The most common fear bike owners have are failing brake systems. Brake failure can mean a quick disaster for you, especially on those downhill descents. A common reason for brake failure is disc overheating.
So, can a disc brake system overheat? Let’s take a moment to talk about how discs can overheat and what you should do if you notice any signs of disc overheating.
What Are Bike Disc Brakes Made Of?
Let’s first understand your bike’s disc brakes and how these brakes are installed on a bike. A bike disc brake is made up of a metal rotor that gets pressed against two spring pads. This assembly is then mounted to the outside of the fork, and the levers which control this is attached to the handlebars.
How Does a Disc Brake On a Bike Work?
Disc brakes are a relatively simple concept. You have a caliper that houses the brake pads and a disc that runs in between attached to the wheel. The brake pads are controlled by a remote lever that sits on your handlebars. When the lever is pulled, the pads will grip the discs, and in turn, the wheels slow down.
These brakes come in two different types. You get mechanical and hydraulic. Mechanical brakes use a cable to control the pads, you pull the lever and which pulls the cable, and the pads grip the disc.
Then you have hydraulic brakes, which use fluid to push the pads into the disc. You pull the lever. It pushes the fluid down the system and pushes the pads against the disc. Hydraulics are harder to set up but by far the more powerful braking system and is much easier to use.
How Do Disc Brakes Overheat?
Many bikers complain that their brakes get too hot after riding for a while at high speeds down a hill or long descent of any kind. Again, riding your bike in hot weather increases the chances of brakes overheating. When riding your bike, the overheating of the brakes results from too much friction that develops between the brake pads and the brake disc.
This isn’t very common to happen, and typically this would be on an alpine climb or very aggressive descent. You will notice a huge change in performance when they get too hot, but they won’t stop altogether. Typically people notice that the disc is sometimes misshapen after they have stopped. Only in extreme circumstances will they glow.
Related: How to Adjust Brakes On Your MTB
How Hot Can Bicycle Disc Brakes Get?
Disc brakes on a bike can reach temperatures of up to 800 degrees, but this is not enough to be a serious safety concern in normal braking conditions. With most well-designed bikes, the bike frame and the braking system come with built-in cooling and heat sinks, enough to mitigate the overheating potential.
What Should I Do If My Disc Brakes Are Overheating?
First of all, if you notice any signs of intense heat coming from your brakes, you should immediately slow down. If this continues and they don’t work, you need to check your discs and pads are not contaminated and are still useable within the manufacturer’s range.
Can Disc Brakes Overheating Cause Braking Failure?
When your bike’s brake pads and rotors overheat, they can transfer the excessive heat to the bike’s brake fluid via the caliper piston. This results in a density change in the fluid and can cause the water in the old fluid to boil. Once this happens, the fluid loses its compression ability slightly, thus reducing braking efficiency.
How to Cool Down My Hot Rotors?
If your brakes get too hot, you need to stop and let them cool down by themselves. Putting cold water on them isn’t a great idea. Shaking your bike around won’t make much difference. All you want to do is let them cool themselves. If not, you can damage them further.
What To Do When Brakes Overheat
When your bike’s disc brake overheats, you should reduce your speed and apply the brakes as gently and evenly as possible. To prevent future heart problems, you should consider getting your brakes serviced or checked for faults and even consider upgrading to a larger set of discs and brake pads.
Should My Bike’s Brake Fluid Boil?
Bike brake fluid doesn’t boil. What boils is the water that’s dissolved in the brake fluid if you’re using grubby old oil. You will need to see a mechanic if this is happening and get it looked at and fixed as soon as possible.
When Should I Replace My Brake Pad?
Over time, the brake pads on your bike will wear down. This is why it is important to make sure that you inspect them regularly to make sure that they are still moving smoothly and not creating excessive heat.
If you notice that your disc pads are worn or damaged, be sure to change the brake pads right away. At the same time, be sure to inspect the rest of your disc brakes as well to make sure everything else is in good shape.
All said, bike brakes are not a serious safety concern, and the high temperatures they reach DO NOT pose a safety threat as it does not impact braking power. If you are riding your bike on a steep hill descent, the kinetic energy build-up is an ok reason for temperature rise on the brakes. Once you slow down, the brakes cool off naturally.
But as always, be the best judge and regularly inspect your bike’s braking system to ensure that any heat build-up is not from unnatural causes.