Replacing brake pads or a brake disc

A fatbike is heavy and fast — which is precisely why the brakes deserve more attention than they usually get. This guide helps you determine when brake pads or the brake disc are due for replacement, which size you need and what to watch out for when fitting.

When to replace? The wear indicators

Brake pads

• There is less than about 1 mm of brake lining (friction material) left on the metal backing plate.
• The brake squeals or grinds persistently, even after cleaning the disc.
• The brake lever has to be pulled further and further for the same braking effect.
• The lining is smooth/glazed or worn unevenly (at an angle).

Brake disc

• The disc is thinner than the minimum thickness the manufacturer has stamped on the disc (often around 1.5 mm).
• Deep grooves, blue discolouration (overheating) or a visible warp (wobbling between the brake pads).
• Oil or grease on the braking surface that can no longer be cleaned off.

Measuring the disc size: 160 or 180 mm

Fatbikes typically use brake discs of 160 mm or 180 mm diameter. Here's how to determine the size:

• Using a ruler or tape measure, measure the full diameter of the disc, straight through the centre (centreline of the hub): outer edge to outer edge.
• If you measure about 16 cm, it's 160 mm; about 18 cm is 180 mm.
• Replace with the same size. A different disc size requires a different adapter position for the brake calliper and is not a direct swap.
• Also note the mounting: most fatbikes have a 6-bolt disc; check this on your wheel.

Mechanical or hydraulic?

• Mechanical disc brakes are operated with a cable. Easy to adjust yourself, and pads are relatively easy to replace.
• Hydraulic disc brakes work with brake fluid: more braking power with less hand effort and self-adjusting pads. Maintenance such as bleeding requires more knowledge and tools.

Many hydraulic fatbike brakes work with mineral oil. When topping up or bleeding, use only the fluid your brake system specifies: mineral oil and DOT brake fluid are not interchangeable, and the wrong fluid damages the seals. Important for both systems: brake pads come in dozens of shapes that differ per calliper model. So never order "by eye", but match the model against the specifications.

Bedding in new pads

New brake pads (and a new disc) only deliver full braking power after bedding in, during which a thin layer of brake material is transferred onto the disc:

• Find a quiet, flat spot with no traffic.
• Accelerate to a moderate speed and brake firmly but in a controlled way to almost a standstill — without locking up and without coming to a complete stop.
• Repeat this 10 to 20 times per brake; you'll feel the braking power increase each time.
• Don't touch the braking surface of the disc and pads with bare hands; skin oils reduce braking performance.

On the first rides after replacement, brake deliberately earlier and more gently: full braking power only arrives after bedding in.

Quick step-by-step plan

• 1. Assess the pads (lining thickness) and the disc (thickness, grooves, warp).
• 2. Measure the disc diameter (160 or 180 mm) and check the mounting (6-bolt).
• 3. Determine which calliper model you have and choose the matching pads — compare this with the specifications.
• 4. Fit cleanly and to the correct torque, or have it done by a bike repair shop.
• 5. Bed in the new pads before you take to the road.

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