How to bleed shimano hydraulic brakes on a bike


bleed, shimano, hydraulic, brakes, bike

There are many different pads, both in terms of material of manufacture and in form factor. But it is the material of the pad rubbing against the rotor that affects the braking force.

Varieties with increasing braking power:

  • Organic. good modulation, but relatively low friction (weak braking power);
  • Semi-metallic. fairly good modulation, higher braking power;
  • Metallic. medium modulation, high level of frictional properties;
  • Ceramic. Highest friction properties, but extremely expensive and rarely used by riders.


If all the previous variations and differences in hydraulic brakes were related to the general design and had a mediocre (if at all) relation to the quality and level of brakes, then further we will consider the differences that affect the level of the system.


  • Single-layer. the most budgetary version of the rotors, consisting of a one-piece steel disc;
  • On a spider. consists of several elements fastened together. The spider (the inner part of the disc) is usually made of aluminum to better dissipate the heat generated from the pads rubbing against the disc;
  • Floating. the same rotor on a spider, but the spider is attached to the brake pad by means of a special rivet. Such a system of fastening the rotor elements is designed to increase heat dissipation due to the gap between the fastened layers of the disc.


Let’s consider how hydraulic brakes differ from each other from different manufacturers and for different bicycles.

Symptoms of a hydraulic brake malfunction

The first symptom of a malfunction of such bicycle brakes is that it begins to brake on its own. This can be explained by the fact that air has entered the brake system. This could have happened due to the fall of the bike, a low level of brake fluid in the reservoir, or when the hydraulic circuit is open.

Since air tends to be compressed, unlike liquids, when it enters the system, it works like a gas spring. That is, the air creates the pressure of the brake fluid, which activates the brakes.

Also, the braking system can engage in similar self-activity, in case of jamming of the working piston. And the reason for this is the ingress of water into the hydraulic system.

And, of course, the brakes urgently need to be repaired if the brake lever is not as elastic as before, or the hydraulics no longer responds to the cyclist’s command to stop the vehicle.


The caliper attaches to the frame or fork in different standards, depending on which standard the manufacturer decides to use on its products. Also, the mount is influenced by the attachment point (front or rear wheel) and the size of the rotor, depending on which it is necessary to mount the caliper at a certain distance from the center of the wheel. For the interaction of all these standards with each other, special fastening adapters (adapters) are used.

  • (PM). Post Mount. now the most common standard used on most modern bicycles;
  • (IS). International Standart. outdated mounting option. If it is used somewhere, then it will most likely be the so-called Ashanbayki;
  • (FM). Flat Mount. A rare standard commonly found in road and cyclocross bikes.

Brass compression fitting with nut and cam

The hydraulic hose is disconnected from the discs and pads, which must be removed from the working area so that the parts are not contaminated with brake fluid flowing from the disconnected tube. Carefully examining the tube, a cam and a compression fitting are found. The first is necessary so that the hydraulic hose, made of plastic, does not deform under strong heat and cannot fall out of the cam. These elements are needed to hold the hydraulic hose in place when heated.

Next, the clamp is cut off, without which it will not be possible to pass it through the fasteners. This is done using a special tool. a cutter, which cuts easily, ensuring an even cut. In the absence of such, they are eaten with a knife or blade, but carefully. Nippers can also cut off the hydraulic hose, but they will not give a smooth and clean cut, and it is important for putting on the cam and installing the fitting.

Before threading the mountings through the hydraulic line, make sure that it is laid correctly for the given bike: the hydraulic hose does not rub against the fork crown and leg.

Fork companies will deny part warranties if this rule is violated. From constant friction against the crown, the long hose gets damaged, so it is recommended to carefully tighten it. But, the length should be such that the hydraulic hose is not damaged when turning the bicycle handlebars. It must be pulled to the mount through the holes in the bike frame, and then directed to the car, which is then attached to the frame. When cutting it, do not forget to leave a loop that is inserted into the machine. It is recommended to leave a margin of 7-20 millimeters.

After the undercut has been completed, the compression fitting or olive should be installed by first putting on the nut and then the clamp. Before performing work, be sure to read the instructions from the manufacturer attached to the disc brakes, because some clamps can be directional, others can be chamfered.

After they are placed, the fitting is inserted. To make it sit tight, use clamps that help the hose to sit tight and prevent damage to it. The fitting is driven in with a hammer, and then a nut is placed, having lubricated it first so that it fits well into place. Tighten the nut by hand. If the nut has stopped, the hose is pushed all the way into the machine. After that, tighten it to the required value without overtightening (use the tori key). It remains to pump the hydraulic brakes of the bike.


Dot (DOT 5.1, DOT 4.1). This type of brake fluid is used mainly by the Hope and Sram brands. It has a different chemical composition and slightly differs in properties from mineral oil. caustic substance. Therefore, when pumping the brake system, it is necessary to ensure that the pillbox does not fall on the elements of the bicycle. And if you hit, then try to remove it as quickly as possible with a rag from the paintwork and plastic elements of the bike.

Hydraulic bicycle brakes

Hydraulic brakes. fluid hose instead of cable

The mechanism of action of hydraulic brakes is very similar to that of their mechanical counterparts (disc and rim brakes). The main difference is that mechanical brakes use bicycle cables, while hydraulic brakes use a special hydraulic line instead of a cable. This hydraulic line connects the brake levers to the brake itself, which can be a mechanical disc or V-brake pads.

The bottom line is that there is oil or brake fluid under pressure in the hydraulic line. There are cylinders at both ends of the hose. When you press the brake lever, the brake cylinder transfers force to the brake line, which activates the other cylinder at the other end of the tube, which in turn activates either the rim or disc brake, whichever you use. If you use brake fluid inside your tube, you need to have the fact that this fluid is poisonous and corrosive to paintwork. Therefore, this liquid can be replaced with oil.

Advantages and disadvantages of hydraulic brakes, their application

The main advantage, in fact, which prompts the owners of hydraulics to use it, is the accuracy of the braking performance, its clarity and responsiveness. With prolonged use of mechanical brakes, either the brake pads are worn out, or the cables wear out (sometimes break). Using hydraulic brakes will not present you with this problem. The main thing here is not to allow kinks of the tube in which the brake fluid is located, well, with a damaged tube, you can, accordingly, be left without brakes altogether. The rest of the hydraulics is at a high level and there must be a future behind it.

Since the use of hydraulics makes the brakes feel better and makes them act more clearly, they are very often used on powerful bicycles. For example, on bicycles designed for freeride or trial. For bicycles that are used in extreme conditions, where the speed of the bicycle’s reaction to braking is one of the main selection criteria.

The disadvantages include the complexity of the repair. For example, in the field, a punctured hydraulic line can become a significant problem for you, which will be quite difficult to eliminate. If this happens during the race for the winner, there is a big chance that you will be the last one. Some more disadvantages lie in the fact that there are difficulties in installing the trunk, since the brake line can become a hindrance in this. Difficulties in removing and putting on wheels on forks. you need to be very careful so as not to accidentally damage the brake pipe.

Installation of hydraulic brakes

To apply the rear brake to the frame, the brake hose must be disconnected because the brake hose will need to be threaded through the mount. Usually the hose is simply attached to the frame. Remove the pads before working with hydraulic disc brakes, as the brake fluid will spill and dirty them during operation. Make sure you have clean hands before starting. Remove the pads, move the discs and pads away from the bike and then you can disconnect the brake line and pass it through the frame again connect and bleed the system.

Cam and compression brass fitting with nut

Disconnect the hydraulic hose from the discs and pads. Keep them away from the work area. When the hose is pulled out, the brake fluid may become contaminated. So, if you now bring the end of the hose closer and take a closer look, you can see the cam and the compression fitting. The brass fitting is used to prevent the plastic hose from shrinking from the heat and from jumping out of the cam when the system is very hot, that is, the cam and the fitting simultaneously hold the hose in place when it heats up.

Before threading the brake hose into the mount, make sure that the hose gasket fits your bike. Fork manufacturers today require that the hose does not rub against the crown or the leg of the forks otherwise they will void the warranty. Do not leave the hose too long so that it does not touch the crown or it could damage it with constant friction. Pull it carefully, but so that the steering wheel does not break the hose at maximum turns. Pull along the frame, through the holes, straight to the mount, and from there outward to the clipper. Now you can attach the clipper to the frame.

Now we need to cut the hose, leaving a small loop. Remember that the hose is inserted into the machine, so do not cut it too short at the very entrance to the machine body. It is necessary to add 7-10 millimeters to the length. When you have cut the hose, you can put in a new olive and compression fitting. First, we put on the nut that holds them, then the clamp. There are directional clamps, so it is very important to read the manufacturer’s instructions for the specific disc brake system. Some clamps have a chamfer. When the clamp is on, insert the compression fitting. It should fit snugly and clamps should be used to hold the hose firmly without damaging it. Then take a hammer and drive in the fitting. When the fitting is in place and the clamp is ready, put the nut on, lightly lubricating the clamp and nut so that everything fits into place. Tighten it by hand and when you think that it will stop push the hose all the way into the machine, now you can tighten the nut and again try not to overtighten, it is better to use a special tori wrench. To tighten the compression nut to the desired value.

If the nut is tightened properly, you can start pumping.

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Bleeding hydraulic brakes

When bleeding the disc brake system, keep the discs and pads away. First of all, unscrew the master cylinder and fasten it again so that the top of the cylinder is horizontal. Since we will inject liquid into the system, it is better to work with a flat surface. Now you need to remove the top cover from the master cylinder. Most likely it is secured with Phillips screwdriver screws. Make sure the head of the screwdriver is sharp. Some screwdrivers are thorium-coated. As with everything, it is important to use the right tool in your work. like with a girl.

By unscrewing the cover of the master cylinder, you can see the membrane of the master cylinder. It expands and contracts as the temperature of the brake fluid changes. Under it you can see the brake fluid. It must be emphasized that you must use fluid for your disc brake system. If the fluid is not the right one, you run the risk of serious injury due to inoperative brakes. But most importantly, you can damage the entire brake system, and its repair is very expensive.

Tools that will be needed for pumping

Each disc brake system can be pumped differently. Read the manufacturer’s instructions. You can use your own methods, but be extra careful and be sure to check the brakes before riding. Here we will be looking at pumping the shimano system. A special tool is used for it, which is attached to the main cylinder body. Liquid is collected in its bottle, it can be hung on the handle. It looks like a bottle with a tube extending from its cap, which adapts to the brake system. When we pump the liquid from the pad through the system with a syringe, it will pass through the master cylinder into the tube. There is a small hole on the bend of the tube with a tube and the liquid will flow into the bottle.

Now you need to draw the liquid into the syringe. It uses a bottle of Shimano mineral-based disc brake fluid. I emphasize once again that you need to use the correct fluid. Draw liquid into a syringe. To bleed the brake system, you need to dial as much as possible. If you get air bubbles in the syringe, flush them back into the bottle so that no air remains in the syringe, otherwise you will not reach your goal. You bleed the system in order to get rid of the air in it and fill it 100% with brake fluid.

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Now you need to inject the liquid through the machine. When you inject fluid through a typewriter, it can immediately open the piston valve and there is a possibility that the valve will pop out of the body, so many disc brake manufacturers include a gasket with them, which can be placed where the pads are usually located when pumping. If the gasket does not fit your brakes, you can use a spare brake lever and something else that will prevent the valves from coming out of the machine body.

Bring fluid to the very end of the hose and slide the hose onto the inlet nipple. Open the inlet nipple with a wrench. You can now supply fluid to the system. Gradually. When pumping fluid through the system, it is important that it does not leak. Some brake fluid compounds can damage paint. The mineral composition is harmless. And with other compositions, I advise you to cover the frame with something to protect the paint from damage. When pumping fluid into the system, tap on the pipes with an assembly wrench or other tool so that air that could remain in the main cylinder housing is released. Stop dispensing beforehand. Now close the inlet nipple and you can pick up the tube. Check again that the valves are all recessed into the machine body. The fluid that you pump through the system can now be removed. The fluid should reach the top edge of the master cylinder housing. There should be no air here. Clean the master cylinder diaphragm, if necessary, so that there is no contamination. Put it on top and close the lid.

The disc cleaner can be used to wash off the remaining brake fluid from the steering system, clean discs and pads, if required. Clean the clipper. It is recommended to use technical wipes that do not generate lint. If you use an old rag, it will leave a lot of small particles, fluff, which will get into the brakes and can cause leakage or dirt.

Be sure to wash your hands before installing the pads in the system. You have pumped the brake system and most likely you have brake fluid residues on your hands. You don’t want to get the pads dirty by inserting them into the brake system. When working with the brakes, your hands must be clean, as oil, grease, brake fluid will contaminate them and you will need new pads. As you know these disc brake pads can be expensive.

Adjusting the hydraulic brake pads

If you have correctly adjusted the machine and the brake disc is exactly in the center, but still clings to the pads, this usually means that one of the valves protrudes from the body more than the other. Once you are sure that the disc is exactly in the center of the clipper you can do one trick to even out the distance between the pad and flange. It will take two people here. One should press the disc against the valve, which is too protruding, and the other will work with the pads, sliding and extending them. The valves will align. Due to the pressure of the disc, one valve works more than the other, that is, with the help of the disc, we press one valve into the body, while the second moves further. This is how we align the valves using a disc. But don’t push the disc too hard, you can bend it.

  • Bicycle brakes are not a luxury, they are a must. Which brakes you put on your bike will determine the degree of your personal safety while riding.
  • Cost for popular hydraulic brake models:

I want to say that using hydraulic brakes, if the speed of the bike is high enough, you need to be extremely careful so that it does not work like on


For this process, pads and discs are not required and must therefore be removed. Only the cylinder and main tubes are used. First of all, you need to unscrew the cylinder and fix it vertically. Next, you need to remove the cover, under which the membrane is located, and under it is the liquid. It is very important to use one type of liquid, otherwise there is a great risk of device malfunction. We fill a special syringe so that there are no air bubbles. Then we introduce the composition using a typewriter. At this point, the valve may jump out of the body and it is better to use a special gasket. The liquid is supplied to the end of the tube, which slides over the nipple. Carefully open the inlet nipple with a key and supply liquid.

It is not at all difficult to bleed and adjust the brakes and pads on your own. setting and adjusting the bike is easy to do with your own hands, you just need to approach the process carefully. It is better to tap the tubes during the delivery of the composition to allow air to escape. We close the inlet nipple, remove the tube. We put the membrane and close the housing cover. If the mixture gets on the outside of the bike, it can corrode the paint. Some mineral fluids do not have this property, but otherwise the frame should be protected. Bleeding hydraulic brakes must be done carefully, it is important to make sure that there is no air in the cylinder and remove dirt from the diaphragm and housing.

Hydraulic brakes for bike

How to set up, adjust and bleed hydraulic brakes? Device, adjustment and bleeding of the Shimano disc brake on a bicycle.

A bicycle is a relatively safe form of transport. The good functioning of all its components depends on the quality of the parts, the principle of operation and the frequency of use. Regular inspection and adjustment of systems allows it to work properly under all circumstances. Particularly noteworthy are the hydraulic brakes on the athlete’s bike.

Working principle and features

Classic mechanical devices work very simply: the wheels are driven by a cable. The hydraulic brakes are operated by a hydraulic line. It connects the handles and the mechanism itself. The last element can be either a disc or a V-break pad.

The principle of operation of such a system is simple, but the liquids are quite toxic and environmentally unsafe. The bicycle is considered a non-polluting transport, but such devices contradict this.

Positive and negative sides

Hydraulic disc brakes offer several distinct advantages:

  • Speed ​​of response;
  • Reliability;
  • Accuracy of work.

Such systems allow you to easily stop transport at the right time or on a difficult section of the road. The main thing is that for effective work they need to be pumped and configured on time. Modern companies offer a large selection, which makes it possible to purchase a ready-made kit. The quality of the devices is at a high level, you can put the equipment on the bike yourself.

Bicycle brakes of this type also have negative aspects. For many riders, the cost of disc brakes is a deciding factor. It is quite high and the repair of transport can significantly hit the. In addition, the device of braking systems has its own difficulties and not every owner will be able to properly set up the work. In this case, you will have to turn to professionals for help, which, again, will lead to certain financial expenses.

Disc brakes

It is worth mentioning the equipment based on discs and hydraulics. Their main difference from the rim is the stopping due to the clamping of the brake disc. Its attachment is carried out by pads, which are fixed on the frame at the back and the fork stays at the front. The disc brake cylinder can be of various designs. Thus, hydraulic disc brakes can be of the following types:

  • Multi-piston;
  • Single piston;
  • Two-piston with floating pistons;
  • Twin-piston in addition to opposed pistons.

The most popular are the models of the latter type. They are the most efficient and powerful. Single-piston disc brake designs are rare, but they have a large number of drawbacks, due to which they are practically not used. Disc brakes have many advantages, it is worth noting the high accuracy of work. Also, they do not need frequent adjustment, you do not need to constantly adjust the pads at all.

Hydraulic disc brakes are difficult to repair in the wrong conditions. The disadvantage is that due to the small distance between each other, the pads quickly deteriorate. If, when choosing this component, you pay more attention to the manufacturer and quality, then you can count on a long service life of the part.

Both oil and brake fluids are suitable for the operation of such disc brakes. It all depends on the individual preferences of the vehicle owner. Also of the features, it can be noted that the rear brake caliper on a bicycle in some cases interferes with the installation of the trunk, but it all depends on the design of the frame and, directly, the caliper itself plays an important role.


Various companies, such as Shimano, offer a huge selection of disc brakes. They all have a certain quality, popularity and value. It is worth noting the Shimano brand at least for the fact that their products are of excellent quality, and they rarely need repairs, the pads do an excellent job with their functions. Shimano’s latest series of system models have good clamping, but require careful selection. The set of this brand is quite acceptable and meets the criterion “price-quality”.

The quality of CLIM 8 CLARK’S hydraulic brakes is also at a high level, but during installation it is necessary to carefully match the pads to the discs. Unlike Shimano, this brand of braking systems has an interesting handle design, but this is not for everybody, the main thing is convenience.

The braking device can be selected in any price category. The quality of the braking systems will be at the appropriate level, it is just that repairs will be made less often for models that have proven themselves from a good side.

Features of the

There are few nuances in such equipment. The braking power depends on the type of caliper and the size of the disc. It is also important that the handle clamp responds accurately and quickly to movement. It activates the stop equipment. Comfortable positioning of the lever in the cyclist’s hand is essential.

Pads require special attention. They are necessary for the friction that drives and gives the braking force. Brake pads can be adhesive or metal-filled. The latter option is more popular and durable. This species also has good resistance to high temperatures.

Periodic checks and repairs of the hydraulic brakes keep the bike functional.

how to bleed hydraulic brakes on a bike

How to bleed shimano hydraulic brakes on a bike

Bleeding hydraulic brakes

I’ll show you how to bleed hydraulic brakes using the Tektro Auriga Comp brakes as an example.

At first it may seem like a difficult process, but in reality it is not, you just need to prepare well 🙂
What is useful to us for this?
– mineral oil with a viscosity of 10W. (50ml, if on front and back)
I used Shimano oil 50ml on tap in ChilinGrilin for 100r., But you can take others with the same viscosity. I had enough 12ml for the front brakes. If you change the oil for another, then do not forget to drain the old one completely. Do not forget that only mineral oil is poured into the Tektro and Shimano brakes, and the rest of the DOT!
-tubules (diameter such that it adheres well to the calliper fitting).
The easiest way to get a drip kit is from a pharmacy. In January 2010 I took it for 6.50 rubles. Or 30-40cm flexible tubes with a diameter of about 2.5-3.5mm
– syringe 5-12ml.
The larger it is, the more convenient it will be in the process, so as not to jump and type all the time.
– keys (asterisk T8, adjustable, but preferably open-end 7, possibly end-end 7, hexagon 3 and 5).
– jar for draining.
It is desirable to keep it clean and dry. If you bleed an empty brake, then the oil can be reused.
– plug for pistons.
I used a bent piece of iron, did it for 30 minutes, if anyone needs it and suits, I can borrow it. Someone inserts 5 ruble coins, someone inserts batteries and much more rubbish, in general, improvisation is possible here.
– newspapers and rag.

We will need approximately such a set.

Let’s start with preparation. We will spread the newspapers, we do not regret them, because if something goes wrong (let’s say a tube breaks off the fitting), then everything within a radius of a meter will be splattered, you can reach the ceiling, if pressure builds up, it will take a long time to get out.

We unscrew the calliper with a 5 hexagon, unscrew the pad screw with a 3 hexagon, remove the pads and the spring. This is in order not to flood them with oil and not damage them, some pump them without removing the cars, but this is fraught with damage to the rotor, the pads themselves and the crooked position of the pistons.
We put a tube on the calliper fitting, insert a plug between the pistons.

Now we need to fix the brake lever in a horizontal position. I did this on the steering wheel itself, I just moved the handle to the other side and turned the tank up (I have it adjustable). I put the bike up against the wall and put up a couple of stools to keep it from falling. he stood perpendicular to the floor. We unscrew the cover of the expansion tank using a screwdriver with a nozzle. an asterisk T8. We do this carefully so that we do not have to repair the entire handle later. After the first unscrewing, it is advised to replace the native screws with new ones for a “minus” screwdriver with the same length and M3 thread. This will allow you not to steam next time, that they may not get out.

We return to the calliper and the straw. We lower the other end into a jar or make a special bottle for this (a bottle, into the cork of which we insert the end of the tube and make another hole to let air out of the bottle). In general, it doesn’t matter where to drain, the main thing is not on the floor 🙂

After that, we unscrew the union, as I said, preferably with a 7 open-end wrench. I no longer had oil in the brakes (I had them after repair), it was not scary to unscrew it with a socket wrench, removing the tube from the fitting. If you have oil in the system and you cannot turn it off with an open-end wrench, then before that you should screw the tank down (otherwise you will have an oily fountain from the tank), lift the calliper above the tank, gently unscrew the fitting slightly with a socket wrench, put on the tube and put the jar under the other end. after which you can lower the calliper down and unscrew the expansion tank cap again;)

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If you need to pour out all the oil from the brakes, then you need to lower the calliper as low as possible and turn so that both holes with a hydraulic line and a tube on the fitting are as low as possible. This will help drain the old oil out of the piston system completely. We pump it out by pressing the brake lever until the oil stops coming out and only air comes out.

Then we put the oil into the syringe (if you have oil in some tall and narrow jar, you can put an extra 10 cm of tubes on the syringe for the convenience of drawing oil). We transfer the calliper to a standing position (so that the fitting is perpendicular to the floor). We fill the entire expansion tank with oil from a syringe.

How to quickly bleed the brakes without using up all the oil and nerves?

Press the brake lever and hold it in the clamped position until it stops.
2. Clamp the tube extending from the fitting. (You can do this with your fingers, or you can leave the clip on the dropper).
3. Let go of the brake handle. We see how atmospheric pressure pumps oil from the tank into the system.
4. Unclench the tube extending from the fitting.
5. Add oil to the tank. (it is possible not every time, but after every second repetition of 1-4 points, the main thing is to prevent the tank from emptying, which will lead to air ingress and we will have to do everything from the beginning again).

The oil is quite liquid, if you don’t do this, you can pump the brake for a very, very long time. 🙂

We repeat these actions, tapping the hydraulic line so that all the air goes out as quickly as possible. With such simple actions, we pump oil into the hydraulic line until clean new oil comes out of the fitting without large air bubbles.

When we see that the bubbles are no longer coming, we clamp the tube and tighten the fitting (the main thing here is not to be too zealous, because the calliper is fragile). Then we can remove the tube from the fitting and put on the cap.

Next, it remains for us to fill the tank with oil, you can do this not to the brim, leave 1mm to the edge, insert the rubber gasket, close the lid and tighten the screws.

After that, we just have to pull out the piston plug, wipe everything from oil residues (it is better to wash and dry), return the pads to their place, hang and adjust. The main thing until the moment everything returns to its place, it is better not to press the brake lever, so as not to forcefully return the pistons back. If, for some reason, they nevertheless pressed, then you can dilute with an ordinary knife or flat screwdriver, inserting between them and slightly turning.

Bleeding the brakes on a bicycle. the final stage of repair

After all the parts of the system are fully inspected and assembled, it remains only to add brake fluid and competently bleed the hydraulics. This procedure is carried out in order to get rid of air bubbles that can accumulate in the cylinders and pipes of the system and interfere with its correct operation.

So how do you upgrade your bike? This can be done by anyone who understands at least something in technology and knows how to handle tools. There are quite a few ways to carry out pumping, we will consider the simplest and most proven of them.

How to bleed hydraulic brakes on a bike

Hydraulic brakes are useful on mountain bikes designed for mountain biking, bumps and bumps. The hydraulics provide quick response and a high degree of reliability. In addition, high-speed bikes are also equipped with this system, since its use allows you to quickly decelerate.

The frictional force in hydraulic brakes is significantly lower compared to mechanical counterparts. This is achieved through the use of brake fluid and cylinder-piston groups, which, among other things, increases the life of the system.

Despite all the advantages, hydraulics are not without drawbacks, one of which is poor maintainability. For example, a breakdown of a hydraulic line in the absence of appropriate tools cannot be repaired and the only thing that can be done is to bleed the brakes on a bicycle.

How the hydraulic braking system works

The design of any hydraulic brake consists of cylinders connected by a line with pistons. The line is a hose that can withstand high pressure. When you press the brake, the brake fluid is forced out by the piston and is directed from the master cylinder to the working one. Here, the pistons are advanced under pressure and press against the pads, which rub against the rotor. This is how braking comes in.

Diagnostics and repair of hydraulic brakes on a bicycle

The first sign that the braking system is malfunctioning is its spontaneous braking. This could be due to air entering the system, a jammed working piston, or an open circuit in the hydraulics. In addition, the brakes need urgent repair if the brake lever has lost its elasticity or does not respond at all to pressing.

To identify a malfunction, it is necessary to dismantle the wheel where the problem appeared, and then remove the brake pads. After the access to the working pistons opens, they must be pressed in with a screwdriver and the brake lever pressed. If one of the pistons is seized, this is a signal to change the repair kit. Finally, it is necessary to inspect the entire hydraulic line. it should not be damaged, and their presence indicates the need to replace the line.

We will need:

  • bottle or can;
  • oil or brake fluid, depending on the system;
  • keys;
  • a clean cloth for wiping the system;
  • a hose made of transparent material, the diameter of which is suitable for the bleed bolt.

First of all, it is necessary to put one end of the transparent tube-hose on the bolt for bleeding, and place the other end in a bottle with a small amount of brake fluid poured into it. Then the tank with the liquid must be opened and made sure that it is completely full. Please note that a certain type of brake fluid is suitable for each bicycle model. They cannot be mixed or replaced.

The second step is to bleed the disc brakes. After pressing the brake lever several times and fixing it in the pressed position, unscrew the screw on the brake machine. In the process, you will take away the air bubbles coming out of the tube. Tighten the screw immediately and then release the handle. Repeat this procedure several times until the system is working properly.

As you can see, bleeding hydraulic brakes on a bicycle is no big deal. This simple procedure will help you troubleshoot the brake system.


Be careful if the brake fluid gets on the brake disc or pads, the braking properties will deteriorate.

Use only the brake fluid recommended by the manufacturer.

Position the brake lever so that the expansion barrel is horizontal and facing up.

Put a cambric on the bleeder bolt and lower it into a bottle or other container to collect excess brake fluid.

Unscrew the cap of the expansion barrel (this usually requires a 3-4 sprocket)

Gently fill the brake fluid up to the MAX level.

Smoothly press the handle several times until you feel that it is pressed tightly, press and hold the handle.

Using a 7 key (in different models in different ways), slightly unscrew the bleed bolt (on which you put the cambric) and immediately tighten it. Do not release the handle at the same time. Do not forget to add fluid to the expansion tank.

Repeat steps 5 and 6 until the handle becomes tight.

Bicycles with disc brakes are very effective in bad weather and rough conditions. Watch the braking system and you can always stop your bike on time.

Video how to bleed hydraulic brakes:

How to Bleed Shimano Disc Brakes – Mountain Bike Maintenance

How to bleed hydraulic disc brakes?

Bleeding hydraulic disc brakes is a serious and responsible job, therefore, you need to approach it prepared.

The main symptoms that you need to bleed the brakes are as follows:

When you press the brake lever, it reaches almost to the grip, and the brake does not grasp, but the pads are in good condition. 2. The handle just fails when pressed.

If you press the brake sharply after it is applied, the handle will still move smoothly.

The cause of these symptoms is air that has entered the hose. This can happen due to damage to the brake line, overheating of the caliper and oil boiling, a sudden temperature drop, an incomplete expansion tank, or a loose fitting on the caliper.

Before you start bleeding disc brakes, you need to check the hose for cracks, oil leaks, etc. And also check the wear of the brake pads. If everything is in order, you can proceed.

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.


-Be careful if the brake fluid gets on the brake disc or pads, the braking properties will deteriorate.

-Use only the brake fluid recommended by the manufacturer.

The main symptoms when you need to pump the brakes

When you press the brake lever, it reaches almost to the grip, and the brake does not grasp, but the pads are in good condition. 2. The handle just fails when pressed. 3. If you press the brake sharply after it is applied, the handle will still move smoothly.

The cause of these symptoms is air that has entered the hose. This can happen due to damage to the brake line, overheating of the caliper and oil boiling, a sudden temperature drop, an incomplete expansion tank, or a loose fitting on the caliper.

Before you start bleeding disc brakes, you need to check the hydraulic line for cracks, oil leaks, etc. And also check the wear of the brake pads. If everything is in order, you can proceed.

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 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 the brake bleeding.
  • Wipe the brakes from possible brake fluid leaks. Profit!

Although pumping the brakes requires certain skills, there is still nothing to worry about. You need to thoroughly prepare and not confuse anything during pumping. Most importantly, do not 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.

How to bleed disc brakes on a bicycle

Bicycle Repair: How To Bleed Disc Brakes

Perhaps your brake has begun to slow down worse, the handle falls through almost to the grip, but no braking occurs? Do the brakes quickly overheat and “boil” on descents? Most likely air and water have leaked into your brake system! Today we will give a couple of tips on how to bleed your brakes.

Our article covers the following aspects:

The process of bleeding the brakes in step-by-step instructions

When the hydraulic brake system is completely repaired, you only need to fill in the brake fluid and then pump it over. Bleeding is needed in order to remove all air from the system, which is an obstacle to the correct operation of the mechanism.

There are several options for pumping hydraulics on a bicycle. Let’s describe the simplest version of how the hydraulic brakes of a bicycle are pumped. First, make sure you have the following tools and materials:

  • The tube is transparent, which will fit the diameter of the bleed bolt.
  • Brake fluid or oil, depending on the pumped type of system. for Shimano this is a special oil.
  • Allen key or sprocket for loosening the bolt on a device with a master cylinder.
  • Two syringes.
  • Cloth for cleanliness during work.
  • The upper bolt on the brake lever. caliper is unscrewed. To prevent oil from leaking out of the cylinder, the mechanism must be moved 5-10 degrees to the upper position.
  • After unscrewing the bolt, you need to remove the rubber ring (sealing).
  • You need to firmly install a suitable size tube into the hole, and connect a syringe or a plastic bottle on the other side of it (it is better to use 200 ml syringes). This container will be used to collect the expelled oil from the system along with air.
  • Now you need to take another 200 ml syringe with a tube and fill it with new oil or liquid.
  • Air must be expelled from the syringe with a tube, after which the free end of the tube must be connected to the pumping connection provided by the system on the brake caliper.
  • After the tube is tightly put on, you need to unscrew a little bolt for bleeding. Now you need to slowly inject the liquid into the system from the syringe, and observe its exit into the container originally installed in the mechanism on the steering wheel.
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When bleeding the brakes, it is also recommended to tap the brake hose to accelerate the release of air bubbles upward. After bleeding the system, you must first screw the bolt on the caliper, then remove the syringe with the hose. Before disconnecting the container connected to the master cylinder on the steering wheel, you must first pour the displaced fluid into another container or install the handle, while creating a vacuum. After that, you can disconnect the syringe, install the O-ring, and tighten the fixing bolt.

As you can see, the process does not present any difficulties, and can be done by hand at home. This method is considered to be the simplest and most effective. Remember to remove oil and fluid spills with a clean piece of cloth.

Diagnostics and preparation

To determine the exact cause of the breakdown, you will need to carry out diagnostics. Dismantle the wheel on which there is a suspicion of a system malfunction. If the brake machine is dirty, then it should be thoroughly cleaned using a toothbrush. After that, you need to dismantle the pads, and make sure that the pistons are working. To do this, the pistons are pushed inward, and then the brake lever is squeezed out. If both pistons move forward, there is no problem. If one of them (or both) is jammed, then you will need to make repairs using a repair kit. Repair of pistons provides for their replacement, and also O-rings are changed.

It is interesting! Shimano hydraulic systems use mineral oil, most other models and companies use DOT brake fluids.

Preparatory work includes the following:

  • Protect discs and pads from oil ingress. Discs can be degreased, but with pads it is more difficult, since they will have to be disposed of. To protect them, you need to cover with a rag.
  • Check pads for integrity. If they have wear, burrs, chips and other defects, they should be replaced.
  • Check the rotor. If the disc shows signs of damage, then it must be replaced. Dirt, debris and oil should be removed from the brake pads and rotor. The quality of tightening of all bolts that attach the device to the wheel is checked.
  • The condition of the hydraulic line is checked for leaks. If such leaks are found, the hoses should be replaced before bleeding the system.
  • Make sure the wheel is installed correctly.

After that, you can proceed to the procedure for bleeding the brakes.

Method of bleeding the brake system “for the lazy”

There are many ways to bleed hydraulic brakes, so consider another one that will also be useful when the brake lever is slightly loose. If you have changed the brake hose, then this method is not suitable. The principle of its implementation is as follows:

  • Move the master cylinder so that the bolt hole is at the highest point.
  • The bolt is unscrewed, after which a syringe without a piston or another container of a suitable diameter is inserted into the hole to be installed in the cylinder bore.
  • After that, you need to pour oil or brake fluid into the container, and start pumping.
  • You need to operate the brake lever to evacuate air from the system. With each movement of the lever, the handle will become more rigid.
  • The duration of pumping takes from 2 to 15 minutes, depending on the speed of the handle.
  • For greater efficiency, tap on the hose lines to expel any remaining air bubbles.

This method can be implemented even in the field if the brakes are missing. Finally, the syringe installed in the barrel is removed and the locking valve is screwed on. So that at the moment of removing the syringe, the remaining liquid in it does not leak out, you need to install the handle (plunger) into the syringe and remove it.

Hydraulic brake design

The hydraulic braking system is based on details such as two cylinders with pistons. These cylinders are connected to the handle on the handlebars using hoses (hydraulic lines) that can withstand high pressure. There is a fluid inside the hoses, which, when the brake lever is pressed, presses on the master cylinder, transmitting force to the working devices. Under pressure, the pistons move forward, transmitting force to the pads. The latter touch the brake disc, and due to the frictional force, the speed is reset.

In the design of the mechanism, cylinders of different sizes are used. main and working. The slave cylinders that act on the pads are larger than the master cylinder on the brake lever. This makes it possible for the cyclist to exert little force when pressing the brake lever to stop the vehicle.

Common breakdowns of hydraulic brakes

Hydraulic maintenance is not done as often as mechanical disc devices need it. Before each ride, you do not need to adjust and adjust the hydraulics, which is one of the important advantages. However, along with the advantages, there are also disadvantages that manifest themselves in the form of breakdowns. The most common types of breakdowns are:

  • Lever failure when no deceleration effect is observed when the handle is depressed.
  • Damage to the hydraulic line, as a result of which it is necessary to replace the hose.
  • Pads abrasion.
  • Failure of the O-rings. These are special O-rings located on the brake lever (caliper).
  • Loss of properties of brake fluid or mineral oil, depending on the type of system.

It is possible to determine the malfunction of the mechanism by such a sign as self-braking of the bicycle. This means that air has entered the system and the expansion springs cannot open the pads from the disc. There are various factors that cause air to enter the system:

  • Falling vehicle.
  • Low amount of fluid or oil in the system.
  • Opening the hydraulic circuit.
  • Boiling liquid.

If water gets into the hydraulic system, the working piston can jam. It is imperative to expel air from the system, otherwise it will lead to rapid wear of the pads and discs of the brake system. While riding, you will need to adjust the effort, as the pads will rub against the disc. The sound in the form of a squeak will also help to determine the malfunction of the mechanism. If the bike squeaks, then it’s time to adjust the brake mechanism by pumping fluid.

It is interesting! If mechanical brakes have disappeared on the bike, then they can be repaired even in the field, but for the repair and pumping of the hydraulics, you will need not only a garage with tools and materials, but also knowledge of the process.

Features of bleeding hydraulic brakes on a bicycle

Hydraulic brakes on bicycles have appeared relatively recently, and have already won the sympathy and vocation not only among beginners, but also among experienced cyclists. Such devices are used when high accuracy and reliability are important. Bleeding the hydraulic brakes on a bicycle is carried out when the system has been repaired. Although the mechanism does not have to be repaired often, the time comes when you need to pump the device for its operability.


When carrying out work, safety precautions must be observed, since brake fluid is an acid, which, if it gets on parts of the body, will provoke a burn. Also, do not allow liquid and oil to get on the brake disc and pads. If this happens, then the disc can be wiped off, but the pads will have to be replaced.

How To Bleed Shimano Hydraulic Disc Brakes

If liquid gets on the bike’s paintwork, it can corrode it. To prevent this from happening, you need to handle the liquid with care and avoid direct contact. After carrying out the work, you need to check the correct operation of the brake system, and make sure that the procedure is carried out correctly.

Leakage and replacement of brake fluid

If a person takes care of his bike, he will certainly regularly change the brake fluid from time to time, since it becomes dirty from moisture, as well as dirt after a certain period of use. It is important to use the brake fluid recommended by the manufacturer, since most choose an option for themselves that is suitable for the price and is far from the brand that is needed. There is also a contingent of people who can replace the brake fluid with mineral oil, automobile fluid. During replacement, you should be careful not to contaminate the brake pads with fluid and try not to press on the calipers or brake levers in the process.

Before you start changing the fluid, the bike must be upright and stationary (preferably on a bike rack). Do not try to turn the liquid upside down as this will trap air into the cables. Before starting work, make sure that you have no leaks from the cables or caliper (when replacing some parts). Bleeding and maintaining the hydraulic brakes of a bicycle is not considered a difficult process, and it is worthwhile to weigh your capabilities and abilities well. If the bike is equipped with hydraulic brakes, then the rider immediately has a lot of advantages:

  • maximum reliability while traveling;
  • the ability to slow down in the most extreme situations;
  • full confidence in their capabilities;
  • long service life.

Bleeding and maintenance of hydraulic bicycle brakes

Not everyone can understand the function of hydraulic disc brakes or know how to change brake fluid. Why is this question relevant? Many of us just love to spend our free time cycling. Such a means of transportation is considered the most practical, economical and at the same time useful. Often, the brake system in bikes is hydraulic, due to which such facts will certainly come in handy.

Bleeding and maintenance of hydraulic bicycle brakes

This type of brake works in much the same way as disc brakes on cars. They use a caliper that is usually attached to the forks. They slow down or stop the bike by applying pressure to the brake levers. This pressure is transmitted to the calipers through fluid, which forces the brake pads against the discs (rotors). Friction forces the bike to slow down, to stop. friction is achieved through the use of soft pads, which provides more stopping power. Harder compound pads tend to last longer and are more suitable for wet and muddy conditions.

Bleeding hydraulic brakes on a bike

The bleeding of the brake system in each bike model will be different. To change the brake fluid, the brake manufacturer’s instructions must be followed closely to know the exact process as they are brand specific. To replace and bleed, you will need the following:

  • a tube of a certain diameter (for the pumping bolt), necessarily with transparent walls;
  • 4mm hex wrench and other tools;
  • certain brake fluid;
  • small flat head screwdriver
  • container (bottle or jar);
  • rags to remove dirt.

Hydraulic systems have reservoirs that can usually be accessed by removing the cap from the top of the brake arm. This reservoir is an important feature of the system because when the brake fluid heats up, it expands and needs to be moved. The reservoir acts as a release of excess fluid to prevent cable splitting.

How to bleed hydraulic brakes on a bike

Brake fluid leak is a process that allows trapped air to escape from brake cables and calipers. If there is air in the system, this will result in a much slower braking response. Keep all parts of the system clean, especially the reservoir and cushions. Remove the wheels, taking care not to damage the discs as they pass through the caliper. Remove the brake pads and replace them with cardboard or wood shims or some old shims. The bike must be positioned in such a way that the cable constantly climbs uphill between the caliper and the reservoir.

The top surface of the reservoir should be parallel if not adjusting the brake levers. Take a drain pipe and attach it to the drain nipple on the support. Use elastic tape to attach the plastic bag to the other end of the pipe. Be sure to wipe the dirt off the brake lever and around the reservoir. Unscrew the reservoir lid and remove the lid. Fill the reservoir up to the top with the correct brake fluid.

Unscrew the elbow nipple one turn. Re-pump the brake lever. The fluid in the reservoir will bubble and the level is likely to drop. The reservoir will be completely filled when the level drops. Click on the cable to release any trapped air. Liquid will eventually start to flow out of the nipple. just close it.

After such actions, any hydraulic system (for example, a shimano bicycle) will work properly and correctly, which will give the maximum level of comfort and reliability for a person.