BIKE HYDRAULIC BRAKES, BLEEDING THEM
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.
BIKE HYDRAULIC BRAKES: ALL THE PROS AND CONS
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.
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, by means of 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 already 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, then 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 THE HYDRAULIC BRAKES ON A BIKE
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 leaving. 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 free 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 necessary. 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 are probably in the remaining 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 would like to note that if the speed of the bike is high enough, then use the hydraulic brakes very carefully.
The very first sign that a bicycle‘s brakes are malfunctioning is when they brake on their own. This can be explained by the fact that there was a small amount of air inside the system. This could happen due to the fall of the bike, when the hydraulic circuit is opened, as well as when the level of brake fluid in the reservoir is low.
Since the property of air to compress significantly distinguishes it from liquids, when it enters the system, it can work as a gas spring. This builds up fluid pressure, which activates the brakes. The rear hydraulic brake can be engaged in such an independent action in the event that the working piston begins to jam. This could be caused by water entering the hydraulic system. Another point that should alert you is the loss of elasticity of the brake lever in comparison with the early period of use. And if the hydraulics does not react at all to your command to stop the bike, then there will be only one solution. the immediate replacement of the entire system.
Hydraulic brake and its circuit. Hydraulic brakes for bike
The brakes, both mechanical and hydraulic, have only one direction of action. to stop the vehicle. But there is a whole host of questions regarding both types of schemes. It is worth taking a closer look at the hydraulic brake. Its main difference from the mechanical one is that a hydraulic line is used to drive the pads, and not cables. In the version with hydraulics, the brake mechanism is connected to the levers directly.
Advantages and disadvantages of hydraulics
The widespread use of such a brake system can be explained by the dosing accuracy and the high reaction rate of the mechanism to pressing the handle. However, the advantages do not end there, but it was they that became decisive for many athletes in the issue of turning to hydraulics.
Another important point is the excellent endurance that the hydraulic disc brakes have. Accuracy of actuation is considered to be no less significant. The system has proven itself to be reliable over many years of use in automobiles. With proper care, a hydraulic brake mounted on a bicycle will be much more reliable than a mechanical brake. A heightened sense of dosing force makes it possible to use the brakes as accurately as possible. It’s a must for extreme sports.
Among the disadvantages of the hydraulic system, several main ones can be distinguished. The cost of such a system is noticeably higher in comparison with a mechanical one, so the price of a bicycle with hydraulics will be significant. Such a device is a technologically advanced and very complex unit that requires skills in maintenance and a clear understanding of the design features. Not every biker has the necessary knowledge to disassemble and repair a hydraulic brake on their own.
Such components as brake hoses and pipes require a careful attitude towards themselves. These are very vulnerable spots that have a direct impact on the functioning of the entire system. Hydraulic brakes on a bike can be picky about the quality of the oil or brake fluid, so bleeding should be done after a smart choice. Quite often they are used in tandem with traditional disk drives. It is worth saying a little about them too.
If we consider the hydraulic brake drive, then it is appropriate to note the possibility of using oil or a special fluid. Each of the options has both disadvantages and advantages, but so far there is no unequivocal opinion on this matter. The caliper can be monolithic, due to which the structure becomes light and rigid, and composite, characterized by a lower price, but more complexity in terms of maintenance.
The hydraulic disc brake is reliable but difficult to repair in the field. True, it fails in extremely rare cases. There are a number of problems associated with the fact that disc hydraulics have a very small gap between the pads, and in the presence of heavy dirt they wear out much faster. However, in this case, the mechanics cannot boast of at least some advantage, since damaged pads cannot be adjusted on the go, and in the case of hydraulics, this is done automatically during wear.
Disc brakes are much more expensive than rim brakes, their load on the hub during braking is greatly increased, although this issue can be called controversial. It is not necessary to delve into this topic in more detail, it is better to talk about the manufacturers on the market of hydraulic brakes.
Next, you need to put a cambric on the pumping bolt, and then immerse it in a container to collect the remaining liquid. After that, you need to unscrew the cover of the expansion tank and fill it with liquid to the maximum level. You should press the brake hand several times, but it is recommended to do this smoothly and slowly. It is required to press until tightness appears. Further, while holding the handle, unscrew the bleed bolt together with the cambric and add fluid to the expansion tank. It is recommended to carry out such a procedure until the handle has acquired the required level of rigidity. After that, you can screw on the expansion tank, and then remove all tools. Everything is ready, now the brakes are fully pumped.
Why do you need pumping?
If you press the brake lever, and it goes to the grip, that is, its stroke is too great, but the pads do not move or do not reach the brake disc, then you can draw conclusions about the need for bleeding. A similar situation is observed if the lever is too easy to move when pressed or fails altogether. When the handle is pressed sharply, and after the system is triggered, it does not return to its original position, it is also required to pump the hydraulic brakes onto the bike.
In these cases, the reason for the failure of the system was the air that was inside. First of all, you need to find the place through which the passage is carried out. It should be noted that this may be preceded by damage to the hydraulic fittings, weakening of the pumping union on the cylinder, boiling of the liquid, which is associated with overheating. When the entire system has been checked for fluid leaks, you can begin to repair it.
If you need to bleed the hydraulic brake, physics in this case speaks about the need to do it on a horizontal flat surface. The pads must be spread apart so that they do not reach the disc. Next, you need to unscrew the master cylinder, and then fix it horizontally. For each system, the pumping features may differ, so you should use the instructions, in which everything is detailed.
Although there are so many types of braking systems out there, hydraulic brakes are now quite common on mid-range bikes. With the growth of their popularity, a noticeable drop in can be noted. Therefore, it is possible that you decide to convert your bike to a hydraulic brake system. There are many examples of this, but we will give only a few.
One of the manufacturers is Shimano. Hydraulic brakes of this brand are presented in several lines. The most recent was Deore. Its characteristic is stable operation of the master cylinder, handles that are comfortable and pleasant to use. The cyclist can get real pleasure from how the whole system works well and behaves obediently. The picture is slightly overshadowed by the rattling of the brake lever itself. The new collection is presented in two rotor mounting options: bolted and pinned. One set contains two types of pads. metallized and rubberized. The wear of the latter proceeds as quickly as possible. All in all, this is a superior quality hydraulic brake that is well worth the money you spent on it, namely 50.
CLIM 8 CLARK`S brakes are characterized by the fact that buying a device for the price of a single-cylinder brake, you get a full-fledged multi-cylinder device. However, everyone knows that miracles do not happen, so the design of the pens is a little alarming here, but this parameter also finds its fans. But the hydraulic hoses received metal and Kevlar reinforcement.
The most interesting six-cylinder design is found in the caliper. This system is characterized by such a disadvantage as an increase in mass. In addition, during the installation process, it is required to fit the pads to the discs as carefully as possible.
Principle of operation
To understand how a hydraulic brake works, it is necessary to consider its design. To fill the hydraulic line, a special oil or brake fluid under low pressure is used. Pressing the special handle displaces fluid from the hydraulic system, as a result of which it exerts pressure on the working cylinder mounted on the fork or bike frame. As a result, the brake pads and piston are activated, which leads to the wheel blocking.
It’s pretty simple. The hydraulic brake diagram provides a visual representation of the operation of the entire system described. Working with such a device requires understanding that brake fluid is extremely toxic, which often causes severe poisoning. In addition, it can have a detrimental effect on plastic parts and paintwork.
Hydraulic brake design
The hydraulic braking system is based on details such as two cylinders with pistons. These cylinders are connected to the handle on the handlebars using hoses (hydraulic lines) that can withstand high pressure. There is a fluid inside the hoses, which, when the brake lever is pressed, presses on the master cylinder, transmitting force to the working devices. Under pressure, the pistons move forward, transmitting force to the pads. The latter touch the brake disc, and due to the frictional force, the speed is reset.
In the design of the mechanism, cylinders of different sizes are used. main and working. The slave cylinders that act on the pads are larger than the master cylinder on the brake lever. This makes it possible for the cyclist to exert little force when pressing the brake lever to stop the vehicle.
How to adjust everything yourself
It may be necessary to adjust the hydraulic brakes if you notice extraneous sounds while driving. creaking or rustling. A simple test will help to make sure that the adjustment is necessary: lift the wheel of the bicycle and spin it. If the pads touch the brake disc, the wheel will quickly stop spinning.
The relative position of the pads and the rotor must be very accurate, because this affects the performance of the brake. To check the position of the disc in the typewriter and the position of the pads, place a white sheet under them and, if necessary, shine a bright light on it. against such a background it is easier to notice deviations.
Adjust the hydraulic brake as follows: 1. Loosen the caliper mounting bolts as much as possible so that it can move freely to the sides.
Squeeze the brake lever so that the pads are fully pressed against the rotor.
Check the position of the pad valves. they should be symmetrical, at the same distance from the rotor. Move the caliper slightly to the left or right if necessary.
Without releasing the brake lever, tighten the caliper mounting bolts.
How to fix a Shimano hydraulic brake without bleeding it.
Release the handle and check the brakes. Ideally, the pads should be at a minimum distance from the brake disc, but not touching it.
If you notice that one pad is located closer to the disc than the other, but the rotor itself is perfectly centered in the machine, do the following (preferably two people): press the disc against the more protruding pad and apply a little brake. Due to the fact that one valve works more than the other, they will align, and the problem will be eliminated.
The final touch is to set the position of the brake lever relative to the steering wheel. Sitting in the saddle, check if you feel comfortable using the brake lever and if you can quickly press it in an emergency. If the knob is too far for you, tighten the adjusting hex a little more. this will bring the knob closer, but at the same time the pads will move closer to the rotor. The main thing here is not to overdo it and not to make the stroke of the pads too small.
Features of bleeding hydraulic brakes on a bicycle
Hydraulic brakes on bicycles have appeared relatively recently, and have already won the sympathy and vocation not only among beginners, but also among experienced cyclists. Such devices are used when high accuracy and reliability are important. Bleeding the hydraulic brakes on a bicycle is carried out when the system has been repaired. Although the mechanism does not have to be repaired often, the time comes when you need to pump the device for its operability.
How to adjust hydraulic brakes on a bike
Diagnostics and preparation
To determine the exact cause of the breakdown, you will need to carry out diagnostics. Dismantle the wheel on which there is a suspicion of a system malfunction. If the brake machine is dirty, then it should be thoroughly cleaned using a toothbrush. After that, you need to dismantle the pads, and make sure that the pistons are working. To do this, the pistons are pushed inward, and then the brake lever is squeezed out. If both pistons move forward, there is no problem. If one of them (or both) is jammed, then you will need to make repairs using a repair kit. Repair of pistons provides for their replacement, and also O-rings are changed.
It is interesting! Shimano hydraulic systems use mineral oil, most other models and companies use DOT brake fluids.
Preparatory work includes the following:
How To Bleed Shimano Hydraulic Disc Brakes
- Protect discs and pads from oil ingress. Discs can be degreased, but with pads it is more difficult, since they will have to be disposed of. To protect them, you need to cover with a rag.
- Check pads for integrity. If they have wear, burrs, chips and other defects, they should be replaced.
- Check the rotor. If the disc shows signs of damage, then it must be replaced. Dirt, debris and oil should be removed from the brake pads and rotor. The quality of tightening of all bolts that attach the device to the wheel is checked.
- The condition of the hydraulic line is checked for leaks. If such leaks are found, the hoses should be replaced before bleeding the system.
- Make sure the wheel is installed correctly.
After that, you can proceed to the procedure for bleeding the brakes.
A way to bleed the brake system for the lazy
There are many ways to bleed hydraulic brakes, so consider another one that will also be useful when the brake lever is slightly loose. If you have changed the brake hose, then this method is not suitable. The principle of its implementation is as follows:
- Move the master cylinder so that the bolt hole is at the highest point.
- The bolt is unscrewed, after which a syringe without a piston or another container of a suitable diameter is inserted into the hole to be installed in the cylinder bore.
- After that, you need to pour oil or brake fluid into the container, and start pumping.
- You need to operate the brake lever to evacuate air from the system. With each movement of the lever, the handle will become more rigid.
- The duration of pumping takes from 2 to 15 minutes, depending on the speed of the handle.
- For greater efficiency, tap on the hose lines to expel any remaining air bubbles.
This method can be implemented even in the field if the brakes are missing. Finally, the syringe installed in the barrel is removed and the locking valve is screwed on. So that at the moment of removing the syringe, the remaining liquid in it does not leak out, you need to install the handle (plunger) into the syringe and remove it.
Adjusting the brake lever travel
This adjustment allows you to adjust the position of the handle when the brake engages. There are no specific recommendations on this matter. Someone is more comfortable for the bike to brake at the slightest pressure on the handle, someone more like the presence of a small idle and a dead grip in the middle of the lever path.
This adjustment is carried out using a screw located in the brake lever housing. The final adjustment of the sharpness of the seizure of the brake is made by the cable tension thumbscrew.
Attention! After completing all adjustments, check that the pads are equidistant from the rotor. It is possible that the fixed friction lining will have to be readjusted.
How to make the brakes brake well
Use quality pads and center the caliper against the rotor in a timely manner so that the disc bends as little as possible.
What fluids are suitable for bicycle brakes?
What fluids are suitable for bicycle brakes?
Brakes are 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 is used. (how to bleed hydraulic disc brakes)
Basically, each manufacturer recommends their own hydraulic brake fluids, Shimano produces a special mineral oil and does not recommend using anything else. Hope recommends using DOT 4 or DOT 5.1 automotive brake fluid.
High requirements are imposed on liquids:
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 water that enters it (water in the hydraulic brake system not only causes corrosion, but can also boil when the caliper heats up).
Some of the existing brake fluids:
There are two fundamentally different types of fluids that are poured into brakes. these are mineral oils (Magura, Shimano) and DOT3 / 4/5 brake fluid (Hayes, 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, the brake must not be filled!
Automotive brake fluids.
DOT3. glycol base boiling point. 205C stability viscosity at 40C. 1.5 ultra-high hygroscopicity, service life. 10-12 months
DOT4. glycol base boiling point. 230C (actually. about 260) stability viscosity at 40C. 1.5 high hygroscopicity, service life. 24 months
DOT5. silicone base boiling point. 260C (actually. up to 300) stability viscosity at 40C. 1.5 practically zero hygroscopicity, high lubricating properties, with a complete absence of anticorrosive properties; service life. up to 15 years
DOT5.1. glycol base boiling point. 250C (actually. about 280) stability viscosity at 40C. 1.5 highest fluidity, low hygroscopicity, service life. up to 5 years properties of slurry are provided by synthetic additives
Mineral oils for hydraulic brakes:
Hydraulic brake device
Any hydraulic brake consists of at least two cylinders with pistons, connected by a line, or, more simply, a hose that can withstand high pressure. When the cyclist presses the brake lever, the piston displaces the brake fluid from the master cylinder and transfers it to the slave cylinder located in the machine. Here, under the action of pressure, the pistons begin to extend and press on the brake pads. And already due to the friction of the pads on the rotor (brake disc), braking occurs.
The cylinders in the brake machine are always larger than those in the brake lever. Due to this, in accordance with the law of hydraulics, the working brake pistons press on the pads several times more force than the cyclist does by pressing the handle. Also, this law works here due to the fact that two cylinders are installed on the brake machine, or even all 4, 2 on each side.
Pumping. the final stage of the repair
When the entire system has already been completely sorted out and assembled, it remains only to fill in the brake fluid and properly pump the hydraulics. The system is pumped in order to expel air bubbles from all pipes and cylinders, which prevent the hydraulics from working correctly.
There are a lot of ways how the hydraulic brakes of a bicycle are pumped. Anyone can do this at home, if they know how to handle tools a little. Someone uses syringes, and someone uses old and proven methods. Consider the simplest and most time-tested option.
To bleed the brakes, you will need the following components:
- a transparent tube, suitable in diameter to the bleed bolt;
- brake fluid or oil, depending on the specific system;
- required keys;
- jar or bottle;
- a piece of clean cloth to keep it clean.
First you need to put a transparent hose on the bleeding bolt, and lower its other end into a jar, where there should be some brake fluid. Next, you need to open the brake fluid reservoir on the handle and make sure that it is at the maximum level. If necessary, the liquid must be topped up.
Attention! The brake fluid is unique for each bike model and cannot be mixed or replaced.
After that, you can start bleeding the disc brakes on your bike. Pressing the brake lever several times, you need to fix it in the pressed state and at the same time unscrew the screw for bleeding on the brake machine. In this case, you can observe how air bubbles will go out of the tube. After that, the screw must be tightened immediately, and only then you can release the handle and swing again.
This procedure must be repeated several times until the whole system works as it should. This can be felt by the stiffness of the brake lever.
And one more way to pump the hydraulic line for the lazy:
Symptoms of a hydraulic brake malfunction
The first symptom of a malfunction of such bicycle brakes is that it starts to slow down on its own. This can be explained by the fact that air has entered the brake system. This could have happened due to the fall of the bike, a low level of brake fluid in the reservoir, or when the hydraulic circuit is open.
Since air tends to be compressed, unlike liquids, when it enters the system, it works like a gas spring. That is, the air creates the pressure of the brake fluid, which activates the brakes.
Also, the braking system can engage in similar self-activity, in case of jamming of the working piston. And the reason for this is the ingress of water into the hydraulic system.
And, of course, the brakes urgently need to be repaired if the brake lever is not as elastic as before, or the hydraulics no longer responds to the cyclist’s command to stop the vehicle.
Adjusting and bleeding hydraulic bike brakes
Hydraulic brakes are used primarily on bicycles where precision, responsiveness and reliability are required. First of all, these are heavy, massive mountain bikes designed to overcome steep slopes and climbs. Also, hydraulics have become an integral part of high-speed bicycles, as it allows you to very accurately and in the shortest possible time reduce speed.
The principle of operation of hydraulic brakes is very similar to mechanical brakes, where the brake pads are operated by a cable. The only difference is that in the hydraulics, instead of cables, brake fluid is used, and levers and eccentrics replace the cylinder-piston groups. Thanks to this approach, the frictional forces in the system are significantly reduced, and this increases its service life.
Despite this, hydraulics also has disadvantages, first of all, it is difficult to repair in case of breakdown. For example, in the event of a breakdown in the hydraulic line, the brakes cannot be repaired in the field. The most that is possible with the tools is to bleed the hydraulic brakes.
Troubleshooting and repair
To understand what exactly happened to the braking system of your faithful two-wheeled friend, you first need to do some experiments. The first step is to remove the wheel where the problem appeared. Next, you need to clean the brake machine well, the easiest way to do this is with a toothbrush. Well, the main goal is to remove the pads.
When access to the working pistons opens, you need to press them in with a screwdriver, and then gently press the brake lever. Both pistons should move forward. If one of them is stuck, you need to use a repair kit to eliminate the malfunction. Also, the piston system must be carefully inspected for leaks, if they are present, then the cylinder-piston group is worn out. As a rule, in this case, the pistons or special O-rings on them are changed.
In conclusion, you need to carefully inspect all hydraulic line. There should be no kinks, dents or other damage on it. If present, the hose must be changed.
When repairing hydraulics on a bicycle, it is unacceptable for brake fluid to get on the pads or rotor. If this happens, the elements must be cleaned immediately with fine sandpaper. Otherwise, the brake pads will not work efficiently and quickly fail.
It is also important to know that brake fluid is poisonous and can be harmful to health, therefore it is not recommended to get it on the skin. Eye contact should be especially avoided. In addition, it is a good solvent. easily corrodes the bulk of paints and varnishes.
Types of hydraulic disc brakes
The main difference between a disc brake and a conventional rim brake is that braking occurs by clamping the brake disc, rigidly fixed to the hub, with brake pads, which are fixed at the rear on the frame and at the front on the fork stays.
The design of the main brake cylinder can be different, and depending on this, hydraulic brakes are divided into the following types:
- Single piston;
- Twin-piston with opposed pistons;
- Two-piston with floating pistons;
Mostly used two-piston with opposed pistons. There are also single-piston ones, but due to shortcomings, they were almost completely replaced by two-piston ones. Complex multi-piston systems are used mainly for downhill, where power plays a decisive role, rather than simplicity of design.
Due to the type of fluid used in hydraulic systems, brakes can operate on brake fluids and oil. Each of them has its own advantages and disadvantages, but there is no unequivocal opinion on this matter. The caliper can be monolithic, which makes the structure stiffer and lighter, and composite. cheaper in price, but more difficult to maintain.
The hydraulic disc brake is very reliable, but it is not easy to repair and adjust it in the field. True, to bring the hydraulic brake to a coma state, you need to try very hard.
There are some problems associated with the fact that disc hydraulics have a very small gap between the pads and in the presence of heavy dirt, the pads are subject to increased wear. But mechanics have no advantages in this case, since worn-out pads cannot be adjusted on the fly, while hydraulics are automatically supplied in the course of wear.
They are more expensive than rim ones, slightly increase the load on the hub during braking, although this is a controversial issue. We will not delve into the details of the drive in detail, since this is a separate topic for conversation, but for now let’s proceed to consider what the manufacturers have prepared for those who want to put hydraulic brakes on the bike.
Advantages and disadvantages of hydraulics
Dosing accuracy and the speed of response of the mechanism to pressing the handle are the two main qualities that have led to the widespread use of hydraulic brakes. These are not the only advantages, but they are the ones that made the downhill athletes turn to hydraulics.
The excellent endurance of the hydraulic brakes also played a role in the migration of hydraulics to the bike. As well as the accuracy of actuation, this was a very important quality for downhill.
The reliability of the system has been proven over the years of its use in automobiles. With proper care, hydraulic brakes on bicycles are many times more reliable than mechanics. The heightened sense of the strength of the dosage allows you to manipulate the brakes with jewelry precision. In extreme sports, this is a must.
The disadvantages of hydraulic brakes include the following: The cost of a hydraulic system is much higher than a mechanical one, therefore a bicycle with hydraulic brakes will be more expensive. Complexity of service. The hydraulic system is a rather complex and technologically advanced unit that requires skills in maintenance and a clear knowledge of the design and its features. Not every biker is able to independently sort out the system and carry out its high-quality repair. Also, field repairs in the absence of experience can be difficult. Brake pipes and hoses require careful handling. They are quite vulnerable and the quality of the entire system depends on their condition. Also, brakes can be picky about the quality of the brake fluid or oil, so you should make a deliberate choice when pumping.
Most often, hydraulic brakes are used in tandem with disc brakes. Literally a few words should be said about them.
Review of the best
Out of a million types of braking systems, hydraulics are increasingly found on mid to very mid-range bikes. As their popularity grows, the price falls accordingly. Therefore, it makes sense to consider converting your bike to a hydraulic braking system. There are many examples, but we will give only two. For contrast.
Shimano unveiled a new collection earlier this year, revamping the Deore line. Nice grips, stable operation of the main brake cylinder gives real pleasure from precise actuation and obedience of the entire system as a whole. A slight rattling of the handle itself darkens the picture a little.
The new range offers a choice of splined or bolted rotor mounting. Shimano Deore comes with two types of pads. rubberized and metallized. The former wear out very quickly. The hydraulics in general are of excellent quality and their 50 is definitely worth.
CLIM 8 CLARK`S. The advantage of these brakes is that for the price of a single cylinder you get a full multi-cylinder hydraulic brake. But miracles do not happen, and you have to pay for everything. The design of the handles is a little alarming, but this is not for everybody. But the hydraulic hoses are reinforced with Kevlar and metal.
The caliper has an interesting six-cylinder design that promises to be reliable. The disadvantages of this system are the slightly increased weight. In installation, they are also not as easy as they seem. during installation, they require careful adjustment of the pads to the discs.
Features of Hydraulic Bicycle Brakes
The vector of action of the brakes, both mechanical and hydraulic, is one. stop. a car. But there are a lot of nuances and questions to both one and the other brake drive circuit. Today we will try to wash the bones with hydraulic brakes.
Their main difference from mechanics is that a hydraulic line is used to drive the brake pads, and not cables. The hydraulics connect the brake levers directly to the brake mechanism. In the role of which can be both disc hydraulic brakes and conventional rim.
Principle of operation
The brake line is filled with a special oil or brake fluid under low pressure. When the brake lever is depressed, the bicycle brake cylinder displaces fluid from the hydraulic system, and it exerts pressure on the slave cylinder, which is mounted on the fork or bike frame. In turn, the slave cylinder drives the piston and brake pads, which block the wheel by means of the brake disc. Very simple. Here is a diagram for clarity.
When working with hydraulic brakes, it is worth considering that brake fluid is very toxic and can cause severe poisoning. It also has a detrimental effect on paintwork and plastic parts.
Bleeding the brake hydraulic system
Reasons why you should do brake bleeding:
- when you press the brake lever, it goes out to the grip itself, i.e. has too long a stroke, but at the same time the pads do not move, or do not reach the brake disc;
- the brake lever falls through when pressed or has too little movement;
- when the handle is pressed sharply, after the brake is activated, the handle continues to fall smoothly.
All clear. The reason for the failure of the brake system was the air that got inside. The first step is to find the place where the system grabbed the air. This can be damaged hydraulic fittings, boiling of the liquid due to overheating, a weakened pumping union on the cylinder. After checking the entire system for fluid leaks, you can start pumping.
We always pump the hydraulics on a flat and horizontal surface. The pads should be spread apart so that they do not reach the disc. Next, we unscrew the master cylinder and fix it strictly horizontally. Each system has its own characteristics of pumping, so it is better to do it according to the instructions. The pumping fluid must correspond to the brand indicated in the passport.
Now you should put the cambric on the bleed bolt and immerse it in a container to collect the remaining fluid. We unscrew the cover of the expansion tank, fill in the liquid to the maximum level. Several times smoothly and slowly press the brake lever. Press until it becomes tight. Now holding the handle, unscrew the bleed bolt with a cambric, without releasing the handle. Add liquid to the expansion tank. We carry out the procedure until the handle becomes stiff. We twist the expansion tank and remove the tool. Done, brakes pumped.
So the rumors about the difficulty in servicing hydraulic brakes are greatly exaggerated. Along with some disadvantages, such a system has more advantages. But in principle, the principle of operation of this or that mechanism is not so important to a real biker as the very fact of free movement in space.