Single piston vs. dual piston master cylinders.

Before I can answer the question of how to mount a master cylinder, I have a couple other things that I want to discuss

Which master cylinder should you purchase, and why there’s differences in different master cylinders.

So if you’re going to purchase a master cylinder and you are running a streetcar and it’s, and it’s a heavy street cart. We will need four pistons in the rear and four pistons up front to provide enough stopping power. 

If we’re building a lightweight Top sportsman or Promod drag car, we will install a single piston upfront and a dual piston in the rear.  We are choosing our brake system setup according to the weight of the car.  Up to 2800 lbs we recommend a single on the front and a dual on the rear.  ANything above that we will install a dual piston on the front and a dual on the rear.

Master cylinder bore size

Master cylinders have different bore sizes; you may see one that says 1-1/32” bore one that says 1-1/8 bore. Well, that’s where this comes in. If you, if you’re running a four piston in the front and a four piston in the rear, then common sense says you’re going to want. 1-⅛” bore because you need more pressure for this dual four piston caliper setup. The 1-1/32  would be the single in front and the dual piston in the rear set up. 

Where to mount a master cylinder

Now that we have figured out what size master cylinder we need, where do I mount the master cylinder?  Let’s say that you already have your pedals mounted in the car and we need to figure out what height to mount the master cylinder 

There’s an easy formula which will give you the correct height. Your master cylinder company is going to list a ratio of usually a 5:1or a 6:1 pedal ratio.  There are other ratios as well, but that is the usual range and the formula works with whatever ratio is called for.  

First you measure the height of your pedal from the center of the shaft to the center of the brake pedal.  Then we divide that number by the pedal ratio.  

So let’s say the distance between the center of the pedal saft and the brake pedal is 8 inches and our pedal ratio is 5.5:1.  We divide 8” by 5.5 and we get 1.45.  So we know that the master cylinder needs to placed 1.45” above the pedal shaft to give us our correct pedal ratio.  Which is going to give us really good braking and the proper braking listed by the manufacturer of the master cylinder. Giving us proper brake pressure from the master cylinder, to each caliper in your brake system.  

If we mount the master cylinder too high, the brake pedal is going to be too soft. If we mount the master cylinder too low the brake pedal is going to be too hard. We’re not going to get any brake pressure if we mount too high or too low. 

So let’s say in a typical brake system, we should be able to have a 1000 to 1500. PSI in our brake pressure system. So if I’m up too low or too high we might get 300 to 400 PSI.  That’s  nowhere near enough brake pressure to stop your race car creating a serious safety issue. So it’s very important that we get this correct ratio right.

Proper master cylinder mounting

Now, one thing that I want to point out is that you can’t, you can’t mount your master cylinder through the upright of the pedal.  This will not work because as this is pushing forward, you have no leverage on it.  What you do want to do is you want to have a piece of tubing that’s welded right to the front of the pedal upright, and that is where your heim will attach to the master cylinder rod.  Now, you also want to make sure that this rod is level.  We don’t want to have it all the way mounted to the very top and then as we’re trying to push this pedal forward, it’s trying to lift it up even more. So make sure that the master cylinder rod is level, when you’re mounting.