How to Measure the Size of the Brake Master Cylinder?
May 15, 2025
How to Measure the Size of the Brake Master Cylinder?
Understanding the correct size of your brake master cylinder is essential for vehicle safety and brake performance. Whether you're replacing a Ford master cylinder, upgrading a trailer brake master cylinder, or fitting a custom braking system, measuring the master cylinder correctly ensures compatibility and function.
What Is the Size of a Brake Master Cylinder?
The "size" of a brake master cylinder typically refers to its bore diameter, which affects the volume and pressure of brake fluid delivered to the brakes. Bore sizes are usually measured in inches or millimeters (e.g., 7/8", 1", 25.4mm). 1"=25.4mm.
How to Measure It
Remove the Master Cylinder (If Necessary)
In most cases, you'll need to remove the master cylinder from the vehicle to get an accurate measurement. Be sure to drain any remaining brake fluid safely before removal.
Inspect the Bore Size Marking
Some Top brake master cylinder models have the bore size stamped or cast directly on the body. Look for numbers like “1.00” (indicating a 1-inch bore).
Manual Measurement
If no marking is visible, you can measure the bore directly:
Remove the reservoir (if detachable).
Use a caliper to measure the internal diameter of the cylinder bore.
Make sure to measure at the widest internal point for accuracy.
Check Manufacturer Specifications
If you know your vehicle’s make and model, you can look up the specifications in the service manual or parts catalog to identify the correct master cylinder size.
Why Size Matters
Using the correct size ensures proper brake pressure and pedal feel. For instance, a trailer brake master cylinder must deliver sufficient volume to multiple wheel cylinders or calipers, often requiring a different size than a passenger vehicle master cylinder.
If you really don't know the size of the brake master cylinder, you can consult the brake master cylinder manufacturer KOMP. With 24 years of manufacturing experience , one-year or 30,000 km warranty and 24-hour online service, KOMP has become a trusted name among auto parts retailers.
