How to Bleed SRAM Hydraulic Brakes

How to Bleed SRAM Hydraulic Brakes

If you’ve worked through the diagnostic guide and confirmed you actually need a bleed (and not just new pads or a clean rotor), this is the procedure for SRAM brakes that use DOT fluid and don’t have SRAM’s “Bleeding Edge” port (the newer one with the lever-action bleed fitting). Most SRAM Guide, Code, Level, and Force/Rival/Red hydraulic brakes from the last decade are in scope.

This procedure does not apply to Shimano, Magura, Hope, Hayes, Formula, or TRP. Those use mineral oil instead of DOT and have different ports and procedures. Mixing fluids between systems will destroy seals. If you’re not on SRAM, find the right procedure for your brake before starting.

This is the longest article in this series. Brake bleeds aren’t difficult once you’ve done one, but there are a lot of small steps and the cost of skipping any of them is air bubbles trapped in the system, which is the exact thing you’re trying to fix.

A safety word about DOT fluid

DOT brake fluid is corrosive. Not just “wear gloves to be safe” corrosive. It will:

  • Strip paint on contact
  • Damage rubber seals it isn’t designed for
  • Irritate your skin (and seriously irritate your eyes)
  • Absorb moisture from the air (which is partly why you’re bleeding)

Wear nitrile gloves. Wear eye protection. Have a stack of rags ready and wipe up every drop the instant you see it. Cover the floor and the frame with old sheets or a drop cloth if you’re working over carpet or near painted surfaces. Keep a spray bottle of isopropyl alcohol handy: it neutralises spilled DOT and cleans up the residue.

Used fluid is hazardous waste. Don’t pour it down the drain or into the trash. Most auto parts stores will take used brake fluid for recycling.

Tools and supplies

  • A bleed kit. The easiest path is SRAM’s own Pro Bleed Kit, which has guaranteed-fit adapters and the right fittings. Aftermarket options that work: Park Tool BKD-1, Birzman, Epic Bleed Solutions SRAM-specific kit, Pedro’s Pro Bleed Kit.
  • A piston press. The Loam Goat 5 In 1 Disc Brake Tool has one built in. Park Tool’s PS-1.2 is a single-purpose alternative.
  • T10 Torx (for the bleed port screws)
  • 2.5mm hex (for the pad pin on most SRAM calipers)
  • Needle-nose pliers (for clips and cotter pins)
  • A toe strap, rubber band, or anything that can hold the brake lever pulled to the bar
  • A torque wrench
  • Isopropyl alcohol and plenty of rags
  • A repair stand
  • Fresh DOT 5.1 fluid (or DOT 4 if your brake calls for it, check your manual)

Do not use DOT 5. That’s a silicone-based fluid and it’s not compatible with SRAM brakes, despite the similar name.

Step 1: Lever prep

Mount the bike in the stand. Angle the bike so the hose from lever to caliper takes the shortest, most downward path possible. Air bubbles rise through fluid, so the cleaner the run from caliper up to lever, the easier the bleed.

Set the lever reach. For the bleed to work properly, the reach (the distance from the centreline of the bar to the tip of the lever) needs to be between 75mm and 80mm. Measure with a ruler. If you’ve adjusted yours tighter or wider for ride feel, write down your current setting so you can return to it after the bleed.

If your lever has a contact-point adjuster (the dial that changes where in the lever travel the pads engage), turn it counter-clockwise to the stop. This puts the lever in its bleed-friendly position.

Tie a rag loosely around the lever body to catch drips.

Step 2: Remove the wheel, pads, and prep the caliper

Wheel off. Pads out.

To remove SRAM pads:

  1. Pull the pin retaining clip with needle-nose pliers (it’s a small wire clip near the pad pin).
  2. Unthread the pad pin with a 2.5mm hex.
  3. Pull the pads out by hand. They sometimes need a push from underneath.
  4. If your caliper uses a cotter pin instead of a threaded pin, straighten the cotter ends with pliers and pull the pin out.

Use the piston press to push the pistons all the way back into the caliper. This makes room for the bleed blocks.

Install the bleed blocks where the pads were. Secure them with the pin you just removed, or with a zip tie or rubber band. If the caliper is a four-piston design (Code, Code RSC, etc.), use both blocks.

Optional but recommended: unbolt the caliper from the frame and let it hang from the brake hose, positioned so the hose runs upward to the lever without any sags or loops. The straighter the hose, the easier the bubbles can rise during the bleed.

Step 3: Bleed kit prep

Take both syringes out of the kit. Install the double-ended hoses onto each syringe with the over-encapture (the wider end of the hose) facing away from the syringe body. Thread on the red adapter ends (M5 thread fitting).

Fluid loading:

  • Lever syringe: fill ¼ full with fresh DOT fluid.
  • Caliper syringe: fill ¾ full with fresh DOT fluid.

For each syringe: hold the hose end up so the air sits at the top. Push the syringe plunger gently to evacuate as much air as you can. Once the air is out and only fluid remains in the hose, close the clip on the hose to lock the state in.

Both syringes should now be primed: full of fresh fluid, no visible air bubbles, clipped off.

Step 4: Install syringes at the brake

At the lever:

  1. Remove the bleed port screw with the T10. There’s a small O-ring on the screw. Make sure it comes out with the screw, not stuck inside the port.
  2. Thread the lever syringe (¼ full) into the bleed port. The O-ring on the adapter needs to seat squarely in the port as you thread it in. If you cross-thread it you’ll either strip the lever or get fluid leaking out as soon as you pressurise.
  3. Clip the syringe into the syringe holder, which mounts on your handlebar.

At the caliper:

  1. Remove the bleed port screw with the T10.
  2. Thread the caliper syringe (¾ full) into the bleed port.

Wipe up any drips immediately. DOT fluid does damage in seconds, not hours.

Step 5: The bleed

Now unclip both syringe hoses so fluid can flow.

Push fluid through

Hold the caliper syringe with the tip pointing down. Push the plunger slowly to send fresh fluid up through the system into the lever syringe. As you push at the caliper, the lever syringe fills.

Hold the lever syringe upright as it fills, so any bubbles that come up with the fluid float to the top instead of getting trapped.

Stop and start over if the fluid coming out is dirty. If you can see discoloured fluid (brown, grey, or visibly dirty) arriving in the lever syringe, you’re flushing the contaminated old fluid through the system. Push all of it into the lever syringe, then remove both syringes, dump the dirty fluid, refill both syringes with fresh fluid, and start the push again. You’re aiming for fresh fluid throughout the system, not a 50/50 mix of new and old.

Stop pushing when the lever syringe is about ¾ full and the caliper syringe is about ¼ full. You’ve now replaced the bulk of the old fluid.

Clip the lever syringe

Close the clip on the lever syringe to seal it. Fluid can’t move from caliper to lever now.

Pressure-vacuum at the caliper

Pull the brake lever firmly to the bar. Hold it there with the toe strap, rubber band, or whatever you’ve got. The lever needs to stay pinned to the bar for the next bit.

Now at the caliper syringe:

  1. Pull the plunger slowly to create vacuum. You should see bubbles rise out of the caliper into the syringe. The vacuum pulls air out of the caliper body that the fluid push didn’t catch.
  2. Push the plunger to pressurise. This forces any remaining bubbles in the caliper back toward the lever side.
  3. Pull again. Bubbles out.
  4. Push again.

Repeat until no more bubbles appear when you pull vacuum. Could be three cycles, could be ten.

Release the lever (the tricky bit)

While pushing gently on the caliper syringe to keep slight positive pressure, release the lever from the toe strap. The lever should return slowly to its resting position as you bleed pressure back.

If you release the lever without pushing the syringe at the same time, the lever’s master cylinder will pull a vacuum and you’ll suck air back into the system. Pushing the caliper syringe as the lever returns prevents that.

Remove the caliper syringe

Once the lever is back to rest:

  1. Clip the caliper syringe hose closed.
  2. Unthread the syringe from the caliper.
  3. Quickly reinstall the bleed port screw with the T10 (with its O-ring).
  4. Wipe up any drips.

Vacuum and flush at the lever

Now back to the lever syringe.

  1. Unclip the lever syringe hose so fluid can move.
  2. Pull the plunger to vacuum. Bubbles will rise into the syringe from the lever body.
  3. Push the plunger to pressurise.
  4. Let the syringe equalise (pressure drops back to neutral).
  5. With the syringe at rest, pull and release the brake lever ten times. Each pull pushes air toward the syringe; each release relaxes the master cylinder. After ten pulls, look at the fluid in the syringe. You should see bubbles that came out of the lever during pumping.
  6. Push the syringe plunger once more, equalise, repeat the pull-and-release sequence.

Keep going until no more bubbles appear during pumping.

Final cap-off

  1. Push the syringe plunger slightly to leave positive pressure.
  2. Release the syringe (let it equalise).
  3. Clip the hose closed.
  4. Unthread the syringe.
  5. Reinstall the bleed port screw with the T10 (with O-ring).
  6. Wipe.

Step 6: Reset the bike

  1. Remove the bleed blocks from the caliper. Wipe out any fluid residue inside the caliper body with alcohol on a clean cloth.
  2. Reinstall the pads. Don’t touch the friction surface with bare fingers. If you do, wipe them with isopropyl alcohol before installing.
  3. Reinstall the pad pin and clip (or cotter pin).
  4. If you unbolted the caliper from the frame, bolt it back on (don’t fully torque yet).
  5. Reinstall the wheel.
  6. Reset the lever reach to your normal setting.
  7. Pull the brake lever three times. This lets the system self-adjust to the actual pad thickness now installed.

Spin the wheel and check for rub. If there’s any, the caliper needs realigning. (see: How to Fix a Rubbing Hydraulic Disc Brake)

Once the brake is clean and rub-free, torque the caliper bolts to spec (typically 6-8 Nm).

Step 7: Test ride before riding for real

Find an empty piece of road or a parking lot. Pull the brake hard at low speed. You’re looking for:

  1. Firm lever feel. No spongy bottom-out. The lever should hit a solid stop short of the bar.
  2. Symmetric front and rear feel. If one feels softer than the other, that one needs another bleed.
  3. No drag when released. Spin the wheel after braking. Pads shouldn’t be touching the rotor at rest.

If you swapped pads at the same time as the bleed (a common move), bed them in before the first real ride. (see: How to Bed In New Brake Pads)

Step 8: Clean the bleed kit

DOT fluid sitting in the syringes and hoses will degrade the rubber seals in your kit over time. After every use:

  1. Pump alcohol through both syringe hoses to flush the DOT out.
  2. Disassemble the syringes.
  3. Wipe every piece that touched fluid with alcohol on a rag.
  4. Lay everything out to dry before reassembling.

A clean kit will last years. A neglected kit will start leaking at the syringe seals after a few uses.

Common screwups

  • Mixing DOT and mineral oil systems. Shared bleed kits between Shimano and SRAM brakes is how seals get destroyed. Keep two kits, one for each fluid, and label them. Or do one type and let a shop do the other.
  • Forgetting the O-ring. If the bleed port screw goes back in without its O-ring (or with the O-ring still stuck in the port), the brake will leak. Always check both ends.
  • Releasing the lever without pushing the syringe. Sucks air right back into the caliper. If you did this, you’ll feel it on the test ride and need to bleed again.
  • Not flushing dirty fluid first. If your fluid was old and dark, a single pass doesn’t get all of it. Drain, refill, and re-push to actually replace the fluid rather than diluting it.
  • Touching pad friction surfaces with bare fingers. Bleeds often coincide with new pads. Skin oil contaminates the pad face. Always handle pads by the backing plate.

This article is based on Park Tool’s video SRAM Brake Bleeding Procedure.

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