Guides
How to change bike brake pads — and how to tell when they are due
The steps, and the wear limits from the manufacturer manuals — once you know that they measure different things.
Short answer
Changing them: wheel out, retaining pin or split pin out, old pads out, push the pistons fully back with a flat plastic tool, new pads plus spring in, pin back and secured, then pump the lever before you ride until the bite point returns — and bed them in.
When: Shimano say 0.5 mm of friction material, Magura 2.5 mm including the backing plate, SRAM 3 mm in total — different figures because they measure different things. Park Tool's workshop rule is at least 1 mm of friction material. 🔴 A disc brake gives you no warning: the wear compensation keeps the bite point where it is right to the end. You have to look.
Changing disc brake pads, step by step
The job itself is short. The two places it goes wrong are pushing the pistons back — and riding off without pumping the lever first.
- Take the wheel out so you can see into the caliper and get the pads out sideways.
- Remove the retaining pin. Depending on the brake this is a split pin, a threaded pin or a clip. Note which way the pads and their spring sit — the spring goes back in the same orientation.
- Pull the old pads out together with the spring, usually downwards or towards the wheel side.
- 🔴 Push the pistons fully back. Use a flat plastic tool or a dedicated piston press, evenly and without force. Never a screwdriver — a scratched piston will not seal. Without this step the new, thicker pads simply will not fit.
- Do not touch the friction surfaces — not the pads, not the rotor. Finger grease contaminates them, and Magura say contaminated pads belong in the bin even after an attempt to clean them.
- Fit the new pads with the spring, slide the pin back through and secure it.
- Wheel back in, then pump the lever repeatedly until the bite point is firm again. The pistons have to come back out to the pads first. Skipping this means your first pull of the lever does almost nothing.
- Bed them in. Accelerate to a moderate speed and brake down to walking pace without coming to a stop, ten to twenty times, until the bite is even. New pads need to transfer a film onto the rotor before they reach full power.
The wear limits — and why they look contradictory
Put the manufacturer figures side by side and they seem to disagree wildly. They do not. They measure different things: Shimano quote the friction material on its own, Magura and SRAM include the metal backing plate.
| Source | Limit | Measured how |
|---|---|---|
| Shimano | 0.5 mm | friction material only (2 mm when new) |
| Magura | 2.5 mm | including the backing plate |
| SRAM | 3 mm | total: backing plate plus friction material |
| Park Tool | at least 1 mm | friction material, workshop rule of thumb |
🔴 And a disc brake does not warn you. It has automatic wear compensation, so the bite point stays put and the lever travel does not grow as the pads thin out. That is comfortable and it is a trap: the usual signal that tells you something is wearing simply never arrives. Magura's instruction to check before every ride follows directly from it.
On a rim brake it is the opposite — the lever travel does grow, and the grooves in the pad disappear. There the rim itself is also a wear part: Ryde name a remaining wall thickness of 0.9 mm and a check every 2,000 km or 100 operating hours, Mavic work with 0.4 mm of wear, and Shimano fit a wear indicator to the braking surface.
The rotor is a wear part too
| Source | Minimum | Note |
|---|---|---|
| Shimano | 1.5 mm | replace at or below |
| SRAM | 1.55 mm | on 1.85 mm rotors |
| SRAM | 1.7 mm | on 2 mm rotors such as HS2 |
| Magura | 1.8 mm | 2.0 mm when new |
| Trickstuff | 1.6 mm | minimum braking surface thickness |
Shimano put the consequence in plain words: a rotor that has become too thin can break. This is not a performance question.
How long do they last? Nobody will tell you
No manufacturer publishes a kilometre figure — Shimano, SRAM and Magura define wear purely in millimetres, and they are right to. The ADAC offer a rough order of magnitude: around 1,000 km for rim brakes, up to 5,000 km for disc brakes. But the real spread runs from one set per descent (downhill riding in snow, a handful of kilometres) to around 8,000 km for a light rider on dry, flat roads.
Which is why a number on a calendar is the wrong instrument here, and a look into the caliper is the right one.
Squealing is not automatically a verdict
Shimano list noise when braking among the possible signs that the wear limit has been reached. Park Tool, though, also attribute squealing to contaminated pads — oil, chain lube overspray, brake cleaner residue. So measure first and check for contamination second, rather than buying pads on the strength of a noise.
If they are contaminated, Magura are unambiguous: replace them, even if you have tried cleaning them. And keep chain lube away from the rotor — which is the reason our chain lube guide tells you to cover the brake before you start.
Common questions
How do I know when bike brake pads need replacing?
On disc brakes: only by looking and measuring. They have automatic wear compensation, so the bite point stays where it is and the lever travel does NOT get longer as the pads wear. Magura therefore state explicitly that wear should be checked before every ride. On rim brakes the growing lever travel is a genuine signal, and the grooves in the pad disappear.
At what thickness do brake pads have to be replaced?
It depends on WHAT is being measured, and the manufacturer figures only look contradictory. Shimano: 0.5 mm, measured on the friction material alone (2 mm when new). Magura: 2.5 mm, measured including the backing plate. SRAM: 3 mm total thickness of backing plate and friction material together. As a workshop rule of thumb Park Tool name at least 1 mm of friction material.
How many kilometres do brake pads last?
No manufacturer publishes a kilometre figure — Shimano, SRAM and Magura define wear exclusively in millimetres. As a rough order of magnitude the ADAC name around 1,000 km for rim brakes and up to 5,000 km for disc brakes. The real spread is enormous, from one set per descent (downhill in snow, a few kilometres) to around 8,000 km (road, dry, flat, light rider). A kilometre rule does not replace measuring.
Does the rotor need replacing too?
Yes, it is a wear part. Shimano: replace at 1.5 mm or less. SRAM: 1.55 mm on 1.85 mm rotors, or 1.7 mm on 2 mm rotors such as HS2. Magura: 2.0 mm when new, limit 1.8 mm. Trickstuff: minimum braking surface thickness 1.6 mm. Shimano warn clearly that a rotor that is too thin can break.
My brakes squeal — does that mean the pads are done?
Not necessarily. Shimano list noise when braking as a possible sign that the wear limit has been reached, but Park Tool also attribute squealing to pads that are oiled or otherwise contaminated. So measure the thickness first and check for contamination. Magura say contaminated pads should be replaced, even after an attempt to clean them.
How often should I check them?
Magura say before every ride. SRAM recommend a monthly check, more often in wet and muddy conditions. On rim brakes the braking surface of the rim wears too — Ryde name every 2,000 km or 100 operating hours for that check.
Sources
- Shimano – Dealer's Manual, disc brakes (pad 0.5 mm, rotor 1.5 mm, vapour lock)
- Magura – Workshop manual, disc brakes (2.5 mm pad, 1.8 mm rotor, wear compensation)
- Park Tool – Disc Brake Pad Removal and Installation (1 mm rule)
- Trickstuff – Rotor fitting instructions (1.6 mm)
- Shimano – Wheel manual (rim wear indicator)
- Mavic – Technical Manual (rim wear, 0.4 mm)
- Ryde – Safety instructions (0.9 mm remaining wall, 2,000 km check)
- ADAC – Replacing bicycle brake pads (kilometre and cost figures)
- Zinn / Velo – Technical FAQ: durability of disc brake pads
Das rechnet BikeCare für dich
BikeCare tracks brake pads as their own part, with a forecast from your actual rides — and reminds you to look, because a disc brake will not tell you itself.