I freaked out the first time when my motorcycle front brake locked up.
Fortunately, rear brake was working fine.
Still, brakes locking up is a nuisance.
It can be more frustrating if the disc starts meshing with the front wheel or worse, the front wheel stops moving and, in the process, completely halts your bike.
So, what to do when motorcycle brakes lock up? First, check the master cylinder reservoir, brake lever, brake fluid and the caliper.
Next, if brake fluid is old, replace it with a new one. Adjust the brake lever to provide enough free play. Remove the excess fluid in the caliper, if any.
And finally, clean the holes of master cylinder reservoir if they are clogged up.
Let’s deep dive into these action steps along with the reasons for motorcycle brakes locking up.
Why do motorcycle front brake locks up? Reasons
Here are the reasons why a motorcycle front brake locks up:
- Clogged-up hole in the master cylinder reservoir
- Excess brake fluid in the caliper
- Brake fluid is old
- Brake lever has insufficient free play
Before going into the details of the reasons for front brake locking, we need to have a basic understanding of how the front brake mechanism works.
Whenever you apply the front brake by pulling in the brake lever on the right, you are essentially applying pressure to the disc located in the front wheel.
The front-wheel braking is a disc brake system wherein the brake pads arrest the movement of rotating discs that are attached to the wheels.
As opposed to directly arresting the wheel movement just like the rear brake.
(Nowadays both front and rear wheels have disc brakes. But earlier rear brakes sued to have drum brakes, which are different from disc brakes.)
As you pull in the lever, the brake fluid from the master cylinder reservoir passes down the pressure all the way to the pistons located in the caliper.
The brake fluid pressure on the piston makes the component move towards the disc.
The brake pads which are attached to the piston come in contact with the disc. Then stop the disc. Which stops the wheel attached from moving further.
That’s the simplified version of the front brake mechanism.
Let’s now deep dive into the causes of front brake lock-up.
#1. Clogged up hole in the master cylinder reservoir
Inside the master cylinder reservoir, typically you will find two holes.
These two holes are significant for the movement of brake fluid. Especially the smaller hole which is responsible for the return of the fluid that is released when you apply the brakes.
If these holes get clogged, the brake fluid movement won’t be smooth and the braking will become difficult.
The smaller hole, if clogged up, can be very problematic as it will prevent the fluid from returning and as a result, you will see the front brake lever not returning as well.
#2. Excess brake fluid in the caliper
This situation can arise whenever you have applied harsh or panic brakes.
When you pull in the brake lever a bit too harshly, excess brake fluid would have released from the master cylinder into the caliper.
Accordingly, this excess fluid creates additional pressure which results in the caliper pistons not retracting back completely.
The brake pads will be in a semi-engaged situation and consequently, the brakes are still being applied on the disc.
In this situation, all you need to do is remove the excess fluid from the caliper system.
Once the excess fluid has been removed, the pressure eases off and the brake pads will release the disc and the brake lever will ease back simultaneously.
#3. Brake fluid is old
Another possible reason why your motorcycle’s front brakes are locking up could be because you have not changed the brake fluid for a long time.
If the brake fluid in your motorcycle is too old, more than two years old, then most possibly the braking fluid is the culprit here.
Here is a detailed post on how often should you change the brake fluid in a motorcycle.
The old brake fluid won’t function properly and will not provide optimal performance in braking.
So, all you need to do here is to replace the old brake fluid with a new one.
#4. Brake lever has insufficient free play
Although this might not be as common, if the front brake lever has insufficient lever movement for free play, it could cause the front brakes to lock up.
If there is insufficient free play for the brake lever, there is a high chance that this condition has resulted in a blocked return port.
You need to add some more room for movement to the brake lever and check whether the lock-up has been resolved.
What happens when motorcycle brakes lock up?
Now that we know the causes of the front brake locking up, let’s look into the symptoms and effects of this lock-up on a motorcycle.
These effects of brake lock up include:
- Disc brakes get jammed
- Front wheel will not rotate freely
Disc brakes get jammed
When there is excess pressure built up in the caliper, the caliper pistons exert force on the brake pads which in turn, will try to halt the disc.
As a result, whenever you ride with a locked-up front brake, you will feel the disc brakes jamming up, preventing the easy movement of the motorcycle.
Front wheel will not rotate freely
This is an extension of the previous condition.
When the disc brake is forced to slow down or stop due to the semi-engaged position of the brake pads, the movement of the front wheel will obviously not be smooth.
The uneven braking will eventually result in the front wheel not able to rotate freely. Thereby halting the motorcycle ride.
Things you need to do when motorcycle brakes lock up
Here are the things you need to do when your motorcycle’s front brakes are locked up.
- First, locate the root cause of the lock-up. Check each of the related components – master cylinder reservoir, brake lever, brake fluid, and the caliper, one by one.
- If the brake fluid is old, i.e. more than 2 years old, change the fluid. Replace the old brake fluid with a new one.
- If there is not enough free play for the front brake lever, adjust the cable to give some more free movement for the lever to move easily.
- If there is excess fluid in the caliper that is pressurizing the brake pads to a semi-engaged position, attach a small pipe to the caliper to remove the excess fluid. Slowly unscrew the nut and the fluid will flow out to the pipe. Once removed, tighten the nut back. That should resolve the brake locking situation.
- For clogged holes in the master cylinder reservoir, use a small wire to unclog the hole. Once cleaned, the holes in the master cylinder reservoir will function properly and will automatically unlock the front brake.
Preventive Measures
In order to prevent the motorcycle front brake from locking up, you can follow certain preventive measures.
First, change the brake fluid regularly in your motorcycle. A thumb rule is to change the brake fluid at least once in 2 years.
Next, while changing the brake fluid, do not fill the new fluid to the maximum.
Fill it slightly below the maximum possible, so that there is no excess fluid pumped into the caliper pistons.
Lastly, regularly check for clogged holes in the master cylinder reservoir and ensure enough free play in the brake lever whenever you are adjusting them.
Summing Up
The main reasons why the front brake of your bike is locked up is because of:
- Clogged-up hole in the master cylinder reservoir
- Excess brake fluid in the caliper
- Brake fluid is old
- Brake lever has insufficient free play
The effects of front brake lock-up include: jammed disc brakes the and front wheel not rotating freely
Here are the things you need to do when the motorcycle front brakes are locked up –
- Solution #1: Unclog the holes of the master cylinder reservoir.
- Solution #2: If the brake fluid is old, replace it.
- Solution #2: Adjust the front brake lever to provide enough free play.
- Solution #3: Remove any excess fluid in the caliper.
To prevent the front brake lock-up, ensure that brake fluid is changed regularly – once in 2 years, and while changing the fluid, fill it slightly below the maximum.
Before you go…
Here are a few more mtorocycle brake related posts for you:
- Different brake fluid types
- When to replace brake fluid, brake pads, and disc rotors