Spongy brake lever: when and how to bleed a mineral oil brake

Does it need a bleed?

Not every soft lever needs a full bleed. Check these first, because some have a quicker fix.

Lever is soft after the bike was upside down or on its side

Shimano's MT200 manual says the brake is not designed to work upside down, and air from the reservoir can move down to the caliper. Pump the lever a few times before riding. If it is still soft, hold the lever level and pump it gently so bubbles rise. If that does not fix it, bleed it.

Lever pulls far or feels spongy (SRAM DB8)

SRAM's first step is a piston massage to free sticky pistons, then a bleed only if that does not help. Steps are on the DB8 page.

Lever travel grows as the pads wear (SRAM DB8)

The pistons are not moving out to follow the pads. Wind the reach adjuster all the way out, counting clicks, pull the lever hard 5 times and wind it back. No bleed needed.

Pads drag or the pistons come out unevenly (Shimano)

This is a piston problem, not air. Shimano's fix is to push the pistons back, cycle them with the pad spacer fitted and check they come out evenly. See the XT M8100 and 105 pages.

Lever suddenly travels further on a long descent

Shimano calls this vapor lock: water or air in the oil heats up. Bleed with fresh oil, and do not drag the brakes continuously.

Lever is soft after the hose was cut, replaced or disconnected

Air got in. Bleed it.

The oil is noticeably discolored, or it is due

Shimano says to change the oil when it is noticeably discolored. SRAM says to fully bleed a DB8 at least every other year, more often if you ride a lot, hard or below freezing.

Lever is firm but the bike does not stop well

Not air. Check for oil on the pads or rotor and for worn pads. See the disc brake pad page.

Oil is leaking from the lever or caliper

Stop riding the bike. A bleed will not fix a leak. Have a bike shop check it.

Which guide is yours

The model number is printed on the caliper and lever. Each guide has the full bleed steps and torque figures for that brake.

Shimano's DM-BROIL document lists BR-MT200, BL-MT200, BR-M8100, BR-M8120, BL-M8100, BR-R7170, ST-R7120, ST-R7170 and the CUES BR-U8000, BR-U8010, BR-U8020 and BL-U8000 under SHIMANO Hydraulic Mineral Oil. Tiagra 4700 uses cable rim brakes, so there is nothing to bleed. For Tiagra brake work, see the Tiagra page.

SRAM DOT brakes are not covered

This page does not cover SRAM Level, Guide, G2 or Code brakes. SRAM uses DOT 4 or DOT 5.1 fluid in all of its current DOT brakes, including every Level, Guide, G2 and Code model. SRAM says DOT and mineral oil parts are not compatible, and that the wrong fluid damages all the rubber and plastic parts in a brake. If DOT fluid has gone into a DB8, SRAM says the whole brake, lever and caliper, must be replaced. Never put DOT fluid in any brake on this page, and never put mineral oil in a DOT brake.

To tell a DB8 apart: SRAM dyes Maxima Mineral Brake Oil green, and the seals at the DB8 bleed ports are green to match. SRAM's DOT fluid is yellow.

The right oil

• Shimano: use only SHIMANO Hydraulic Mineral Oil from a clean, sealed bottle. Shimano says never to mix it with SHIMANO Low Viscosity Oil. Shimano's MT200 manual also says never to reuse oil drained from the bleed point, because old oil can hold water and cause vapor lock.
• SRAM DB8: use only Maxima Mineral Brake Oil and only the SRAM Mineral Oil bleed kit; the DB8 bleed ports do not fit SRAM's DOT kits. SRAM has not tested other brands of mineral oil and does not cover them under warranty.
• Do not swap oils between brands. Each maker's manual names only its own oil.

Shimano funnel method

All the Shimano brakes here are bled the same basic way: oil is pushed up from the caliper into a funnel screwed into the lever, then air is let out at the caliper and the lever. The amount you open the bleed point, the lever angle and the torque figures differ by model; see the differences table below and follow your model page for exact steps.

Before you start: wear eye protection and gloves and work somewhere ventilated. Take the pads out first so no oil can reach them. Pads that touch oil must be replaced. Clean spills with isopropyl alcohol or a dry cloth, never commercial brake cleaner, which Shimano says damages the seals.

1. Remove the wheel and pads. Fit the yellow bleed spacer in the caliper, put the bike in a stand, and set the lever so its bleed screw is level.

2. Remove the lever bleed screw and its O-ring and screw in the oil funnel. Do not fit the stopper yet.

3. Fill the syringe with oil, connect its tube to the caliper bleed point and open the bleed screw or nipple by the amount for your model. Push oil up until the oil coming into the funnel has no bubbles. Do not pull the brake lever while you add oil. If you do, Shimano says to drain it and start again.

4. Close the bleed point for now. Remove the syringe with a rag over the tube end and fit a tube with a bag instead.

5. Open the bleed point and let oil and bubbles run out on their own. Tapping the hose, reservoir or caliper gently, or moving the caliper, helps the bubbles out. Keep the funnel topped up so no air is drawn in. When no more bubbles come out, close the bleed point.

6. Hold the lever pulled and open and close the bleed point quickly, about half a second each way, 2 to 3 times. Then tighten it with a torque wrench to 4–6 N·m (all four Shimano brakes here use this figure). Fit the cap.

7. Pump the lever. Bubbles rise into the funnel. When they stop and the lever feels stiff, tilt the lever by the angle for your model and repeat until no more bubbles appear. If the lever will not go stiff, go back to step 5.

8. Set the lever level again. Push the oil stopper into the funnel, O-ring side down, and lift the funnel out with the stopper in it.

9. Refit the lever bleed screw and O-ring so a little oil overflows as it seats, which means no air is left in the reservoir. Tighten it with a torque wrench to the figure for your lever. Do not touch the lever while you do this.

10. Wipe off all spilled oil with isopropyl alcohol. Remove the bleed spacer, refit the pads and the pad spacer, and pump the lever until firm. Then do the brake test.

    From Shimano DM-MBBR001 (MT200), DM-MADBR01 (XT M8100) and DM-LADBR01 (CUES), adding mineral oil and bleeding air

Shimano model differences

The 105 BR-R7170 bleed has extra steps: after pushing oil up, you close the bleed screw, pump the lever about 10 times, tilt the lever so the funnel sits at 20° and work the lever slowly until no bubbles rise, then push more oil from the caliper. Shimano warns that bleeding at the wrong angle can trap air. On 105, do not overtighten the lever reach adjustment screw, which Shimano says can stop the bleed working properly. Full steps: 105 BR-R7170 bleed.

On XT M8100 levers the funnel also has to be fitted whenever you push the pistons back, or the oil pressure can damage the lever diaphragm. That matters during pad changes too.

SRAM DB8 syringe method

SRAM bleeds the DB8 with two syringes instead of a funnel: one threaded into the lever, one into the caliper, and oil is pushed down and pulled back up between them until the bubbles stop. The DB8 caliper has a threaded port with a T10 bleed screw, so follow SRAM's "Threaded" steps, not the Bleeding Edge ones.

1. Fill the lever syringe about three quarters with Maxima oil and put a little oil in the caliper syringe. Push the air out of both.

2. Remove the wheel, the e-clip, the pad retainer bolt and the pads. Fit the DB8 bleed block (included in SRAM's mineral oil bleed kits) and hold it in with the retainer bolt. Thread the caliper syringe into the caliper bleed port.

3. Set the lever blade 75–80 mm from the center of the bar and thread the lever syringe into the lever bleed port.

4. Push oil down from the lever syringe into the caliper syringe, then draw it back up. Repeat until only small bubbles appear. If the oil coming out is discolored, push all the old oil through and start again with fresh oil.

5. Close the lever syringe clamp, remove the caliper syringe and refit the caliper bleed screw at 1.6 N·m (14 in-lb).

6. Open the clamp, squeeze the lever 3 to 5 times, then pull and push the lever syringe plunger until only a few bubbles come out. Remove the syringe and refit the lever bleed screw with a torque driver.

   From the SRAM Mineral Oil MTB Disc Brake Installation, Hose Shortening, and Bleed Manual, Mineral Oil Bleed Procedure

SRAM's two documents give different torques for the DB8 lever bleed screw: 1.6 N·m (14 in-lb) in the bleed manual and 1.2 N·m (11 in-lb) in the DB8 service manual. The DB8 bleed guide has every step, the full torque table and what to do about this.

Torque, cleanup and brake test

Oil on pads or rotor: wipe any oil off the rotor with isopropyl alcohol. Pads that touched oil cannot be cleaned and must be replaced. Shimano says brakes may not work if oil or grease gets on the pads or rotor.

1. Check both bleed screws are in and tightened with a torque wrench or torque driver to the figures above. These are small screws with low torques, so a low-range tool is needed.

2. Clean the lever, caliper and hose with isopropyl alcohol. Check every fitting for oil.

3. Refit the pads and advance them: Shimano pumps the lever with the pad spacer fitted; SRAM uses the pad spacer wedge. Refit the wheel.

4. Squeeze the lever hard several times. It must feel firm, stop at the same point every time and stay well short of the bar. If it is still soft, bleed it again.

5. Spin the wheel and check for rotor rub. Re-center the caliper if needed.

6. If you fitted new pads or a new rotor, bed them in before you ride normally. Steps are on the pad page.

If the lever is still soft after a second bleed, or you see oil at any fitting, do not ride the bike. Have a bike shop check the brake.

Related: Replace disc brake pads, SRAM DB8, Shimano XT M8100 brakes, Shimano MT200 brakes, Shimano 105 R7100 brakes