Bike component manufacturer Shimano might have plans to introduce its first ever nine-tooth sprocket on a 12-speed cassette, a new patent has revealed.
Dated 3 November 2022, the US patent application is titled ‘rear sprocket assembly and lock device’ and comes with attached drawings of a 12-speed cassette, with a smallest sprocket counting just nine teeth.
While it is unknown what bike the design is intended for, the Japanese company currently only offers a nine-tooth on its nine-speed Capreo groupset, intended for small-wheeled folding bicycles. Its current road bike cassettes only go down to 11 teeth.
It is thought that this new cassette is most likely for an updated gravel GRX 1x groupset.
If it does eventually materialise on the road, it'll likely be on Dura-Ace to start with, but a new version of that is not due soon since the groupset was relaunched just last year.
Historically, manufacturers have struggled to create sprockets with 10 or fewer teeth that fit on a standard freehub. The patent application, however, appears to circumvent this issue by creating an add-on mount for the two smallest sprockets, made up of 10 and nine teeth respectively.
The patent notes that a cassette with smaller sprockets will provide a “wider gear range”, which is likely to offer riders a higher top speed, particularly on downhill stretches or in time trialling, while keeping low gears for climbing.
When American manufacturer SRAM introduced its X-range 10-tooth cog, the company noted: “Smaller cogs allow you to use smaller chainrings to get to the same top speed. If the largest cog on the cassette remains the same size, you can stay in the big ring longer and limit the number of front downshifts you have to make.”
In the past, there have been concerns about smaller tooth sprockets and their effect on drivetrain efficiency. SRAM highlighted that, while they do increase friction between the chain and the sprocket, this can be resolved by changing other components, such as the size of the chainring or the thickness of the chain.
There are currently limited nine-tooth sprocket options on the market. In 2017, Italian brand 3T created two 11-speed cassettes, both with a 9-32 gear ratio, for use on its Strada single-chainring aero road bike. Campagnolo also offers its 13-speed Ekar, a gravel groupset with a 9-42 ratio.
Asked for further details on the patent application, a Shimano press contact told Cycling Weekly: “Shimano never speculate on future product developments.”
A revolutionary derailleur and solar-powered mudguards?
Another patent filed by Shimano suggests the company is looking to redesign the rear derailleur, building it in line with the cassette to increase the clearance between the mech and the ground.
Within the application, Shimano notes that this design favours bicycle travels on “uneven terrain”, so it is fair to assume it is intended for gravel or mountain bike riding.
But historically many of the innovations introduced off-road have evenutally found their way onto road bikes, disc brakes being the most obvious example.
Further innovations can be seen in patent applications from SRAM, which include thru-axle batteries, mudguards with solar panels and an aero-minded gravel suspension fork.
Of course, it is worth remembering that these are only designs, and may never see the light of day.
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