Degree of difficulty for the screwdriver work on the road bike disc brakefor talented hobby mechanics
The right tool for bleeding Shimano disc brakes
- Hexagon socket
- Torque spanner
- Screwdriver
- Pointed pliers
- Venting set
- Handlebar bracket
Material & auxiliary materials
- Brake fluid approved by the manufacturer
- absorbent cloths
- Plastic bag
Tips for bleeding disc brakes on a road bike
CHECK
Pull the brake levers after bleeding and always before every ride. A solid pressure point must be established immediately. It must not be possible to pull the lever all the way to the handlebars. If you have to pump until the lever gradually builds up pressure after about a third of the way, you should not ride. Bleed the system.
LIQUIDITY
The fluid varies from manufacturer to manufacturer. Shimano uses mineral oil, SRAM a DOT fluid. Only use approved fluids. Please note that DOT fluid is aggressive to skin, clothing and paintwork. Always wear adequate protective clothing, at least work gloves, goggles and old clothing.
INSTRUCTION
Brakes are not standardised, they differ in design and handling. This also applies to the bleeding process. Please also follow the instructions on the manufacturer websites of Shimano, SRAM, Campagnolo or Tektro. When dismantling, always place all individual parts in such a way that you follow the correct sequence when reassembling.
HELPER
Bleeding brakes often requires the famous "third hand". It is best to have a helper who assists when the brake lever has to be pulled on the handlebars, the brake calliper held and the bleed screw opened at the same time.
CONTROL
Check the tightness of the bolts after 100 to 300 kilometres of driving and then every 2,000 kilometres. At this interval, you should also check whether all connections and lines are tight. To do this, pull the brake levers and hold them for a few seconds.
Bleeding Shimano road bike brakes: the do-it-yourself guide
1 Remove fuse from brake pads
Hang the bike on an assembly stand with the handlebars fixed. Detach the brake hose from the fork and unscrew the brake. Dismantle the brake, pull the split pin from the pad holder and unscrew the pad holder.
Remove 2 brake pads
Remove the brake pads and use the plastic spacer from the bleeding set to gently press the brake pistons back into their end position. Insert the spacer and secure it with the pad holder, which only needs to be screwed in slightly. Gently hang the brake calliper downwards.
3 Remove cover
Pull the brake lever slightly and unscrew the cover fastening screw completely. Keeping the lever pulled, release the cover at the bottom forwards and remove it upwards.
4 Attach the funnel to the brake lever
Loosen and remove the bleed screw together with the sealing O-ring. Turn the funnel in carefully and only slightly, it should be vertical, make sure that the O-ring is seated properly on the connection piece. Place the open container of replacement brake fluid on the worktop.
5 Fill the syringe
Fill the syringe with the bleeder hose at least two thirds full of brake fluid. Then: Turn the syringe upside down, first draw the fluid completely into the piston and then press the air completely out of the tip and hose.
6 Attach the hose to the brake calliper
Place the appropriate ring spanner or open-end spanner on the hexagon of the bleed screw. Push the filled hose onto the bleed screw of the brake calliper. Secure the hose with the holder to prevent it from slipping off.
7 Venting the system
Open the bleed screw by a maximum of a quarter of a turn. Press the piston of the syringe in slowly and evenly. Oil will now come out of the top of the funnel. Keep pressing until no more air bubbles escape. Caution: Do not pull the brake lever of the racing bike disc brake!
8 Close the vent hole
If there are no more bubbles in the funnel, screw the vent hole back on. Leave the hose on the bleed screw and remove the syringe. Insert the venting tube into a transparent plastic bag and secure it with a rubber ring.
9
Hold the brake calliper firmly and open the bleed screw. Brake fluid escapes. The aim is to ensure that there are no more air bubbles in the fluid.
10
When the level in the funnel drops, close the bleed screw at the bottom and top up with brake fluid. Make sure that there are no bubbles in the funnel before opening the brake calliper again and draining more fluid.
11
While you are doing this, repeatedly tap lightly first on the top of the brake lever and then on the brake calliper. This will loosen any bubbles that may have adhered. If there are no more bubbles, close the bleed screw.
12 Pull brake lever for last air bubbles I
Pull and hold the brake lever. Open and close the bleed screw two to three times for a brief moment. Then pull the brake lever several more times to allow the last bubbles to rise into the funnel. The pressure point must be stable after about a third of the theoretical lever travel.
13 Pull brake lever for last air bubbles II
Turn the wheel so that the funnel is tilted slightly backwards and then in the opposite direction. Keep pulling the brake lever to release any bubbles that may still be inside. The pressure point must be stable after about a third of the theoretical lever travel.
14 Seal oil stopper
If everything fits, seal the connection of the oil funnel with the oil stopper, to which a sealing ring is attached. Unscrew the oil funnel with the oil stopper in place.
15 Unscrew the oil funnel
Have an absorbent cloth ready to soak up any escaping brake fluid. You can reuse clean brake fluid. Milky discoloured fluid should be disposed of properly at a collection point.
16 Screw in the screw on the brake lever
Tighten the screw plug sensitively to 0.3 to 0.5 Newton metres. Ensure that the sealing O-ring is seated properly. Some brake fluid will leak out, which is desirable.
17 Clean brake fluid from the lever
Wipe the area dry. Remove the hose and bag from the brake calliper. Close the cap on the bleed screw. Also wipe the brake calliper clean. Remove any excess brake fluid with a little brake cleaner.
18 Removing the brake lever
Hang the decorative cover on top and tilt it downwards. Screw the cover tight. Pull the rubber handle forwards and hook it into all corners and edges.
19 Refitting the brake pads
Undo the fixing bolt and remove the plastic spacer. Press the pads together slightly against the spring tension and guide them into the brake calliper correctly positioned in the direction of travel. Secure the brake pads with the brake pad bolt and push on the locking pin.
20 Aligning the brake calliper
If necessary, replace the removed wheel. Check the route of the brake line and position the brake calliper on the fork. Initially, only tighten the screws slightly; the brake calliper must still be able to move. Secure the brake hose to the fork.
21 Tighten the brake calliper
Pull the brake lever so that the brake calliper can align itself in the centre. Tighten the screws to the specified torque. Turn the wheel and apply the brakes. Release the lever and turn the wheel again: the disc must not drag. If it does, you will have to loosen and align it again.
You can find more workshop tips and wrenching instructions for road bikes here here on the TOUR website.
TOUR author Dirk Zedler is the owner of the Zedler Institute for bicycle technology and safety GmbH. Zedler - Institut für Fahrradtechnik und -Sicherheit GmbH specialises in testing bicycles and components in its own test laboratory. The company also develops and builds test systems and equips test laboratories for bicycle manufacturers.
