Each pad wear pattern has a root cause. Replace pads without addressing the cause and the same pattern returns in 10,000 miles. This is the map that turns the wear pattern into the right repair.
PATTERN 01 · EVEN WEAR
Inner and outer pads worn the same. Across the face of each pad, wear is uniform end to end. This is the goal.
| Diagnosis | Caliper sliding, piston returning, hardware functional |
| Fix | Pad + rotor service. Clean and re-lube slide pins. New hardware kit. |
PATTERN 02 · INNER PAD WORN
Inner pad significantly thinner than outer. Sometimes worn metal-to-metal while outer still has 6+ mm left. Brake drag, pulsation when warming up.
| Root cause | Caliper piston sticking · seized piston seal · contaminated brake fluid · seized parking-brake mechanism (integrated EPB) |
| Fix | Replace caliper (or rebuild). Replace fluid. Verify EPB retracts. New pads + rotor + hardware. Bleed system. |
PATTERN 03 · OUTER PAD WORN
Outer pad worn while inner has plenty of material. The caliper isn't moving on its slides, so the piston pushes only the inner pad against the rotor and the outer pad rides without applying.
| Root cause | Seized slide pins · torn slide pin boots admitting water/dirt · corroded caliper bracket · damaged abutment clips |
| Fix | Service or replace slide pins + boots. New hardware kit. New pads + rotor. Lubricate slides with synthetic caliper grease. |
PATTERN 04 · TAPERED WEAR
One end of the pad worn significantly more than the other. The leading or trailing edge is making contact preferentially because the pad isn't square to the rotor or one abutment is loose.
| Root cause | Damaged or missing abutment clip · worn caliper bracket slot · bent caliper bracket from impact · uneven slide pin movement |
| Fix | Inspect bracket for damage. New hardware kit (including abutment clips). Service both slides. Replace bracket if slot is worn. |
PATTERN 05 · RIDGED WEAR
Pad has a raised section at one edge where it didn't make contact with the rotor — the rotor has worn a step. The pad never spread out to cover the full rotor face.
| Root cause | Pad too small for the rotor (wrong part) · rotor wear step beyond pad coverage · sticking caliper held the pad in a fixed position |
| Fix | Verify pad part number. Replace rotor (the wear step won't go away). Service caliper. New hardware. |
PATTERN 06 · CRACKED / GLAZED
Radial cracks across the pad face. Surface looks shiny and glassy. Friction material may have crumbled at the edges. Brake pedal feels hard and pads bite poorly when hot.
| Root cause | Dragging caliper · seized parking brake · stuck-on master cylinder return port · downhill riding the brakes · undersized brake spec for vehicle use case |
| Fix | Find the heat source first (caliper, master cylinder, parking brake). Replace pads, rotors. Bleed fluid. Consider upgraded friction or rotor spec if duty cycle is heavy. |
PATTERN 07 · SIDE-TO-SIDE MISMATCH
Both pads on one side of the axle worn much more than both pads on the other side. Vehicle pulls during braking. The hydraulic or mechanical balance between left and right is off.
| Root cause | One caliper sticking applied · restricted brake hose on the less-worn side · ABS modulator stuck · differing rotor thickness or runout · pulling alignment masking which side does more work |
| Fix | Inspect both calipers, both hoses (squeeze test for restrictions). Cross-check rotor runout. Verify ABS modulator function via scan tool. Service both sides as a pair — never just one. |
Slide pins corrode and seize in years, not miles. Salt-belt cars eat them fast. If you don't pull the pins, clean them, and re-lube with synthetic caliper grease at every brake job, the new pads will wear unevenly within months. Lubricant is cheap. Slide service is the difference between a 50,000-mile pad job and a 15,000-mile one.
Abutment clips and anti-rattle clips fatigue. Reusing them after pad service leaves the new pads with worn retention points. Use the hardware kit included with the pads. If pads came without a kit, source the OE hardware separately. Cost: $8. Avoided comeback: priceless.
Side-to-side wear mismatch means you fix BOTH sides. Replacing pads/rotor on the heavier-wearing side leaves the customer with mismatched friction levels — leads to pull, ABS-event triggering, premature wear on the new side. Always service brakes as an axle pair.
DOT 3 and DOT 4 brake fluid absorb water from the air. After 2–3 years, water content is high enough that the fluid boils under heavy braking (vapor lock) and corrodes caliper bores (sticky pistons → uneven wear). Test moisture content or replace fluid every 3 years. Flushing a system at every brake service prevents many of the patterns above.
Print this. Stick it inside your toolbox lid.
| Pattern | Cause | Repair beyond pads |
|---|---|---|
| Even wear | Normal | Hardware + slide service |
| Inner pad only | Piston not releasing | Caliper · fluid · EPB |
| Outer pad only | Caliper not sliding | Slide pins · boots · bracket |
| Tapered | Pad not square to rotor | Hardware · bracket inspection |
| Ridged | Wrong pad or rotor step | Verify pad p/n · new rotor |
| Cracked / glazed | Sustained overheat | Find heat source first |
| Side-to-side mismatch | Hydraulic imbalance | Both calipers · hoses · ABS |
Always: service slides, replace hardware, flush fluid every 3 years, service brakes as axle pairs.