Hydraulic disc brake maintenance

Brakes are one of the most critical safety component on your bike, so you should pay close attention to them during maintenance.

Hydraulic disc brakes are subjected to significant forces and various external influences, requiring regular attention to ensure optimal performance. These systems contain several moving parts that need proper maintenance. The hydraulic system should be bled periodically and checked for leaks, and it's important to ensure the brake fluid remains clean. DOT brake fluid, in particular, absorbs water over time, which can degrade performance and necessitates routine replacement.

It's also crucial to avoid any contact between brake discs and brake pads with oil, as this can compromise their effectiveness. Additionally, the pads and discs must be correctly matched to work efficiently together. Regularly inspecting the wear on both the pads and discs is another key aspect of maintenance. As you can see, maintaining your brake system is essential to achieving maximum performance and ensuring safety. We strongly recommend conducting preventative maintenance rather than waiting for defects or noticeable performance drops to occur.

In this guide, we'll focus on exemplary brake maintenance for Shimano, SRAM, and Magura systems, as these are among the most commonly used. While the basic principles of brake maintenance are similar across manufacturers, there are some minor differences in procedures like bleeding and filling. These variations may also depend on whether you're working with mountain bike or road bike brakes.

Step 1: Prepare tools Step 2: Remove wheels and check brake discs Step 3: Check brake hoses Step 4: Remove brake pads Step 5: Mobilize pistons Step 6: Fill & Bleed Step 6.1: Shimano Step 6.2: SRAM Step 6.3: Magura Step 7: Install pads and brake caliper Step 8: Test ride and bedding in

Rides: Downhill, Enduro, Road
Bikes: Santa Cruz Megatower, Santa Cruz Tallboy, Focus Atlas, Surly Krampus, Surly Cross Check

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1. Tools

To help you get everything ready and avoid searching for tools with dirty or oily hands, here’s a list of the tools and supplies you’ll need.

Bleeding kit (for Shimano, SRAM, or Magura)
Mineral oil or DOT brake fluid (depending on the manufacturer and brake)
Bleeding spacer (depending on the manufacturer and brake)
Brake piston tool
Open-end wrenches (7mm and 8mm)
Hex keys (set)
Torx keys T25 and T10
Torque wrench and bit sockets
Optional: Bottom bracket tool (for Shimano Centerlock discs)
Flathead screwdriver
Caliper gauge
Brake cleaner
Cloth, gloves, toothbrush, cotton swabs

We strongly recommend using only the tools, bleeding kits, and fluids specified by the manufacturer for each brake system. Mixing components from different manufacturers can cause serious functional issues and will also void any manufacturer warranty.

2. Remove Wheels and Inspect Brake Discs

Before working on the braking system, you’ll need to remove the wheels from the bike. However, before doing so, check the brake discs for any signs of warping. A warped disc can be identified if it "wobbles" sideways in the brake caliper when rotating. Minor warping is acceptable and can often be corrected using a truing tool. This may cause a slight pulsing sensation while braking, which is generally tolerable. However, if the warping is severe and prevents the brake caliper from being adjusted without rubbing, the disc may need to be replaced.

Next, inspect the friction surface of the discs. While the discs wear down more slowly than brake pads due to the hardness of the steel, wear still occurs over time. You can often detect this by running your fingernail along the transition between the friction surface and the carrier arms—if you feel a "step," it indicates thinning. Use a caliper to measure the exact thickness. If the thickness is close to or below the wear limit (typically printed on the disc), replacement is necessary.

Discoloration, such as reddish or bluish tones, indicates the disc has experienced high temperatures, likely during a descent. This is generally not a cause for replacement unless the disc appears entirely "burned out." Examine the friction surface closely for embedded fragments of pad material, which can occur when the pads overheat and bond with the disc. This indicates the pads have reached their thermal limit. If you’re using organic pads, consider switching to sintered metal pads, which are more heat-resistant.

It’s also a good idea to check the disc’s attachment to the hubs. Use a torque wrench to ensure proper tightness. Torque specifications are typically printed on the disc or the center lock ring. If no specifications are available, use 6–7 Nm for 6-bolt discs and 40 Nm for center lock systems.

If the brake discs are oily or heavily soiled, they must be cleaned. Use a standard brake cleaner sprayed onto a clean, oil- and grease-free cloth, and thoroughly wipe both sides of the braking surface. For optimal results, wipe the disc again with a water-soaked cloth, as brake cleaner can leave residues that reduce friction and temporarily impair braking performance.

3. Inspect Brake Hoses

Brake hoses should be free of damage and securely connected. A visual inspection will typically reveal any significant issues. In some cases, internally routed hoses may rub against the inside of the frame if proper guides are not used—this is particularly common with aluminum frames. If you notice visible cracks or deep cuts on the hose, it’s time for a replacement.

Pay special attention to the connections, as this is where problems are most likely to occur. Look for any signs of oil leakage or a pinched hose that could indicate a fault. To inspect these areas thoroughly, pull back the rubber sleeve at the brake lever and, for Shimano systems, remove the protective cap from the bleed nipple on the caliper.

A thin, film-like layer of oil is usually not a cause for concern, especially if the brake’s pressure point remains defined and firm. Minor sweating of oil can occasionally occur on hot days. However, if you notice a drop of oil forming, this indicates a sealing issue. In such cases, the brake is not properly sealed, and the hose will need to be reconnected or replaced.

4. Removing and Inspecting Brake Pads

Shimano and SRAM both use a very similar retaining screw to secure the brake pads, which is held in place with a safety pin to prevent it from loosening. Magura is an exception: the MT5 brake pads (one-piece, connected by a bar) don’t require a retaining screw, as they are held by hooks, integrated in the caliper. As such, there is no option to install a screw. The two-piece pads of the MT7 and the 2-piston MT models, however, lack hooks and are traditionally secured with a retaining screw. If a safety pin is present, remove it first. Then unscrew the retaining screw, and the pads are free to be removed.

The pads can now simply be pushed toward the center and pulled out. With some calipers, it’s easier to do this from the top, while with others, it’s better from the bottom. This can sometimes be a bit tricky—just try and don’t get frustrated!

Take a close look at the pads from both sides: if you notice oil residue, it could indicate that the caliper is leaking at the piston. The caliper itself should also be dry. This can sometimes be hard to spot, but your phone’s flashlight is usually helpful here. Check the condition of the pads carefully. Is there still enough material left? If the pad thickness is significantly less than 1mm, you should replace them. Uneven wear could be a sign of a seized or sticky piston.

After removing the pads, you can use a cloth to wipe through the caliper and remove any coarse dirt or brake dust.

5. Mobilize the Pistons

Before bleeding a brake system, it’s important to clean and mobilize the pistons, as brake- and trail-dust tend to settle into every crevice. Over time, this buildup can cause a piston to become sticky or, in the worst case, seize completely. For the best access, it’s recommended to remove the caliper.

Gently pull the brake lever a few times and observe the pistons in the caliper. You’ll quickly notice if they extend unevenly. However, don’t overdo it—without the resistance of the brake discs and pads, the pistons can extend too far, potentially causing them to leak. Follow the general approach shown in the illustration below. Once the pistons are extended, clean the sliding surfaces thoroughly using a toothbrush or cotton swab and brake cleaner. After cleaning, the pistons should extend more or less synchronously.

Blow away any loosened dust and dirt with brake cleaner, then carefully push the pistons back into place. Ideally, use a flat tool made of a soft material, like plastic or wood. Be cautious to push them back evenly and straight, avoiding any tilting. Once fully retracted, the pistons should sit flush with the inside of the caliper.

Caution: If the pistons are difficult to push back or resist movement, you may need to open the bleed screw at the brake lever to relieve pressure from the diaphragm inside the lever. In this case, a drop of brake fluid may escape from the bleed opening on the lever, which is completely normal.

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6. Fill & Bleed

Air bubbles in brake fluid naturally rise to the top—that’s simple physics. To assist with this process, position the brake, so the caliper is downward, and the hose is vertical to the ground. However, this ideal positioning is only achievable if the brake system is completely detached from the bike. When the hose is routed through the frame, this position isn’t possible. In such cases, we recommend placing the bike in a repair stand, ensuring the brake lever is as high as possible and the caliper is positioned as low as possible. If the system is detached, you can usually lower the caliper even further, making it easier to work on compared to when it’s fixed to the frame.

For optimal filling, adjust the brake lever on the handlebars so that the bleed screw and the reservoir beneath it are as horizontal as possible.

At this point, methods diverge: While the basic principles of hydraulic brake operation are consistent, the filling and bleeding process varies significantly between manufacturers and requires specific tools. Here, we divide the process by brand—Shimano, SRAM, and Magura - as these are the most commonly used systems. You can find links to the manufacturer’s instructions below.

Critical Note: Always use the brake fluid specified for your brake system! Shimano and Magura exclusively use mineral oil, while SRAM historically used DOT fluid for all brakes, but lately also started offering brakes that use mineral oil. Be certain of your brake type and use the specified fluid. We strongly recommend sticking to the original fluid from the manufacturer, as different mineral oils and DOT fluids have varying chemical compositions. Using the wrong fluid can result in serious performance issues or even complete brake failure.

The same advice applies to brake pads: always use original manufacturer accessories for the best performance and safety.

Shimano SRAM Magura

FILLING & BLEEDING: SHIMANO

Step 1: Remove the bleed screw

Now, unscrew the bleed screw from the brake lever.

Caution: Beneath the screw head is a small O-ring that acts as a seal. When you remove the screw, the O-ring may stay on the screw shaft or remain in the brake lever. Be careful not to lose it! Small parts like this have a knack for disappearing into the floor when dropped - so handle it with care.

Now, unscrew the bleed screw from the brake lever.

Step 2: Screw on the funnel

At the brake lever, Shimano uses a funnel that is screwed directly into the brake lever via a threaded connection. No tools are required for this—the funnel is simply screwed in by hand.

Caution: Make sure to align the threads properly before tightening. The plastic threads are not very forgiving if cross-threaded. Set the supplied stopper (a stick with an O-ring at the bottom) aside for now—it will be used later. Add a small amount of mineral oil to the funnel, just enough to cover the drain.

For Shimano road and gravel brakes, you’ll need to push back a section of the lever rubber to access the bleed screw. Because the bleed port is recessed in these levers, you’ll also need a different funnel than the one used for MTB brakes. This version has a longer connection piece to reach the recessed thread. Both types of funnels—for MTB and road/gravel brake levers—are included in the Shimano bleed kit linked below.

At the brake lever, Shimano uses a funnel that is screwed directly into the brake lever via a threaded connection. No tools are required for this—the funnel is simply screwed in by hand.

Step 3: Insert the bleed block

Now insert the yellow bleed block into the brake caliper and secure it with the pad retaining screw.

The block ensures a defined distance between the pistons in their resting position, providing a consistent lever travel to the pressure point.

Now insert the yellow bleed block into the brake caliper and secure it with the pad retaining screw.

The block ensures a defined distance between the pistons in their resting position, providing a consistent lever travel to the pressure point.

Step 4: Connect the syringe to the caliper

On the brake caliper, you'll find a fill port on Shimano brakes. Attach the syringe, pre-filled with Shimano mineral oil, to the port using the connected hose. While the brake system doesn't require a large amount of oil, it's a good idea to draw a bit more into the syringe to ensure you have enough to refill the entire system.

Use a 7mm open-ended wrench to loosen the fill port by about a quarter turn—this opens the system.

Use a 7mm open-ended wrench to loosen the fill port by about a quarter turn—this opens the system.

Step 5: Filling & Bleeding

Now, use the syringe at the brake caliper to push fresh mineral oil from the bottom to the top. The old, usually contaminated oil will appear in the funnel at the top. Once the fresh oil reaches the funnel, it’s easy to spot the difference—the new oil is clean and clear, free of particles or debris.

At this stage, pull the brake lever several times and let it snap back. This action often dislodges tiny air bubbles trapped in the lever assembly, which will rise and evade into the funnel. When no more bubbles appear, the system is typically air-free.

Next, insert the stopper into the funnel and gently pull back on the syringe at the caliper. If there are any remaining air bubbles trapped in the caliper, this action will draw them out through the syringe

Step 6: Close the hydraulic system

Once this step is complete, close the bleed port at the caliper using a 7mm open-ended wrench and then remove the syringe. At the brake lever, insert the stopper into the funnel, unscrew the funnel, and securely reattach the bleed screw along with the O-ring.

Check for any oil residue at the bleed ports on the brake lever and caliper. Use a cloth and some brake cleaner to thoroughly clean these areas. Be sure to dispose of all used oil properly, following local regulations.

Moving On: Install Pads and Caliper

FILLING & BLEEDING: SRAM

Step 1: DOT or Mineral Oil?

Before you begin bleeding your SRAM brake, make sure you know exactly which model you have on your bike. SRAM now offers both traditional DOT fluid brakes and mineral oil brakes.

Using the wrong fluid can render your brake system unusable in a short amount of time. So, be absolutely certain about which fluid your brake requires before proceeding.

Before you begin bleeding your SRAM brake, make sure you know exactly which model you have on your bike. SRAM now offers both traditional DOT fluid brakes and mineral oil brakes.

Using the wrong fluid can render your brake system unusable in a short amount of time. So, be absolutely certain about which fluid your brake requires before proceeding.

Step 2: Remove the bleed screw

If you have a SRAM brake with an adjustable contact point, turn the adjustment screw on the brake lever counterclockwise to maximize the space for the brake fluid (either DOT 5.1 or mineral oil, depending on the model). This step is essential to allow later adjustment of an earlier, defined contact point with minimal free stroke by turning the screw clockwise. The abbreviation for brakes with an adjustable contact point often includes "RSC" (the "C" stands for Contact Point).

Next, remove the bleed screw from the brake lever using a T10 Torx tool. Like Shimano brakes, there is an O-ring under the screw head that seals the reservoir. Be careful not to lose it.

For SRAM road and gravel brakes, you’ll first need to push back a section of the lever rubber to access the bleed screw.

Next, remove the bleed screw from the brake lever using a T10 Torx tool. Like Shimano brakes, there is an O-ring under the screw head that seals the reservoir. Be careful not to lose it.

For SRAM road and gravel brakes, you’ll first need to push back a section of the lever rubber to access the bleed screw.

Step 3: Connect the syringe to the brake lever

The first syringe is filled to about 2/3 and screwed onto the brake lever.

The first syringe is filled to about 2/3 and screwed onto the brake lever.

Step 4: Insert the bleed block

Once the pistons are pushed back and flush with the inside of the caliper, insert the red bleed block. If it's wobbling or falling out, you can secure it with the pad retaining screw.

Once the pistons are pushed back and flush with the inside of the caliper, insert the red bleed block. If it's wobbling or falling out, you can secure it with the pad retaining screw.

Step 5: Connect syringe to caliper

Fill the second syringe to 1/4. If you have a Guide, Code, or Level caliper, screw the compatible "Bleeding Edge"-adapter (red wing nut) onto this syringe. This adapter is then inserted into the bleed port on the caliper, where it should click into place and be turned about a half turn counter-clockwise until you feel it stop. The port is now open.

For traditional SRAM calipers without a "Bleeding Edge" connection, remove the bleed screw with a Torx key, just like at the brake lever.

For traditional SRAM calipers without a "Bleeding Edge" connection, remove the bleed screw with a Torx key, just like at the brake lever.

Step 6: Fill the brake

Now, use the syringe at the brake lever to push the brake fluid through the system into the lower syringe at the caliper. You’ll notice discolored, contaminated brake fluid, often with black particles. Once the fluid suddenly becomes clear, the system is fully refilled with fresh fluid.

If you’re using a "Bleeding Edge" adapter, tighten it clockwise and then detach the syringe from the caliper. For calipers without a Bleeding Edge connection, simply remove the syringe and hose, then reinsert and tighten the bleed screw with its O-ring.

Step 7: Bleed

Next, bleed the brake lever assembly itself using the upper syringe, as air bubbles often remain trapped there. To do this, gently create a vacuum by pulling back on the syringe to draw out the bubbles. Caution: Don’t overdo it! Excessive suction can cause the syringe connection to leak, allowing air from the outside to enter. Instead, pull gently on the syringe and wait until all the bubbles have disappeared.

Once complete, pull the brake lever a few times and let it snap back to release any remaining bubbles trapped in the lever. When no more bubbles appear, detach the syringe and reattach the bleed screw with its O-ring to the brake lever.

Finally, thoroughly clean any fluid residue around the bleed ports on both the brake lever and the caliper using a cloth and some brake cleaner. For DOT brake fluid, a final rinse with water can be helpful.

Be sure to dispose of the used brake fluid from the syringes in accordance with proper waste disposal regulations.

Be sure to dispose of the used brake fluid from the syringes in accordance with proper waste disposal regulations.

Moving On: Install Pads and Caliper

FILLING & BLEEDING: Magura

Step 1: Prepare and fill the syringes

Magura uses two standard 30ml syringes, commonly available at pharmacies, for filling and bleeding. One of the syringes must have a small hole at the 30ml mark. If you only have a regular syringe, you can simply create a small hole yourself near the 30ml mark on the scale.

Attach the hose with the connector for the bleed port to the syringe without the hole. Then fill this syringe with approximately 30ml of Magura Royal Blood mineral oil.

Attach the hose with the connector for the bleed port to the syringe without the hole. Then fill this syringe with approximately 30ml of Magura Royal Blood mineral oil.

Step 2: Insert the bleed spacer

Once the pistons are pushed back and flush with the inside of the caliper, the yellow bleed block is inserted.

It can be clicked into the pad retaining screw, if needed, to prevent it from slipping.

Once the pistons are pushed back and flush with the inside of the caliper, the yellow bleed block is inserted.

It can be clicked into the pad retaining screw, if needed, to prevent it from slipping.

Step 3: Connect syringe to caliper

Now remove the bleed screw from the caliper and screw in the syringe with the connector.

Now remove the bleed screw from the caliper and screw in the syringe with the connector.

Step 4: Remove EBT screw from brake lever

Now, remove the so-called EBT screw (the bleed screw at the brake lever) with a Torx T25. It's made of slightly flexible plastic, so it doesn't need an O-ring for sealing. Since only atmospheric pressure prevails in the compensating reservoir, a special seal isn't necessarily required.

Step 5: Connect syringe to brake lever assembly

The second syringe with the hole is now (empty) simply inserted into the bleed hole on the brake lever assembly without the need for a special connector.

Since the entrance at the brake lever is conical, the syringe holds itself in place. Important: Pull the plunger of the syringe all the way out, or until it stops, so that the hole at 30ml is open.

The plunger must be behind the hole, or, as shown in the picture, removed. This way, the air in the syringe is displaced by the oil during filling.

The second syringe with the hole is now (empty) simply inserted into the bleed hole on the brake lever assembly without the need for a special connector.

Since the entrance at the brake lever is conical, the syringe holds itself in place. Important: Pull the plunger of the syringe all the way out, or until it stops, so that the hole at 30ml is open.

The plunger must be behind the hole, or, as shown in the picture, removed. This way, the air in the syringe is displaced by the oil during filling.

Step 6: Fill the brake

Now, pump the mineral oil through the system using the lower syringe at the caliper. You’ll see the fluid rise into the syringe at the brake lever. As the old fluid is pushed out, deposits and debris will come with it. Once the mineral oil becomes clear, you’ll know the system has been completely refilled with fresh fluid.

Be careful not to spill any oil through that upper hole.

Be careful not to spill any oil through that upper hole.

Step 7: Bleed

Now, pull a bit of oil back with the caliper syringe to remove any possible air bubbles from the caliper. Then, push everything back up into the brake lever syringe. Throughout filling, you should pull the brake lever a few times and let it snap back. This way, even the smallest air bubbles can escape from the brake lever and rise into the syringe. When no more bubbles rise, the brake is bled.

Remember to hold the upper hole in the syringe plugged before removing it from the brake lever, otherwise, the mineral oil will run right out of the syringe upon its removal.

Remember to hold the upper hole in the syringe plugged before removing it from the brake lever, otherwise, the mineral oil will run right out of the syringe upon its removal.

Now for the trick with the hole in the syringe at the brake lever:

Remove the syringe from the brake lever, push the plunger back into the syringe, and expel some oil until about 20ml remains in the syringe. Next, pull the plunger slightly to draw about 5ml of air into the syringe. Then reattach the syringe to the brake lever.

By gently pulling on the plunger, you create a vacuum that forces any remaining air bubbles in the brake lever to rise into the syringe.

Repeat this process of pulling and pushing the plunger a few times. Once no more bubbles appear, pull the plunger past the hole, leaving the top of the syringe open. This allows just enough mineral oil to flow back into the system.

When disconnecting the syringe from the brake lever, cover the hole in the syringe with your finger to prevent the mineral oil from spilling out.

Now for the trick with the hole in the syringe at the brake lever:

By gently pulling on the plunger, you create a vacuum that forces any remaining air bubbles in the brake lever to rise into the syringe.

When disconnecting the syringe from the brake lever, cover the hole in the syringe with your finger to prevent the mineral oil from spilling out.

Step 8: Close the hydraulic system

Now you can screw the EBT screw back into the brake lever. Be careful: as mentioned, it's a plastic screw, so tighten it very gently by hand. If you have a torque wrench with a very small torque range, tighten this screw to 0.5Nm - otherwise, use your judgment and fingertip feel.

Next, unscrew the lower syringe located at the brake caliper. If possible, it's advisable to position the brake caliper above the brake lever to prevent any oil from leaking. Now, screw the bleed screw back into the brake caliper and tighten to 4Nm.

Lowering the brake caliper a bit helps here, raising the oil level so that no air is trapped. You can clean any residues at the bleed ports on the brake lever and caliper with a cloth and some brake cleaner. Please dispose of the mineral oil from the syringes properly.

Moving On: Install Pads and Caliper

7. Install pads and caliper

After removing the bleed block, you can reinstall the brake pads. Make sure that the spreader spring is correctly positioned and does not extend into the surface of the pads with its hooks. After bleeding, the piston gap is optimized for new brake pads with full material thickness, so we recommend installing new pads. However, if the old pads are still in good condition (more than 1/3 of the thickness remaining), they can also be reused. After all, we don't want to waste any material!

Now reinstall the pad retaining screw and insert the safety pin. Next, mount the brake caliper back onto the fork or frame, aligning it with the brake rotor. Tip: Tighten the caliper bolts just enough so the caliper is slightly loose and can still move slightly without torque.

Pull the brake lever firmly. This will automatically center and align the caliper with the rotor. While holding the brake lever, gradually tighten the caliper bolts alternately and gently, ensuring that the caliper doesn’t shift out of alignment as you tighten. This method usually provides a quick and accurate alignment, ensuring the caliper is centered and the pads don’t rub on the rotor.

If the gap between the rotor and the pads is very small and the rotor lightly brushes against the pads during rotation, it’s generally not an issue as long as there’s no noticeable braking effect. To confirm, rotate the wheel slowly and observe whether it slows abruptly. For example, Magura brakes typically have a smaller gap between the rotor and pads than Shimano brakes, which can sometimes result in minor rubbing.

Finally, tighten the caliper bolts to the specified torque. If no torque specification is provided in the manual, 7–8 Nm is a reliable guideline.

8. Test ride and bedding in

Your brake system is now ready for action. If you’ve installed new pads, they need to be bedded in to adapt to the brake rotor. While you can do this on the trail, exercise caution: With new pads, the brake has less than half of its usual stopping power, leading to significantly longer braking distances. Setting a defined braking point before a curve will also be challenging. Less experienced riders should perform the bed-in process on a downhill, low-traffic road or a dirt path to stay safe.

For proper bedding-in, avoid constant dragging of the brake. Instead, brake in short, firm bursts. Continuous braking can cause the new pads to overheat and glaze, rendering them ineffective.

To speed up the process, you can lightly sand the new pads with fine-grit sandpaper prior to assembly. This roughens their smooth surface, increasing the friction coefficient with the rotor and reducing the time needed for bedding-in.

Now you’re ready to hit the trails with freshly maintained brakes! Off to new adventures! If you have any questions about maintenance or accessories, feel free to reach out to our service team.