What Happens When Disc Brakes Go Aero
Disc brakes have come to road bikes in a big way, but last year, they were primarily spec’d on adventure or all-road and endurance models. But the UCI recently began softening toward the technology; at the Interbike trade show this year, we saw discs making their way onto race models. One model, the BH G7 Disc, takes that trend a step further by marrying aero road with disc brakes.
In designing the next incarnation of the Basque bike maker’s G6 aero race bike, engineers identified the front caliper brakes as an area where they observed significant wind resistance. Removing that rim brake provided the most notable savings over the previous-generation G6, but engineers also reshaped the head tube; lowered the seatstays to help channel air through the rear end of the bike (which should also improve compliance); and added a new integrated seatpost clamp to save some watts, too. BH says that the combination of these changes outweighs the aero penalty of adding discs—which the company adds is only a penalty at specific yaw angles, a statement consistent with findings by Specialized in a separate wind tunnel exercise—and enabled the G7 Disc to “blow away the G6” in wind tunnel testing.
RELATED: Why Ride Disc Brakes on Road Bikes?
Perhaps even more impressive is that BH managed to design the G7 with a frameset 50 grams lighter than last year’s version of the superlight climbing bike, the Ultralight. (However, the complete bike will weigh more than the Ultralight because of the weight penalty of discs). Part of this can be attributed to BH’s new no-cut, “semi-integrated” carbon seatmast—it offers the adjustability of a seatpost, but reduces weight from a normal post.
Other key features: Thru-axles are shaping up to be the standard for disc road. The G7 Disc gets 142x12mm thru-axles front and rear, which should help prevent rotor rubbing and add stiffness to the ride. The bike sports asymmetric chainstays and, though it only ships complete in a mechanical configuration, the frame has internal routing for either mechanical or electronic shifting systems—and a Di2 battery can hide in the seatpost.
The G7 Disc will be available as a frameset for $3,399, or complete with an Ultegra mechanical group for $4,799. For that, you get some quality parts in addition to the smooth-shifting groupset: Shimano hydraulic disc brakes with 140mm rotors, a slippery Easton aero flat-top bar, Prologo Zero 2 saddle, and generous 25mm Vittoria Zaffiro Pro Slick tires.
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