Shimano BR-R785 road hydraulic disc brakes - first look

Hydraulic disc brake system for road bikes

Shimano have announced their first hydraulic disc brakes for road bikes. Set to be sold in kit form rather than as part of a groupset, they should be available soon, with prices to be announced. The kit includes dedicated wheels, hubs, Di2 shifters, and the brake calipers and discs themselves. 

Unusually for Shimano, this technology will not debut exclusively on the top-end Dura-Ace component line. Instead, it will go without series branding and be targeted at an Ultegra level. Levers aside, anyone familiar with Shimano's mountain bike discs will find a lot of similarities between those designs and the BR-785.

ST-R785 dual control lever

The new brakes are compatible with Di2 shifting only – that's due to the lack of gubbins inside compared to a mechanical setup. The ST-R785 shifter incorporates its mineral oil resevoir within the lever; there are no nasty humps or any ergonomic compromises relating to this. The reservoir also provides automatic pad clearance adjustment. Both the left and right levers also get reach and free stroke adjustment.

Shimano ST-R785 dual control lever

BR-785 hydraulic disc brake caliper

Aesthetics aside, the BR-R785 caliper looks near identical to Shimano's current BR-M785 mountain bike brake. It's an opposed two piston design and is compatible with Shimano's Ice Tech pads. For those not in the know, these include a raised finned section that protrudes from the top of the caliper – it acts as a cooling fin and works to bring brake temperature down.

Shimano BR-R785 hydraulic disc brake caliper

SM-RT99 rotor

The SM-RT99 rotor is a tried-and-tested part borrowed from the latest Shimano XTR mountain bike line. The braking surface is part of a three-layer sandwich construction that uses a combination of stainless steel and aluminium to manage heat build-up more effectively than traditional designs. The rotor also incorporates 'FREEZA' aluminium fins just inside the braking surface, further improving heat dissipation. 

Shimano found that a 140mm rotor was the optimum size for on-road duties, so they're standard fit. For heavier riders or those looking for more power, a 160mm rotor option will also be available. As is the norm for Shimano, both discs will use the firm's Centre Lock standard to attach the disc to its hub.

Shimano SM-RT99 rotor

WH-RX31 wheelset

Road-specific discs mean road-specific wheels, but Shimano also recommend the new 11-speed RX31 wheelset for cyclocross use. These disc-only hoops do without a regular braking surface, and instead get Center Lock-compatible hubs. A 17mm rim means these wheels are best suited to wider rubber.

First ride impressions

We had a brief ride on a test bike equipped with a pre-production set of BR-R785 hydraulic disc brakes. The level of modulation and feel was very similar to that of Shimano's current mountain bike hydraulic discs, and anyone familiar with those will know that that isn't a bad thing. 

Power was also good, just as we'd expect, but we were genuinely impressed at how the narrow tyres of the test bike resisted locking. Still, riders not familiar with hydraulic discs are going to have to recalibrate their fingers accordingly. 

It's interesting that Shimano have chosen to sell this kit at an Ultegra price point; it's a strategy that should bring more discs to OE and consumer bikes, faster. Despite Shimano being beaten to the great hydraulic road race by SRAM, we think these will soon be everywhere.

UPDATE: BikeRadar have since put further miles in and tested the R785 hydraulic brakes and Di2 shifter combo, click here to read the full review.

Weights

Component

Weight (g)

Spec

Shifter

515

Caliper

263

Hose

61.5

BH59

Oil

21.5

Rotor

205

RT99-140

WH-RX31 wheels

1,795

Total

2,861

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