Shimano BR-RS805 / ST-RS685 / SM-RT99 disc brake system

These Ultegra-level brakes set the standard for hydraulic road discs

Ok, let’s simplify this a little. Until Shimano launched the new Dura-Ace R9120 and R9170 groupsets, the Japanese giants had actually refrained from uniting a disc brake system with a specific groupset. Until that launch, the BR-RS805 calipers were the highest-spec system it made, and tended to come packaged with either Dura-Ace or Ultegra drivetrains.

With the launch of the R9120 and R9170 Dura-Ace systems, the industry has naturally shifted the BR-RS805 system to Ultegra’s level, instead of a Dura-Ace/Ultegra crossover.

That’s fine by us, because as we’ve seen in various bike tests over the past year or so, it’s an excellent system and has generally kept Shimano current with higher-end disc brake bikes. As an aside, we also like the hint with the new Dura-Ace that Shimano are looking to tidy up their disc brake offering by giving spec-level names to their rotor stoppers too.

Despite the launch of that Dura-Ace setup, the BR-RS805 calipers, and accompanying shifters and rotors, remain a super system if you’re considering making the switch to disc brakes.

The BR-RS805 calipers are flat mount, a setup which has had notable positive impacts on disc-brake frame design, and of course are hydraulic, resulting in greater modulation once the pads make contact with the rotor itself. Also, you can happily run 140 or 160mm rotors without issue.

Now, the rotors we tend to see matched up with the BR-RS805 calipers are the SM-RT99 rotors, which feature the first iteration of Ice Tech technology to assist with rotor cooling under prolonged use. In fact, time was that frame manufacturers were worried about the problems associated with heat sinking at the caliper and rotor.

Merida, for example, even went to the trouble of creating its own disc cooler fitment for the rear brake on the Scultura Disc, while we’ve seen Lapierre use higher Tg (melting point) resin at its frames around the key dissipation zones.

However, Shimano has done its bit by using Ice Tech, which takes the form of a three-layer, stainless steel-aluminium-stainless steel sandwich construction in each of its SM-RT99 rotors. This is said to help the rotors radiate heat as efficiently as possible in tandem with the cutaways and moulded fins, while the Ice Tech pads specifically designed for use with the rotors generate up to 25 per cent less heat under that load than with standard ones.

RCUK 100 2017 - Shimano disc brakes - ST-RS685 shifters, BR-RS805 calipers, rotors
RCUK 100 2017 - Shimano disc brakes - ST-RS685 shifters, BR-RS805 calipers, rotors

Shimano BR-RS805 / ST-RS685 / SM-RT99 disc brake system

Up at the contact points, for mechanical drivetrains, the general trend has seen ST-RS685 shifters fitted (ST-RS785 for Di2 shifting), and they represent a serious downsize over the 105-level ST-RS505 levers thanks to tidier integration of the hydraulic hoses. This keeps ergonomics relatively natural, although this has since been improved on again by the new Dura-Ace.

Shimano have ensured much of the adjustment capability of normal STI levers too, with 10mm of reach adjustment available to riders with especially small or large hands, as well as an compact throw in order to actuate easy shifts.

Time and tech moves on, of course, but the now second-tier hydraulic disc brake system from Shimano set the bar for road discs and will continue to feature on high-end bikes well into 2017.

[monetizer101 search=’Shimano BR-RS805 disc’]


Selected for The RCUK 100 2017

View the full 100
Newsletter Terms & Conditions

Please enter your email so we can keep you updated with news, features and the latest offers. If you are not interested you can unsubscribe at any time. We will never sell your data and you'll only get messages from us and our partners whose products and services we think you'll enjoy.

Read our full Privacy Policy as well as Terms & Conditions.