Muddy Brown's Blog: Fresh Goods Sunday - Shimano Disc Brake Flat Mount Calipers BR-RS805

When I ordered the Mason I noticed it had the newer flat mount adaptors on the frame & fork for the disc calipers. You can buy adaptors to convert them into post mount but don't look the best. So time to buy some new flat mount Shimano calipers. I was building the bike with Ultegra Di2 so opted for the BR-RS805 version (Ultegra level). They are hard to find in the UK and only now is there stock of front ones, rears are sold out, so I bought a pair from bike discount in Germany and landed within 3 days. Fitting is simple enough with two bolts and a spacer on the front to switch between 140 - 160mm rotors. The rear fits 140mm discs only (no adaptor in box). They do not come with hoses etc but I already had some with the Di2 levers. I fitted new olives, oil etc and bleed them through. I am not running ice tech rotors and still have plenty of stopping power for what I need. Since fitting I have re bleed them once and never had to adjust the caliper on the frame for clearance. As with all Shimano disc brakes there is plenty of progressive stopping power. The only thing I don't like is the amount of travel on the levers before you get a good bite on the rotor. Sram roads discs feel much better on this point but don't have the same stopping power in my eyes. There is a cheaper road disc available BR-RS505 around £32 each, not bad considering the rrp is £20 on replacement shimano pads! which look very similar indeed and a BR-RS405 around £30 each.

RRP £119.98 f & r and I paid £79.64 for the pair inc p&p

Details

- High performance low profile hydraulic road disc brake for efficient braking in all conditions
- Rear wheel use for 140 mm flat mount frames, can be used with adapter for 160 mm

- Front wheel use for flat mount forks with adapter to flip between 140 and 160 mm
- Oversized 22mm phenolic pistons optimized for heat insulation, lightweight and stiffness
- Opposed 2-piston design reduces leading effect and optimal pad wear increases braking control
- Increased pad to rotor clearance reduces the chance of rotor drag
- Forged calliper design is lightweight and rigid
- One way internal fluid circuit makes bleeding easy
- Mineral oil brake fluid is non-corrosive and less hazardous than conventional hydraulic brake fluid
- Shim-less mounting bracket allows for quick installation and setting up
- Recommended for use with Ice Tech FREEZA Centre-Lock SM-RT99 rotors for optimum braking performance
- Comes complete with resin compound aluminium radiation fin pad further improves heat dissipation reducing brake surface temperature by 50 deg C
- Inline hose routing for low profile design