Bleeding Shimano’s R785 hydraulic disc brake for road bikes

Removing air from the Japanese component giant's new fluid-operated stoppers

Riders contemplating hydraulic disc brakes for road bikes will need to know how to ‘bleed’ the system of air before filling it with fluid.

Once fitted, the rider shouldn’t need to repeat the process regularly: the system is sealed. Additionally, Shimano use a mineral fluid, less susceptible to moisture absorption than the ‘dot’ fluids used in some rival systems.

Bleeding air and adding mineral oil is an infrequent but necessary procedure for hydraulic disc brakes

That said, ingress of air into the system, or loss of fluid, can lead to spongy braking. With this in mind, it’s worth checking the system annually, according to our maintenance expert, Jon Hayes, mechanic at Ride in Dorset.

During our recent trip to Sicily to test Shimano’s new R785 hydraulic brake, we were shown how to bleed the system of air. Here’s a step-by-step guide.

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