Olympic Bike: Laura Bennett’s BMC TMR01

Published August 3, 2012 07:19PM

This prototype aero road bike from the Swiss bike maker is tuned specifically for the London Games.

Laura Bennett is one of the best swimmers in the ITU pack. With her elite open-water speed, she is likely to face the wind during the early stages of the ride and might even set herself up for a breakaway. On the utterly flat bike course, riding solo means aerodynamic drag can have a bigger influence on her performance than many other athlete and she has just the right bike for these conditions.

At the Tour de France last month, BMC unveiled the TMR01, this entirely new aero road frame designed with some of the concepts in their TM01 tri bike. Bennett got one of the very first frames and has it built for the Olympic triathlon. The tubeshapes behind the head tube look identical to the tri bike. They have the same tapered shape and “tripwire” dip on the leading edge.

Aerodynamic tubing on road frames is nothing new, but the TMR01 also has a feature that other aero road bikes lack: and integrated fork and front brake. Like BMC’s triathlon bike, its uses a V-brake hidden within the fork. A molded carbon plate bolts on to the front of the fork to shield the caliper. The upper segment of the fork stretches up to block the headtube. The front brake cable and housing route through the top of this fairing. BMC hid the rear caliper—also a V-brake—beneath both chainstays. Its cable routes through the top of the headtube on the non-drive side and the cluster of Shimano Dura-Ace Di2 wires route through the same hole. The rear shift wire emerges behind the seatstay so almost none of it touches the air.

The components used to create her fit were carefully chosen to maximize her comfort in the aero position. ITU rules state that the aerobar tips cannot extend past the longest point of the shifters. Road drop bars have evolved in the past few years to have a shorter horizontal reach distance from the clamp to the tip of the bars. This change brings the shifters closer back to the rider, which limits the aerobar length an athlete can ride. The tiny aerobars used by most ITU racers provide very little surface for the forearms to rest, so the rider must support their own weight muscularly rather than comfortably leaning onto their forearms.

Team USA mechanic Joe Santos confirmed that Bennett specifically selected her Zipp bar and stem combination to maximize the length of her aerobars. Instead of using a new-style drop bar with a 10cm stem, she opts for an 8cm stem with a traditional long-reach bar. As a result, her aerobars—which look like Hed Clip-Lite clamps with Zipp pads and S-bend extensions—are nearly two centimeters longer than the other athletes’. They are wrapped with electrical tape instead of traditional bar tape, and the right shifter has two Velcro patches with nothing attached. Perhaps she will use them to carry something on race day. Her stem is positioned in the negative 6-degree orientation and is propped by three centimeters of riser.

Her TMR01 rolls on Zipp 303 wheels with 23c Vittoria Corsa EVO CX tubular tires glued to the rims. Santos says she plans to ride 100-105 psi if it is dry and will go all the way down to 90psi should it rain. She is riding a Shimano Dura-Ace SRM power meter and uses a SRM Power Control 7 computer mounted between her aerobars.

Santos recommended that all the athletes use cassettes with gears tightly clustered instead of wide-ranging options such as an 11-25. Bennett and the other Americans are on 12-23 cassettes with 53-tooth chainrings. The flat course makes it highly unlikely that they will need a climbing gear or the bigger gears required to hit 40+ mph. “Quicker, tighter shifts” was Santos’ reasoning for recommending these tight gearing ratios.

Bennett was one of the first athletes to adopt an ISM Adamo saddle, and she still rides one. Her crank arms are 172.5cm and she opts for two bottle cages on the downtube.