Hydraulic disc brakes have transformed the way we ride, offering remarkable stopping power and improved control on the road.
However, there are times when these brakes can experience a loss of pressure. And as a cyclist, you know how important it is to have reliable brakes on your bike.
The main reason why hydraulic disc brakes have no pressure is because there is air in the braking system.
In this article, I’ll break down all the reasons behind hydraulic disc brakes no pressure and show you how to bleed your brakes.
No Pressure in Hydraulic Disc Brakes – Causes
The most likely reason why there is no pressure on hydraulic disc brakes when braking is due to the presence of air in the brake system.
Most hydraulic disc brake systems will take in air as time passes.
Also Read: Disc brake vibration
Air can also enter the system through other means, such as improper bleeding, a damaged or worn-out seal, or a leak in the hydraulic lines.
When air gets trapped within the brake system, it creates a compressible effect.
Unlike the hydraulic fluid, which is incompressible, air can be compressed, leading to a soft or spongy brake lever feel and a noticeable reduction in braking power.
This is often referred to as “brake fade” or “brake mush”.
Some of the other reasons for hydraulic disc brakes no pressure include:
Leaks in the Brake System
Leaks in the brake lines or calipers can allow hydraulic fluid to escape from the system.
As the fluid leaks out, it reduces the overall pressure within the system, leading to a loss of braking power.
Worn-out seals, damaged hoses, or loose connections can be the culprits behind these leaks. If the seals wear out over time or become damaged, they may fail to create a proper seal, allowing fluid to escape.
Similarly, damaged hoses or loose connections can result in fluid leakage.
Also Read: Bike brake not releasing
Other Reasons
Worn-out brake components, such as worn brake pads or excessively worn rotors, can result in reduced braking performance and a loss of pressure.
As the pads and rotors wear down, the surface area available for effective braking decreases, leading to a diminished braking force.
Similarly, a misaligned caliper can cause uneven pad-to-rotor contact, resulting in inconsistent braking power and a potential loss of pressure.
How To Fix Hydraulic Disc Brakes No Pressure
The solution to your pressure-related hydraulic braking problem is to bleed your bike’s braking system to eliminate air.
Here’s a step by step DIY guide on how to bleed your bike breaks:
Step 1: Gather the Necessary Tools and Materials
Before you begin, make sure you have the following tools and materials ready:
- A bleed kit specific to your brake system (usually available from the brake manufacturer)
- A set of Allen wrenches or Torx keys (depending on your brake caliper)
- A small plastic catch bottle or container to collect brake fluid
- Clean rags or paper towels
- Isopropyl alcohol or brake cleaner (optional, for cleaning)
- A pair of gloves (to protect your hands)
Step 2: Position Your Bike
Find a suitable location to work on your bike. Ideally, choose a clean and well-lit area where you can comfortably access the brakes and work without any distractions.
You may want to use a bike stand or prop your bike up securely.
Step 3: Remove the Wheel
To access the brake caliper and brake lever more easily, start by removing the wheel from the bike.
Also Read: Why Does My Tire Keep Popping
Loosen the quick-release lever or unscrew the thru-axle, depending on your bike’s setup.
Gently slide the wheel out of the dropouts and set it aside in a safe place.
Step 4: Prepare the Bleed Kit and Brake Fluid
Follow the instructions provided with your bleed kit to prepare it for use. This usually involves attaching the syringe, tubing, and fittings correctly.
Make sure the bleed kit is ready, and have the appropriate brake fluid for your brake system on hand.
Common brake fluids include DOT (e.g., DOT 4 or DOT 5.1) or mineral oil (for some brands).
Step 5: Open the Bleed Port
Locate the bleed port on your brake lever. It is usually a small screw or cap on the top or side of the lever assembly.
Use the appropriate Allen wrench or Torx key to loosen and open the bleed port.
Be careful not to overtighten or strip the screw.
Step 6: Attach the Bleed Kit
Connect the syringe from your bleed kit to the bleed port on the brake lever. Ensure a secure fit, making sure the tubing is properly attached and won’t come loose during the process.
If necessary, consult your brake manufacturer’s instructions for specific attachment details.
Step 7: Prepare for Fluid Collection
Position the catch bottle or container beneath the brake caliper to collect the brake fluid that will be expelled during the bleeding process.
This prevents any spilled fluid from damaging your bike or the surrounding area.
Step 8: Begin the Bleeding Process
Starting at the brake lever, gently squeeze it a few times to remove any excess air and ensure the brake caliper is ready for bleeding. Next, slowly pump the brake lever a few times and hold it in a partially squeezed position.
With the lever held, open the bleed port on the caliper slightly to release any trapped air or contaminated fluid.
Close the bleed port once the lever feels firm.
Step 9: Repeat the Bleeding Process
Continue the bleeding process, gradually moving down to the brake caliper. Repeat the steps of squeezing the lever, opening the bleed port, and closing it once the lever feels firm.
Monitor the fluid level in the syringe and ensure that air bubbles are not being reintroduced into the system.
Step 10: Finalize the Bleeding Process
Once you’ve bled the brake lever and caliper multiple times and there are no more air bubbles in the brake fluid, close the bleed port on the caliper and disconnect the bleed kit.
Clean any spilled brake fluid using isopropyl alcohol or brake cleaner and wipe the surrounding areas with a clean rag or paper towel.
Double-check that all connections are tight and secure.
Step 11: Reinstall the Wheel and Test the Brakes
Put the wheel back onto the bike, making sure it is securely attached. Tighten the quick-release lever or thru-axle according to the manufacturer’s specifications.
Once the wheel is in place, test your brakes by gently squeezing the lever.
Always make sure that the lever feels firm, and the brake pads engage the rotor smoothly.
Bottom Line
If you’re experiencing no pressure in hydraulic disc brakes, it’s because there is air in the brake system.
By bleeding your hydraulic disc brakes, you can remove the air bubbles and contaminants from the brake system which will restore proper pressure.
FAQs
Shimano Hydraulic Disc Brakes No Pressure?
Shimano hydraulic disc brakes will lose pressure if there are air bubbles in the brake lines, insufficient brake fluid, leaks in the system, or issues with the brake caliper or master cylinder.
Is It Safe To Ride If There Is No Pressure In Hydraulic Disc Brakes?
No, it is not safe to ride a bicycle if there is no pressure in the hydraulic disc brakes. If disc brakes have no stopping power you run the risk of accidents and injuries.
