Shu, who was created by Atum and is the primordial God of air, is our ultra-light road race concept bike. It was designed and built around one of our sponsored athletes.

The Request
Our professional triathlete needed a race-dedicated bike. The stakes are high in the bike stage of a triathlon, which amounts to nearly half of the total race time. Elite athletes are generally allowed to draft, and so ride similarly to a normal road race. He wanted a bike which was responsive and technically capable to attack and pedal through corners. He needed a bike which was stiff, yet superlight- and a bike which would allow him to make a solo break and still have strength left in his legs for the final run stage.

The Task
This riders demands could not be met by "standard" frame geometries. Road bike position is not aerodynamic enough whilst time-trial bikes are both tough to handle in a peloton and back-crippling before the final triathlon leg - the run. We needed to find a compromise where a steeper seat-tube angle was allied to predictable handling: where the rear end was responsive to power but dampening of road-shock; where the steering was precise but shrewdly stable; and where no unnecessary weight would be tolerated. 

Above: We really have to be careful that this uber-light-weight steed doesn't float away on a breeze

The Bike
There are two ways that we can make you more aerodynamic- either flex you more at the hip or move your seat forward over the bottom bracket whilst maintaining the same hip angle. In this case the hip flexion would put too much strain on our triathlete's hamstring muscles and hence affect his run performance, yet a time-trial geometry was not wanted for group riding. So we did something cunningly in-between. We tipped him forward a few degrees, so that his centre of gravity was optimized nearer the cranks, and adjusted the steering geometry with a fractionally slacker head tube angle. This was designed with a pair of Easton’s superlight but super-rigid forks in mind for accurate but stable handling. We tucked the rear wheel right in to re-balance his weight over the bike and thus shortened the wheelbase to improve directness of steering. We used a triangular and fractionally sloping double-butted toptube to improve torsional strength and weld contact area onto the headtube. This allied to an oversized double-butted downtube results in a more rigid ride when out of the saddle to sprint. We neatly tucked the rear brake cable into one of the lower faces of the toptube to minimize snag-risk in the transition area.

We used double-slotted rear-facing key-hole slots for the seattube clamp for better aerodynamics and increased clamping surface, and added a front derailleur braze-on to the double-butted seattube for precision and lightweight. A traditional bottom bracket drop of 70mm ensured plenty of clearance for aggressive pedalling through corners.

We had some difficult decisions to make about the rear triangle. A more compliant rear end might be wasteful of sprint power, however too rigid and we would tire our athlete unnecessarily before the run. So with a fractional and considered weight penalty we opted for the best of both worlds. In order to ensure optimal power transfer, we designed bespoke seattube-chainstay fillets to improve bottom bracket rigidity when pushing hard. These encourage the rear drive unit to function truly as one where standard chainstays may allow the rear axle to torsion- and hence lose power.

This freed us up to use a more compliant seatstay solution. We agreed that we would use curved seatstays, however before committing to the more commonplace downwards curve, we decided to analyze the forces placed on these parts. In particular the small amount of brake deformation which occurs in smaller diameter seatstays will tend to draw such a curve even further downward, effectively encouraging the rear wheel off the ground! So the pragmatic solution was a set of reverse radius narrow seatstays, compliant vertically to attenuate some road-shock, yet tending to lengthen the rear triangle and hence push the rear wheel onto the road under heavy braking. This rear triangle configuration allied to the machined Atum22 dropouts would be light, power-sparing, and comfortable.

The bike was suitably built up with a range of lightweight, high quality components; the groupset is SRAM’s new road group, Force; Extralite wheels are extremely light and surprising stiff considering the weight; the bars and stem are both Easton.

The Result
The Shu's request list was not going to be easy to meet. But we welcomed it into our studio before addressing each design factor face-to-face. The race-stiff frame weighs in at a respectable 1380grammes.  The total bike weighs in at a podium beating 6.2kg!

It delivers power when needed, and is particularly rigid when sprinting out of the saddle. It gives the triathlete the edge with its aggressive aerodynamics without compromising group-handling and stability. And it delivers all of this in a way that spares him vital energy for the final leg of his event.

Does it do the job? Let the proof be in the pudding! Have your cake, eat it, and still win... easy!