Shimano BR-RS805 flat mount hydraulic road bike disc brake caliper

There has been a lot of speculation since Shimano first announced a new brake mount specific to road, but little in the way of details. Ironically coming on April 1st in Japan, Shimano is finally showing their hand and introducing two new hydraulic road disc brakes built specifically for the Flat Mount fitment. Announced along with a new 10 speed Tiagra group and WH-RX010 road disc wheelset, the new BR-RS505 and BR-RS805 disc brakes are non-series components at the 105 and Ultegra level respectively.

We have a feeling we’ll be learning more about these new brakes come Sea Otter, but the preliminary details are after the break…

Shimano BR-RS805 flat mount hydraulic road bike disc brake caliper

Beneficial to both the frame and the caliper design, Flat Mount uses an all new caliper that bolts up from the bottom instead of through the top like most calipers. On the rear brake that results in a true “Flat Mount” with the caliper sitting directly on the chainstay. Caliper mounting bolts are inserted through the bottom of the chainstay and thread into the caliper making a very tidy rear triangle of the frame. While the mounting and shape of the caliper changes, the brakes still use one-way bleeding with a bleed nipple at the highest point in the caliper’s hydraulic workings.

Shimano BR-RS805 flat mount hydraulic road bike disc brake caliper

Due to the fact that the caliper bolts up through the bottom, the front brake will still need an adapter which is then bolted to the back side of the fork leg. Shimano tells us that you can still use additional adapters to run larger rotors while the brakes are capable of running 140mm.

Shimano BR-RS505 flat mount hydraulic road bike disc brake caliper

Shimano BR-RS505 flat mount hydraulic road bike disc brake caliper

Visually, there is little difference between the BR-RS505 (105 level) and BR-RS805 (Utlegra Level), other than the finish. We wouldn’t be surprised to find that there is more to it beneath the surface though. Both calipers will use new brake pads which are not mountain bike compatible, likely meant for much higher heat applications.


Completing the RS-505 level hydraulic system is the new ST-RS505 hydraulic/mechanical shift lever which brings Shimano’s hydraulic road performance down to the most affordable level yet. Compatible with either of the new Flat Mount disc calipers or even previous Shimano hydraulic road calipers, the 11 speed mechanical shift lever with Vivid Indexing includes reach and free stroke adjustments as well.


As promised, frames equipped with the new Flat Mount standard will still be able to run standard road brake calipers with one of the Shimano adapters. That means frames will be backwards compatible, but the new Flat Mount brakes will not be since they can only be mounted to frames with the Flat Mount provisions.


Along with the ST-RS505 brake levers, the RS505 system includes a new 105 level Centerlock hubset to facilitate custom wheel builds that are 11 speed road disc compatible.


The Flat Mount brakes will continue to use the current Shimano Centerlock rotors with the SM-RT81 and SM-RT99 Freeza rotors available down to 140mm.

Updates on availability: The Ultegra level flat mounts will be available in July. The 105 level calipers and 105 hydro/mechanical shifters will come out in October 2015.

We’ll update the story as pricing and weights become available.


  1. me on

    Why all shima calipers have this fugly black plastic on top of the pads??? I just don’t buy because of that, Life is too short to ride bike with fugly black plastic on top of the pads.

  2. bikertidy on

    It’s not plastic, it’s the pad backing extended into a heating to help keep the brakes cool. It’s literally a very cool feature.

  3. Mike on

    They are anodized aluminum cooling fins.

    It’s one of the reasons why Shimano brakes operate at a much cooler temperature.

  4. Kerry on


    If you haven’t been following along with Shimano moutain tech, those are cooling fins that dramatically increase heat dissipation over non-finned pads. Read: You modulate speed better and experience less brake fade. This makes for a happier ride, where you might spend more time looking ahead on the trail/road/gravel than looking down at your brake caliper.

  5. Graham on

    So with a flat mount frame, and the new flat mount brakes, you’re restricted one rotor size in the back? Hmm. Also those levers looks very interesting…….

  6. jeffnbose on

    So, which companies are on-board to produce disc compatible frames? Is carbon fiber still a frame material option?

  7. MikeC on

    If the bleed nipple on the rear caliper is at the highest point, to facilitate bleeding, it’s at the lowest point on the fork, to ________ bleeding.

  8. Glenngineer on

    “me” is why I don’t miss working in consumer product design…there are consumers at the other end of your work.

  9. T on

    Oh Shimano, you tease. Those hubs aren’t 15/12mm axle compliant! It is a good business model, changing the disc standards from mountain.

  10. anonymous on

    Make a new standard, and only release a brake that requires an adapter for it. Good job Shimano.

    Also, that shifter/brake unit almost made me throw up a little.

  11. anonymous on

    Also, it’s a shame the hubs aren’t thru axle. If the industry is going to settle on standards for the future of road disc brakes, it really should do it now, all at once.

  12. Frippolini on

    What’s the advantage except the looks for this new standard? Does the disadvantage include the change of “squeezing” the chain stay tube if not properly using a torque wrench? What was wrong with what is in place today? In general I’m all for evolution and technological innovation, but come’on are there no limits to how many variations of “standards” that the bike industry needs to adapt to? An interesting topic in itself, how many variations of frame affection variables are required until the frame producers says enough no-more? OR is the total market value of sold “adapters” sufficiently profitable to offset the disadvantage of 1000’s of possible variations?

    As for the looks of the brifter… I’ll rather stick with rim brakes until something nicer looking comes out from the great S-factories.

  13. JBikes on

    @ Graham – not technically. If a larger rotor fits in the frame, an adapter could be used to move the caliper toward the crank and upward.

    @ Frippolini – I’d think most manufacturers would place tubes spanning vertically across, thereby eliminating any clamping of the chainstay. All bolt clamping forces will be applied directly to the tubes, be they metal or composite, leaving the chainstay wall to remain as thin as desired. At least that is the way I’d do it.

  14. Gunnstein on

    So, on the front brake the cooling fins are parallell to the airflow. In the rear they are more or less perpendicular. Would like to know what guided that decision.

  15. PeteG on

    I like the idea of the flat mount. Esp if it means theres a lack of thread in the frame for people to screw up. Replacement caliper a lot cheaper than a frame.

  16. JBikes on

    @ Gunnstein,
    There is certainly enough turbulent flow around the cooling fins to displace any heated air, which is all that is needed. They just act as a heat sink. There is no reason to have f/r specific pads with “aligned” cooling fins.

  17. Gunnstein on

    @JBikes Sure, but then it would at least look better if they where rotated 45 degrees, aligned semi-radially. But perhaps the logic is that efficient cooling is more important at the front, which does most of the braking, so even if the difference is marginal they would optimise for the front.

    @MikeC seems to have a good point about bleeding the front.

  18. fast foreward freddy on

    as long as the bleed nipple is at the very top or bottom, you’re fine. The front probably bleeds nicer. just open the valve and let gravity do the work for you.

  19. Nico on

    Why do you think thru axle will we the new “standard” for road bikes? At best it will be the second standard.
    They way thru axle works now, it will be impossible to use in the protour. Try changing a flat wheel/tyre in sub 15sek, like they do today, with a thru axle.

  20. Dude on

    What is up with that new lever? Huge bulbous knob and either a long body or skinny blades – looks totally out of sync with the rest of the Shimano line up. On the one hand, I’m dying for Deore-level hydros for the CX/gravel machine, on the other, it’s got to at least have familiar ergonomics.

  21. imalittlegurl on

    @swmmo totally agree. my trek 8900 is the greatest bike ever, still blowin’ past all the h8’ers on the trail. the 22mm mount for the rear caliper was the shiznit. also, thru axles are for the nerds who cant get their wheel in str8. open dropouts forever!

  22. pdxfixed on

    @fffreddy, that’s not how one-way bleeding works. If you look at the front caliper, any bubbles on the non-drive side will be trapped at the top of the piston, up and to the left of the “S” in the logo, where the shape draws to a point.

    Also, I second the question of “How am I supposed to line these things up??”

  23. mike on

    is the new one can squeze the brake from booth side? or the same like ultegra, from one side only?
    in from one side only like ultegra, better buy trp brakes

  24. muf on

    im not sure to see what the new standards in this one bring to the table (except being incompatible)
    ive riding a disk brake bike for hours downhill and braking all along.. on a road bike.. because im a chicken.. sure it ran hot but nothing happened. my mtb appears to run around as hot eventually …

    as for the flat mount, meh ive had such brakes, its the same really. I feel like all this is just to be incompatible with MTB and thus have a different price range/buy twice/etc.

  25. Rob on

    @pdxfixed and @gibbon – Looks like the frame needs to be slotted to line up the brakes rather than the calipers as we are use to. Makes sense to me.

  26. gringo on

    One point worth noting for anyone who asks ‘why?’ Any performance or maintenance benefits touted here are the bait to get OEM’s on board.

    With this new interface, if shimano can sell OEM’s a certain amount of spec in a given model year, this interface will ensure that all bikes from said model year will always be shimano equipped as SRAM et al. do not produce brakes to fit this interface. After riding the bike for a few years, the consumer wants to upgrade or refresh some parts, goes online or to their LBS and is either bound to Shimano, or will need to add a (heavy) adaptor to their light and fast road bike.

    This will result in a fairly nice chunk of additional aftermarket revenue for Shimano simply by selling OEM’s on a (for now) proprietary interface.

    Shimano makes amazing components, but also has some savvy minds driving the business.

  27. gumby on

    @fast foreward freddy I think you’re optimistic expecting to bleed it with the bleeder at the bottom of the calliper unless it’s water you’re removing.

  28. i on

    The reason for the new mounting pattern is cosmetic. Shimano have so much as said so in the past. The reason they are pursuing a new brake mount for mostly cosmetic reasons can be found in about half the comments on this and most any other post about how ugly something is, and that’s all that matters to a large percentage of riders… er, people that buy bike stuff (if you’re that worried about how your brakes look, I have doubts about how much you actually ride).

  29. ah on

    One of the beauties of the old system was that if the customer screwed up a thread the adaptor was the only part that got ruined, cheap and easy to replace. Now with threads in the caliper any thread damage is going to be very expensive.
    I also wonder how the front is supposed to work, how do you align it when the bolts are trapped behind the adaptor, and as already mentioned the bleeding just seems to have got as bad as it could be…

  30. gringo on

    @ Anonymous.

    If you think Shimano is going to spend development time on a new interface then promptly give it away to SRAM or Hayes then I got bridge in Brooklyn with your name on it!

  31. 'Merika on

    It’s interesting that in the bike world, the components suppliers dictate the standards. Can you imagine Shimano going to BMW and telling them to start making their cars differently because of the brakes Shimano is developing?

  32. Skip on

    Since I do not see any tubes, it must be the new hydraulic wireless fluid system we have heard so much about. What a cool concept…………;-) Will probably see more about it at Sea Otter.

  33. UK on


    the front caliper looks to bolt on to a thin mount which then i presume will be floating like the old system.

    will no more next week as going to see the new system & ride it

  34. anonymous on

    It’s a stanrdard. Shimano released the mounting standard quite a while ago for frame manufacturers, and it’s an incredibly easy thing to reverse engineer.

    It’s not like Shimano’s new cable pull standard stopped microshift from copying it. Shimano’s 4 bolt 110 BCD didn’t stop oval rings from making rings that matched. Shimano’s freehub pattern didn’t stop SRAM from copying it. Shimano’s 24mm hollowtech 2 axle, you can get all sorts of 3rd party BBs.

    Unless Shimano found something to patent with this new interface like they did with octalink.

  35. OiFatty on

    @’Merika – 04/01/15 – 11:40am

    “It’s interesting that in the bike world, the components suppliers dictate the standards. Can you imagine Shimano going to BMW and telling them to start making their cars differently because of the brakes Shimano is developing?”

    No, because Shimano don’t make components for BMW…. derrrrr

  36. Tim Watson on

    Cheering, but where’s the Shimano 1 x 16sp road gear to go with it?
    Sram’s gonna do nicely unless they reply to their 1x road group.

  37. John on

    @Tim: “Cheering, but where’s the Shimano 1 x 16sp road gear to go with it? Sram’s gonna do nicely unless they reply to their 1x road group.”

    SRAM’s new 1x CX “road” group simply dropped one chainring and added a clutch-based rear derailleur. It didn’t change the existing 11-28t or 11-32t road cassettes at all. That may be fine for an hour at a time, on a specific CX course, but that’s not going to cut it as a road group.

    To make that work they’d have to bring the XD driver to road wheels (for their wider 10-42t cassettes), make a right road shifter that supports their MTB X-Actuation rear derailleur and package a clutch-based XX1/X01/X1/GX(1) rear derailleur to go with it.

  38. Craig Harris on

    I’m surprised by the lack of alignment adjustment on these, post mount calipers have elongated mounting holes to allow sideways adjustment to perfectly align with the rotor – I can’t imagine frame builders, hub manufacturers and rotor manufacturers will be perfect enough to eliminate the requirement for such adjustments.

    @nico – through axles can be changed quicker than QRs

  39. ClydeEMIII on

    Ok I’ve been doing some digging & the whole through axle is to stablize wheel.
    It has nothing to do with the speed of changing a tire.

    The brake force on disc pushes the wheel down & back which in turn actually works the older quick release loose and the wheel can actually pop out.

    On rim brakes the force its the exact opposite it it pushes the wheel up & fwd.

    So on disc brakes havig a through axle does 2 things
    1- It prevents that risk of drop out.
    2- It stablizes the wheel so there is almost no wobble. We fail to realize that on rim brakes the the pad clearence is much wider. I know everyone has had pads rub the rim causing the wheel to drag, What a pain in the ass that is.
    On disc calipers pads they have like 1-2 mm clearence. Once that caliper is set the wheel is free spinning you don’t even think about it. Even after countless tire changes or falls on a MTB. Which is why they brought that over to road bikes
    It is consistent placement.

    They are making standard 135 mm rear through axles now
    The Domane is 142 MM the bigger makes it that more stiffer.

    I’ve the Domane disc RS685 really 785 the caliper is the same & one of my riding crew said dude you never have to adjust your brake for anything I laughed caused I didn’t even realize it.


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