From the Workbench: At-Home Brake Bleed 2

From the Workbench: At-Home Brake Bleed

Sick of your mushy, spongy, lever-to-the-bar brakes but you're too scared to attempt a bleed? In this tutorial, we'll walk you through the process of bleeding two of the most common brake brands on the market, SRAM and Shimano. The biggest culprits to those less-than-stellar feeling levers are H2O and air, both of which have different ways of ruining your ride. Water, which is absorbed by glycol-based fluids such as DOT 3, 4, and 5.1 (what SRAM brakes use), lowers the boiling point of the fluid (bad in hydraulic brakes). Air, which can be introduced by a poor bleed or other factors, contributes to that mushy feel and non-distinct lever pull. A simple bleed, which can be done in as little as 20 minutes once you master it, is usually the fix for a poorly performing brake.

Note 1: We recommend checking for contaminated or worn pads, as well as kinks in your brake line before proceeding with a bleed. Addressing these issues may solve your brake performance troubles.

Note 2: There are a few different ways to skin a cat when it comes to bleeding brakes, and every mechanic seems to have their own theory as to why their method works best. We'll walk you through the most basic and straightforward process. 

From the Workbench: At-Home Brake Bleed

Tools Needed For Sram Bleed

Tools Needed For Shimano Bleed

Please be aware that the bleed procedures and fluids used for SRAM brakes and Shimano brakes are different. You will need a SRAM- or Shimano- specific bleed kit, as well as the proper fluid for each brand of brake. DO NOT bleed a SRAM brake with mineral oil and DO NOT bleed a Shimano brake with DOT fluid. If you're bleeding Shimano brakes, skip over our "Bleeding SRAM Brakes" section of this tutorial completely. If you're bleeding SRAM brakes, this next section is for you.

*We recommend wearing gloves throughout this job, especially when working with DOT fluid.*

Bleeding SRAM Brakes

Step One - Remove Wheel

This step is pretty basic so we won't go over it again. If you don't know how to remove your wheels, you can refer to our At-Home Tubeless Conversion tutorial. 

Step Two - Remove Brake Pads

Remove the retaining clip by hand and store it in a place you won't lose it. If you can't remove the clip by hand, you can use needle-nose pliers. Once the clip is out, remove the brake pad retaining bolt with a 2.5mm allen key and set aside. Grab the pads, squeeze them together and remove them by pulling them out from the top end of the caliper. Use care not to contaminate the pads by touching the pad material or placing them pad-side-down.

Step Three - Set Pistons and Install Bleed Block

Occasionally, the pistons will be too far out to insert the bleed block. To set them back into the caliper, you can use a number of methods including using a brake pad piston press, using the bleed block itself or using a small box wrench to push them back in. No matter the tool, use care not to damage the pistons during this process. Once the pistons are set, insert the bleed block. 

Step Four - Level Out Brake Lever

Take a T25 Torx wrench and slightly loosen the lever clamp bolt. Bleed port in location will vary based on brake model. Rotate your lever on the bars so that the bleed port is pointed up. Snug down the lever clamp bolt to prevent shifting during the bleed.

Step Five - Lever Adjustments

If your lever has a contact adjustment, turn it all the way in the opposite direction of the arrow. If your levers have a lever reach adjust knob, turn it until your lever sits at 75-80mm from the handlebar. 

Step Six - Prepping the Syringes

SRAM now includes two different syringe tips, two screw-in tips, and their Bleeding Edge quick-connect tip. Determine if your brakes are equipped with Bleeding Edge technology and install the proper tip to the Syringe. Using DOT 5.1 fluid, fill the syringe that will be used on the rear caliper one-quarter full (this will be the Bleeding Edge syringe if your brakes use this system). For the lever syringe, fill it three-quarters full with DOT 5.1 fluid. We like to remove as much air from the syringe as possible, but skipping this isn't a huge deal as air from the brakes will likely be reintroduced to the syringe during the bleed process. Clip the syringes closed before proceeding. 

Step Seven - Connecting the Syringes

Keep a rag or paper towel handy during these next few steps to catch and clean up any DOT fluid that may escape. Starting at the lever, using a T10 Torx or a 2.5mm allen wrench, carefully remove the bleed port screw. Set the screw somewhere safe as it's small and easy to lose. Completely screw in the syringe that's filled three-quarters full and move on to the caliper. 

If your brakes are equipped with Bleeding Edge, you should see a rubber caliper bleed plug which will need to be removed (ours must have fallen out prior to this tutorial). With the syringe that's filled one-quarter, firmly push the Bleeding Edge quick-connect tip into the bleed port until you feel a distinct click or snap when it's in place. NOTE: Safety goggles are not a bad idea here, as DOT fluid can splash a bit when the Bleeding Edge tool is inserted, as it did in our case. DOT fluid does not feel good in your eyes. With the tip fully inserted, turn it one complete revolution counter-clockwise to open the system. 

If your brakes use a 2.5mm bleed port bolt like the one found on your lever, use a 2.5mm allen to remove the bolt and screw in the syringe that's filled one-quarter full. 

Step Eight - The Bleed

Unclip the syringes so fluid can be pushed and pulled through the hose. Starting with the lever, hold the syringe vertically and plunge the fluid into the system making sure to stop before any air from the syringe enters the tube. You should see the caliper syringe filling with fluid. Now is the time to check on the condition of your fluid. If the fluid coming out of the caliper is discolored, clip closed both syringes, remove them, properly dispose of the old fluid and restart the bleed procedure with new fluid in both syringes. 

If the fluid comes out clean, it's time to pull the fluid back through the caliper to the lever. To do so, hold the caliper syringe vertically. With your other hand force the lever plunger up using your thumb while gripping the syringe. This can be a bit tricky, especially if you're bleeding the rear brake. Stop before any air enters the caliper. Close the caliper syringe by either snapping the hose clip it or turning the Bleeding Edge tool a full turn clockwise, leaving the caliper syringe on the caliper.

With the lever syringe still open, squeeze the lever blade a couple times. Pull the plunger on the syringe a couple times to create a vacuum, then, push the plunger firmly to pressurize. Repeat this process until no air is coming out of the lever. Compress the plunger one last time, close the syringe and remove the syringe. Using the T10 Torx wrench, reinstall the bleed port screw. Clean up any DOT fluid on the lever or bars with denatured alcohol and a rag or paper towel. You can now remove the caliper syringe and reinstall the bleed port screw or Bleeding Edge plug. Don't forget to clean up any fluid. 

Step Nine - Reassemble

Remove the bleed block. Making sure there's no DOT fluid on your brakes (or hands), holding the pads together with the spring between them, slide the pads into the caliper until the retaining bolt holes line up. Screw in the retaining bolt using a 2.5mm allen and reinstall the retaining clip. 

Install your wheel. With the wheel (and rotor) in place, return the contact and lever reach adjustments to your preferred position. Use a T25 Torx to loosen the lever clamping bolt and return your levers to your preferred angle and re-tighten. Squeeze your brake lever to push the pistons out and check for any rubbing. Should the pads rub the rotors, skip down to the end of this article where we explain how to align your calipers or check Step Six, Installing the Fork and Controls of our At-Home Fork Installation guide. 

DOT Fluid Disposal

DOT fluid is not a happy chemical as far as the environment is concerned. Put used fluid in a sealed container and check your local laws and regulations to dispose of it safely.

Boom! Now you know how to bleed your SRAM brakes and keep them running strong! Repeat this whole process with the other brake and you should be left with a solid, positive feeling system for some time. You can skip the Shimano Bleed tutorial below, but if you've missed our other From the Workbench tutorials, skip down to the bottom of this article to check them out. 

Bleeding Shimano Brakes

Step One - Remove Wheel

This step is pretty basic so we won't go over it again. If you don't know how to remove your wheels, you can refer to our At-Home Tubeless Conversion tutorial. 

Step Two - Remove Brake Pads

Remove the retaining clip by hand and store it in a safe place. If you can't remove the clip by hand, you can use needle-nose pliers. Once the clip is out, remove the brake pad retaining bolt with a 2.5mm allen key and set aside. Grab the pads, squeeze them together and remove them by pulling them out from the top end of the caliper. Use care not to contaminate the pads by touching the pad material or placing them pad-side-down.

Step Three - Set Pistons and Install Bleed Block

Occasionally, the pistons will be too far out to insert the bleed block. To set them back into the caliper, you can use a number of methods including using a brake pad piston press, using the bleed block itself or using a small box wrench to push them back in. No matter the tool, use care not to damage the pistons during this process, especially if your pistons are white, which means they're ceramic and can be brittle. Once the pistons are set, insert the bleed block then use the pad retention bolt to hold the block in place. 

Step Four - Level Out Brake Lever

Using a 4 or 5mm allen wrench, slightly loosen the lever clamp bolt. Bleed port location varies by brake model. Rotate your lever on the bars so that the bleed port is pointed up. Snug down the lever clamp bolt to prevent shifting during the bleed.

Step Five - Connecting the Bleed Kit

Using a 2.5mm allen, unscrew the bleed port screw on the lever. There is a rubber o-ring that sometimes comes out with the screw. If it doesn't, remove it from the lever. Set the o-ring and screw aside somewhere safe so they won't get lost. Thread the white funnel onto the lever (it can be finger tight). Add mineral oil to the funnel, filling it about 1/3 full. 

Fill the syringe about half full with mineral oil. To remove the air, hold the syringe vertically with the hose up and with a rag or paper towel at the end of the hose, slowing push the air out by pressing down the syringe plunger. 

Remove the bleed nipple rubber cap from the caliper completely (it gets in the way), put your 7mm box wrench around the bleed nipple. Making sure there is no air at the end of the syringe tube, slide it over the nipple until it's completely over the nipple and you feel it notch into place. 

Step Six - The Bleed

Making sure the plug is not obstructing the flow of oil into the funnel, turn the bleed nipple about an eighth of a turn counter-clockwise with the box wrench to open the system. We leave the plug just sitting in the funnel, but not plugging it, for the majority of the bleed. Slowly push the oil from the syringe into the caliper. You should see oil filling the funnel. If you feel resistance and no oil filling the funnel, open the bleed nipple a little bit more. Push fluid through the system until there are no air bubbles coming from the lever into the funnel. Be sure not to introduce any air into the system from the syringe, too. Once they're are no more bubbles, using the 7mm box wrench, close the bleed nipple and remove the syringe. 

Using the plastic bag, clip, and hose (we just yanked the hose off the syringe), clip the hose and bag together so that oil can drain into the bag and not spill. Attach the bag and hose to the caliper bleed nipple. Add oil to the funnel until it's about half full or just under, and use the 7mm box wrench to open the bleed nipple an eighth of a turn. Oil should be flowing from the funnel, through the system, and into the bag. If not, give the brake lever a squeeze to get things started. Let the oil flow through the system until bubbles no longer come out of the caliper. Tapping the caliper and hose with the box wrench can speed this process up by dislodging any trapped bubbles in the system. Making sure the oil level in the funnel stays high enough to prevent air from entering the system (add more if needed), once there are no more bubbles close the bleed nipple with the box wrench. 

With both the funnel and bag still attached, give the lever a good squeeze with one hand and while still squeezing, open and close the bleed nipple a few times. A toe strap to hold the lever down can be helpful here to free up your hands. If no air bubbles come out of the caliper when opened, close the bleed nipple, remove the bag and hose, and replace the nipple cap. 

Returning to the lever, remove the toe strap if you used one. Making sure there's still fluid in the funnel, give the lever a few firm squeezes and watch for bubbles. If no bubbles come out, loosen the lever clamp bolt with a 4 or 5mm allen wrench and carefully rotate the lever up a bit to change the angle and give a few more squeezes. This helps to dislodge any trapped bubbles that may have worked their way into a crevice. Once you get all the air out of the system, the lever should feel nice and firm. 

To remove the funnel, return the lever so that the bleed port is up and snug down the lever clamp bolt. Insert the funnel plug into the funnel to prevent any oil from leaking, and carefully unscrew the funnel from the lever and place it in its stand. Using a 2.5mm allen, thread the bleed port screw, making sure the o-ring is in place, back into the lever. 

Step Seven - Clean Up and Reinstall

Use the 2.5mm allen wrench to remove the brake pad retaining bolt, then remove the bleed block. Making sure there is no mineral oil on your brakes or hands, hold the pads together with the spring between them, slide them into the caliper until the retaining bolt holes line up. Screw in the retaining bolt using a 2.5mm allen and reinstall the retaining clip. 

Install your wheel. With the wheel (and rotor) in place, squeeze your brake lever to push the pistons out and check for any rubbing. Should the pads rub the rotors, skip down to the next section of this article where we explain how to align your calipers. Put used fluid in a sealed container and check your local laws and regulations to dispose of it safely. 

Boom! Now you know how to bleed your brakes and keep them running strong! Repeat this whole process with the other brake and you should be left with a solid, positive feeling system for some time. 

Aligning Your Calipers

To align your caliper properly, there are a few different ways. But, no matter which way you do it, you’ll need either a 5mm allen wrench or a T-25 Torx to tighten the bolts. To center the caliper, you can eyeball it while you snug down the bolts, making sure both pads are evenly spaced around the disc. You can grab the front brake lever so the pads make contact with the rotor and snug the bolts down.

We used Birzman’s clam tool, which is thin spacer that goes around your rotor. To align the caliper, put the tool over the rotor and while holding it, slowly rotate the wheel so that the tool slides into the caliper. The spacer takes up the room between the pads and the rotor, effectively centering the caliper. Snug down the bolts, remove the clam and we’re done.

A quick tip no matter which way you go about this step is to always “sneak-up” on the bolts. What we mean by “sneak-up” is slowly tighten each caliper bolt a little bit at a time. This helps prevent the caliper from shifting as you tighten the bolts up.

Stay tuned for more From the Workbench tutorials covering a variety of topics. And, if you missed our General Drivetrain MaintenanceAt-Home Tubeless Conversion, At-Home Fork Installation, and At-Home Headset Installation tutorials, check them out.

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2 comments
  • Brendon_Newton

    12/3/2016 12:07 PM

    Well written article and something anyone who lives somewhere with long descents especially could do more often. Couple things I'd add though...

    -Sram brakes (going all the way back to juicy models) get bled at about a 45 degree angle, not flat, so that the bleed port is at the top of the system. And anything with a Taper Bore master cylinder (All Elixirs) needs to be bled with the tip of the lever blade between 75 & 80mm(not degrees) from the center of the bar.

    -Clean your pistons with alcohol before you push them back in when installing the bleed block! Never a good idea push dirty pistons back into the caliper.

    -Mineral Oil brake fluid is not any better for the environment OR human exposure. The MSDS recommendations are almost identical for disposal and exposure between Shimano Mineral oil and DOT fluids. Both require adherence to local law for disposal... do not flush Shimano fluid down the drain just because it says "Mineral" on it.

    -Another thing I didn't see mentioned is that Mineral oil brake fluid IS NOT cross compatible between brands and it is very different than what's found in the drug store. Shimano's mineral oil is very different than Magura's (Magura Blood boiling point is barely better than water for starters) so use the Shimano stuff if those are the brakes you have.

  • jrcd

    12/3/2016 10:19 AM

    Thank you for the well written and thoroughly documented article! I'd love to see more!