Because we prefer to have a booster we need to have more calculations.

I have decided to use MITSUBISHI GALANT V Master Cylinder with 1” diameter.

This will pump enough brake fluid to those big Jaguar Calipers.

Big MC will move more fluid but will produce less pressure for the same amount of force at the feet.

The pedal travel will be shorter and that is what I like a firm pedal. But it will be more progressive because the clamping pressure is lower.

So you will have here more feeling at you feet.

But we need a booster to help us with some force. We don’t need a huge booster but just enough to help us.

So we continue with the calculations on sheet 2, but we use the collected information from sheet 1. (Continue on next page)


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The AC Cobra Replica Site

People that have visited this page from 20-Dec.-03

Revised at 14 - June.-2007


-            The Brakes doesn’t stop your car.

-            Your tires will stop the car. Use the best tires that you can afford.

-            It is not the vacuum that boost your pedal force, but the atmospheric air pressure.


If you want to improve your car brakes performance, start by:



You want pads that have the highest “friction coefficient” at every temperature. Never use a "Hot Brake Pads” on the road, these will never work for the normal street use, because they never will get on the working temperature, they are for circuit use only,



You want to maximize the brake power at the rear wheels. The force at the rear wheels should be maximum, and should be stop just before the tires start to lock, this would be the best setup.

I have made a spread sheet calculation to determine the BRAKE PEDAL RATIO that I need on my AC Cobra Replica.


Black cells are variables (Input figures) the rest are calculated according the formula.

First we calculate a system with dual master cylinder.

One for the front calipers and the other for the rear calipers. We will need to use two different size of MC to adjust the balance.

Using this method you can size the front “master cylinder” (MC) and select at the rear a bigger one (less pressure). Via this way, we don’t need to have a “proportional valve” because the ratio front to rear is defined by the two different sized MC.

But this system would not fit every Cobra and you don’t have a “Booster” so, your pedal force will be a bit higher.


The conclusion with this first method is:

You need a Pedal ratio of 6.25 and you feet force should be 35 kg.

Because this will be difficult task on the AC Cobra (SPACE)I have decided to use the standard Booster/Master cylinder combination.


See the calculations bellow.