Spongy lever. Inconsistent bite point. Lever pulling is closer to the bar than it used to be. These are the signs your hydraulic brakes need a bleed, and if you've been putting it off, you're riding with less stopping power than your brakes are capable of.
Bleeding hydraulic brakes removes air from the system and replaces old fluid with fresh fluid. It's one of the highest-value maintenance tasks you can do at home, and once you've done it a couple of times, it takes under 30 minutes per brake.
This guide covers the two most common brake systems we see at Dunbar Cycles and Corsa Cycles: Shimano MTB hydraulic brakes and the SRAM Maven. These systems use different fluids, different bleed ports, and different procedures, so we're treating them separately.
Before You Start: What You Need to Know
The #1 Rule: Never Mix Fluids
Shimano and SRAM Maven both use mineral oil, but they are not the same and are not interchangeable. Shimano mineral oil and SRAM Maxima mineral oil are formulated differently. Using the wrong fluid, or using a bleed kit contaminated with a different fluid, can damage seals and cause brake failure.
Keep your bleed kits separate. Label them. Do not improvise.
Fluid guide overview:
| Brake | Fluid Type | Fluid Brand |
|---|---|---|
| Shimano XT / SLX / XTR | Mineral oil | Shimano Mineral Oil only |
| SRAM Maven | Mineral oil | SRAM Maxima Mineral Oil only |
| SRAM Code / G2 / Level (older) | DOT 5.1 | Any DOT 5.1 — separate kit required |
When to Bleed
-
Lever feels spongy or pulls closer to the bar than usual
-
Inconsistent bite point that moves between rides
-
After cutting or replacing a brake hose
-
Annually as preventative maintenance (every 2 years for mineral oil systems is the manufacturer recommendation, but annually keeps things dialled in)
-
After a crash that may have introduced air into the system
Tools You'll Need
For both systems:
-
Bike stand (highly recommended — working on the floor makes everything harder)
-
Isopropyl alcohol (90%+) and clean rags
-
Nitrile gloves
-
2.5mm and 5mm hex keys
-
Bleed block for your specific brake model
-
Torque wrench (helpful but not essential for home use)
Shimano-specific:
-
Shimano Bleed Kit (includes funnel cup, catch bottle, and tubing)
-
Shimano Mineral Oil
SRAM Maven-specific:
-
SRAM Mineral Oil Bleed Kit (includes Bleeding Edge hex-lock syringe and lever syringe)
-
SRAM Maxima Mineral Oil
-
Maven-specific bleed block (5mm — different from older SRAM Code block)
-
T10 Torx key
How to Bleed Shimano MTB Brakes
Shimano uses a gravity-bleed system; fluid flows from the lever reservoir down through the hose to the calliper. It's one of the more forgiving bleed procedures for home mechanics once you understand the flow direction.
Step 1: Set Up the Bike
Mount the bike in a stand. Rotate the brake lever so the bleed port on top of the lever body is the highest point in the system; typically this means the lever is roughly parallel to the ground or slightly angled.
If you're bleeding the rear brake, removing the calliper from the frame mount and letting it hang freely makes it easier to get air out.
Step 2: Remove Pads and Install Bleed Block
Remove the wheel. Remove the brake pads, and handle them only by the backing plate; never touch the friction material. Set them somewhere clean and away from the work area.
Push the calliper pistons back gently with a plastic tire lever or piston press. Insert the Shimano bleed block and secure it with the pad retaining bolt. The bleed block keeps the pistons in position while fluid and air move through the system.
Step 3: Set Lever Adjustments to Full Out
Wind out the reach adjuster and the free-stroke adjuster to their maximum open positions. This expands the fluid volume in the system and makes it easier to purge air. Note your preferred settings before doing this step so you can return them afterward.
Step 4: Open the Lever Bleed Port
Locate the bleed port screw on top of the lever body; it takes a 2.5mm hex key on most Shimano MTB levers. Remove the screw and O-ring carefully and store them somewhere they won't get lost or contaminated. Thread the Shimano bleed funnel cup into the port and fill it halfway with fresh Shimano mineral oil. Leave the stopper in for now.
Step 5: Open the Caliper Bleed Nipple
Connect the catch bottle tubing to the bleed nipple on the calliper body. The nipple location varies by model; on most Shimano MTB callipers, it's on the top or side of the calliper. Remove the rubber dust cap, attach the tubing, and use a 7mm spanner to crack the nipple open approximately half a turn.
Step 6: Gravity Bleed
Remove the stopper from the bleed funnel cup at the lever. Fluid will begin flowing down through the system from the lever into the catch bottle at the calliper. Keep the funnel cup topped up; do not let it run dry, or you'll introduce air back into the system.
Tap along the length of the brake hose firmly with your fingers to dislodge any air bubbles clinging to the hose walls. You should see bubbles appearing in the catch bottle or in the funnel cup.
Continue until the fluid coming through runs clear and bubble-free. This typically takes 1–3 minutes depending on how much air was in the system.
Step 7: Lever Pump and Final Purge
With the bleed nipple still open and the funnel cup still attached and topped up, pull the lever gently 10–15 times in short strokes. This encourages any remaining bubbles in the lever body and master cylinder to rise up into the funnel cup. You should see small bubbles appearing in the cup during this process.
When no more bubbles are visible, hold the lever pulled in and close the calliper bleed nipple. Release the lever. Top up the funnel cup one final time.
Step 8: Rotate the Lever and Check
Loosen the lever clamp bolt slightly so you can rotate the lever freely on the bar. Rotate it to horizontal, then 30 degrees up, then 30 degrees down, pulling the lever a few times at each position. This step finds any air pockets that only reveal themselves at different angles. Add a few drops of fluid to the cup if needed.
Step 9: Close Up and Clean
Replace the stopper in the funnel cup, then remove the cup and reinstall the bleed port screw and O-ring. Tighten snugly; do not overtighten. Remove the catch tubing from the calliper and reinstall the bleed nipple dust cap.
Clean the lever, calliper, hose, and rotor thoroughly with isopropyl alcohol on a clean rag. Mineral oil on a rotor will contaminate your pads; be thorough.
Remove the bleed block, reinstall the brake pads, and reinstall the wheel.
Step 10: Bed In and Test
Squeeze the lever several times until it firms up. Test with a hard pull; it should feel firm and consistent. If it still feels slightly soft, repeat the lever-pump step once more before going for a ride.
How to Bleed SRAM Maven Brakes
The SRAM Maven uses a two-syringe system with SRAM's Bleeding Edge port at the calliper. It's more involved than the Shimano gravity bleed but gives you precise control over fluid volume and pressure in both directions. The Maven also benefits from a "piston massage" step that SRAM recommends and that makes a real difference to bite point consistency.
Important: The Maven bleed kit is incompatible with older SRAM DOT-based bleed kits. You need the SRAM Mineral Oil bleed kit with the hex-lock Bleeding Edge syringe. Do not use a standard threaded syringe on the Maven calliper port.
Step 1: Set Up the Bike and Lever
Mount the bike in a stand. Set the brake lever so it is slightly below horizontal; the bleed port at the lever should be at the highest point of the system. Set the contact point adjuster all the way out, then turn the adjuster a few clicks back from fully out.
Step 2: Remove Pads and Calliper and Do the Piston Massage
Remove the wheel and brake pads and unbolt the calliper from the frame. Set pads aside away from the work area.
With the calliper off the bike, gently push the pistons back with a plastic lever. Then, and this is specific to the Maven, perform the piston massage: push the pistons out slightly by squeezing the lever a few times until they contact the bleed block, then push them back in again. Repeat 5–6 times per piston pair. This breaks down initial friction between the pistons and seals, which This is what causes the Maven's bite point inconsistency when skipped. Install the Maven bleed block (5mm) and secure it with the pad bolt.
Step 3: Attach the Caliper Syringe
Fill the Bleeding Edge hex-lock syringe about halfway with SRAM Maxima mineral oil. Insert it into the bleeding edge port on the calliper and rotate to lock. Pull the plunger back slightly to draw out any air trapped in the calliper port before pressurizing the system.
Step 4: Attach the Lever Syringe
At the lever, remove the bleed port screw with a T10 Torx bit. Thread the lever syringe, and fill it with a small amount of fluid (5–10ml) so there is a fluid buffer at the top of the system.
Step 5: Push Fluid Through
Push fluid upward from the calliper syringe toward the lever. Go slowly and steadily. You should see air bubbles and any old fluid moving up through the system into the lever syringe. Keep tapping the hose and calliper body firmly with your fingers to dislodge stubborn bubbles.
Continue until no more bubbles are visible coming from the calliper into the lever syringe. This can take longer than expected; be patient and keep tapping.
Step 6: Equalise and Remove Air from Lever
With fluid flowing freely, gently pull and push the calliper syringe plunger in short strokes to cycle liquid back and forth through the calliper. This is particularly effective at clearing bubbles sitting in the calliper body.
Pull the brake lever 10–15 times with the lever syringe attached. Tap the lever body to dislodge any air in the master cylinder.
Step 7: Close the System Under Pressure
When the system is bubble-free, hold a small amount of positive pressure on the calliper syringe (pushing slightly toward the lever). While holding this pressure, close the bleeding edge port at the calliper by rotating the hex lock syringe to the closed position. Maintain lever pressure and close the lever bleed port by reinstalling the T10 screw with the syringe still attached, and then remove the syringe.
Closing under positive pressure prevents air from being drawn back in as the ports close.
Step 8: Clean and Reinstall
Clean all surfaces with isopropyl alcohol. Pay particular attention to the rotor; any mineral oil contamination requires rotor cleaning and likely pad replacement.
Reinstall the calliper, brake pads, and wheel. Reattach the calliper to the frame.
Step 9: Test the Lever and Reset Adjusters
Squeeze the lever multiple times until it firms up. Reset your reach and contact point adjusters to your preferred positions. Test with a hard pull; the lever should be firm, consistent, and engaged at the same point every time.
If the bite point is still wandering after two or three bleeds, the issue is almost always due to the piston massage step being incomplete. Take the calliper off again and spend extra time on that process.
Signs the Bleed Didn't Work
If your lever still feels soft after bleeding:
-
Air is still in the system; repeat the process and spend more time tapping the hose
-
The bleed block was the wrong size, leaving the pistons in a partially extended position during the bleed
-
The fluid reservoir ran dry during bleeding and air was reintroduced
-
On Maven specifically: the piston massage was skipped or insufficient
If lever feel is good immediately after bleeding but softens within a few rides, there is likely a small leak at a hose fitting, banjo bolt, or calliper port. Inspect these connections carefully.
When to Leave It to the Shop
Brake bleeding is a task that most home mechanics can handle. But there are situations where taking the bike to a shop is the right choice:
-
The lever still feels soft after two complete bleeds
-
You suspect a hose cut, fitting failure, or caliper seal issue
-
You're not confident working near your pads and rotors with fluid; contamination is a real cost
-
You don't have the correct bleed kit for your specific brake model
Our mechanics at Dunbar Cycles at 622 East Broadway, Vancouver, and Corsa Cycles at 38123 Cleveland Avenue, Squamish, do brake bleeds regularly. If you're unsure whether you need a bleed, a hose replacement, or a full service? Bring the bike in, and we'll tell you exactly what's needed.
Shop Brake Service Supplies at Dunbar Cycles & Corsa Cycles
We carry brake bleed kits for Shimano and SRAM systems, as well as brake pads, MTB disc brakes, and brake parts at both locations. Free shipping across Canada on orders over $150.
