Japanese manufacturer Shimano has released details of its new top-end Dura-Ace groupset, which now features 11-speed components.
The groupset was first seen on a couple of the professional riders' bikes at the Giro d'Italia during May.
In addition to adding an extra sprocket, Shimano's designers have concentrated on improved ergonomics and on set-up and maintenance. One key area of improvement from this side of things is in the front shifter.
For those obsessed with the scales, the target weight (we were given these numbers in February before final production parts could be weighed) was five per cent less than Dura-Ace 7900: Shimano want the 9000 Dura-Ace mechanical group to weigh less than 1,965 grams.
To fit in the extra sprocket, Shimano has chosen to increase the width of the freehub body by 1.85mm rather than reduce the thickness of the chain, sprockets and chainrings.
This does mean that older wheels won't be compatible, and that the new hub width is 131mm. Older cassettes can still be used with the new hubs by using spacers, and frames will simply be spread by an extra millimetre. Cassette options: 11-23T, 11-25T, 11-28T, 12-25T and 12-28T.
The rear derailleur will now happily run a 28-tooth rear sprocket despite being shorter in overall length. It also gains a more linear shift feel, with each gear change now requiring the same force at the shifter, wherever you are on the cassette.
While the styling is slightly different, there are few functional changes. The mech does, however, gain the side-mounting screw, as per an electronic front mech, to prevent any danger of rotation under load.
The shifters have all-new cable routing to improve ease of maintenance and set-up. This also reduces the friction internally so that the effort required to shift has been reduced by a claimed 43 per cent. The shifter body itself has been reduced in scale and is now similar to the Di2 body size.
Shimano's designers have altered a few aspects of the Dura-Ace brakes, claiming a 20 per cent improvement in braking power. The improvements are two-fold: a new winding procedure in the cables, plus a new polymer coating massively reduce cable friction. Secondly, a new caliper design.
Dubbed SLR EV, it shortens the levers within the calipers from 39mm to just 22mm. Rather than a standard dual pivot brake seen previously, the brake pivots around two stud pivots almost level with the tyre. These shortened levers flex far less and a version is compatible with a new mounting stud that can be used on time trial bikes with 'hidden' brakes.
One of the most eye-catching changes in the new DA 9000 line-up is the new chainset, which has altered to a four-arm design. During rig testing, Shimano's engineers found that the reduced force acting at certain points in the cranks rotation meant that the hollow chainrings didn't actually need the support of five arms - instantly saving weight.
The chainset will be available in compact 50-34, standard 53-39, semi-compact 52-36 and TT with a larger 55-tooth big ring. All sizes share the same proprietary bolt circle diameter.
The new non-directional chain is PTFE coated for improved durability, the engineers found that the new plate design ran as smooth as the older direction-specific 7900 chain and fitting is a quicker process.
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