Replacing mechanical disc brakes with hydraulic

anewman

My skill level: no experience of work on bikes, though I have done some DIY on cars, and own two torque wrenches so have reasonable mechanical understanding.

I recently bought a Cannondale Quick CX4 2013. I decided to upgrade the mechanical brake discs, Tektro Novela, to hydraulic as I felt the brakes were quite poor. I bought front and rear Shimano XT M785 along with a 180mm and 160mm Shimano RT86 ice tech 6 bolt rotors, and a 180mm post mount adapter. Now I have tried them out they are obviously light years ahead. Although the lever actuation vs brake force has very different characteristics, and takes more of a pull to "bite".

On to my questions:

1. I have mounted the rear caliper using the existing IS to post mount adapter. This leaves the hose and bleed nipple facing downwards towards the front of the bike, sending the hose along the chainstay. On all bikes I have seen with hydraulic disc brakes, the bleed nipple is at the top. Is this orientation ok for normal operation?

2. The Shimano instructions state "180mm rotors ... and so the flexing of these rotors is greater. As a result they will interfere with the brake pads." I get a periodic rub when spinning the wheel, which suggests the disc is slightly warped. It is inaudible when riding above other noises, and does not appear to affect operation. Is this type of rub something I should expect and live with?

Many thanks in advance

The Rookie

1. For a chainstay mounted caliper, perfectly normal.
2. Ideally the disc shouldn'be warped, you can tweak them straight, but not sure I'd do it with an icetech, look and see why it may be rubbing.

thelonegroover

You should be able to see if the disk is slightly warped or bent by spinning the wheel and looking at the distance between the pads and disk. Small tweaks with an adjustable wrench can resolve but be careful.

anewman

Thanks I have managed to greatly reduce the front rotor rubbing with spinning and observing the point at which a noise is made, and which pad it rubs on. Probably need to spend another hour or two to make it 100% perfect.

02gf74

the bleede nipple should be uppermost otherwise it can be difficult to bleed the brakes as air gets trapped.

this shouldn't be a problem if the calliper is mounted to the seat sta. there are sone bikes Trek/Gary Fisher and Klein of aroound 2000 era that had calliper nounted to the chain stay - there is Hope nad Avid model of calliper that bolts to there.

I have Gary Fisher frame and have fitted Magura calliper that has the bleed nipple too low - it cannot be bled in the normal postiion so I need to remove the calliper and tied it to the stay with a piece of steel in between the pads to bleed it. A bit of a palaver but only had to do it twice so far in mayber 2 years.

..... but to answer what I think is the question, the brake work perfectly well if the nipple is not uppermost as long as there is not air in the system.

The Rookie

Or just lift the front of the bike (see Avid video on you tube).