Bleeding is the basic maintenance of the hydraulic disc brake. On Shimano calipers, it’s not complicated. You just have confidence in your actions and have the right tools.
You need a complete bleed kit for Shimano brakes or a compatible set. This consists of a syringe with its connection, a funnel, the funnel cap, but also a reducer which allows the funnel to be fixed on the latest generation of brakes. Caution, it is sold separately at Shimano. You will also need a piston wedge. We will add Shimano oil of course, if we want to preserve the warranty. The other mineral oils also work very well, but as they have another color, we will immediately see that you have tinkered… You will then need a spirit level, Allen keys for your stem (4 or 5 mm), a 2 or 2.5 mm allen key and a 7 mm spanner. With all this you can start…
Pictures© Frédéric Iehl
Time and difficulty
You have to be methodical and patient when bleeding your Shimano brakes. You will have half an hour for the two stirrups. The thing to keep in mind is to avoid air bubbles. You do this to expel the air, so there’s no need to add it. The syringe is filled to the brim so that there is no air in it. Finally, this kit is only used for mineral oil. Never use equipment that has reached DOT 5.1 under penalty of irreparably damaging your braking system. A few drops are enough…
We will loosen the stem to tilt the handlebars and bring the lever to the correct position.
You have to tilt the lever to bring the bleed hole to the horizontal, the highest point of the system. The top of the spirit level is aligned with it…
We tighten the stem to prevent it from moving during the purge. We certainly do not press on it, but it is better that everything holds. Especially the funnel…
At the top of the lever, under the hood cover, there is the bleed screw.
We loosen the screw and avoid losing it or losing the O-ring…
The funnel adapter is screwed onto the bleed screw. We don’t touch the lever or the pistons.
Then screw on the funnel. We make sure that everything is properly blocked.
The funnel plug is then placed to close the circuit.
At the caliper, there is a small rubber plug that covers the bleed screw. It must be removed, do not lose it.
We disassemble the pads, and we put a piston wedge. We also remove the wheels. Mineral oil is relatively safe for the skin, but not for the eyes. But if the oil is deposited on the disc or the pads, it will be almost impossible to have effective braking…
The bleed screw must not be removed for bleeding. It contains a little oil, taking it apart and putting it back on can reinject air into the circuit. The bleed screw includes a flange that blocks the syringe hose.
The syringe and its hose filled to the brim, connect the fitting to the bleed screw. We lock with the tightening (yellow part) that we press on the brake caliper.
The bleed screw is opened by opening less than a quarter turn maximum. No more.
We put oil in the middle of the funnel. Then remove the funnel cap.
Slowly push the plunger. We do not hesitate to put small strokes of a metal tool on the stirrup to « take off » any bubbles. By « passing » two-thirds of the syringe, we had to drive out all the bubbles. We still check that the rising liquid is bubble-free.
The oil level is rising, the bubbles have escaped.
Tighten the bottom bleed screw. The syringe can then be removed, with a cloth to soak up the excess oil.
Gradually press the brake lever several times to drive out the last air bubbles. The lever should become « harder » over time.
Then replace the funnel cap.
We loosen the funnel, being careful not to spill anything ! It will be necessary to find a container for the used oil (funnel and syringe too) and dispose of it in the recycling center. Then remove the reducer.
Put a little mineral oil on the upper bleed screw and its hole to reduce the risk of air bubbles.
And tighten the bleed screw. Pass a cloth over the 2 bleed screws to remove the oil. We will then be done with bleeding the Shimano brakes.
All that remains is to put the hood covers, pads and wheels back in place. Several static braking operations will be carried out to ensure that the braking sensation is constant. If it softens a lot, something has been closed incorrectly, or there is a leak in the hoses… If you want to get started but are not completely sure of yourself to bleed the Shimano brakes bike, do the back first. You will see if the result is good and in case of trouble, you will have the most powerful: the front! But if you take the time, there will be no problem. If you do a lot of purges, put on gloves, it’s better! Finally don’t forget to put back and tighten your handlebars in the right position. And we tighten the bleed screw. Pass a cloth over the 2 bleed screws to remove the oil. We will then be done with bleeding the Shimano brakes.