shared
Today I will tell you how to bleed the Shimano Deor 615 hydraulic brake, which is installed on the Merida Kalahari bike, without a special kit. Everything that will be described below will work for any other Szyman brakes!
Navigation:
Choosing mineral oil for hydraulic brakes
The most important thing we need to bleed the brakes is mineral oil and the necessary tool.
Note that there are two types of hydraulic brakes, one using mineral oil and the other DOT-4. These fluids are not compatible. If you mix them up, you'll ruin your brakes and you'll have to throw them away. Be careful!
Brake manufacturer Shimano recommends buying their special mineral oil for servicing. This oil now in stores costs 1200-1300 rubles per liter. But you can save money and buy mineral water as good as Shimano. This oil is called "LHM +" and costs around 400 rubles per liter. Agree, the difference in price is 3 times! Most bike shops and cyclists use it.
Liter can of Febi Bilstein mineral oil 06162 When I went to the store for LHM+, it was out of stock. The seller offered to buy an analogue - mineral oil Febi Bilstein 06162 (for power steering) for 600 rubles. I decided to take it. At home I have already read on various forums that Febi oil is also great for bicycle hydraulics and even slightly outperforms LHM +.
With tools, as well as with oil, you can also save decently. Shimano offers to buy a special funnel (Shimano SM-DISC Oil Stopper) for bleeding the brakes, which costs from 250 to 350 rubles. You will also need a small bottle of oil and a tube (SM-DB-OIL), which are connected to the brake caliper and cost about 500 rubles.
Shimano brake bleeder and tube
All these original tools can be replaced with 3 syringes of 20 cubes each (even two can be used) and a dropper from any pharmacy and meet less than 100 rubles.
- The first syringe will be filled with mineral oil and will be connected via a dropper to the caliper.
- The second syringe will be stuck into the hole on the brake lever where the funnel is installed (pictured above). The syringe will be used without a plunger.
- The third syringe is needed in order to pump out excess oil from the second syringe so as not to stain the bike.
Preparatory work before pumping
- When bleeding the system, it is necessary to protect the brake discs and pads from oil as much as possible. If it gets on the discs, they can be degreased, and the pads will most likely have to be thrown away. Therefore, they should be covered with rags or removed from the bike during this procedure. In order not to stain the discs, it is enough to remove the wheels, and the pads will need to be pulled out of the brake calipers.
I usually set wheel from another bike, which does not have a brake disc, this allows you to work comfortably without a special stand and there is no danger of dirtying the disc.
Don't press the brake lever after the pads have been removed, otherwise the pistons will have to be bred! To prevent this from happening, you need to use the plastic plugs that usually come with new brakes. I didn't have these plugs with me when I bled, so I used a wheel mount and a small rag to keep the mount tight.
If suddenly you still pressed the brake and brought the pistons together, separate them using a pry bar or something safe (plastic), since pistons can be ceramic and a screwdriver can crack.
- Before you start bleeding the brakes, you need to loosen the clamp of the brake lever of the brake that you will pump and install it parallel to the ground, then (in point 2) you will understand why this was necessary.
Shimano Brake Bleeding Process
1. We collect brake fluid in the first syringe. We cut off a small piece from the dropper and connect it to the syringe. We fill the tube with mineral oil and attach it to the fitting on the brake caliper. (Try to avoid air bubbles in the syringe and tubing)
Syringe with mineral oil before connecting to the brake calliper. I then squeezed out the air at the tip of the tube, filling it with oil. 2. Next, use the second syringe, which is inserted into the pen. We remove the piston from it. It is necessary to take the tip with the needle and remove (cut off) the needle (I did it with pliers). This tip must be put on the syringe and screwed in instead of the cork, the plastic from the needle should be tightly screwed into the threaded hole and not leak. Next, we need to pour some oil into this syringe.
I start screwing the syringe into the brake lever. The syringe should wrap well along the thread and sit tight. 
This is what happened after screwing in the syringe. 3. Now we need to unscrew the inlet nipple on the brake machine so that the liquid from the first syringe goes into the hydraulic system. We press on the piston and drive the liquid through the hydraulic line into the syringe at the top.
The photo shows the border between Szyman's oil (red) and my Febi oil (green). This means that there is a new mineral water in the entire hydraulic line. 
I recommend securing the syringe with a tie in the position shown in the photo so that the air that is in the system comes out to the top and does not get back into the hydraulic line when the piston is pressed. We press until a little oil remains in the first syringe - this means that you have definitely squeezed out all the air from the system.
Since I got a full syringe of mineral oil, I still have 1/3 left. We twist the inlet nipple to which the dropper was connected, and remove the syringe in place.
4. In this step, we need to make sure that there are no bubbles left in the system. We begin to actively press on the handle and see if air comes out of our syringe installed in the brake lever. I also recommend taking a hexagon and changing the position of the handle (put it a little higher and work with the brake, then a little lower and work with the brake). After making sure that no more bubbles come out, you can proceed to step 5.
5. Now insert the plunger into the second syringe and carefully unscrew it from the handle (this is necessary in order not to spill everything on the bike and the floor). Next, at a fast pace, we twist the cork and put the brake lever in a comfortable position.
Congratulations! Your brakes are pumped! It remains now to test them in combat conditions! Good luck!
Video with the process of bleeding Shimano brakes using a special tool:
Shimano brakes that can be bled this way: Acera M395, Alivio M4050, M355, M365, M315, M396, MT500, M596, M6000, M425, M445, M447, M505, M506, M575, Saint M820, SLX M675, SLX M7000, XT M8000, XT T785, XTR M9000, XTR M9020, XTR M985, XTR M987, XTR M988, ZEE M640.
(Visited 12 243 times, 6 visits today)
brakes It is one of the most important elements of a bicycle. They can be mechanical - this is when a cable is used to transfer energy from the handle to the braking mechanism, as well as hydraulic, in this version brake fluid. ()
Basically, each manufacturer recommends its own hydraulic brake fluids, produces special mineral oil and does not recommend using anything else. Hope recommends using DOT 4 or DOT 5.1 automotive brake fluid.
Liquids are subject to high requirements:
1) The liquid should not cause corrosion of metals, as well as destroy oil seals and seals;
2) Liquids must be resistant to low temperatures, must not thicken and freeze;
3) It should also be resistant to high temperatures, should not expand and boil when heated;
4) Must be able to chemically bind the water that enters it (water in the hydraulic brake system not only causes corrosion, but can also boil when the caliper is heated).
Some of the existing brake fluids:
There are two fundamentally different types of fluids that are poured into the brakes - these are mineral oils (Magura, Shimano) and DOT3 / 4/5 brake fluid (Haes, Hope, Formula).
Since these liquids have different bases, they should never be mixed or replaced. Brake fluid has a more aggressive effect on metals and seals, therefore, in brakes designed for mineral oil, “brake fluid” cannot be filled in!
Automotive brake fluids.
1. DOT3- glycol base
boiling point - + 205C
<1500
viscosity stability at +100С — >1.5
ultra-high hygroscopicity, service life - 10-12 months
2. DOT4- glycol base
boiling point - + 230C (actually - about 260)
viscosity stability at -40С —<1800
viscosity stability at +100С — >1.5
high hygroscopicity, service life - 24 months
3. DOT5- silicone base
boiling point - + 260C (actually - up to 300)
viscosity stability at -40С —<900
viscosity stability at +100С — >1.5
almost zero hygroscopicity, high lubricating properties, while the complete absence of anti-corrosion properties; service life - up to 15 years
4. DOT5.1- glycol base
boiling point - + 250C (actually - about 280)
viscosity stability at -40С —<900
viscosity stability at +100С — >1.5
highest fluidity, low hygroscopicity, service life - up to 5 years
slurry properties are provided by synthetic additives
Mineral oils for hydraulic brakes:
1. Branded Shimano and Magura oils.
2.Motorex Hydraulic Fluid 75
3. Citroen Hydraulic.
4. Any mineral oil from an auto shop with the least amount of any additives.
Hydraulic brakes on a bike provide predictable responsiveness, absolute precision, and they are much more powerful than mechanical brakes, so they are mainly installed for extreme and high-speed riding.
The mechanism of action of hydraulics is similar to mechanical: the brakes begin to work as a result of the tension of the cables, but in the hydraulic system brake fluid works instead of cables, and the lever and eccentric are replaced by a cylinder-piston group.
Therefore, hydraulic brakes are much easier to brake, because less effort is expended during braking than mechanical ones.
But, unlike mechanics, hydraulic brakes are much more difficult to repair, if a hydraulic line breaks down, it is impossible to repair the system in field conditions, the only thing that can be done without professional equipment is to pump the brake system.
You can read about what bicycle brakes are.
The structure of hydraulics
A hydraulic brake consists of a "tank" with fluid on the brake lever, the hydraulic line itself and a caliper consisting of a cylinder and a piston.
The brake reaction is initiated by pressing the brake lever, which drives the piston, which in turn squeezes the fluid out of the main reservoir and directs it through the hydraulic line to the work area.
In the cylinder, under the pressure of the fluid, the pistons move and act on the pads, as a result of friction, braking occurs.
The cylindrical mechanism in the brake machine is always larger than in the control lever, so the pressure on the brake pads is produced in a reinforced amount, much greater than the pressure on the lever.
Bicycles, scooters, components
Also, the load is increased when installing several brake cylinders.
mechanism breakdown
The main symptom of a hydraulic failure is the "failure" of the brake lever during braking.
This is due to the appearance of air bubbles in the hydraulic system, due to a drop, a drop in the liquid level, or a break in the connected circuit inside the hydraulics.
When air enters, it compresses, creates pressure, sets the pistons in motion and starts the mechanism.
To find out the cause of the failure, it is necessary to exclude ordinary pollution, for this the pads are removed, the brake machine is cleaned.
After that, the pistons are pressed in with a special tool: the brake lever is pressed until both pistons are fully extended, if they are jammed, the cylindrical system is worn out, in this case the pistons and special sealing rings are changed, the oil in the system is replaced.
Also, independent operation of the brakes can occur as a result of jamming of the brake piston after water has entered.
Hydraulics need to be repaired even with minor failures.
In addition to mechanical damage to the shell, over time, the brake fluid or hydraulic oil changes its consistency and begins to absorb air and moisture through microscopic gaps.
As a result, the fluid changes its color, the brake lever fails, and the efficiency of the system decreases.
Air infiltration is also possible due to the expansion of the tank, this happens when you pull the lever on an upside down bike.
To resume normal operation, it is necessary to carry out maintenance of the hydraulic brakes on the bicycle: completely bleed the hydraulic system.
Hydraulic purge
Hydraulic fluid varies from manufacturer to manufacturer.
In the hydraulic system of Shimanu, Tektru, Maguru bicycles, mineral or semi-synthetic oils are used, all other companies use DOT brake fluid.
It should also be taken into account that Avit and Formulu hydraulics do not have connecting pipes for pumping, so you will need a syringe kit with an M5 / 0.8 sleeve.
The main difference between liquids: DOT brake fluid is hygroscopic, i.e. over time it absorbs moisture and may lose its properties, it should be changed every 2 years, regardless of mileage, oils do not absorb moisture, but over time it darkens, and if all the same water gets into the liquid, then when mixed it becomes "whitish".
In addition, mineral oils are not chemically aggressive and do not harm the plastic or paintwork of the bike.
Maintenance methods
There are two ways to maintain a bicycle's hydraulic brakes:
Direct pumping
With direct bleeding of the hydraulic system, oil is poured directly into the expansion tank and, after clamping the lever, is directed down the hydraulic system.
During operation, it is necessary to constantly monitor the oil level indicator and add a new portion of liquid to prevent the tank from emptying, while tapping the tank and hydraulic lines with a wrench or screwdriver to expel air from the system.
During the passage of the liquid, the hose is blocked, after which the lever is lowered to the limit several times and the valve opens. Under the influence of pressure, air passes into the pipe, the brake lever is held and the valve is closed.
Liquid is poured into the expansion tank and this continues until an oil of a homogeneous consistency and without air bubbles appears.
At the end of the operation, brake fluid is added and the tank is closed.
Reverse pumping
- A 200 ml syringe is inserted through a short tube onto the caliper valve;
- The lever is closed and air is sucked in from the caliper and hydraulic cord;
- The caliper valve is closed, the hose with the syringe is disconnected, air bubbles are squeezed out;
- The syringe is inserted into place and the procedure is repeated until the hydraulics are completely free of air;
- The next step is to completely fill the hydraulic system with brake fluid.
In this way, it is convenient to pump fluid into the brakes if it is not possible to squeeze all the air out of the system during direct bleeding. And pumping the first way requires more time.
Also, in this way air is pumped out of the opposite half of the caliper without its own valve.
Detailed video guide for hydraulic brake maintenance:
Bicycle brakes from different manufacturers may have significant design differences, but one principle unconditionally unites them: brake fluid should be changed once a year, regardless of how well or poorly the braking system works.
If a cyclist spends a lot of time in the saddle and rides in areas where frequent, strong or sharp braking is required, then it is possible that the replacement of the brake fluid will be required even more often: once every six months.
Visually determining the need to replace the fluid is not difficult: by setting the brake lever parallel to the ground and unscrewing the cap of the expansion tank, the cyclist can assess whether there are impurities in the brake fluid, whether its color has changed, whether it has become cloudy. All of the above factors indicate the need for an oil change.
Preliminary preparation for self-replacement
To avoid oil contamination of the brake pads, it is recommended to remove them from the bike before changing the oil. For the same reason, it is desirable to cover the wheels with something.
When choosing a fluid for the brake system of your bike, it is important to follow the manufacturer's recommendations. It is not worth replacing the original oil with analogues for car brake systems: automobile oil may not match the viscosity parameters, contain additives that are not suitable for bicycles.
In addition, automotive fluids can corrode rubber seals, causing damage to the entire bike brake system.
Tools for changing brake fluid
Before you start changing the brake fluid on your bike yourself, you need to take care of a set of tools. You will need a few of them: a Phillips screwdriver, a No. 7 wrench, a set of hex keys, a container for draining used oil, a piece of plastic tubing and a medical syringe (optional, but a very convenient device for filling oil).
Brake Fluid Replacement
To drain the used fluid, 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.
Pressing the brake lever helps drain the used fluid. After making sure that the liquid has drained completely, 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 brim, and press the brake handle several times. The liquid will begin to go into the hydraulic line, squeezing out air bubbles. As the level of liquid in the tank decreases, it must be added little by little so that the tank does not remain completely empty.
When the hydraulic line is filled to capacity, and excess liquid will pour out of the tube into the supplied drain 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 opened again and the brake fluid must be added by pressing the brake handle until a hard pressure is felt.
Tightly closing the valve of the brake caliper, and removing the tube, you need to add liquid to the expansion tank to the very top, after which the tank cap can be screwed on.
Novice cyclists who do not understand all the intricacies of the bike and care for it, probably faced questions about the operation of the brake system. The handle has been squeezed, new pads do not slow down well, when to change the brake fluid - we will try to answer the main questions in our article.
Running in new brakes
All new disc brakes, brakes that have been overhauled or partly replaced require a break-in period. It does not matter if they are mechanical or hydraulic. During the break-in period, the efficiency of the brakes is reduced, so it is not advisable to jump “right off the bat” and use the brakes to the fullest. Particular attention should be paid to new brakes when both the brake disc and pads are not rolled in at the same time. You should not forget about running-in when replacing brake pads - in this case, the running-in time is reduced.
During the break-in period, 2 important things happen. First- the smooth surface of the new brake pads should become rough. Second- the material of the brake pads must get into the surface of the brake disc. Thanks to the break-in, the operation of the brakes improves - braking becomes smoother, the efficiency of the entire system increases, vibration and extraneous sounds disappear.
When running in the brakes, you can do a set of measures:
- Make 3-4 stops slightly harder than normal braking. This will warm up the rotors so that thermal shock does not occur during break-in.
- Make 8-10 hard brakings without coming to a complete stop, for example from 35 km/h to 5 km/h.
- In the process of braking, you may feel that the brakes have become “wadded” - this is the norm, because. they got very hot. After braking, ride for 5-10 minutes so that the rotors can cool down from the oncoming air flow.
Mineral oil or DOT?
Hydraulic disc brakes use a special brake fluid to transfer power from the brake lever to the caliper brake pistons. In the process of evolution of bicycle brake systems, manufacturers have come to two brake standards - DOT and mineral oil.
- DOT (US Department of Transportation)- has become a common name for working brake fluid in vehicles (not just bicycles). A key feature of DOT is the high boiling point of the liquid. At the same time, the boiling point drops as the DOT begins to absorb water, so it's ideal to change the DOT every 12-18 months.
- Mineral oil- is made from oil and is a mixture of hydrocarbons separated from gasoline. It is used in various industries (including cosmetology), including being used as a brake fluid. Fluid compression levels and boiling points are roughly similar to DOT.
Other things being equal, the boiling point of mineral oil and DOT is approximately the same, but the “mineral water” has one important nuance - it does not absorb moisture, but accumulates it in the hydraulic system. If the accumulated water in the bunker reduces the efficiency of the brakes, then in the "mineral water" at a high temperature of the brakes, the water evaporates and leads to the failure of the system. Similarly, mineral water brakes are not recommended to be used in the cold season, since the water accumulated in the system expands when frozen and the rubber bands of the pistons in the caliper or brake lever can simply be squeezed out. Having accelerated and started to slow down, you can find that there are no brakes, therefore, for year-round use of the bike, it is recommended to use the brakes on the bunker or change to mechanical counterparts.
Another very important nuance is brake fluids. NOT INTERCHANGEABLE! Systems designed to work on mineral water will not work on bunkers and vice versa. Systems such as Avid/SRAM, Formula, Hayes and Hope use DOT 4 or 5.1. Systems Magura, Shimano And Tektro use mineral water.
Brake pads - organic or metal?
Organic brake pads are made from a mixture of fibers and resins that bind them together. Due to their softer structure, they are considered to be much quieter than their metal counterparts. However, silence has the other side of the coin - they quickly overheat and, with prolonged braking, begin to lose their properties. In addition, in damp conditions, their wear increases significantly, there were examples when the pads were completely worn down during a short trip in the rain.
Metallized pads are much more reliable, because. contain metal fibers compressed at high temperature. They tolerate dirt and dampness better, they do not wear out as much when wet, and their key difference from organics is that they do not lose their properties and remain effective during long-term braking. Their main disadvantage is noise during operation and overheating of the hydraulic fluid.
I have everything slows down perfectly, do I need to service?
There is an opinion that brake maintenance includes only the timely replacement of pads. As we found out above, not only pads, but also brake fluid require replacement, preferably once a year or two, depending on the intensity of use.
At the forefront is the ingress of air and fluid into the brake system. Over time, the brake lever begins to fall through to the grip, braking efficiency decreases and bleeding of the brakes is necessary. As you use the brakes, you may need to service the handles and caliper - either a complete enumeration of the system, or a bulkhead with partial replacement of rubber bands and seals.
Four tips for caring for your brakes:
- Try not to contaminate the brake system. Be careful with chain lubrication - it is advisable not to use a spray dab and a chain cleaner in the form of a spray, as oil or grease-based cleaners that get on the rotor or caliper will damage the brakes. When washing your bike, be careful not to kick the dirt off the bike and chain towards the rotor.
- Clean the rotor with a brake cleaner. Special solvent-based products remove dirt and oil particles from pads and rotors, which improves brake performance.
- Check the tightness of the bolts or the fastening of the center-lock of the rotors. If the tightening is poor, the rotor starts to “walk”, causing vibrations and reducing the effectiveness of the brakes, which can lead to an accident.
- Inspect hydraulic lines and mechanisms for leaks. No one ruled out wear and tear - it is likely that over time the rubber bands can become dull, become unusable and the hydraulic fluid will begin to leak. Early diagnosis allows you to solve the problem with the least loss, while driving with a leak can damage pistons and other parts.
