Choosing the correct master cylinder is critical to achieving a properly set up braking system. If you select one that’s too small for the application, you’ll end up with a system that will never generate its optimum braking pressure.

But if you go with one that’s too large you’re going to need to hit the squat machine because applying the brakes is going to require some serious muscle.

We spoke with the folks at Tilton about some of the common concerns that pop up when choosing a master cylinder, and how best to tackle them.

What variables does a car builder need to consider before selecting a master cylinder bore size?

Through our form, there’s a list of the variables we need customers to supply us for making bore size recommendations.  Once we get this information from the customer, we will assign a pedal effort, center of gravity height, tire coefficient and brake pad coefficient to their particular vehicle and type of racing.

Click on the photo to see the full build sheet for our Factory Five Challenge car’s master cylinders.

Is there a mathematical formula that someone can use to simplify selection?

There are formulas, but it is best left to the experts that can use their experience to determine is the recommendations/results from the calculations make sense.  Output from the calculations could be greatly skewed if bad or incomplete information is entered into the formulas. An expert can weigh the output from the calculations against their experience in real world master cylinder sizes that are typically being used in similar applications.

If a car owner was to change rotor diameter, yet keep the same size caliper, would there be a benefit to altering master cylinder size?

Yes, changing rotor diameters can effect which master cylinder sizes to use.  Typically, installing larger diameter rotors will allow the use of larger bore master cylinders.   On the other hand, unless there is a big change in rotor diameters, you really shouldn’t have to change the master cylinder bore size being used on the car.

Would you recommend a serious driver, perhaps a sportsman-level racer, utilize a psi gauge to verify correct master cylinder sizing and pressure at the caliper?

Generally, they are not needed, but they can be a good way to verify and get an understanding of the brake system.  When we do the calculations for customers to suggest master cylinder bore sizes, our program will predict line pressure for the Front and Rear brakes.  We can provide customers with the predicted line pressures and they could use the psi gauge to verify the results.

Drop us a line in the comments if you have any questions about how to choose the proper master cylinder for your vehicle, and be sure to head over to Tilton’s site for additional details.