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How to bleed Sram road disc brakes

Cyclist magazine
26 May 2020

Walkthrough guide from Sram tech Jan Mueller using the Red disc brakes

Although the FlatMount calipers are visually very different to the original Sram Red calipers, there is little mechanically different (a slightly different banjo and bleed screw) so the process remains virtually unchanged. Regardless Sram tech Jan Mueller tells us that it’s a process many consumers struggle with, so he put on a demonstration for us of best practices, and highlighted a few common pitfalls.

How to bleed Sram road disc brakes

Time taken: 30 minutes

Equipment required: Dot 5.1 fluid, Sram bleed kit, set of allen keys, toe strap and some rags. Gloves and eye protection also recommended when dealing with DOT fluid.

1. Remove the pads

Bleeding SRAM Disc Brakes Tutorial

Removing the pads is absolutely essential when doing any maintenance work. The Sram road discs use Dot 5.1 fluid, which is pretty nasty stuff, so contact with the pads contaminates the surface and renders them useless.

Sram recommends using the included plastic block as it keeps the pistons in the correct place and prevents any damage. It’s probably worth adding a note that you should never pull the levers without the pads in (or the plastic block) as the pistons can pop out of the caliper and no one wants that.

2. Prepare the syringes

Bleeding SRAM Disc Brakes Tutorial Step 3

To bleed the system you require two Sram syringes. One should be empty and the other 2/3 full of fluid. Official recommendation from Sram is to have both partially filled but that just creates a bit of a problem later on.

Once filled, lock off the syringe and pull on the plunger to create a vacuum and draw out any air that has been absorbed by the brake fluid. Then push up the plunger to remove any air from the line.

3. Attach the syringes to the caliper and lever

Bleeding SRAM Disc Brakes Tutorial Step 4

Both the caliper and lever have small screws to keep the fluid reservoir sealed. Only ever remove one at time, as removing both would drain the system, and Jan recommends starting with the one at the caliper.

Once both syringes are attached (fluid filled one at the caliper) push on the plunger at the caliper end, which sends fluid through into the other syringe. You want to leave about 1-2cm of fluid in the caliper syringe for later.

4. Lock off the system and bleed the caliper

Bleeding SRAM Disc Brakes Tutorial Step 6

Jan told us that the most common mistake people make is to forget to lock off the two ends of the system so when they’re bleeding they’re drawing fluid from all over the system. To prevent this pull the brake lever back to the bar and keep it there with a toe strap.

This closes off the master cylinder and allows you to bleed the caliper separately. Once this is done lock off the lever syringe with the red plastic clip.

With the system closed off you begin to slowly draw on the caliper syringe plunger. If there is air at the caliper end it will be drawn into the syringe.

Once you see air come out into the main body of the syringe, push back on the plunger to fill the air space with fluid. Be careful not to pull too hard as you an end up drawing in air through the syringe’s connection with the caliper. Repeat this until no more air comes through and then lock off the syringe.

5. Bleed the lever

Bleeding SRAM Disc Brakes Tutorial Step 11

Bleeding the lever is the same process as on the caliper. Once you’ve bled the lever, remove the toe strap and allow the lever blade to return to normal. Then unlock the caliper syringe and push through the remaining fluid.

6. Adjusting lever bite point and lever reach

 At the moment there is no easy way to adjust the lever bite point although Jan recommends a work around. With the caliper syringe locked off and the lever syringe open, pull the brake lever to the desired bite point, then lock off the lever syringe. This leaves the correct amount of fluid in the system for your desired bite (or free stroke).

Once this is done, remove both syringes and replace the bleed screws, clean up any excess fluid and reinsert the pads.

The lever reach is much more easily adjusted with a dedicated screw that is accessed from underneath the lever body. Note – this does not affect the bite point or the brakes.

The original version of this article by Jordan Gibbons first appeared on Cyclist.co.uk in June 2015