Brakes
Brake bleeds: yearly for DOT, honest for mineral
Brake fluid is the only consumable you can't see wearing out. It fails on the fifth minute of the longest descent of your trip, which is exactly why it's on a calendar clock, not a feel clock.
DOT vs mineral: why the schedules differ
DOT fluid is hygroscopic: it pulls water out of the air through hoses and seals. Water lowers the boiling point: fresh DOT 5.1 boils around 260°C, but at 3% water it's down near 180°C, right where a long alpine descent operates. That's why DOT brakes get a yearly bleed regardless of feel.
Mineral oil doesn't absorb water, so it ages more gracefully, but water that does get in pools at the caliper (the hottest spot), and the oil still collects wear debris and air. Bleed every 1–2 years, or immediately when the lever goes spongy.
Per-brand schedule
| Brand | Fluid | Bleed interval | Notes |
|---|---|---|---|
| SRAM | DOT 5.1 | 1 yr | Bleeding Edge fittings make it a 15-minute job. |
| Shimano | Mineral | 1–2 yr / when soft | Wandering bite point = bleed first, suspect seals second. |
| Magura | Royal Blood (mineral) | 1–2 yr | Tolerant of neglect; EBT lever port makes top-ups easy. |
| Hope | DOT 5.1 | 1 yr | Rebuildable forever: seals and pistons all serviceable. |
| TRP | Mineral | 1–2 yr | Same logic as Shimano. |
| Formula | Model-specific | 1 yr (DOT models) | Cura runs mineral; older models DOT. Check yours. |
Never mix fluids. DOT in a mineral system (or vice versa) destroys the seals; a full rebuild at best. And DOT strips paint: cover the frame, wear gloves.
Pads and rotors ride the same clock
- Pads: replace at ~1 mm of friction material. Sintered pads last longer in wet grit; organic bite harder cold but wear fast in mud. E-bikes eat pads roughly twice as fast.
- Rotors: every rotor has a minimum thickness stamped on it: typically 1.5 mm (Shimano) and 1.55 mm (SRAM) from ~1.8 mm new. Below that they warp under heat and can fail. A vernier caliper check takes ten seconds.
- Bed in new pads and rotors: ~10 controlled stops, increasing force. Glazed pads from skipping bed-in never reach full power.
Symptoms decoder
| Symptom | Likely cause | Fix |
|---|---|---|
| Spongy lever | Air in the system | bleed |
| Bite point wanders | Old fluid / micro air under heat | bleed |
| Power fades on descents | Boiling fluid or glazed pads | bleed + pads |
| Honking / howling | Contaminated or glazed pads | new pads, clean rotor |
| Pump-up (lever firms mid-descent) | Overfilled system or old DOT | bleed to spec |
FAQ
Can I just top up instead of bleeding?
Top-ups replace volume, not fluid condition. Water and debris stay in the caliper where the heat is. A proper bleed pushes everything through.
My lever feels fine. Skip the yearly DOT bleed?
Feel tells you about air, not water. DOT with two seasons of absorbed moisture feels perfect in the car park and boils on descent five. Calendar wins.
Rotor is shiny and blue. Problem?
Blueing means it got seriously hot at least once. Check thickness against the stamped minimum; if it's above and runs true, ride on. If it pulses or is below minimum, replace.
Loam remembers your last bleed
Calendar clocks for bleeds, wear tracking for pads and rotors (front and rear, e-bike-aware), all reset independently. Free, no ads, private.
