Brake Maintenance

Everyone checks pad thickness. Fewer people understand why a spongy lever survives a bleed, why glazed pads aren't actually worn out, or why brake fluid needs replacing on a schedule even if you never touch the lever.

Pads: thickness isn't the only thing that goes wrong

• Check thickness regularly — most pads have a minimum marked, but as a rule of thumb, less than 1mm of friction material left means replace now.
• Mud and sand accelerate pad wear a lot faster than road riding — check more often than the manual suggests if you ride wet or sandy terrain often.
• Glazed pads look worn but aren't. Repeated hard braking, or dragging the brake lightly on a long descent, can overheat the pad surface into a smooth, shiny glaze that grips poorly no matter how much material is left — that's why a lever that "went soft on the way down the hill" often has plenty of pad thickness. A light pass with sandpaper to break the glazed surface restores bite; if it keeps happening, the pad compound may be too soft for how you ride.
• Bed in new pads gently for the first few stops — grabbing hard immediately glazes them before they've even worn in.

Discs

• Look for deep grooves, warping, or a blued colour (a sign of serious overheating, often from dragging a brake or a stuck caliper piston).
• A warped disc shows up as a pulsing brake lever/pedal, not just at high speed but even braking gently — that pulsing is not "normal", replace it.

Fluid: why it needs replacing even if it "still works"

DOT brake fluid is hygroscopic — it actively absorbs moisture from the air, even through a sealed system, over months. That absorbed water lowers the fluid's boiling point. Under hard, repeated braking (a long downhill, or dragging the rear brake through whoops) the fluid gets hot enough that the absorbed moisture flashes to vapour, and vapour compresses — that's what a spongy lever actually is, and it's why bleeding out air doesn't fix it: there's no air in there, just water-contaminated fluid that needs replacing outright, not bleeding.

• Change fluid at least once a season, more often if you ride hard or in wet conditions.
• Never top up old DOT3/DOT4 fluid with DOT5 — DOT5 is silicone-based and doesn't mix with glycol-based DOT3/4, and can damage seals not designed for it. Stick to what your system already uses.
• Check the fluid level regularly; a dropping level usually means the pads are wearing (normal, the caliper pistons extend to compensate) — but check for leaks too (not normal).

Bleeding without introducing more air than you remove

• Keep the reservoir topped up throughout — let it run dry mid-bleed and you'll pump fresh air straight back into the line you just cleared.
• Work from the caliper bleed nipple, opening it only enough to let a controlled stream out, and close it before releasing the lever/pedal — releasing with the nipple open draws air back in through the same path.
• Tap the line and caliper gently while bleeding; small bubbles cling to the inside of the hose and won't move on their own.

Warning signs that mean "stop and fix it now"

• A lever or pedal that goes soft or comes further to the bar/floor than usual.
• A grinding noise (metal-on-metal — the pads are gone).
• Any visible fluid leak at the caliper, line or reservoir — brake fluid also strips paint and eats certain plastics, so clean it off immediately if you spill any.