How to fill a bike with brake fluid

How to fill a bike with brake fluid

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.

    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

    Pros and cons of brake fluids

    All of the above brake fluids have their own advantages and disadvantages. For convenience, we will indicate them in the table below:

    One of the fluids important for the normal operation of a car is brake fluids. About what this fluid is needed for, how often it needs to be replaced and what kind of brake fluids to use for optimal operation of the machine’s braking system. in our today’s article.

    Composition and properties of brake fluids

    The basis of the chemical composition of most brake fluids is polyglycol (up to 98%), less often manufacturers use silicone (up to 93%). In the brake fluids that were used on Soviet cars, the base was mineral (castor oil with alcohol in a 1: 1 ratio). It is not recommended to use such fluids in modern cars due to their increased kinetic viscosity (thicken at 20 °) and low boiling point (at least 150 °).

    The remaining percentages in polyglycol and silicone TK are represented by various additives that improve the characteristics of the brake fluid base and perform a number of useful functions, such as protecting the surfaces of the working mechanisms of the brake system or preventing the oxidation of TK as a result of exposure to high temperatures.

    It is not for nothing that we dwelt in detail on the chemical composition of brake fluids used in cars, since many motorists are interested in the question. “is it possible to mix technical specifications with different chemical bases?” We answer: it is strongly not recommended to mix mineral brake fluids with polyglycolic and silicone fluids. From the interaction of the mineral and synthetic bases of these fluids, clots of castor oil can form, which clog the lines of the brake system, and this is fraught with malfunctions of the brake system. If you mix mineral and polyglycolic TK, then this “infernal mixture” will be absorbed into the surface of the rubber cuffs of the brake hydraulic drive parts, which will lead to their swelling and loss of sealing.

    Polyglycolic TZ, although they have a similar chemical composition, and can be interchangeable and, but mixing them in one brake system is still not recommended. The fact is that each manufacturer of technical specifications can change the composition of additives at its discretion, and their mixing can lead to a deterioration in the main operational characteristics of the working fluid. viscosity, boiling point, hygroscopicity (ability to absorb water) or lubricating properties.


    Silicone brake fluids must not be mixed with mineral and polyglycolic ones, as as a result, the working medium becomes clogged with precipitated chemicals, which will lead to clogging of the brake system lines and failure of the brake cylinder assemblies.

    Classification of brake fluids

    Today, most countries around the world have uniform brake fluid standards known as DOT (after the name of the agency that developed them. the Department of Transportation. the United States Department of Transportation). such markings are often found on brake fluid containers. It means that the product is manufactured in accordance with the regulatory federal vehicle safety standards FMVSS 16 and can be used in the braking systems of cars and trucks, depending on the technical characteristics of these vehicles. In addition to the American standard, brake fluids are labeled in accordance with the standards adopted in a number of European and Asian countries (ISO 4925, SAE J 1703 and others).

    But they all classify brake fluids according to two parameters. their kinematic viscosity and boiling point. The first is responsible for the ability of the working fluid to circulate in the brake system line (hydraulic drive, pipes) at extreme operating temperatures: from 40 to 100 degrees Celsius. The second is for preventing the formation of a steam “plug” that forms at high temperatures and can lead to the brake pedal not being activated at the right time. When classifying TZ by boiling point, two states are distinguished. the boiling point of a liquid without water impurities (“dry” TZ) and the boiling point of a liquid containing up to 3.5% water (“humidified” TZ). The “dry” boiling point of the brake fluid is determined by a new, freshly poured working fluid, which did not have time to “collect” water and therefore has high performance characteristics. The “humidified” boiling point of TK refers to a working fluid that has been in operation for 2-3 years and contains a certain amount of moisture in its composition. about this. in the section “Service life of brake fluids”. Depending on these parameters, all brake fluids are divided into four classes.

    DOT 3. The “dry” boiling point of this brake fluid is not less than 205 °, and the “wet” one is not less than 140 °. The kinematic viscosity of such a TZ at 100 ° is not more than 1.5 mm² / s, and at 40. not less than 1500 mm² / s. The color of this brake fluid is light yellow. Application: intended for use in cars, the maximum speed of which is no more than 160 km / h, in the braking system of which disc (on the front axle) and drum (on the rear axle) brakes are used.

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    DOT 4. The “dry” boiling point of this brake fluid is at least 230 °, and the “wet” temperature is at least 155 °. The kinematic viscosity of such a TZ at 100 ° is no more than 1.5 mm² / s, and at 40. no less than 1800 mm² / s. The color of this brake fluid is yellow. Application: intended for use in vehicles with a maximum speed of up to 220 km / h. Disc (ventilated) brakes are installed in the braking system of such cars.

    DOT 5. The “dry” boiling point of this brake fluid is at least 260 °, and the “wet” one is at least 180 °. The kinematic viscosity of such a TZ at 100 ° is not more than 1.5 mm² / s, and at 40. not less than 900 mm² / s. The color of this brake fluid is dark red. Unlike the above TK, DOT 5 is based on silicone, not polyglycol. Application: intended for use on special vehicles operating in conditions of extreme temperatures for braking systems, and therefore is not used on ordinary cars.

    DOT 5.1. The “dry” boiling point of this brake fluid is not less than 270 °, and the “wet” one is not less than 190 °. The kinematic viscosity of such a TZ at 100 ° is not more than 1.5 mm² / s, and at 40. not less than 900 mm² / s. The color of this brake fluid is light brown. Application: intended for use in braking systems of sports racing cars in which the temperatures of the working fluids reach critical values.

    The role of brake fluid in the “body” of a car

    The braking system, which is responsible for the timely stop of the car and therefore plays an important role for the safety of the passengers of the car, cannot work without brake fluid (TK). It is she who performs the main function of the brake system. it transfers through the hydraulic drive the force from pressing the brake pedal to the brake mechanisms of the wheels. pads and discs, as a result of which the car stops. Therefore, even in driving schools, novice motorists are strongly advised to periodically check the levels of four service fluids: engine oil, antifreeze, glass cleaner and brake fluid, on which the optimal operation of the car depends.

    When to change the brake fluid?

    The life of the brake fluid directly depends on its chemical composition.

    Mineral TK, due to its chemical characteristics (low hygroscopicity, good lubricating properties), has a fairly long service life (up to 10 years). But when water enters the liquid, for example, in the event of a depressurization of the brake system, its properties change (the boiling point drops, the viscosity rises), and it can no longer perform its functions, which can lead to brake failure. Periodic inspection (once a year) of the brake system and fluid condition is recommended, which can be determined in laboratory conditions.

    Polyglycolic TK has an average or high degree of hygroscopicity. therefore, her condition should be checked twice a year. It is possible to assess the state of polyglycolic TK visually: if the liquid has darkened or precipitation is noticeable in it, then it must be completely replaced. Such TK is capable of absorbing up to 3% moisture per year. If this figure exceeds 8%, then the boiling point of the brake fluid can drop to 100 °, which will lead to boiling of the TK and failure of the entire brake system. Automotive manufacturers recommend changing polyglycol-based brake fluids every 40,000 kilometers or every 2-3 years. Usually such a brake fluid is completely changed during the installation of new external brakes (pads and discs).

    Silicone TK is distinguished by its durability of operation, since its chemical composition is more resistant to external influences (moisture ingress). As a rule, replacement of silicone brake fluids is carried out after 10-15 years from the moment of filling in the brake system.

    How to fill a scooter with brake fluid

    Gravity method

    We will change the brake fluid by gravity, without pumping. An important aspect of this replacement method: to prevent air from entering the brake line, otherwise you will have to pump it. which, of course, is not scary, but these are unnecessary actions.

    We unscrew the bolts of the tank cover of the brake machine, take out the plug and the rubber membrane.

    fill, bike, brake, fluid

    There will be something like this ugly picture:

    Uncorking a bottle of brake fluid.

    Now, with a wrench, unscrew the union by about a quarter of a turn (or even less). It is not necessary to unscrew it strongly, otherwise air bubbles will go. The brake fluid should slowly pour into the container.

    As the brake machine reservoir is empty, add new brake fluid. It is very important that the reservoir is always filled with liquid.!

    By the way, the photo shows that I spilled liquid. this is not good. Brake fluid is aggressive to paint, so if it gets on the scooter, it must be washed off. And to avoid accidental spills, you can put a napkin under the neck of the bottle.

    After a while, the old liquid will merge, and a new one will go into the drain, this is always visible by its color.

    The volume of three or four brake reservoirs is enough to flush everything.

    We close the fitting, add liquid to the tank to the level, and everything is ready!

    Pumping method

    However, if at some point you have missed the liquid, and air has entered the brake line, then it will not merge by gravity. Then we will act by the pumping method.

    • Filling the brake reservoir.
    • Open the drain fitting half a turn with an open-end wrench.
    • Squeeze the brake lever all the way and do not release it.
    • With the handle pressed, close the fitting.
    • Letting go of the handle.
    • We repeat steps 2-5 until all air bubbles come out of the tube (forgetting to replenish the liquid in the tank).

    How to change the brake fluid on a scooter

    Brakes are the most critical unit in a scooter’s device: if the engine is faulty, the scooter simply won’t go, and problems with the brakes can lead to an accident. Sometimes, when using a scooter, you may notice that the disc brake has become less effective. The first step is usually to check the brake pads, if they are intact, control the disc, and if there is no oil on it, the problem is probably in the waste fluid.

    Brake fluid is the main element of the hydraulic braking system, used for power transmission and movement. It does not shrink under pressure, does not absorb water and does not lose its other characteristics under adverse weather conditions. Use dot3 or dot4 brake fluid on the scooter (according to the manufacturer’s recommendations). Like any operating oil, brake fluid loses its properties over time. it attracts water, the boiling point decreases (when boiling, gas bubbles reduce the effectiveness of the brakes, the likelihood of souring of the pistons in the calipers increases) and must be replaced. Experts recommend changing it every two years, but many scooters neglect these rules.

    To change the brake fluid it is necessary to prepare:. A new portion of the brake fluid Containers for draining waste liquid, such as a cut plastic bottle A short hose for connecting it to the brake fluid drain connection A small enema to suck up old fluid Key for 8 Screwdriver.

    Step-by-step instruction

    Unscrew the brake tank cover on the steering wheel. Remove the rubber gasket dispenser. 2. Use a small enema to remove all waste slurry from the tank. 3. We move to the calipers: cleaning the dirt from the pistons, we must drown them in the brackets as much as possible. Use a screwdriver to work carefully so as not to scratch the pistons. 4. If there is no liquid, it is necessary to fill in a new dose, almost to the edge, and proceed to pumping. 5. To pump the hydraulic lines, put a drain hose of a suitable diameter on the drain fitting and lower it into a prepared container. 6. Press the brake lever while unscrewing the drain connection. There is no need to unscrew the union to the end, just turn it a couple of times. 7. In this step, you will notice that the brake lever has fallen as far as it will go. Without releasing it in this position, it is necessary to tighten the drain nut, and only after this operation can the brake be released. 8. Press the lever until the pistons press the pads against the disc and it stops falling. 9. At this time, the system should start pumping fluid from the tank, while simultaneously disposing of the waste material. 10. Continue pumping until a new clean liquid begins to flow into the prepared dish and, which is very important, without air bubbles.

    Possible malfunctions and deterioration of the clutch and brake system after replacing the TJ

    Modern types of brake compounds can be mixed, however there are strict restrictions. This rule applies only to those auto-fluids that meet the same characteristics. However, it is worth considering the fact that products from different manufacturers can have not only different manufacturing recipes, but also a different basis. For this reason, mixing fluids should not be allowed, since after replacing them, the brake system may fail.

    A change in shade is one of the main signs of the need to replace the composition. It does not indicate the presence of detergents, which is applicable for engine oils, but about contamination with dust particles and wear products. If you do not change the clutch fluid and in the hydraulic drive for a very long time, then irreversible changes can begin in it, for example, an increase in viscosity. All this can cause seizure of brake cylinders, brake failure and clutch failure. Varnish-like deposits may appear on the internal parts and assemblies of the system. It is advisable to change the darkened liquid immediately, without waiting for the end of the operational period.

    Fluid change must be done not only in a timely manner, but also correctly. During the bleeding of the brake system, the old fluid is replaced with a new one without admixture of air bubbles. To carry out this procedure, a volume of the composition is sufficient, exceeding the volume of the container by one and a half times. If air enters the system, the brake pedal will operate from the second or third time. Pumping is carried out until the pedal becomes stiff and stops at the same point.

    It is advisable to use only the brake fluid recommended by the car manufacturer. When purchasing this composition, it is necessary to accurately verify all specifications and characteristics.

    The key to the durability and performance of the brake system is the timely replacement of the fluid. If you buy a used car, then it is better to replace it immediately and pump the entire system according to the regulations established by the manufacturer.

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    Chevrolet lacetti

    Attention! When operating a car with a trailer and frequent trips on mountain roads, the brake fluid must be replaced every 15,000 km.

    We carry out the work on a viewing ditch or overpass.

    It is necessary to pump the hydraulic drives of the brake system and clutch until new fluid (lighter than the old one) starts to come out of the bleed fittings of all working cylinders.

    Replacing the hydraulic fluid of the brake system

    We carry out pumping to replace the fluid with the engine off, first on one circuit, and then on the other in the following sequence:

    • right rear wheel brake
    • left front wheel brake
    • left rear wheel brake
    • brake mechanism of the right front wheel.

    Before pumping, check the level of the working fluid in the brake and clutch hydraulic reservoir. Add liquid if necessary.

    We carry out bleeding of the brakes with an assistant.

    We clean the pumping fitting of the brake mechanism of the right rear wheel from dirt.

    We put a hose on the fitting, and immerse its free end in a container partially filled with working fluid.

    The assistant must vigorously press the brake pedal until it stops 1-2 times and keep it pressed.

    In this case, liquid will flow out of the hose, and the brake pedal should be pressed all the way.

    As soon as the liquid stops flowing out of the hose, we wrap the fitting, and only after that the assistant can release the pedal.

    We repeat this operation until a new brake fluid (lighter than the old one) comes out of the fitting.

    We remove the hose, wipe dry the pumping fitting and put on a protective cap.

    Remove the protective cap from the bleed fitting of the brake mechanism of the left front wheel.

    We put a hose on the fitting, and immerse its free end in a container partially filled with working fluid.

    Similarly, we pump the brakes of another circuit.

    When pumping, you need to monitor the fluid level in the tank and add fluid.

    Replacing the clutch fluid

    Before pumping, check the fluid level in the reservoir on the master brake cylinder. Add working fluid if necessary.

    It is advisable to install the container below the level of the nozzle.

    The assistant presses the clutch pedal several times and holds it down.

    With the clutch pedal depressed, unscrew the bleed nipple by 1 / 2–3 / 4 turn. In this case, the liquid is displaced into the container. Keeping the pedal pressed, wrap the fitting and repeat this operation until a new brake fluid comes out of the fitting (lighter than the old one).

    Remove the hose and put a protective cap on the fitting.

    After bleeding the brake and clutch hydraulic drives, we bring the fluid level in the tank to normal.

    There is an even simpler option for replacing the brake fluid. This method does not require the presence of an assistant. With this method, a certain amount of brake fluid is desirable (at least 1 liter).

    We install the car on a viewing ditch or overpass and provide free passage between the brake fluid reservoir in the engine compartment and the brake cylinders of all wheels.

    We pump out the brake fluid from the reservoir with a rubber bulb or syringe. Add new liquid to the upper edge. To speed up the process (in order to release fluid from all cylinders at once), it is advisable to pick up four pieces of tubes that fit tightly on the pumping fittings of all cylinders. We lower the free ends of the tubes into transparent bottles of a small capacity.

    We unscrew the fittings of all brake cylinders. Make sure that the liquid has flowed through all four tubes. We control the decrease in fluid from the reservoir located on the brake cylinder and immediately replenish the reservoir. We observe an increase in the level of liquid in bottles located near the wheel brake cylinders.

    It is necessary to move several times from the position of observing the outflow of fluid from the unions of the brake cylinders to a position where it is possible to check and replenish the fluid level in the reservoir located on the brake cylinder in order to prevent the reservoir from draining.

    Typically, the level rises most rapidly in the bottle into which the hose from the front left brake cylinder is dipped. As soon as there is about 200 ml of liquid in the bottle of the front left wheel, we wrap and tighten the fitting of this cylinder. Next, we wait for the same result for the front right wheel cylinder and also wrap its bleed fitting. The process can be completed after 200-250 ml of liquid comes out through the fitting of each rear wheel.

    We are convinced of the tightness of all fittings. We put on protective caps. We clarify the fluid level in the reservoir of the master brake cylinder.

    Changing the fluid in the hydraulic clutch of LADA cars

    Currently, the hydraulic clutch drive is used on Lada XRAY, Vesta, Largus and 4×4 vehicles. Correct operation of the clutch release hydraulic drive is possible only if there is no air in the system, due to which the clutch may not be completely disengaged. As a result, gear shifting will be difficult or impossible. Let us consider in detail the process of bleeding the clutch hydraulic drive or replacing the brake fluid in the hydraulic drive.

    When to change the brake fluid in the clutch system:

    • LADA 4 × 4. every 30,000 km. mileage.
    • Largus, Vesta and XRAY. every 90,000 km. mileage or after 6 years of operation (whichever comes first).

    To change the fluid, bleed the clutch hydraulic actuator. The criterion for completing the replacement is the termination of the exit of the old brake fluid from the valve for air release.

    The procedure for removing air (pumping, changing fluid) from the clutch hydraulic drive:

    • Check the brake fluid level in the clutch reservoir (for Niva 2121/2131) or the brake master cylinder (for other LADA models). If necessary, add fluid to the “MAX” level.
    • Remove the protective cap from the valve for bleeding the clutch slave cylinder (it is more convenient to get to it from the bottom of the car, see the hydraulic drive device).
    • Put a transparent hose on the valve and lower its end into a container with a small amount of brake fluid.
    • Ask the assistant to slowly press the clutch pedal 10-15 times with an interval of 2-3 seconds and lower the pedal.
    • We loosen the union with a key “8” (for Niva 2121/2131). Use a screwdriver to pry on the spring clip of the tube and raise it by 1 click. We shift the tip from the branch pipe of the working cylinder by 10 mm (for other LADA models).
    • Ask an assistant to depress and hold the clutch pedal. Liquid will run out of the hose into the container.
    • As soon as the liquid stops running out: fix the union with a wrench (for Niva) or push the hose tip into the branch pipe of the clutch release slave cylinder and secure with a spring clip.
    • Release the clutch pedal and wait 5 seconds.
    • Repeat steps 4-7 until the fluid in the actuator has been completely pumped (a clear fluid without bubbles should come out of the hose).
    • We put on a protective cap on the air removal valve.

    While bleeding the hydraulic actuator, periodically check the fluid level in the reservoir. Do not allow the level in the tank to fall below the tube fitting, otherwise air will enter the system and pumping will have to be repeated. Add brake fluid if necessary.

    Signs of the presence of air in the clutch release hydraulic actuator:

    • the pedal is pressed all the way, and the clutch is not completely disengaged (“leads”), which is accompanied by a crunch, rattle when the reverse gear is engaged.
    • shifting gears is difficult or impossible.

    An example of pumping the clutch hydraulic drive on a Lada Vesta:

    For other clutch problems, follow these inspection instructions.

    Requirements for clutch brake fluid

    Except for the basic requirements. viscosity and boiling point. brake fluids must meet some others:

    No negative impact on rubber parts. Rubber cuffs are located between the hydraulic pistons and the cylinders. The tightness of these connections increases, provided that the rubber expands in volume under the influence of the brake fluid by no more than 10%. After pouring the composition, such parts should not lose strength, plasticity, deform.

    Lubrication of friction pairs. The level of wear of pistons, surfaces of brake cylinders and lip seals depends on the lubricating properties of the composition.

    Resistant to temperature extremes. In the range from 40 ° C to 100 ° C, clutch brake fluids must maintain operational properties, not delaminate, not settle on nodes and parts.

    Replacement of the composition should be carried out on average once every 2-4 years, and the frequency depends on the condition of the brake system and the vehicle as a whole. Simply put, the older the vehicle, the more often it is desirable to change the brake fluid. If the composition changes its color ahead of time, then it is immediately changed.

    We recommend watching this video about bleeding the clutch:

    Brake fluid replacement tools

    Before you start changing the brake fluid of your bike yourself, you need to take care of the set of tools. You will need a few of them: a Phillips screwdriver, a wrench, a set of hex keys, a container for draining used oil, a piece of plastic tube and a medical syringe (optional, but very convenient device for filling oil).

    Preliminary preparation for self-replacement

    To avoid contamination of the brake pads with oily fluid, it is recommended to remove them from the bike before changing the oil. For the same reason, it is advisable to cover the wheels with something.

    When choosing a brake fluid for your bike, it is important to adhere to the manufacturer’s recommendations. It is not worth replacing the original oil with analogues for car brake systems: car oil may not match in terms of viscosity, contain additives that are not suitable for bicycles.

    In addition, automotive fluids can corrode rubber seals, damaging the entire brake system of the bike.

    Bicycle brakes from different manufacturers may have significant design differences, but one principle unites them unconditionally: the brake fluid must be changed once a year, regardless of how well or poorly the brake system works.

    If a cyclist spends a long time in the saddle and rides in an area where frequent, strong or sharp braking is required, then it is possible that the brake fluid will need to be replaced even more often: once every six months.

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    It is not difficult to visually determine the need to change the fluid: by installing the brake lever parallel to the ground and unscrewing the expansion tank cap, the cyclist can assess whether there are impurities in the brake fluid, whether its color has changed, or whether it has become cloudy. All of the above factors indicate the need for an oil change.

    Replacing the brake fluid

    To drain the spent fluid, you must put a piece of tube on the brake caliper valve (caliper) and open it with a wrench, directing the free end of the tube into the drain container.

    How To Bleed Shimano Hydraulic Disc Brakes

    Pressing the brake lever will drain the waste fluid. After making sure that the fluid is completely drained, you can proceed to filling the hydraulic system with fresh oil.

    To do this, using a medical syringe or manually, you need to fill the expansion tank to the very edges, and press the brake lever several times. Fluid will begin to flow into the hose, squeezing out air bubbles. As the level of liquid in the tank decreases, it needs to be refilled little by little so that the tank does not remain completely empty.

    When the brake line is full and excess fluid is poured from the tube into the supplied drainage container, the caliper valve can be closed.

    The system should not contain air. this is checked by pressing the brake: soft and sluggish pressing indicates the presence of air. In this case, the valve must be reopened and the brake fluid topped up by pressing the brake handle until you feel a hard pressure.

    Close the brake caliper valve tightly, and after removing the tube, you need to add liquid to the expansion tank to the very top, after which the tank cap can be tightened.

    How often to change the brake fluid and why to do it

    • What is brake fluid
    • Why change brake fluid
    • How to change brake fluid
    • How often to change the brake fluid

    Brake fluid (TF), along with other working fluids, is one of the most important components in the operation of a car. The composition of the TJ should be of the highest quality, since the operation of the entire brake system depends on it. In this article, we will tell you how often to change the brake fluid, how to change the composition and what types of this agent are better to use.

    Types of brake fluid

    All automotive raw materials, including brake fluid, are manufactured according to the existing international and domestic standards. Currently, the production of formulations is based on two standards:

    • FMVSS specification 16. This document has been defined by the US Department of Transportation (USDOT). According to this specification, brake fluid is divided into classes (from DOT-1 to DOT-5).
    • SAE J1703 and SAE J1704 specifications. These documents were published by the Society of Automotive Engineers (SAE).

    In most cases, American standards are used in the production of brake fluid, the second specification is in less demand. In this article, we will describe the types of brake fluids according to the DOT classification. In addition to these groups, there are also formulations based on mineral oil. Such raw materials have different production standards, in practice they are used much less often.

    Next, we will consider the main features of the types of TJ according to DOT, including how often to change each brake fluid.

    • DOT-1, DOT-2. used by manufacturers extremely rarely;
    • DOT-3, DOT-4. the most popular types of brake fluid based on polyethylene glycol;
    • DOT-5. silicones predominate in the composition;
    • DOT-5.1 is an improved version of the DOT-4 composition, it has more advanced properties.

    It is important to consider that the two classes DOT-5 and DOT-5.1 are completely different in their properties. They are not interchangeable.

    Each class is subdivided into two categories:

    • For vehicles without ABS.
    • For vehicles with ABS.

    The category must be marked on the packaging with the composition or indicated in the label itself (DOT-4 / ABS).

    In our country, an amended classification of brake fluids can be used, it includes the names DOT-4.5, DOT-4, DOT-4, etc. However, such subclasses do not exist in the original standard, so these markings can be considered a marketing ploy.

    In addition to how often to change the brake fluid, it is important to know what classes of fluids can and cannot be combined. On this issue, the general rules are as follows:

    • It is acceptable to mix compositions: DOT-3, DOT-4 and DOT-5.1.
    • DOT-5 compound is incompatible with other brake fluids.

    The composition of the first three types of DOT is based on glycolic compounds. They also contain the same additives. Since the formulations are almost identical, these classes of brake fluids can be mixed. Products labeled DOT-5 are manufactured using other substances. The main difference is the large number of silicones. On contact with glycolic compounds, silicones form completely new substances, and the properties of the entire liquid are lost.

    Despite the similar composition, it is also better not to mix fluids of the DOT-3, DOT-4 and DOT-5.1 classes. Modern manufacturers use different types of additives, and when these substances are combined, harmful chemical reactions can begin. It is recommended to combine only formulations of the same manufacturer.

    Why change brake fluid

    Motorists are not in vain worried about the question of how often the brake fluid needs to be changed. The quality of the brakes depends on it. For example, if the fluid is used longer than the prescribed period and has lost its properties, the brakes work worse, the car slows down more slowly.

    It is known that when traveling in urban areas, problems with the braking system are not immediately detected. This is due to the fact that the city road does not have sharp slopes and rises, and the deterioration of the brakes is practically not noticeable. But if such a car starts to brake on a slope, the main brakes may not cope with the task, then the drivers use the parking brake.

    It is important to know how often to change the brake fluid and what type of compound is best to use. To begin with, let’s consider what role TJ plays in a car, as well as the main features of its compositions. The newly purchased brake fluid has all the necessary properties. Its physical characteristics are as follows: the boiling point is about 260 ° C, the liquid is incompressible.

    During operation, water increases in the composition of the product, due to which its compressibility increases. This leads to a decrease in the boiling point (sometimes this figure decreases by two or more times).

    During braking (with pressure on the brake pedal), the caliper pistons are squeezed out and the discs (drums) are compressed. In this case, heat is released, the temperature of the liquid becomes 250 300 ° C (an even greater increase in temperature is possible). Normally, its boiling point is higher and it does not boil.

    If boiling begins, gas bubbles form in the liquid. Gradually, their number is growing, they are increasing in size. Bubbles are compressible, and the TJ as a whole also becomes compressible, thereby losing its properties. The action of the brakes deteriorates, in some cases braking becomes completely impossible. As you can see, it is necessary to frequently change the brake fluid in order to prevent boiling.

    A large amount of water in the brake fluid is detrimental to the braking system. Many of you immediately have a question about how water penetrates into its composition if the entire system is completely sealed. During vehicle operation, the brake fluid heats up. When heated, it expands, respectively, the pressure rises. The liquid is usually contained in a small reservoir, which contains a special valve. To equalize the pressure, it opens.

    In cold weather, on the contrary, the liquid cools, while the pressure decreases to a negative value. To equalize the pressure inside and outside the tank again, the valve opens and lets air in. This air is subsequently condensed and converted to water.

    Water is formed not only during the direct operation of the car. Even if the car is not used or you do not drive often, you still need to change the brake fluid, as with constant use.

    How often to change the brake fluid

    How often do you need to change the brake fluid in your car? As a standard, manufacturers advise changing it every 30-40 thousand kilometers of driving. about once every two years. Electronic ABS systems do not affect this period. Premium cars (for example, sports brands Maserati, Lamborghini, etc.) require even more frequent brake fluid changes. Usually the term of its use is limited to 10-15 thousand kilometers.

    If necessary, you can add TAS to the existing composition, as well as mix two different fluids. It is important to consider some rules here. In general, experts advise mixing only liquids of the same brand, from the same manufacturer. This is because different manufacturers usually use different additives. On contact, they can change and degrade the properties of the entire composition. At the same time, sediment is often formed, which accumulates not only in the tank itself, but also penetrates into other parts of the system.

    If you are buying a used car, it is recommended that you change the brake fluid immediately. It may be that the former owner did not follow the terms of its operation. There are times when the driver changes only the brake fluid, which is located directly in the reservoir, and in the rest of the system the composition is old, which has long lost its properties. If you completely change the brake fluid at once, you will not need to mix several compounds, risking the work of the brake system.

    Sometimes the brake fluid needs to be changed before the specified service life. One of the reasons is a change in the color of the composition. The standard color is light yellow, but sometimes manufacturers use mineral additives in red shades. By this shade, one can judge the quality of the composition: if the color has changed, the liquid has become cloudy, a precipitate has formed in it, it must be urgently changed. Perhaps the problem is related to a change in the chemical composition of the additives. If everything is left as it is, the mirrors of the pistons of the brake cylinders may fail, and the cuffs also swell.