Eurobike 2012: BH Aerolight

The BH Aerolight tri bike. Photo: Aaron Hersh

A new semi-integrated tri bike with unique brake mounts from the Spanish bike maker.

Instead of completely integrating the aerobar attachment system, BH uses a standard steerer tube to mount the bar. The top tube is raised to eliminate the gap behind the stem when in a low position and BH created a swooping stem to blend smoothly with the frame. Shaped steerer tube spacers can prop the stem 45mm above the head tube, just like a typical stem.

The geometry chart BH has on display at Eurobike lacks stack and reach numbers, the best way to assess a tri bike’s fit characteristics. Standard frame dimensions are available and they indicate that the Aerolight fits similarly to BH’s current GC Aero tri bike. Although this conversion is imperfect, top tube and head tube lengths suggest that this bike fits moderately upright riding styles instead of forcing triathletes to prop aerobars high to accommodate realistic riding positions. (Geometry chart is viewable in the photo gallery or here.)

BH uses two bolt bosses on the top tube just behind the stem in addition to two standard frame water bottle mounts to give riders the option of adding aftermarket hydration. The Spanish company has plans to create a hydration or storage accessory capable of mounting to the top tube to fill the gap when riding with a tall stem position, but they do not have a finalized design.

BH’s R&D manager Peter Shigo started to design the bike with a specific bottom bracket standard in mind—BB386, which is quite broad—in order to achieve lateral stiffness goals. They didn’t consider other BB types. Aerodynamic features of the bike were designed outward from that fixed characteristic.

After completing the design of the Aerolight, BH wind tunnel tested a prototype version with the precise shape used in the final bike at the Faster wind tunnel in Arizona. The frame shape was not altered or adjusted because of this test, it was simply “validation,” says Shigo.

Borrowing a strategy from Cervelo, BH blunted the downtube where the water bottle mounts to shroud the bottle to improve performance in real-life racing conditions, not test conditions without bottles mounted to the bike.

As you can see in the photo gallery, the rest of the downtube is a narrow airfoil with a protrusion from the downtube that acts as a front wheel cutout. The headtube is quite broad, again for stiffness, and uses a 1-1/8th headset. Shigo says the frame was designed “with the UCI in consideration,” and all the tube shapes conform to the 3:1 ratio mandated by cycling’s governing body. The chain stays flare out wide from the seat tube to shield the uniquely adaptable rear brake mount.

Instead of using a single brake mount, Shigo included multiple mounts so the Aerolight can use several different brake styles. The display bike and all complete bikes planned for 2013 use TRP V-brakes, but the frame can also accommodate typical road-style calipers.

“The brake mounts give freedom to use practically any brake on the market,” says Shigo. “During the development cycle, there were interesting brake offerings that came out, specifically Magura’s RT 8TT hydraulic caliper, that we wanted to have the ability to accommodate. [Multiple brake mounts] gives flexibility in the price-point while still giving the consumer the ability to build the bike that they want.”

The downside to this versatility appears to be primarily aesthetic—unused brake mounts become unsightly open holes—and shouldn’t impact the bike functionally.

BH will sell the frameset and four complete versions of the Aerolight in the US next year with build kits ranging from extremely high-end to fairly high-end. The GH Aero frame will remain the foundation of their lower priced tri bikes.

http://triathlon.competitor.com/2012/08/gear-tech/eurobike-2012-bh-aerolight_60775