Mechanical disc brake: setup and maintenance

Why mechanical disc?

A mechanical disc brake uses a cable (like a V-brake) to actuate a caliper that clamps a disc. It is simpler than a hydraulic system: no brake fluid, no bleeding, no hoses. In return, the power is slightly lower and modulation is less refined.

You find it on entry-level gravel bikes, hybrid bikes, touring bikes, and some mountain bikes. The reference models: TRP Spyre (dual-piston mechanical — the best on the market), Avid BB7 (micro-adjustable), Shimano BR-M375 (basic but reliable).

Caliper centering

A misaligned caliper rubs. The disc touches one pad continuously, which brakes, wears the pads, and makes noise.

Visual method

1. Loosen the 2 mounting bolts on the caliper (5 mm Allen) — just enough so the caliper can slide laterally
2. Squeeze the brake lever fully and hold it (with a zip tie or elastic band)
3. Tighten the mounting bolts alternating: 1/4 turn on the left, 1/4 turn on the right, and so on up to 6-8 Nm
4. Release the lever and spin the wheel. The disc should no longer rub

Advanced method (by eye)

If the above method is not enough (bent adapters, poorly machined frame):

1. Remove the wheel
2. Loosen the caliper bolts
3. Insert a business card between the disc and the inner pad (fixed side)
4. Insert a second card between the disc and the outer pad (moving side)
5. Reinstall the wheel and tighten the caliper bolts to 6-8 Nm
6. Remove the cards. The gap should be equal on both sides

Cable tension adjustment

Too loose = no braking. Too tight = the pad rubs constantly.

1. Loosen the cable anchor bolt on the caliper
2. Pull the cable by hand to tension it
3. Tighten the cable bolt to 5-6 Nm
4. Check: lever travel should be about 1/3 of total travel before the brake bites. Fine-tune with the barrel adjuster on the lever

Tip for TRP Spyre / Avid BB7: these models have adjustment dials on the caliper in addition to the lever barrel adjuster. This allows much finer tuning. Turn 1/4 turn at a time.

Pad replacement

Mechanical pads wear faster than hydraulic ones (less clamping pressure, so the contact area compensates). Check wear every 500-1,000 km.

1. Remove the wheel
2. Remove the retention pin or clip holding the pads
3. Slide the pads out of the caliper
4. Check thickness: if the friction material is less than 0.5 mm (roughly the thickness of a credit card), it is time to replace
5. Insert the new pads — watch the orientation! The friction material must face the disc
6. Reinsert the pin
7. Re-centre the caliper (see above)

Organic vs sintered

• Organic (resin): more progressive braking, quieter, wears faster, better for dry conditions
• Sintered (metallic): more powerful, more durable, noisier, better in rain and mud

When to upgrade to hydraulic?

Mechanical disc brakes work perfectly well for gravel, city cycling, and touring. But if you want:

• More power with less lever effort
• Finer dosing (modulation)
• No regular cable adjustment

... then hydraulic is worth the investment. The switch requires new levers + calipers + hoses + brake fluid. Budget 150-300 EUR in parts depending on the range.

To find the compatible pads for your caliper or the exact torque spec for the mounting bolts, L'Atelier retrieves this info from technical documentation in seconds.