Shimano Deore XT M8100 brakes: change the pads, line up the caliper and bleed with mineral oil

How to confirm which XT caliper you have

The BL-M8100 lever works with both XT post mount calipers, and Shimano lists the BR-M8100, BR-M8110-R and BR-M8120 as recommended calipers for it.

• BR-M8100 is the two-piston XT post mount caliper. It has a banjo hose joint, a pad axle with a snap retainer, and 5 mm hex caliper fixing screws locked with snap rings.
• BR-M8120 is the other XT post mount caliper. Shimano lists a different set of pads for it than for the BR-M8100. Check the model number on the caliper before you buy pads.
• BR-M8110 is the flat mount version. Shimano covers it in a separate section of its manual and it is not covered on this page.

Both XT calipers bleed through a bleed nipple with a cap, turned with a 7 mm box wrench. The BL-M8100 lever has a top bleed screw (M5) for the oil funnel, a reach adjustment knob and a free stroke screw.

The BR-M8100, BR-M8120 and BL-M8100 all use Shimano Hydraulic Mineral Oil. Never mix it with Shimano low viscosity oil, and never use DOT fluid.

Specifications and wear limits

Torque figures

The pad axle torque for XT (1–1.5 N·m) is much higher than for XTR BR-M9100 calipers (0.2–0.4 N·m). Do not mix them up. On a carbon handlebar or frame, check the torque with the bar or frame maker as well.

Replace the brake pads

Replace the pads when the pad material is 0.5 mm or less at its thinnest point, when the pad presser spring starts hitting the rotor, or as soon as they get oil on them. Buy pads that match your caliper: G05A-RX, G04S, J05A-RF or J04C for the BR-M8100; N03A, N04C, D03S or D02S for the BR-M8120.

Before you start: keep oil and grease off the pads and rotor. Pads that have touched oil cannot be cleaned and must be replaced.

1. Remove the wheel.

2. Remove the snap retainer (retaining clip) from the end of the pad axle, unscrew the pad axle and take out the pads and presser spring.

3. Clean the pistons and the area around them. Do not take the pistons out.

4. Remove the lever bleed screw and thread in the oil funnel first. Then push the pistons straight back as far as they go with a flat tool such as a plastic tire lever. Do not twist them, and never use anything sharp. Without the funnel fitted, the oil pressure can damage the lever diaphragm.

5. Fit the presser spring between the new pads. On finned pads, set the fins as Shimano's diagram shows. Some pads are marked L and R.

6. Slide the pads in, fit the pad axle and tighten it to 1–1.5 N·m with a torque driver. Fit the snap retainer and the red pad spacer.

7. Plug the funnel with the oil stopper, lift it out, and refit the lever bleed screw and O-ring at 0.5–1 N·m. Pump the lever until it feels firm.

8. Take out the pad spacer and refit the wheel. Spin it and check for rub. If it rubs and the wheel is seated correctly, center the caliper.

9. Bed in the new pads and do the brake test before riding.

   From DM-MADBR01, Replacing the brake pads

Whenever the wheel is out, fit the pad spacer so the pistons cannot be pushed out by a pull on the lever. More on pad changes is on the disc brake pad page.

Bed in new pads

New pads and rotors brake harder as they bed in. Resin pads take longer to bed in than metal pads. Bed in again after you fit a new rotor.

1. Find flat, safe ground away from traffic. Shift to the largest rear sprocket and smallest chainring. On an e-bike, turn the assist off so you do not overheat the rotor.

2. Ride while holding one brake lever just hard enough that you can still pedal. Hold it for 20 m, then let go.

3. Repeat at least 10 times. Do the front and rear brakes separately.

   From DM-MADBR01, Replacing the brake pads, and UM-8VR0A, Warm-up operation

Center the caliper

Before you start: you need a torque wrench for the caliper mounting screws. Use only the snap rings supplied for the BR-M8100 and BR-M8120 screws; other snap rings do not fit.

1. Fit the wheel with its rotor. If the yellow bleeding spacer is still in the caliper, remove the snap retainer and pad axle, then the spacer.

2. Fit the presser spring and pads, the pad axle, the snap retainer and the red pad spacer. Pump the lever until it is stiff, then take the pad spacer out.

3. Fit the caliper with its mounting screws loose so it can slide from side to side. If you use a mount adapter, fit it with the mark facing up and use the long and short screws in the positions Shimano shows.

4. Pull and hold the brake lever so the pads clamp the rotor.

5. While holding the lever, tighten the caliper mounting screws to 6–8 N·m with a torque wrench.

6. Fit the snap rings on the screw heads. Spin the wheel and check for rub. If it rubs, loosen the screws and repeat from step 4.

   From DM-MADBR01, Attaching the brake caliper

An international-standard (IS) frame or fork needs a dedicated adapter. Its screws and the caliper screws are both 6–8 N·m and must be secured with snap rings or wire. Rotors of 180, 203 and 220 mm flex more, so a frame mount that is not square to the dropout is more likely to cause rub.

Fit the lever, set reach and free stroke

1. Loosen the clamp band fixing screw. Press the recessed area with a 2 mm hex key to release the safety latch and open the band.

2. Push the O-ring up against the clamp band, fit the lever on the bar and close the band.

3. Set the position and tighten the fixing screw to 4–6 N·m with a torque wrench. With a band-type shifter, keep the shifter band in the range Shimano shows. With an I-SPEC EV shifter, follow the shifter's dealer's manual.

4. Reach: turn the reach adjustment knob by hand. Clockwise moves the blade farther from the bar. Counterclockwise brings it closer.

5. Free stroke: turn the free stroke screw clockwise to shorten the lever travel before the pads touch the rotor, or counterclockwise to lengthen it. Free stroke only moves the starting point of the pull, so adjust reach as well to put the bite point where you want it relative to the bar.

   From DM-MADBR01, Attaching the brake lever, Adjusting the grip width and Adjusting the free stroke

Bleed with Shimano mineral oil

Bleed the brake when the lever feels soft, after hose work, or when the oil is clearly discolored. Shimano's method uses the TL-BR001 syringe at the caliper and the TL-BR003 funnel on the lever. You push fresh oil up from the caliper, let it drain by gravity, then pump the lever to chase the last air up into the funnel.

Before you start: use Shimano mineral oil only, from a clean, sealed container. Never use DOT fluid or mix it with Shimano low viscosity oil. Take the pads out first. If oil gets on the pads they must be replaced.

To drain old oil first: fit the yellow bleeding spacer, set the lever parallel to the ground, remove the lever bleed screw and O-ring, then fit a 7 mm box wrench and a tube with a bag to the bleed nipple and open it. Pumping the lever makes it drain faster. Then fill and bleed:

1. Take out the pads and fit the yellow bleeding spacer. Put the bike in a stand and turn the lever on the bar so it is parallel to the ground.

2. Remove the lever bleed screw and O-ring. Thread in the TL-BR003 oil funnel. Leave the stopper out for now.

3. Do not pull the brake lever while you add oil. It can trap air. If you did, drain and start again.

4. Take off the bleed nipple cap and put the 7 mm box wrench on the nipple. Fill the TL-BR001 syringe with Shimano mineral oil, connect its tube to the nipple and open the nipple 1/4 turn.

5. Push oil in until the oil rising into the funnel has no bubbles. Secure the caliper so the tube cannot come off. Close the nipple for now.

6. Swap the syringe for a tube with a bag. Open the nipple and let oil and bubbles drain by gravity. Gently shaking the hose, tapping the reservoir or caliper with a screwdriver handle, or changing the caliper's position helps. Keep the funnel topped up so no air gets drawn in.

7. When no more bubbles come out, close the nipple.

8. Pull and hold the brake lever. Quickly open and close the nipple, about half a second each way. Repeat 2 or 3 times. Tighten the nipple to 4–6 N·m with a torque wrench, wipe it and refit the cap.

9. Pump the lever until no more bubbles rise into the funnel and the lever feels stiff. If it does not get stiff, go back to step 4.

10. Tilt the lever 30 degrees up and pump again until no bubbles rise. Then tilt it 30 degrees down and repeat.

11. Set the lever parallel to the ground again. Push the oil stopper into the funnel, O-ring side down, and lift the funnel out with the stopper in it.

12. Fit the bleed screw with its O-ring while oil overflows, so no air stays in the reservoir. Tighten it to 0.5–1 N·m. Do not pull the lever while you do this.

13. Wipe up the overflow. Use isopropyl alcohol on oily hoses and tools, not brake cleaner. Remove the bleeding spacer, fit the pads with the pad axle at 1–1.5 N·m, the snap retainer and the pad spacer, and pump the lever until firm. Then center the caliper.

    From DM-MADBR01, Replacing the mineral oil

The general method for Shimano mineral oil brakes is on the mineral oil bleed page.

Free up uneven pistons

Do this if the pistons come out unevenly or the pads stay against the rotor and drag.

1. Remove the wheel and pads. Clean the pistons. Fit the oil funnel on the lever and push the pistons straight back.

2. Refit the pads, the pad axle at 1–1.5 N·m, the snap retainer and the pad spacer.

3. Pump the lever and check that the pistons come out evenly. If they do not, repeat from step 1.

4. Remove the pad spacer, fit the wheel and check for rub. Loosen the caliper mounting screws and re-center if needed.

   From DM-MADBR01, Adjusting a piston defect

Fit a Center Lock rotor

1. Check the wheel is not radially laced. Shimano rotors cannot be used on radially laced wheels.

2. Wear gloves. Rotor edges can cut.

3. Fit the rotor and lock ring. Tighten to 40 N·m with a torque wrench, using TL-LR15 and an adjustable wrench for an internal spline lock ring, or TL-FC36 for an external spline lock ring.

   From DM-MADBR01, Attaching the disc brake rotor

Test the brake before riding

Before you start: do not ride until the lever is firm and the brake stops the wheel.

1. Check the caliper mounting screws are at 6–8 N·m with snap rings fitted, the pad axle has its snap retainer, and the bleed nipple cap and lever bleed screw are in.

2. Squeeze the lever hard several times. It should feel firm and stop at the same point each time, well before the bar.

3. Look for oil at the lever, the hose ends, the banjo and the caliper. Check the rotor and pads are clean and dry.

4. Spin the wheel and check for rub.

5. Push the bike forward and pull the brake. It should stop the wheel firmly. Then do a slow test ride on flat ground and bed in any new pads.

If the lever still feels soft after a bleed, have a qualified mechanic check it before you ride.

Parts and consumables

Tools

• TL-BR001 syringe and tube, TL-BR003 oil funnel and oil stopper
• 7 mm box wrench (bleed nipple), plus a tube and bag
• 2, 2.5, 3, 4 and 5 mm hex keys
• Torque wrench and a low-range torque driver for the pad axle and lever bleed screw
• Plastic tire lever or other flat tool to push the pistons back
• Rotor tools: TL-LR15 (Y12009230) with an adjustable wrench, or TL-FC36 (Y13098000)
• Hose work: 8 mm open-end wrench, TL-BH62 or TL-BH61 (Y8H198030)
• Slotted and #2 cross head screwdrivers
• Isopropyl alcohol, clean rags, nitrile gloves

Troubleshooting by symptom

Pads drag, or the pistons come out unevenly

Follow Free up uneven pistons, then re-center the caliper.

Rotor rubs after centering

Large rotors (180, 203, 220 mm) flex more. A brake mount that is not parallel to the dropout can also cause rub. Re-center as in Center the caliper.

Pistons came out with the wheel removed

Fit the oil funnel on the lever, push the pistons back with a flat tool, and fit the pad spacer whenever the wheel is out.

Lever travel gets longer under long, steady braking

Shimano says not to drag the brakes continuously. Brake, release, and brake again.

Brake barely slows the bike after a bleed or pad change

Oil has probably reached the pads or rotor. Replace the pads.

Leak at the hose end after shortening the hose

The hose must be cut square (90 degrees), and the olive and connector insert must be new and the right type for the hose. Redo the joint with new parts and bleed.

Pad spring touches the rotor

The pads are worn out. Replace them.

Clean the brake with soapy water and a dry cloth. Do not use spray brake cleaners or brake silencers, which can damage seals and plastic parts.

Related: Bleed mineral oil brakes, Replace disc brake pads, Shimano MT200 brakes, Shimano Deore M6100, SRAM DB8 brakes