Some five years in development and introducing several novel features, Look’s ZED carbon monobloc crankset was one of the star attractions of Eurobike ’08. The most obvious of its innovations is the construction of the two cranks and their axle in one piece, which weighs an astonishing 360g. Not strictly new, since the principle has been long-established in BMX and low-cost cycles, it is nonetheless the first application using carbon composites, and has needed the development of an oversized bottom bracket design to provide the space required for installation.
The crank assembly is installed by being passed through the bracket orifice, the dimensions of which are sufficient to allow easy passage. The large diameter bearings are pressed in position by hand pressure from the outside, both sitting on aluminium inserts co-moulded into the carbon. A thread on the non-drive side insert receives a collar with pinch bolt that takes up slack and secures the whole assembly.
The crank moulding, which is hollow as can be seen from the pictures, gets around potential problems with inserts for attachment to a separate axle. It further adopts a new solution to the problem of pedal fitment by doing away with the usual threaded insert in favour of an indent moulded into the carbon matrix and shaped to accept a conical plug with three flats to prevent rotation. This is drawn into place from the back of the crank and secured with a plate.
The plug is machined with its own integrated pedal axle, which is apparently only available to fit Look’s own Keo pedal. By offsetting the centre line of the integral axle, Look have taken advantage of the three possible orientations of the axle plug to offer the three most common crank lengths in one moulding. The obvious drawback to the concept is that owners will have to use the Look pedal, athough there is talk of an ‘open’ patent on the system that will allow rival manufacturers to make pedals with axles that fit.
The other detail of note is the provision of holes in the spider to accept both standard 130mm BCD and compact 110mm BCD chainrings. The system will appear first on the 596 TT bike and is expected to migrate to other Look models as manufacturing capacity gets up to speed.