How to Replace Your Disc Brake Pads

How to Replace Your Disc Brake Pads

Pad replacement is one of the easier brake jobs to do at home, but it’s also one of the most commonly botched. The pads themselves go in fine. What people get wrong is everything around the install: not resetting the pistons, squeezing the lever with the pads out, contaminating the new set with bare fingers, or grabbing a pad shape that almost-but-not-quite fits.

This guide walks through the whole thing properly, plus the gotchas that turn a 15 minute job into a two hour fight.

When to replace

Pads are toast in three situations:

  1. Worn out. Pad material has to be at least 1mm thick. The Loam Goat 5 In 1 Disc Brake Tool has a built-in Shimano pad wear gauge that tells you at a glance. Or stack three business cards together (about 1mm) and use that as a feeler. Less than 1mm of pad left and they need to go.
  2. Contaminated. Brake fluid, chain lube overspray, suspension oil, anything oily that lands on the pad face will ruin it. Contaminated pads squeal, take more lever effort to do the same job, and you’ll often see darker discolouration on the pad face or rotor. No amount of cleaning fixes a properly contaminated pad. Replace them and clean the rotor with isopropyl alcohol while you’re at it.
  3. You want a different compound. Going from organic to sintered for more bite, or sintered to organic for quieter braking, etc.

Picking the right pads

This is where most people get tripped up. Pad shape is brake-specific. The compound (organic, semi-metallic, sintered) is a separate choice.

The easiest path: tell us your brake model and we’ll send you the right set. Find your pads here. Every common shape, in stock.

If you’d rather match shapes yourself, take your old pads out (we’ll get to how in a second) and look for an identical outline. Same shape almost always means same fit.

Also: check what your rotor wants. Some manufacturers print “resin pads only” or “organic only” on the rotor itself. Mixing sintered pads onto a resin-only rotor will glaze the rotor and ruin braking performance. If there’s a label, follow it.

Tools you’ll need

  • Needle nose pliers (for cotter pins or tight fitting pads)
  • A piston press. The Loam Goat 5 In 1 Disc Brake Tool has one built in. Park Tool’s PP-1.2 is a single-purpose alternative, or a clean flat tire lever or cone wrench in a pinch.
  • The right hex, T25, or screwdriver for your retaining pin or adjusters
  • Isopropyl alcohol and a clean rag for the rotor

Step 1: Remove the wheel

Bike in the stand. Wheel off. Don’t squeeze the brake lever once the wheel is out. If you do, the pistons advance and you’ll have to push them back later. It’s not the end of the world but it adds steps. (see: How to Reset Hydraulic Brake Pistons)

Step 2: Remove the old pads

The retention system varies by brake. Look at your caliper and you’ll see one of these:

  1. Threaded pin with a clip. Pull the clip off with needle nose, unthread the pin, slide the pads out.
  2. Cotter pin. Straighten the bent ends with pliers and pull the pin out.
  3. Spring on top. Lift the spring out first, then the pads come out the bottom.
  4. Magnet only. Just pull the pads down and out. If they’re stuck, loosen the pad adjuster (mechanical brakes) or wiggle them.
  5. Clip on the pad itself. It’ll take some force. Grip the tab and pull straight.

If the pads are jammed and won’t come out, loosen any adjuster screws you find on the caliper. That gives them room to slide.

Pull out the spring too if there is one. Most new pads come with a fresh spring.

Step 3: Reset the pistons

This is the step people skip and then wonder why their new pads won’t fit. Old worn pads have less material, so the pistons have advanced over time to keep contact with the rotor. New pads are thicker. If you try to push fresh pads into a caliper with advanced pistons, they won’t fit, or they’ll fit but immediately rub the rotor.

For hydraulic brakes: use a piston press (the 5 In 1 has one built in), the flat side of a tire lever, or a cone wrench. Press both pistons back into the caliper body as far as they’ll go. Apply even pressure on both pistons at once if you can, especially on flat mount Shimano calipers, which have ceramic pistons that don’t love uneven force.

For mechanical brakes: turn the pad adjuster screws counter-clockwise all the way until they stop. Most calipers have a screw on each side. Some only have one.

If you accidentally pull the lever and the pistons come back out, no problem. Push them back in and try again.

Step 4: Install the new pads

Installation is the reverse of removal. A few notes:

  1. Handle pads by the backing plate. Skin oils transfer to the pad face and contaminate them. If you grabbed the friction surface, wipe it down with isopropyl alcohol before installing.
  2. Some springs only go in one direction. If yours has tabs or bends that look directional, match the orientation of the old set before you toss it.
  3. Magnet-style calipers usually want the inner pad first. The outer one is sometimes physically impossible to fit if the inner isn’t already in place.

A correctly installed pad will wiggle slightly side to side. That’s normal, not loose.

Step 5: Re-seat the wheel and pump the lever

Put the wheel back on. Make sure it’s fully seated in the dropouts before tightening the axle.

For hydraulic brakes: pump the lever 5-10 times. The first few pumps will feel soft because the pistons need to travel forward to take up the gap. After a few squeezes you should get a firm lever.

For mechanical brakes: you’ll need to re-align the calipers. (see: How to Align Mechanical Disc Brakes)

Spin the wheel and look for rub. If you’ve got rub, that’s a caliper alignment issue, not a pad issue. (see: How to Fix a Rubbing Hydraulic Disc Brake)

Step 6: Bed in the new pads

Don’t skip this. New pads need to be bedded in before they’ll give you full braking power. The procedure is a quick 5 minutes on a flat road, no traffic, with controlled slowdowns. Full walk-through here: How to Bed In New Brake Pads.

Common problems after install

This article is based on Park Tool’s video How to Replace Disc Brake Pads. The bed-in section is from our shop experience.

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