7.38kg without pedals.
BMC isn't ready to release retail pricing on the GranFondo GF01 just yet – the company wants to wait until it's presented to dealers in a couple of weeks — but BMC road product manager Andrew James tells BikeRadar that it will be comparable to the TeamMachine SLR01.
Complete bikes in various configurations as well as a frameset option will be available following the autumn trade show season.
Check back to Cyclingnews for an upcoming first ride review of the new GranFondo GF01.