If your brakes are behaving strangely, perhaps the braking point moves on the descent, the brake lever can be pulled all the way to the handlebar or the brake is older than a year, then perhaps it is time to carry out a fluid bleed. We show you now how this is done properly with an Avid or SRAM brake, removing all air from inside the system.
for brakes which use DOT Fluid as a brake medium, it is important to change the fluid once a year to ensure that correct function is maintained in all situations.
The basic function of a brake bleed is to ensure that the brake lever is set correctly. This refers not to the ergonomics, but the correct adjustment of the pressure point and lever reach adjustment.
If your model has a Contact Point Adjustment, the adjuster should first be rotated in the opposite direction of the arrow until it stops. If the bleed port is located on the adjuster, turn it back until the screw is at its highest point.
Using the reach adjust, the Lever should be adjusted so it sits around 75-80 mm away from the center line of the handlebar. A quick test to check this is to make sure that still can be pushed forward a small amount. If the reach adjustment is turned too far to the outside, this would not be possible.
Before you start the Contact Point Adjustment should be rotated in the opposite direction of the arrow until it stops and the lever length has to be adjusted as described above.
To ensure the correct bleeding of the system, it is important to place the brake pistons into the correct position. For this, use either the spacer that was supplied with the brakes for transport (brake pads remain in place), or the thicker bleed block provided with the bleed kit, (pads must be removed).
We decided to use the bleed block and therefore removed the brake pads.
The bleed-block is inserted into the back of the brake and the pistons are pushed back completely.
Two syringes must be filled with brake fluid avoiding any any air. Syringe 1 about halfway, syringe 2, only about 1/3.
With a Torx T10 the bleed port can be opened and the half filled syringe gets placed on the caliper.
Afterwards, the bleed port on the lever gets removed and the 1/3 filled syringe gets installed.
The fluid gets replaced from bottom (caliber) to the top (lever). For this reason, the lower syringe will be pushed 2/3 through the system.
Once this is done, the upper syringe gets closed and the brake lever is pulled in and fixed to the handlebar (isolating the caliper from the system).
With the lower syringe a vacuum can now be created by pulling the syringe plunger back. You should now see any air trapped in the system being released at the lower syringe. Thus, the brake caliper and the brake hose are now being bled. When no more air is released, the lever can be released slowly while slight pressure is applied to the lower syringe. When done, the lower syringe can be locked closed.
After the lower syringe has been closed, the upper syringe can be re-opened, again by pulling the syringe out slightly a vacuum is created to bleed the brake lever too.
Here the last little air bubbles can be removed from the lever. Thereafter, both syringes can be removed, and the port screws can be replaced. The last thing to do is to reset your desired reach adjust and realign your brake levers
Should any fluid be leaked, this is best removed with clear water.
We continue next Monday with the next exciting topic for your bike!
Words: Christoph Bayer / Trevor Worsey Picutres: Christoph Bayer