How to bleed the brakes on a gt bike


Hydraulic bike brakes require constant care and maintenance. In order to ride a bike as safely as possible, the braking system must function properly. And for the hydraulic brake to provide maximum safety, it must be properly bled. Bleeding hydraulic disc brakes is a serious and responsible job, so you need to approach it responsibly.


Hydraulic brakes on a bicycle act like their mechanical counterparts (disc and rim brakes). The principle of operation differs only in that the mechanical brakes are actuated using a cable, and the hydraulic ones operate using a special hydraulic line.

With the help of this hydraulic line, the brake levers and the brake mechanism itself are connected, which can be either a mechanical disc or V-brake pads.

bleed, brakes, bike

The fact is that the hydraulic line is filled with oil or pressurized brake fluid. The hose has a cylinder at each end. When the brake lever is pressed, through the brake cylinder, the force is transmitted to the brake line and acts on the second cylinder from the other end of the brake line.

And this cylinder acts on the rim or disc brakes, depending on which brakes you use. If your hose is filled with brake fluid, remember that this fluid contains poisonous substances and will corrode paintwork. For this reason, brake fluid is often replaced with oil.

Pros and cons of hydraulic brakes.

The main advantage, thanks to which the owners of hydraulic brakes use them, is very precise braking, precise and fast response.

If you use mechanical brakes for a long time, then they will either wear off the pads or break the cables. If you use hydraulic brakes, then these problems will not concern you.

In a brake system of this type, the main thing is that the tube with the brake fluid or oil does not bend, but if the tube is damaged, the brakes may stop performing their functions altogether.

Because the hydraulic braking system makes the cyclist feel the brake better and the brake lever responds more clearly, hydraulics are often fitted to high-performance bicycles.

For example, bicycles designed for freeride or trial riding. Bicycles of this class are used for extreme riding, in which the responsiveness of the bicycle brake system to the actions of the cyclist is one of the most important points.

Among the shortcomings, it is worth noting the complexity of the repair. For example, if you pierced the hydraulic system somewhere far outside the city, then this is a significant problem, the elimination of which is very, very problematic.

If this situation happens during any competition, then most likely you will be in last place. Also, the disadvantages include the fact that it will be quite problematic to install the trunk with the hydraulic system installed, because the hydraulic system interferes with the trunk.

Also, there are some problems with removing and putting the wheels on the bike. you should perform these actions very carefully, as you can damage the hydraulic system, but here, of course, there is little good.


Bleeding hydraulic brakes on a bicycle has nothing to do with discs and pads, so we remove them. In this case, the main work is carried out with cylinders and tubes. So let’s get started.

  • First, you need to unscrew the main cylinder and fix it in an upright position.
  • After that, we remove the top cover on the master cylinder. There is a membrane under the cover. There is brake fluid under the diaphragm. It is worth noting that you need to use exactly the fluid that is poured into your brake system. If another fluid enters the brake system, there is a risk of brake failure. But more importantly, damage to the entire brake system can occur, and it is not cheap to repair it. The bleeding of each hydraulic brake system is individual. You can use your own methods, however, you need to be extremely careful here and be sure to check the brakes before driving. Consider a shimano brake system. To pump it, use a special tool attached to the body of the main cylinder. The liquid is collected in its bottle. It looks like a container with a tube, which is adapted to the hydraulic system.
  • Fill the syringe with liquid. Again, the liquid should not be of any other type. To bleed the brake system, you need to fill the syringe as much as possible. There should be no air bubbles in the syringe, because it is to get rid of them that pumping is done.
  • The next step is to inject fluid with a typewriter. During this operation, the valve sometimes jumps out of the body, for this reason, you need to use a special gasket or something else to prevent the valves from escaping the body of the machine. It is necessary to bring the liquid to the very end of the tube and put the tube over the inlet nipple. Now we open the inlet nipple with a key, after which, slowly, we can carry out the fluid supply. When pumping fluid through the system, it is important that there is no leakage. Brake fluid can corrode paint. Mineral-based fluid is harmless; when using a different composition, it is better to protect the frame with something. When pumping fluid, tap the tubes with a wrench or other tool to help air escape from the main cylinder body. You need to stop feeding liquid in advance.
  • After closing the inlet nipple, remove the tube. Check for valves in the machine body. The position of the fluid should be flush with the top edge in the main cylinder body. There must be no air. If necessary, the diaphragm in the master cylinder must be cleaned of dirt.
  • Now, you need to put the membrane on top and close the lid. Clean the steering system of brake fluid residues with brake disc cleaner, if required. The clipper must also be cleaned. You can use technical napkins, from which there are no lint. It is better not to use an old rag, small particles, fluff from it, can get on the brakes, which can cause leakage or pollution.

Wash your hands before installing pads in the hydraulic brake system. You have been pumping the brake system and your hands, for sure, are in the remains of brake fluid. You don’t want to get the pads dirty when installing them in the brake system.

You need to work with the brakes with well-washed hands, because oil, grease, brake fluid can stain the pads, and you will have to buy new ones. And it costs a lot of money.

I want to note that if the speed of the bike is high enough, then you need to use the hydraulic brakes very carefully.

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 is opened, they must be pressed in with a screwdriver and the brake lever pressed. If one of the pistons is stuck, this is a signal to change the repair kit. Finally, the entire hydraulic mowing line should be inspected. it should not be damaged, and their presence indicates the need to replace the mowing line.

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

After all the parts of the system have been 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.

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 fits 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.

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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.

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:

How to bleed hydraulic disc brakes?

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

How to bleed disc brakes on a bicycle

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!

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.

Bleeding hydraulic brakes

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.

How to Bleed Hydraulic Disc Brakes. SRAM /h3>

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.

You will need the following personal belongings and tools:

We remove the wheel. We pull out the pads. To do this, you need to take small pliers for a special protrusion on the block, carefully bring it to the middle (i.e. move towards the working surface of the other block), and pull it up. With some dexterity, you can do all this with your hands. The main thing is not to overdo it. everything is done almost effortlessly.

Insert an open-end wrench between the pistons (caliper pistons). Caution! In the center of each piston there is a pin on which the pads are actually attached. The key MUST NOT rest against it. It is necessary that it rests against the caps on both sides, otherwise, when pumping, the cap will warp, which is highly undesirable. The key can be fixed in the desired position with tape or twine.

We transfer the bike to its normal position, i.e. steering up, so that the caliper is down, and the steering wheel with the master cylinders. up. Loosen the bolts securing the brake lever and turn it vertically upwards. The meaning is this. the brakes are pumped from the bottom up, and this position ensures that not a single cunning air bubble remains in the lines. We use a screwdriver to pick out the plastic plug on the expansion tank, and insert a plastic tube 15-20 cm long into it. The bleeding kit includes a special fitting for attaching the tube to the hole in the tank, in the absence of one, you can do with an adapter made, for example, from paste from a gel pen. We hang the other end of the tube into a soda bottle, which is tied to the steering wheel. Excess liquid will collect in it. We wrap the grips with rags so that they do not suffer from caustic brakes. By the way, about her causticity. It is somewhat exaggerated, i.e. the manual claims to corrode paint. Maybe so, but the paintwork of my Atom did not suffer from it at all. But the inscription HAYES has noticeably faded))).

We fill the bottle for pumping (or a syringe replacing it) with brakes, put on a piece of a tube with a length

10 cm. In order not to fly off, we wrap it with soft wire or a spring. We put it on the pumping union (it is covered with a rubber cap, which must be removed and put away in a safe place). The bike must be positioned so that the said fitting is vertical. Gently squeezing the bottle, pull the bubbles out of the tube. Now everything is ready for pumping.

We turn off the fitting by 1/4 of a turn, and with vigorous movements of the right hand; o) we pump the system. In total, you need to do 5-6 movements. We release the bottle, it straightens out, we observe the floating air bubbles with satisfaction. We repeat these simple movements until the bubbles disappear. This is how we got rid of the air in the caliper. Next in line. master cylinder.

We squeeze the bottle until the liquid comes out of the tube protruding from the master cylinder without bubbles at all. Holding the bottle compressed, pump the master cylinder with sharp movements of the brake lever until the last air bubble is expelled from the system. Without releasing the bottle, close the fitting on the caliper. Do not over-tighten! Aluminum threads are very easy to cut. You just need to close it, not tighten it.

The system has been pumped over. We wipe the traces of our work from the brakes, frame, face and walls of the room, and put in place the plugs of the master cylinder, the rubber cap on the fitting, and the pads. Most likely, after pumping, no matter how hard you try to adjust the clearances, the brakes will mercilessly saw on the discs. It is treated like this: we put on the same tube 15-20 cm long on the caliper bleed fitting, and open it just a little bit. We press on the brake so that 4-5 cm of liquid goes into the tube. We close the fitting. Checking the brakes. If it doesn’t help, we repeat.

How to bleed HAYES brakes?

Hayes Bike Hydraulic Disc Brakes Tuning

Hayes brakes HFX-9 XC, HFX-9 HD and HFX-MAG are one of the most common low-end disc brakes. The reason for this is their low price with minimal acceptable quality, as well as popularity in OEM supplies. They can be seen on GT, NORCO, JAMIS and other brands.

The weak point of the brakes is the tendency to leak (I haven’t noticed it myself, but some of the owners are complaining), the plastic cap of the expansion tank can fly off when driving aggressively or when falling (and if you don’t drive that way, then why are the disks?% O). You can stick it with tape or duct tape.

When, in fact, is pumping necessary? There are several options: you broke the hydraulic line, squeezed out the caps, i.e. In one way or another, they got rid of a certain amount of the working fluid, or did it deliberately, if they bought a boxed version, and cut the hydraulic lines to the size of their bike. This procedure is also shown if the brakes do not work clearly, the handles fail, and on descents, when heated, the discs begin to block.

Actually, the whole procedure is described in the manual, but firstly, not everyone got this storehouse of wisdom in printed form (not included in the OEM delivery), and some do not speak any of the languages ​​in which it is written.


master cylinder. combined with a handle, by pressing which the piston located in the master cylinder creates pressure in the system.

caliper. “machine” brakes, mounted on the frame / fork, contains (in this case) two pistons that transmit pressure from the system to the pads.

piston. piston pressing on the pad.

A few more tips:

It is more convenient to adjust the gaps if you put a sheet of white paper under the bike. against its background it is better to see where the caliper should be moved.

If you were able to flatten the pads (you pressed the brake when the bike was without a wheel) to spread them, you can carefully stick sheets of thick cardboard between them (playing cards are very good) until they disperse. To avoid such a misfortune, make it a rule to always stick a piece of cardboard between the blocks if you remove the wheel.

Sometimes, if a new brake does not want to fit into any one, you have to grind the adapter or put washers. Be careful when choosing an adapter: some forks require specific adapters (eg RS Boxxer or Manitou Sherman, 20mm axle forks). Your best bet is to see which adapter is on a bike with the same fork as yours.

If you buy new brakes, take the version with an 8 “disc. The difference in price and weight is small, but in operation the difference is very noticeable. True, there is a drawback. It is more difficult to adjust the pad clearance, the more chances that the pads will periodically creak on the disc.

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 will be useful to us for this? mineral oil with a viscosity of 10W. (50ml, if on front and back) I used 50ml Shimano oil on tap in ChilinGrilin for 100 rubles, 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 in the rest of the DOT! Tubes (the diameter is 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 5-12 ml. The larger it is, the more convenient it will be in the process, so as not to jump and collect the keys all the time (an asterisk T8, adjustable, but preferably an open-end 7, possibly a 7-end hex, 3 and 5 hex) a jar for draining. It is desirable to keep it clean and dry. If you bleed an empty brake, the piston plug oil can be reused. 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 of a newspaper and a rag is possible here.

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.

How To Bleed New Sram MTB Brakes | Bleeding Edge Technology

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;)

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?

We 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 IV clip on). 3. Let go of the brake handle. We see how atmospheric pressure pumps oil from the reservoir 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 is not to be too zealous here, 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, it remains for us to pull out the piston plug, wipe everything from the remaining oil (it is better to wash and dry it), 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.

How to bleed the brakes on a gt bike

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.

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.

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.

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.

    How to bleed MTB brakes

    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 the 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

    How to bleed the brakes on a bike and what it is for?

    Cycling enthusiasts tend to use good quality speed bikes. In addition, it should also be noted that amateurs often use such bicycles. Those who use them have known for a long time that some problems often arise over time. Problems with brake pads are quite common.

    If you do not notice any changes in the brake operation, then this means that you have everything in order with the brake pads. If you notice any changes, such as a decrease in sharpness, etc., then most likely the brakes on your bike are somewhat outdated and need to be pumped. We will talk about how to do this today.

    Many of those who have been using the same speed bike for quite some time are wondering how to bleed the brakes on a bicycle. To do this, you first need to select a specific set of tools. We will need mineral oil that has already been used on your bike.

    If you want to use a different type of oil, do not forget to drain the old oil and only then fill in the new one. In addition, tubes of different sizes will also come in handy, a set for droppers is perfect. A syringe will be useful, with which it will be much more convenient to fill in liquid.

    It is advisable to choose a larger syringe in order not to constantly collect liquid.

    It is also imperative to pick up several keys. In order to drain the oil, you will also need a jar of some kind, preferably clean and dry. In addition, you will need to prepare a plug for the pistons. In this capacity, a battery, a five-ruble coin, or just some unnecessary piece of iron can be perfect.

    In general, it is best to bleed the brakes on the street or in the garage, just make sure that no foreign particles and dirt get into the pads. If you decide to pump it indoors, then prepare more newspapers and rags in advance, otherwise you can splash oil around everything.

    First you need to unfasten the calliper and the shoe screw, then take out the shoe and the spring. After that, we put the tube on the fitting and put the prepared plug between the pistons. Then we lower the tube into a jar for draining and unscrew the fitting.

    After the old oil is completely drained, it is necessary to fill in the new one with a syringe.

    Which brakes to choose?

    Which brakes should you choose? Rim or disc? Or maybe the foot brake is enough? Every cyclist asked himself this question first when choosing a bike, and then when replacing or upgrading it. In principle, this question can be answered rather briefly.

    The foot brake is suitable for leisurely trips around the city and parks, when the priority is the simplicity of the bike, not its power. This is the same type of brake found on most children’s bicycles. after all, children have more strength in their legs than in their fingers.

    Rim brakes are chosen when ease of setup, low weight and, most often, low price are important. Disadvantages are not the most effective braking and great dependence on weather conditions.

    Disc brakes are used on sport bikes where braking performance is critical. However, maintenance of such brakes is a little more difficult and they cost more.

    In fact, there are even more types of brakes, but these three are most often installed on bicycles sold in Russia. Below is a more detailed description of each of these three types of brakes and recommendations for their use.

    Foot brakes are most commonly found on city bikes and cruisers. Many people remember how they slowed down on their children’s bicycles by pedaling in the opposite direction. This type of brake is considered the simplest and most reliable, but heavy and ineffective. But if you choose a bike only for leisurely rides, which will brake in any weather and does not require special care, feel free to take a bike with this type of brake.

    The design of the rim brakes has undergone significant changes. It all started with cantilever brakes, but as the width of the tires increased, the shape of the rim brakes also needed to be changed. For a while, U-brakes were installed, but in the end they came to V-brakes. Now these brakes are mainly installed on budget mountain bikes and hybrids. “Vibrakes” are the easiest to set up and maintain, because the whole mechanism is quite simple. A steel cable runs from the brake handle to two levers, on which the brake pads are attached, which in turn clamp the wheel rim together. But if it’s that simple, where does the price difference come from? Firstly, the most budget models are made of plastic and have a small resource. Secondly, a lot depends on the pads and the type of rim. Please note that not all rims are designed to be used with rim brakes. They can be distinguished externally, because the rims compatible with rim brakes have flat side walls and a wear indicator.

    V-brakes also have their drawbacks. First of all, they need smooth wheels without “eights”, dents and other violations of the geometry of the rim. Also, such brakes are much less effective in rain or, moreover, in mud. In bad weather, the rims get wet instantly, and the pads begin to make terrible sounds when braking.

    However, road bikes, including most professional road bikes, still have rim brakes. These high level brakes have low weight and good performance on narrow wheels.

    Disc brakes were used in automobiles and motorcycles for a long time before being introduced to bicycles in the late 90s of the last century. At the same time, initially they were only hydraulic and were installed on the most expensive professional-grade bicycles. It was immediately clear that disc brakes are the most effective and require the least applied force from the cyclist. This is especially noticeable in bad weather conditions. The main disadvantage of this type of brake has always been weight. Indeed, in addition to the handle and the brake mechanism, a brake disc is also required. rotor. Some manufacturers, such as Shimano, make Centerlock rotors, but the majority of the rotors are six bolted to the hub.

    It is worth noting the difference between disc mechanics and hydraulics. The mechanical system is powered by a steel cable with its pros and cons. Tourists prefer mechanical brakes just because of their reliability, especially on a long trip it is much easier to replace the cable than to bleed the hydraulic system. However, mechanical brakes require more force to brake well, which is why hydraulics are commonly used in racing. Hydraulic brakes allow for less braking force and clearly modulate braking in difficult terrain.

    Many cyclists who have purchased a bicycle, for example, with rim brakes, often have a question: is it possible to change the brakes to disc brakes on an existing bicycle? Since not all bicycle parts are interchangeable, before an upgrade, you need to clearly understand whether this upgrade is needed at all and whether there is a technical possibility of installing one or another part. To install the foot brake, you only need a suitable single speed hub or planetary transmission. Some frames are equipped with an eyelet on the bottom of the airfoil for attaching the brake lever, but if not, you can install the clamp that is usually supplied with the hub. The foot brake can be installed on any bike that the selected rear hub fits the axle size.

    In the case of rim brakes, there must be “break bosses” on the frame. These are the brakes on the frame and fork. It is impossible to install a rim brake without such mountings. Pay attention to this if you decide to replace the front shock absorber. Many modern forks do not have rim brake mounts.

    In the case of disc brakes, the mountings must be on both the frame and the wheel hubs. There are two types of fasteners on the frame. IS (51mm International Standard) looks like two through holes, to which a brake or caliper is attached through an adapter.

    PM (74mm Post Mount). allows the brake to be fitted without an adapter if the brake disc size is suitable.

    The rotor can be attached to the hub either with six bolts, or according to the Center Lock standard, the diagram of which is shown above. If the frame does not have a disc brake mount, but there are rack mounts, there is an adapter option from these IS mounts.

    But it must be borne in mind that such a frame was not designed taking into account the load from the disc brake. With such an adapter, the geometry of the frame can be violated, up to complete breakdown and unusability. If you are planning to switch from rim brakes to disc brakes, first make sure there are seats available or prepare for even more money.