The brakes are the most important safety component on a motorcycle. Yet they often only get attention when they squeal or the lever goes soft. You can check your motorcycle brakes without tools in a few minutes. Here's what to look for in pads, discs and brake fluid, and when the workshop should take over.
Checking the brake pads
Look into the caliper from the front or below. You can see the two pads on either side of the disc. Many pads have a wear groove in the middle. If it is no longer visible or only about 2 mm of pad is left, new pads are due. Always replace both sides of an axle, so all four front pads on a twin-disc setup.
Warning signs of worn pads:
- Metallic grinding or squealing when braking.
- Noticeably longer braking distance.
- Scoring on the brake disc.
Checking the brake discs
Every disc has a minimum thickness stamped on it, usually as "MIN TH" with a value in millimetres. Use a calliper gauge to check the disc is still thicker. Deep scoring, blue discolouration from overheating or cracks are reasons to replace it. If the lever pulses when braking, the disc may be warped.
Brake fluid: why it has to be changed every two years
Brake fluid is hygroscopic, it absorbs water from the air. Every percent of water lowers its boiling point. New DOT 4 fluid only boils at about 230 °C. With around 3.5% water, the so-called wet boiling point is only about 155 °C.
Why that matters: on long pass descents or after several hard stops the fluid gets very hot. If it boils, vapour bubbles form. Vapour can be compressed, the lever suddenly goes all the way to the bar and the brake barely works. That's why manufacturers and the German automobile club ADAC recommend a change every two years at the latest, regardless of mileage.
- Colour: new fluid is light and clear. If it turns dark brown, it's old.
- Level: if it drops, the pads are often worn. Don't just top up, find the cause.
- Type: only use the type stated on the cap or in the manual. DOT 4 and DOT 5.1 can be mixed, silicone-based DOT 5 cannot.
Changing and bleeding isn't rocket science, but it needs care. Air in the line is dangerous. If you're unsure, let a workshop do it.
Brake lines and levers
Rubber brake lines become porous over the years. Check them for cracks, bulges and damp spots at the connections. Braided steel lines last longer, but they shouldn't chafe either. The brake lever should have a clear pressure point. If it becomes spongy or can be pumped up, there is air in the system or the fluid is too old.
Warning signs: straight to the workshop
- The lever goes almost to the bar.
- The brake pulls to one side or judders badly.
- Brake fluid is leaking.
- The ABS warning light doesn't go out after moving off.
How to brake correctly in an emergency is explained in Emergency braking on a motorcycle.
Summary
You can check pads and discs yourself at a glance, and change the brake fluid every two years. Stick to that and you'll have brakes you can rely on even on a long pass descent. The other points before the season are in the spring check.
Frequently asked questions
How often should motorcycle brake fluid be changed?
Every two years at the latest, regardless of mileage. If the fluid is dark, sooner.
When are brake pads worn out?
When the wear groove is no longer visible or only about 2 mm of pad is left. Grinding noises are a clear warning sign.
Can I mix DOT 4 and DOT 5.1?
Yes, both are glycol-based. Silicone-based DOT 5 must not be mixed. Always use the type stated in the manual.
Why does the brake lever go soft on long descents?
Usually the brake fluid has overheated and formed vapour bubbles. Old fluid with a lot of water boils sooner. Stop, let it cool down and have the fluid changed.
Sources
- Changing or topping up brake fluid (ADAC, German)
- Changing motorcycle brake fluid (Motorrad Online, German)
- Getting your motorcycle ready for the season (ADAC, German)
Last checked: September 2026. The information in your motorcycle's owner's manual applies.