How to Bleed Shimano Hydraulic Brakes

How to Bleed Shimano Hydraulic Brakes

If you’ve worked through the diagnostic guide and confirmed you need a bleed, this is the procedure for Shimano flat-bar hydraulic brakes (XT, XTR, SLX, Deore, MT200, etc.). Shimano drop-bar (road/gravel) brakes use a different procedure (separate article).

Shimano uses Shimano-specific mineral oil only. Not DOT. Not generic mineral oil unless explicitly compatible. Shimano’s mineral oil is dyed red so you can identify it. Using DOT in a Shimano brake destroys the seals and bricks the brake.

Of all the brake brands in this series, Shimano has the most procedurally involved bleed. You’ll use a funnel at the lever for the first phase, switch to a gravity-feed disposal bag at the caliper for the second phase, then “burp” trapped bubbles at the lever in two tilt positions. Take your time.

Mineral oil safety

Less hazardous than DOT, but still wear gloves and eye protection. Wipe spills with isopropyl alcohol. Recycle used fluid at an auto parts store.

Never share a kit between mineral and DOT systems.

Tools and supplies

  • A bleed kit. The easiest path is the Shimano Disc Brake Bleed Kit (uses the TL-BR002 or TL-BR003 funnel set), guaranteed compatibility. Aftermarket options that work: Park Tool BKM-1, Epic Bleed Solutions Shimano-specific kit, Birzman.
  • Shimano mineral oil (the red stuff)
  • Hex wrenches (sizes depend on model)
  • 7mm box wrench (for the caliper bleed nipple)
  • T25 Torx (some models)
  • A piston press. The Loam Goat 5 In 1 Disc Brake Tool has one built in. Tire lever or cone wrench works in a pinch.
  • Bleed blocks (in the kit)
  • Angle finder (or a phone app, needed for the burping step)
  • Toe strap or zip tie (to hold the lever during burping)
  • Disposal bag and zip tie (for gravity bleed)
  • Isopropyl alcohol and rags
  • Gloves, safety glasses
  • Repair stand

Step 1: Lever prep

Before touching the fluid:

  1. Locate the reach adjustment screw on the lever. Wind the lever fully away from the grip. Write down your normal setting so you can return to it. Reach adjustment varies by model: it might be a tool-free knob, an Allen-key screw on the lever body, or a screw behind the lever.
  2. If your lever has a free-stroke adjustment screw (XT and XTR usually do), wind it counter-clockwise three or four turns from fully tight.
  3. Remove the wheel.

Step 2: Bike prep

  1. Mount the bike. Angle it so the caliper-to-lever hose runs consistently uphill. For front brakes, the bike usually sits fine in the stand. For rear, you’ll need to tilt the bike.
  2. Remove the brake pads. (see: How to Replace Your Disc Brake Pads) Store them somewhere clean, any oil contamination ruins them.
  3. Press the pistons all the way back into the caliper using the piston press.
  4. Install the bleed blocks between the pistons. Hold them in place with the pad retention screw, finger tight.
  5. Find the caliper bleed nipple. Location varies: some calipers have an internal nipple under a rubber cover, others have an external nipple on top of the body. Remove the rubber cover completely if present and set it aside in a clean spot.
  6. If you’re bleeding the front brake, it’s often easier to unbolt the caliper from the fork to get better access to the bleed nipple.

Step 3: Lever connection

  1. Remove the lever bleed port screw. Check that the O-ring comes out with the screw, sometimes it stays stuck in the port.
  2. The lever port is M5 thread. The bleed funnel is also M5. But don’t thread the funnel directly into the lever, instead thread the funnel into the purple adapter first (also M5), then thread the adapter into the lever. The two-step approach makes thread alignment easier and reduces the risk of cross-threading.
  3. Gently snug the adapter. Don’t over-tighten.
  4. Remove the stopper from the funnel top.
  5. View the bike from directly the side. Use an angle finder or phone app to set the funnel tilt to 45 degrees forward from vertical. Rotate the lever on the bar as needed to achieve this. Mark or remember the bar position so you can return the lever to its normal orientation later.

Step 4: Syringe prep

  1. Find the hose with one threaded end and one open end.
  2. Thread the threaded end onto the syringe.
  3. Slide the compression sleeve over the open end and pull it up toward the syringe.
  4. Fill the syringe about two-thirds full with mineral oil.
  5. Hold the syringe vertically with the hose pointing up. Pull back to clear air from the tubing.
  6. Slowly push the plunger until fluid just reaches the end of the tubing.
  7. Place the syringe in the holder above the caliper.

Step 5: Phase 1, push fluid up through the system

  1. Place the 7mm wrench over the caliper bleed nipple.
  2. Push the open hose end firmly over the nipple. For external nipples, use the compression sleeve to help secure it.
  3. With the wrench, open the bleed nipple one half turn.
  4. For calipers with a bleed screw instead of a nipple, loosen the bleed port screw a half turn.
  5. Push almost all (but not all) of the fluid from the syringe up through the system into the funnel at the lever.
  6. Watch the funnel for bubbles surfacing. Those are air pockets exiting the system.
  7. If the fluid is dirty, keep pushing until clean fluid reaches the funnel.
  8. Close the bleed nipple at the caliper.
  9. Pull back a small amount on the syringe as you disconnect it from the caliper, this minimises dripping.
  10. Remove the syringe and holder.
  11. If the fluid in the funnel is dirty: install the stopper, remove the funnel, dump the dirty fluid, reinstall the funnel, refill with fresh fluid (over half full). Then continue.

Step 6: Phase 2, gravity bleed from funnel to disposal bag

  1. Find the hose with no fittings on either end.
  2. Install the compression sleeve on one end.
  3. Install the other end into a disposal bag (or other waste container). Secure with a zip tie so it can’t fall out.
  4. Place the 7mm wrench over the caliper bleed nipple.
  5. Attach the open-end hose to the caliper nipple. Use the compression sleeve to secure.
  6. Make sure the funnel is more than half full of fresh fluid.
  7. Loosen the caliper bleed nipple half a turn.
  8. Gently squeeze the lever to start fluid flowing from the funnel, down through the system, out the caliper, and into the disposal bag.
  9. While fluid is flowing, gently tap along the length of the hydraulic hose with a finger. This dislodges any bubbles stuck to the hose walls.
  10. Watch the funnel level. Never let it run dry, that pulls air back into the system.
  11. When no more bubbles appear in the drain hose, close the bleed nipple.

Note: you may not see many bubbles during this phase. That’s normal if the system was already mostly clean from Phase 1.

Step 7: Burp the caliper

This step forces any stubborn bubbles out of the caliper specifically.

  1. Refill the funnel to half-full if needed.
  2. Leave the disposal hose attached.
  3. Pull the lever to the bar to pressurise the system. Hold it there with a toe strap, zip tie, or have someone hold it.
  4. Quickly open and close the caliper bleed nipple (a fraction of a second). Pressure dumps out the nipple into the disposal bag. The lever softens.
  5. Release the strap. Pump the lever until it firms up again.
  6. Re-strap the lever to the bar.
  7. Repeat the quick-open-and-close at the caliper nipple.
  8. Repeat the cycle one or two more times until the lever stays consistently firm.
  9. Remove the strap.
  10. Caliper work is done. Remove the bleed hose. Torque the bleed nipple to 4-6 Nm.
  11. Reinstall the caliper bleed cover (if there was one).

Step 8: Test the lever

Squeeze the lever. It should feel firm. If it’s still soft, repeat the bleed from the start.

Step 9: Burp the lever (two tilt positions)

Even with the caliper and main line bled, small bubbles can hide inside the lever body. Burping at two angles dislodges them.

  1. Rotate the lever on the bar so the funnel tilts 30 degrees back from vertical.
  2. Squeeze and release the lever a few times while watching inside the funnel for bubbles.
  3. Now rotate the lever so the funnel tilts 30 degrees forward from vertical.
  4. Squeeze and release the lever again while watching for bubbles.
  5. When no more bubbles appear in either tilt, rotate the lever so the funnel is back to vertical.
  6. Plug the funnel and remove it (along with the adapter) from the lever.

Step 10: Cap off the lever

  1. Check the lever port for the O-ring before reinstalling the bleed screw. The adapter may have left the O-ring behind.
  2. Install the lever bleed port screw with its O-ring.
  3. Torque to approximately 1 Nm. Very light.

Step 11: Reset and test

  1. Return the lever to its normal riding angle on the bar. Secure.
  2. Wind the reach adjuster and free-stroke screw back to their original settings.
  3. Remove the bleed blocks.
  4. Clean lever and caliper with alcohol on a rag.
  5. Reinstall the brake caliper to the frame (if you removed it). Don’t full-torque yet.
  6. Reinstall the pads (handle by the backing plate only).
  7. Reinstall the wheel.
  8. Pump the lever to advance the pads to the rotor.
  9. Realign the caliper if it rubs. (see: How to Fix a Rubbing Hydraulic Disc Brake)
  10. Torque the caliper mounting bolts (typically 6-8 Nm).

If new pads were installed too, bed them in. (see: How to Bed In New Brake Pads)

Step 12: Clean the kit

Mineral oil doesn’t corrode the kit, so cleaning is less critical than DOT. Still:

  1. Empty fluid from syringes and hoses (back into the bottle if clean, or to a waste container).
  2. Let hoses drain.
  3. Residual mineral oil in the syringe is fine. Disassemble fully only for long-term storage.

Common screwups

  • DOT fluid in a Shimano brake. Brake dead within minutes. Always confirm fluid type before pouring.
  • Generic mineral oil. Shimano’s mineral oil has specific viscosity and additive properties. Generic substitutes often work short-term but may cause seal swelling or contamination over time.
  • Letting the funnel run dry during the gravity-bleed phase. Air goes right back into the system through the open nipple.
  • Forgetting the free-stroke and reach adjusters at the start. If you don’t back them off before bleeding, the lever may not seat properly during the burp phase and you’ll leave air trapped.
  • Over-torquing the bleed nipple or lever screw. 4-6 Nm at the caliper, 1 Nm at the lever. Strip either of these and the next bleed is a much bigger job.

Based on Park Tool’s video Shimano Brake Bleeding Procedure.

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