What Size Is A Brake Bleeder Screw?

Are you bleeding your brakes for the first time? You might have several questions such as “what size is a brake bleeder screw?” or “how does a brake bleeder screw work?” We will answer all such questions in the article below.

A brake bleeder screw is exactly how it sounds – it enables bleeding in the hydraulic system. However, it is important to learn about the concept of bleeding your brakes before carrying out the task yourself. 

Learning the size of a brake bleeder screw is one of the top requirements before you step into the process of grasping the concept of the role of brake bleeder and screw and its purpose in opening the brake system of your vehicle. 

In this article, we shall discuss the same, and we hope that it will help you carry out the simple process of bleeding brake all by yourself. 


What Size Is A Brake Bleeder Screw


What Is a Brake Bleeder Screw?

A brake bleeder screw also referred to as a bleed screw, is a device used to open the hydraulic brake system in a vehicle. 

The purpose of opening the otherwise closed system is to allow the old fluid, air,  or any other unwanted substance to get out of it through the pressure created with the help of the bleed screw. 


You might like to read: Can’t Build Pressure When Bleeding Brakes – What to Do?


How Does the Brake Bleeder Screw Work?

Applying brake bleeder screw work isn’t a complicated process. You need to apply brake pressure, loosen the screw, and raise its end, which allows the fluid or air to pass into the hole at the bottom and through the screw out of the hole on the top. 

Remember that the bleeder should be at the top of the air, or fluid will never get out. If the valve remains at the bottom, the air will not come out on top and won’t get out. 

Another thing to remember is that you should slightly loosen the screw (about ¼ of a turn), and not all the way, to allow the same pressure that would help the fluid or air pass through. So, these are one of the few things to know if you are using the brake bleeder screw by yourself. 

What Size Is a Brake Bleeder Screw?

The standard size of a brake bleeder screw is 5.16 inches x 3.8 inches. However, the perfect screw for your vehicle is the one that allows room for maximum movement. The standard size brake bleeder screw works in most cases, even for bikes and scooters. 

If you plan to bleed the system yourself, you can loosen the brake bleeder screw on the caliper/cylinder and leave it for about an hour or more. 

Once an hour is over, you can remove the screw and top off the master cylinder. Now, do the same on the other break. 


What Size Is A Brake Bleeder Screw


If you wonder how the brake bleeder screw works on the system, it is simple. When you loosen the bleeder screw on the caliper, it purges the air to the top and out of the system. After this, the fluid changes follow. 

When you loosen the bleeder, the air naturally rises to the top of the fluid in the caliper (or gets there via pressure on the brake or compression) and flows out of the system. 

There is also a brake bleeding kit available in the market that needs no special training. Its equipment includes a pump, a reservoir, and a few lengths of tubing. The pump forces air out of the brake lines to get the air bubbles out. It is a good way to practice the process of enabling bleeding in the system. 


You might like to read: What Size Tubing For Bleeding Brakes


Frequently Asked Questions

#1. What size is a brake bleeder screw?

A standard screw is of the size 5.16 inches x 3.8 inches


The standard size of a typical brake bleeder screw is 5.16 inches x 3.8 inches. However, it is recommended to go for the screw that is the best suitable for your vehicle. You can consult an expert or your vehicle’s manufacturer to find the brake bleeder screw that fits well with your vehicle. 

#2. What size wrench is needed for a brake bleeder valve?

Typically an 8mm or 10mm wrench should do the trick.


The perfect size wrench needed for a brake bleeder valve is 8 mm or 10 mm. However, you can use a wrench of any given size to bleed air from the brake cylinders, and you will need the help of bleeder screws to perform the task. 


What Size Is A Brake Bleeder Screw


#3. What size is a brake bleeder hose?

3/16 x 5/16 inches


Not many people know that you can use a hose to bleed brakes. Typically, you should use the size 3/16 inches by 5/16 inches brake bleeder hose to get the job done. You can also consult an expert or experienced person in the field to get the right size of hose for your vehicle. Once you start with the process of bleeding the brakes, you will need to attach the hose to the bleed screw and open it up. You will soon see that the air bubbles or liquid will smoothly flow out.

#4. Can you bleed drum brakes without using a bleeder screw?

Yes, you can.


Yes, you can bleed drum brakes without using a bleeder screw. If your bleeder screw is rusty and old, you can follow a simple process where the tool isn’t needed. Start at the brake that is nearest to the master cylinder. Be sure that the master cylinder is at the maximum gauge and remove the old and unwanted fluid from the cylinder while replacing it with the new one.

#5. What thread are brake bleeder screws?

Typically 7 or 8mm thread.


The thread size of the brake bleeder screws is usually around 7 or 8 mm. The standard size of a brake bleeder screw is 5.16 inches x 3.8 inches, and you can find the one that suits the needs of your vehicle the most. 


You might like to read: Should I Open Brake Fluid Reservoir When Changing Brakes?


A Few Final Words

Bleeding brakes are usually simple and can be done by the vehicle owner. It is mostly a DIY process, and many people even enjoy doing it from time to time. 

However, if you are a first-timer, you should go through the rules of handling the work well and follow the safety precautions. Read, learn and understand the entire concept of brake bleeding and the way it works. 


What Size Is A Brake Bleeder Screw


If you aren’t confident about the process, it is probably best to let an expert or an experienced person handle it for you. You can watch them complete the task, keep it a learning experience, and carry the work by yourself next time. 

Thank you for reading, we hope we answered all your questions. If you still have doubts, drop us a word in the comments section below and we will get back to you with an answer as quickly as we can.

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Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

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