How to fit and set up Shimano road bike hydraulic disc brakes

For internally routed bikes, this job is easier without the headset or bottom bracket installed. But, if the headset and bottom bracket are already fitted on the bike you’re working on, try fitting the hoses around them first to save yourself some extra work.

If you are replacing existing brake hoses, don't remove them – they can be used to guide in the new hoses.

Remove your wheels and brake pads before starting the fitting process and keep them clear until the whole system is installed securely and you’ve cleaned the bike and brakes of any spills. Brake fluid will contaminate brake pads and disc rotors, making them ineffective.

The method for this will vary depending on the design of your frame. If you’re struggling, a routing kit can help. Put the end of the routing cable in your frame and guide it through the frame using a magnet until it emerges from the exit point.

Before you use this to guide the new hose in, consider putting a foam housing over the new hose. This will prevent the hoses rattling in the frame.

Next, attach the new hose to the end of the cable and very carefully pull the cable back through, leaving the hose in its place. Make any hoses extra long at this point, as it’s hard to know how much you need until it is fully installed.

If you had to remove your headset to get the cables through, reinstall the headset, stem and bars before continuing with the next step.

To prepare them for the calliper, fit a barb to the end of your front and rear brake hose. Open up the end of the hose with a pick or pin, then push the barb in as far as you can by hand. If you have one, use a hydraulic barb tool to press the barb snugly into place – simply slide the hose into the clamp, position the barb under the tool, and press it in using the lever.

If you don’t have a barb tool, you can try to open the end of the hose further to make the barb slide in more easily.

Identify the front and rear brake callipers. The front calliper has a plate attached, with a hole on each end and 140mm and 160mm written on it. The rear calliper will have two holes in it, which are used to bolt it to the frame.

Once you've worked out which calliper is which, slide the fixing nut and olive down the hose, press the end of the hose into the receiver on the brake calliper, and carefully thread the fixing nut into the calliper. Tighten with an 8mm or 7mm spanner, depending on your calliper specifications.

This fixing nut crushes the olive to create a hydraulic seal, so it needs to be tightened firmly. But be careful, as these fixtures are often built to be lightweight rather than super strong.

There is a standard length bolt that comes with callipers, but some frames have a slightly different design, and if so, are usually supplied with the correct length bolts. Place the calliper on top of the chainstay and bolt it down. Don’t fully tighten the bolts just yet, as you’ll need to align the callipers on the rotors later.

The chances are, you’ll be using a 140mm rotor on the rear. If so, you can simply bolt the calliper directly to the frame. If you’re using a 160mm rotor however, you’ll need to wedge it with a specially designed plate.

The last thing to do is to put the safety pin through the end of the bolt, if applicable.

Before you attach it to the fork, you need to attach the metal mounting plate to the front calliper. The direction of this depends on whether you’re using 140 mm or 160 mm rotors, and is printed on the side of the plate.

Once the calliper is attached, bolt the plate to the fork.

Put the brake levers briefly onto the bar. This is to position them so you can make sure the hose lengths are correct and cut them down if needed. They don’t have to be exactly right as you can push excess hose into the frame, but make sure you don’t cut them too short.

Take the shifters off again and prepare the hoses as you did at the brake end, by putting a barb in the end, and sliding the retaining nut and olive down the hose. You are now ready to fit the hose into the brake lever. Plug the hose into the port, slide the olive up as far as it can go and then tighten the locking nut into place. Be careful not to overtighten it – it’s quite easy to damage the shifter.

Repeat for the other shifter, then fit the shifters to the bars.

Put the yellow bleed block in the calliper and secure it in place with the pin that would normally hold the pads in place.

Peel back the brake lever hood to reveal the bleed port screw, and tuck some blue roll or a rag around the shifter to protect the rubber hood from the brake fluid.

It's a good idea to put some gloves on too – hydraulic fluid isn't great for your skin.

Now, remove the bleed port screw with your 2.5mm Allen key, ensuring to put it somewhere safe, and attach the bleed block reservoir to the top of the shifter.

For road hydraulic brakes, you’ll need a little adapter to be screwed into the bottom of the reservoir. Take out the little plunger from the reservoir.

Next, fill the syringe with the hydraulic mineral oil, then attach it to the bleed port. Slide the little black collar along the tube and over the bleed valve to hold it in place.

Take your seven millimetre spanner and open the bleed port. This usually only requires a couple of half turns – you don't want to fully undo it.

With the bleed port open, slowly depress the syringe to inject the hydraulic fluid up through the calliper, through the hose and into the shifter. You should start to see fluid coming up into the reservoir that we've attached on the top of the shifter.

Pull the brake lever a few times to work out any bubbles in the system.

Now the system is flushed with the mineral oil, close the bleed port with the spanner. Then, pull back on the syringe plunger and remove it.

Insert the plunger into the reservoir, then unscrew the reservoir from the shift port to remove it. Replace the bleed port screw with the 2.5mm Allen key, taking care not to over-tighten it.

Replace the little dust cap on the bleed port, then clean any mineral oil off the calliper.

Install your rotor. Make sure you put the right rotor on the right wheel, and that you put it on the right way around. Some rotors attach with a cassette tool, and some are attached with a Shimano Hollowtech bottom bracket tool.

However your disc attaches, start it off by hand to make sure you don’t strip the thread in your hub.

The last step for the front brake is to centre the calliper. Loosen the calliper bolts slightly and put the wheel in the frame. Pull the front brake lever, hold it closed, then do up the bolts on the calliper.

To set up the rear brake, reposition the bike so the calliper is the lowest point on the bike. This is to make sure no bubbles get stuck in the hose. Then, repeat the process from step 9.