Bleeding motorcycle brakes
If you have to put the pedal to the metal on a tour to avoid an accident, it is important to be able to rely on fully functional brakes. To keep it that way, you should change the brake fluid once a year. Here you can find out how to keep the hydraulics of the brake system in good working order.
Important: You should only change the brake fluid yourself on conventional brake systems. Integral brakes or servo-assisted brakes are much more complex, as are ABS brakes. They usually require special devices for draining and filling, such as those used in specialist workshops.
It's all about the right brake fluid
A look at your bike's logbook will tell you which DOT class to choose. DOT stands for Department of Transportation, the US Department of Transportation. The different DOT classes are distinguished primarily by their boiling point and cold viscosity. The following classes are available:
DOT 3
DOT 4
DOT 5.1
DOT 5 based on silicone
Brake fluids of DOT classes 3 to 5.1 can be mixed with each other, as these fluids have a glycol base. The situation is different with DOT 5, which has a silicone base and must therefore never be mixed with brake fluids containing glycol. There is a risk of undesirable reactions.
Good preparation is important
Before you start work, cover all sensitive parts near the brake fluid reservoir well. Some of the fluid can quickly spill. As it has a corrosive structure, it can leave unsightly marks on paintwork or plastics. However, there is no need to panic if something spills: Simply wipe the drop away thoroughly immediately. You should therefore always have a clean cleaning cloth within easy reach.
Changing the brake fluid
To do this, carefully open the cover of the expansion reservoir using a suitable screwdriver. Carefully put the cover, the screws and the rubber membrane underneath to one side.
Use a disposable syringe to suck out the old brake fluid. This will shorten the flushing process when filling in the new fluid, as you will then immediately bring new fluid into your system.
The overrun hole at the bottom of the fluid reservoir must remain covered! Otherwise air can get into the brake cylinder. Now fill the reservoir with the new fluid. To prevent it from spilling over when the handlebars are moved, do not fill it more than two thirds full.
Bleeding motorcycle brakes correctly
For the bleeding process, you will find practical brake bleeder sets in various designs in the TecBike online range. Depending on the model, these include a
- transparent hose,
- a one-way valve,
- a nipple adapter and
- a collection container
are included in the scope of delivery. You will also need the right wrench for the bleeder valve on the motorcycle. To prevent slipping and possible damage to the valve, we recommend using a ring wrench instead of an open-end wrench.
Before you attach the hose of your brake bleeding set, attach the ring wrench. This allows you to open or close the valve at any time.
First open the bleed screw by a quarter of a turn. Now actuate the brake lever very evenly and slowly. If you actuate it quickly, some reservoirs tend to shoot the fluid into the air in small fountains. Alternatively, you can simply cover the brake fluid reservoir while pumping.
If the bleeder valve is opened too far, air can enter between the valve and the thread of the brake calliper. You can avoid this. With the bleed nipple closed, pull the brake lever slightly to apply pressure. Then open the bleeder valve. In the meantime, pull the brake lever further. At the end of the lever travel, close the valve again and release the lever. Repeat this process until the system is bled as desired.
Even if this process is similar to a yoga exercise and takes a little longer than the first procedure, air cannot enter the system. This is because it is only opened when under pressure and not under vacuum.
If you want to do without the time-consuming pumping, simply use a brake bleeding device from our TecBike range.
Once the bleeding process is complete, fill the brake fluid reservoir to the correct level. Please note that the rubber membrane can reach into the brake fluid. This in turn increases the fluid level in the reservoir. If you put the diaphragm on, it can overflow.
What to do if no pressure point can be established?
If you have replaced the brake pump or changed the brake fluid hose or brake line, air can get into the system. The pressure point can no longer be built up. To solve the problem, lightly flick the lines.
If you cannot find a pressure point when bleeding the motorcycle brakes, this may be an indication of a defective brake pump. In this case, you should take the motorcycle to a specialist.
Bleeding motorcycle brakes with ABS
Before you start cornering again after bleeding the motorcycle brakes, you must activate the ABS on the motorcycle. To do this, briefly apply the brake once. This opens the valves and the remaining brake fluid mixes with the fluid in the ABS block. You should carry out this process before and after changing the brake fluid.
Our tip: Before reassembly, we recommend cleaning the cover and diaphragm very carefully. If you save yourself this work, the sealing joint of the cover will continue to sweat out fluid for days after the change.
There is air in the system - what to do?
Despite all your care, air has crept in and bleeding is not working? The following trick can help:
With the bleeder valve closed, pump the brake lever to pressure. Secure it in this position with a tensioning strap and leave it overnight. The air bubbles in the line will escape through the brake line and the overrun hole in the brake cylinder.