How to bleed the brakes on a shimano bike hydraulics

We stock up on the necessary tool

Almost every manufacturer has its own brake bleed kit. But the general principle is the same for all sets. You need syringes, flexible tubing (IV tubing works great) and brake fluid.

For SRAM / AVID, the bleed kit looks like this:

bleed, brakes, shimano, bike

You also need open-end or spanner wrenches and tor-x to unscrew the bleed port plugs and nylon cable ties.

Replacing the brake fluid and bleeding the brakes

Brakes from different manufacturers are structurally very different from each other, therefore, the recommendations for the use of brake fluid are also very different.

Before servicing your bike‘s brakes, be sure to read the manufacturer’s instructions.!

In particular, the differences relate to the recommended brake fluid. For example, Shimano produces a special mineral oil for its brakes, and only this oil can be used in all models of the hydraulic brakes of this company. Hope recommends using DOT 4 or DOT 5.1 automotive brake fluid.

Quite stringent requirements are imposed on brake fluid:

  • It must not corrode the metals from which the brake parts are made, and must also not destroy oil seals and seals.
  • It shouldn’t thicken in the cold.
  • It should not expand much when heated (and the disc brake caliper can heat up to very high temperatures during prolonged braking).
  • It should not boil when heated (brake failure on long descents is most often associated with heating the brake parts and subsequent boiling of the brake fluid)
  • It must be able to chemically bind the water entering it (water in the hydraulic system of the brakes not only causes corrosion, but can also boil when the caliper heats up).

Sooner or later, water will penetrate into the hydraulic system, and the ability of the brake fluid to bind this water is limited. Therefore, the brake fluid must be replaced periodically. Usually this does not have to be done often. once every few years.

Changing the brake fluid is described using the example of Shimano 525 brakes.

Checking the condition of the brake fluid

The SHIMANO mineral oil has a bright red color, which dulls and becomes discolored over time. The brake fluid should be changed when it loses its color, becomes pale pink. It is necessary to remove the cap from the expansion tank once a year and check the condition of the brake fluid.

Checking the condition of the brake fluid

We loosen the screws securing the brake lever to the steering tube. 2. We turn the brake lever so that the expansion tank takes a horizontal position.

Unscrew the two screws and remove the cover from the expansion tank. 4. Carefully remove the rubber membrane.

Replacing the brake fluid

For replacement, you will need, in addition to screwdrivers and keys, a piece of PVC tube 30-40 cm long (preferably translucent or transparent) and a basin for waste liquid. It is convenient to pour brake fluid into the expansion tank from a medical syringe. It is better to do the work not in the apartment, but somewhere in the barn, or in the garage. it can get very dirty if you do something wrong.

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The best way to change the brake fluid is to remove the caliper from the bike. In this case, there is no need to be afraid of the brake fluid getting on the disc and pads. In addition, the brakes are easier to bleed when the brake lines are vertical. Place some kind of solid spacer between the brake pads (a piece of cardboard or plastic the same thickness as the brake disc)

Drain the old brake fluid.

We put a tube on the valve located on the caliper, direct the other end of the tube into the basin.

We press the brake lever several times and observe how the old brake fluid is poured into the basin from the tube.

How to Bleed Hydraulic Brakes. Shimano Drop Bar Levers

When the old fluid stops pouring out, proceed to filling the hydraulic system.

Fill in new brake fluid and pump the brakes.

Let us check that

  • Caliper valve open
  • One end of the tube is put on the caliper valve
  • The other end of the tube is lowered into a basin.
  • Pour the brake fluid into the expansion tank to the brim. (You can use a medical syringe)

    Press the brake lever several times. At the same time, air bubbles rise into the expansion tank, and the level of the brake fluid in the tank decreases. it passes into the hydraulic line. As the fluid level in the reservoir decreases, it is necessary to add new brake fluid there, preventing the reservoir from completely emptying. In order for air bubbles to rise up to the expansion tank, you can periodically lightly tap the caliper and hydraulic lines with your fingers.

    At the same time we look at the tube extending from the caliper. When the brake line and caliper are full, brake fluid will start pouring out of this tube into the basin. (The caliper and expansion tank are communicating vessels)

    Close the valve on the caliper with a key.

    Check that there are no air bubbles left in the hydraulic line.

    Make sure a gasket is inserted between the brake caliper pads.

    We press the brake lever. If it is pressed softly, “falls through”, it means that there are still air bubbles in the hydraulic system. In this case, open the valve, and continue to pour liquid into the tank by pressing the brake lever (go to step 2)

    If the handle turns out to be “stiff” and does not reach the steering wheel, then everything is fine. Go to step 6

    We close the valve on the caliper with a key, disconnect the tube from it.

    Top up the brake fluid expansion tank almost to the brim.

    We install a rubber membrane on the tank, screw the lid.

    Wipe the brake lever and caliper from the remaining brake fluid.

    Return the brake lever to its normal position.

    Install the caliper on the frame, adjust its position

    We pump the brakes

    Today our test subjects are Hayes Stroker ACE brakes, which use DOT 5.1 as brake fluid.

    • Place a 6mm wrench over the bleed nipple on the caliper;
    • Connect the syringe filled with liquid to the fitting using a tubing. You should end up with something like this:
    • Without opening the fitting with a key, slightly pull the syringe by the handle, bubbles form inside, which will additionally help to degass the liquid, because the main task is to pump the brakes with new liquid without gas;
    • Unscrew the cover bolt from the handle:
    • Connect the fluid reservoir (or syringe) to the brake lever;
    • Press down on the syringe at the caliper and wait until the air bubbles stop coming out of the handle;
    • If you run out of fluid in the syringe, close the caliper union, disconnect the syringe and draw up fresh brake fluid. Repeat steps 2, 3 and 6;
    • After the bubbles have stopped coming out of the brake lever, close the union on the caliper and disconnect the syringe;
    • Press the brake lever several times and tapping with the back of the screwdriver on the caliper, brake hose and handle, make sure that bubbles do not come out of the fitting; Repeat this procedure until gas bubbles stop coming out;
    • Press down on the brake lever and use a nylon strap to pull it towards the grip. Leave in this position for 5-10 minutes, this will allow all bubbles to finally come out;
    • Remove the clamp and disconnect the fluid reservoir from the brake lever. Screw on the bleed port with the bolt;
    • Done, you have mastered bleeding the brakes.
    • Wipe the brakes from possible brake fluid spills. Profit!
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    Bleeding the brakes, although it requires certain skills, is still not a big deal. You need to thoroughly prepare and not confuse anything during pumping. The most important thing is not to let air into the system, most often it is because of this that you have to pump the brakes. Therefore, avoid any air entering the brake system.

    Determine the type of brake fluid

    So, first you need to decide on the type of fluid used in your brakes. Typically, SRAM brakes use DOT brake fluid, while SHIMANO brakes use mineral oil. Remember that not all DOT fluids are compatible with each other, and mineral oil and DOT are completely incompatible with each other. Using the wrong fluid will likely kill your brakes. Therefore, the exact information about the fluid used specifically in your brakes can be found in the manual for them, do not be too lazy to look there.

    How to choose disc brakes for a bike?

    When choosing a system, it is important to check with the seller about the availability of spare systems on sale, so that in case of a breakdown, you know where to go. For some models it is very difficult to find components, so you will have to change the entire kit.

    Experts recommend buying a disc system for people who are involved in sports or extreme driving. In other cases, it is better to give preference to the simpler options.

    City riding and cycling require mechanical systems. The choice will be fully justified, thanks to reliable and high-quality use.

    The braking speed depends on the rotor assembly. When buying, you should pay attention to its size. The larger the diameter, the faster the brakes respond. The disadvantage of such a component is only in increasing the weight of the bike.

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    The brake pads are responsible for the smoothness of the brake. They can be organic or mechanical. Organic ones make the process smoother. The second option is more resistant to wear, this allows you to increase the operating process.

    SRAM Guide R

    The model contains 4 pistons and a comfortable lever. The course of action can be easily adjusted without the help of auxiliary tools. Delivers brake power in all weather conditions. Customer reviews note the excellent quality of the model and give it an honorable place in the system rating.


    But in terms of maintainability, disc mechanics wins, which can be relatively easily repaired in the field. In the event of a cable failure, it can be easily replaced on site, given that you have a spare. What can not be done with hydraulics. If you caught on a branch and damaged the hydraulic line, it is unlikely that you will succeed in installing a new one, filling in oil and pumping the system without special equipment. Plus, finding replacement parts for bicycle hydraulic disc brakes is much more difficult than for mechanical ones.

    Another point where mechanics win is price. Good hydraulic brakes are more expensive than mechanical ones of the same level.

    Which disc brakes on a bicycle are better: hydraulic or mechanical

    In the list of bike characteristics, the “brakes” column raises no less questions than the “rear derailleur” line. Seven years ago, there was a lot of controversy around retardation systems, since the V-Brake design competed with disc mechanics. Nowadays, mechanical “discs” have already supplanted the double-lever scheme in the budget segment, and hydraulics are offered as a standard. Is it worth overpaying for it? What is safer and what is more comfortable? And, in the end, which configuration slows down better?

    How to choose the right one

    Inexperienced users shout loudly that hydraulics on a bicycle is almost a panacea for all problems. However, there are several important points here, the knowledge of which will help to avoid selection mistakes and save several hundred or thousands of rubles.

    The first question is for the kit) you need to think hard about whether the game is worth the candle.

    Experts say that a quality mechanical type system performs better than cheap hydraulics. This is due to the quality of the materials used. Mechanical calipers themselves are cheaper to manufacture, so the manufacturer can use stronger material alloys and put solid pads in the “stock”. Additionally, with such a system there will be no problems during maintenance. spare parts are always available.

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    As for the cheapest hydraulics, it is fashionable, pretentious, but ineffective. According to the test results, the most budget models show less compression force than comparable mechanics in terms of price. Also an important factor is the low reliability of such systems.

    As a conclusion, we can say that solid mechanical brakes are a much more efficient option than the simplest hydraulics. And the final choice lies directly with the buyer.