Let’s talk about booster pin depth and why it’s important. The booster pin depth, which is often overlooked when installing a new master cylinder, can drastically affect the comfort and efficiency of your driving experience. We’ll discuss symptoms of improper depth and how to properly set it.
A brake booster pin, also known as a brake push rod, works as you press the brake pedal with your foot. The booster pin extends into a piston in the master cylinder to initiate the braking process.
Booster Pin Depth
The booster pin depth should leave a small gap between the end of the pin and the master cylinder. We recommend the ideal depth of 0.020 inches.
If the booster pin depth is not properly set, you will notice several unpleasant symptoms while attempting to slow or stop your vehicle.
On a manual brake system, you may experience brake drag, an uncomfortable feeling of the brake pedal not releasing as a result of the booster pin pushed up too closely against the master cylinder. Brake drag needs to be repaired as soon as possible, since it can force parts to overheat, damage the braking system, or cause an accident.
Soft Brake Pedal
If the push rod depth is set too long, there will be a delay from the time your foot presses the brake pedal until the brakes engage, causing a soft brake pedal.
SIDEBAR - An example of an unfortunate experience: Imagine a gap of 0.250” between the pushrod at the booster and the back of the master cylinder. With a gap of 0.250” and the pedal ratio 4:1, the brake pedal pad where you actually place your foot to stop will move an entire inch before anything happens. The feeling of a soft brake pedal is not comfortable while driving.
Setting the Booster Pin Depth
It’s easiest to set the depth of the booster pin when you install the master cylinder. We make this process simple with the help of our booster pin depth gauge (AC2003). While using the booster pin depth gauge tool is not a requirement, it does make the job very easy by eliminating the need to take multiple measurements and calculate the correct math.
How to Set Booster Pin Depth
1. Check the piston depth at the master cylinder.
2. Flip the tool and use it to check the depth at the booster.
3. Adjust the pin as needed to set at a depth of approximately 0.020”.
4. Assemble the master cylinder onto the brake booster.
Here is a quick video demonstrating the use of the booster pin depth gauge.
Benefits of Setting the Booster Pin Depth
Eliminate the symptoms of an improper depth setting, including brake drag and soft brake pedal, by setting the booster pin depth to a proper distance. This will make your ride experience much more comfortable, safe, and enjoyable, all while eliminating wear on your vehicle. Setting the depth is easy and accurate with a booster pin depth gauge.