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

Hydraulic discs offer brilliant all-weather braking control but fitting them can be a daunting prospect. Here’s how to get it right first time

ClockUpdated 09:00, Monday 20th November 2023. Published 11:00, Tuesday 19th September 2023

Compared to most bike maintenance tasks, fitting and setting up Shimano hydraulic road brakes is a bit of a long job. It might seem like an intimidating task at first, but with enough time and patience, this is a task that any at-home mechanic can do.

We've used Shimano 105 in our demonstration, but the same process applies to other Shimano road hydraulic brakes; Tiagra, Ultegra and Dura Ace.

Read more:

Tools Needed

For internally routed cables, you might need to remove the headset and bottom bracket

Step 1

Prepare the frame

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.

Use a routing kit to guide the hoses through the frame

Step 2

Thread the hoses through the frame

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.

Top Tip

If you’re using an existing bike then use the old hoses as the guide for pulling the new ones through. However, while it might be tempting to use the existing hoses with fresh brakes and callipers and save yourself some installation hassle, we wouldn’t recommend it. The hoses will be contaminated by old fluid and any other gunk that’s got in there.

Use a barb tool to push the barbs into the calliper end of each hose

Step 3

Fit the barbs to the hoses

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.

Slide the nut and olive over the hose, then attach to the calliper

Step 4

Attach the hoses to the callipers

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.

In most cases, the rear calliper will bolt directly to the frame

Step 5

Attach the rear calliper to the frame

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.

The front calliper attaches via a metal plate

Step 6

Attach the front calliper

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 shifters in place to measure and cut the hoses

Step 7

Put the shifters on briefly to measure and cut the hose length

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.

Be careful not to cross-thread the nut

Step 8

Attach the hoses to the brake levers

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.

The bleed block provides resistance while you bleed the brakes

Step 9

Prepare to bleed the front brake

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.

For Shimano road levers, you'll need a small, tube-like adapter

Step 10

Attach the bleed reservoir

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.

Make sure to use the right type and brand of brake oil

Step 11

Fill and attach the syringe to the calliper

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.

Make sure the port is open, then inject the fluid

Step 12

Inject the fluid into the system

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.

Step 13

Close the calliper bleed port and remove the syringe

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.

Put in the plunger to stop any leaks, then remove the reservoir

Step 14

Remove the reservoir from the shifter and close the bleed port IMG

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.

Step 15

Clean up the callipers and install the brake pads

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

Hand-tighten at first, then tighten with a tool

Step 16

Install the rotors

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.

With the calliper bolts loose, pull the brake to centre the calliper

Step 17

Centre the calliper

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 bleed the rear brake, tilt the bike upwards so bubbles can rise

Step 18

Repeat steps 9-17 on the rear brake

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.

Top Tip

If your brakes feel spongy after following these steps, put the reservoir back onto the bleed port, put in some brake fluid, and squeeze the brake lever repeatedly until you can’t get any more bubbles out of the system.

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