Shimano has been working on a cover to shield the rotors of its hydraulic disc brakes. The design, which was filed for a US patent in June 2017, shows a vented structure that covers a majority of the disc rotor’s surface and backs up neatly against one of Shimano’s own flat-mount disc brake calipers. It looks to have been designed to fit a thru-axle fork.
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High-profile incidents involving injuries allegedly caused by disc rotors have previously sparked safety concerns in professional competition. Some riders referred to discs as "spinning knives".
Since then, a generation of disc rotors with chamfered (blunt) edges has been introduced. SRAM already produces chamfered discs and all of Shimano's rotors from the Dura-Ace R9100 series and Ultegra R8000 series are also chamfered. We’ve also seen similar disc brake covers from Italian firm T°Red and German company Tune.
Disc brakes are still divisive among the pro peloton, despite the technology having been used on a trial basis for three seasons already. No rules are currently in place that stipulate the use of a cover such as this one.
The Shimano rotor cover design includes cut-outs and a large side vent that the patent says is “efficiently drawing air flowing in the travelling direction of the bicycle into an inner side of the rotor cover.”
This design may never see the light of day, but it’s interesting to see Shimano's sketch behind this idea nonetheless.
BikeRadar has requested more information on this design from Shimano and is awaiting a response.