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Tech Talk with Master Power Brakes

Selecting the Right Booster/Master Cylinder Combo For Your Classic Car

Posted by toby on Jun 23, 2014 11:30:06 AM

Converting Manual Brakes to a Power System

If you are looking to convert your current manual brakes to a power system, you are probably wondering which MP Master Cylinder Booster combination to choose. 

Some applications are pretty straight forward as there is only one option, but we see plenty of situations where two, three or even four different options can work.  So which one should you choose?

 

1969 Chevrolet Camaro Booster - Master Combo Kit -  BM1744
1969 Chevrolet Camaro Booster - Master Combo Kit - BM1744

 

For the sake of illustration, let’s explore Booster/Master Cylinder options for a 1969 Camaro.  

Here are our most common combinations for older Camaros:

As you can see, owners have some choices to make here.  To figure out which combination will work best for your car, you need to start by thinking about the application and what you want to achieve. 

Are you converting to disc brakes (and if so, what kind?) or are you leaving the car as drum but looking for a better feeling pedal?

If you are converting to disc brakes, you cannot have too much assist in the system. At the same time, there are limitations.  A 9” dual booster might be the preferred scenario, but if your car has a big block engine with tall valve covers, space may be an issue.

In this case, your potential Booster/Master Cylinder combinations are limited by what will fit. In this case, you may need to look at something smaller, so the 8” dual diaphragm booster is probably your best option.

We also get questions about the differences between the 11” single diaphragm booster versus the 9” dual diaphragm booster or some other variation. A booster requires 18 inches of vacuum to operate properly. From there, a booster provides assist, and it's all based on the internal diaphragms.

To determine the assist, you multiply atmospheric conditions by the diameter of the booster and multiple that by the number of diaphragms in the booster. The resulting number is the amount of assist the booster provides.  This is a simplistic way of looking at the situation, but it gets you headed in the right direction. 

Picking a System

Now, let’s get back to our vehicle from above and determine which system to pick. From the above list, the 11” single won’t provide as much assist as the 8” dual, which in turn won’t provide as much as the 9” dual. At the same time, the 11” might fit somewhere that the 9” dual won’t and vice versa.

As we said earlier in this post, go with as much booster as will fit with disc brake conversions. Some vehicles will allow for a larger booster, but others will only allow for a smaller option due to space constraints.

As much as we sing the praises of disc brake technology over drums, not everyone sees things our way.  With this in mind, what are the best options for owners looking to keep their drum brakes?

In this scenario, you don’t want as much assist as possible because too much booster will create a touchy brake pedal that will throw you through the windshield.  In this case, we would recommend a booster that is on the small side and go with a 9” single diaphragm.

Universal 9" Dual Diaphragm Brake Booster

BM17359-1 - Power Brake Conversion Kit - 9" Single Diaphragm Booster

 

Oh but wait, there's more. If you look carefully at the list above for the 1969 Camaro, you’ll see different bore sizes on the master cylinder. The different bore sizes are directly related to the rest of your brake system. The larger piston (like the one used in the Legend Series), calipers typically require a master cylinder with a larger bore size while the smaller but multi-piston calipers require a smaller bore size master cylinder with slightly less volume but more overall pressure.

Even though we used the 69 Camaro and its related Booster/Master combos for illustration purposes, the guidance above will hold true regardless of make, model, and year. 

If all of this gets too confusing, give one of our sales representatives a call and we will gladly walk you through the steps and put you in the correct system based on you, your vehicle and your needs.

 

UP NEXT: Pro-Driver Complete Brake Conversion System Video

 


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Topics: Booster / Master Cylinder Combos, Brake Booster - Master Cylinder Combos, brake systems, classic cars, brake boosters, Converting From Manual to Power Brakes, Master Cylinders

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