Choosing The Correct Brake Booster With Tuff Stuff Performance

It’s widely known that power brakes came into the mainstream during the early-to-mid 1960s. The creation of the brake booster went hand-in-hand with another new component of the times, disc brakes. Disc brakes offer many advantages compared to the old drum systems, except for one critical point, a mechanical advantage. The brake booster is one of the larger components within your engine bay. It functions by utilizing your engine’s vacuum to multiply the force from the brake pedal to the master cylinder. This decreases the pedal force required to apply the brakes. 

With the wide range of designs and finishes, a brake booster can be integral to a properly working and sharp-appearing engine bay.

The mechanical assembly within a brake drum offers compound leverage when compared to the clamping action of disc brakes. When it comes to brake pedal force, a comparable disc brake system — without a booster — makes it more difficult at the pedal to apply stopping power. Thus, disc brakes and brake boosters were applied hand-in-hand.

We spoke to Mike Stasko and Matt Oliver from Tuff Stuff Performance Accessories about its brake booster offerings. Yes, I say offerings, because there are several variations of boosters available, and choosing wisely can mean quality braking, while an ill-selected booster can deliver less-than-stellar results. When looking at the Tuff Stuff website, we find they offer refined versions of original equipment styling with multiple finishes. They also offer various powder-coated colors and their beautiful in-house chrome plating options.

Brake boosters are available in multiple sizes and shapes. Single- and dual-diaphragm designs in 7-, 8-, 9- and 11-inch diameters can fit virtually any hot rod, custom, or muscle car. But they are not a one-size-fits-all.

“A considerable amount of engineering goes into our booster internals,” says Oliver. “Although our in-house plating and powder-coat finishes are what enthusiasts notice first, our valving and diaphragm engineering on the inside allows us to offer custom boosters as small as 7-inches in diameter.”

Brake Booster Basics

Today’s performance braking systems include larger diameter brake rotors and multiple-piston calipers coupled with larger diameter wheels and tires. Big brakes and tires cause a mechanical challenge that requires even more brake line pressure.

Divided by a heavy diaphragm, the engine's vacuum equalizes in both chambers. A valve system releases the vacuum from the rear chamber when applying the pedal. This pressure difference now multiplies your pedal force towards the master cylinder. When you stop braking, a spring returns the diaphragm to the center.

In actuality, the fundamentals of booster operation within the large canister are simpler than you might think. The canister is divided into sections by a large rubber diaphragm. A spring-loaded shaft with various valves runs through the center between the brake pedal linkage and the master cylinder. The booster is connected to the engine, so the engine’s vacuum equalizes in both chambers of the booster. When the brake pedal is depressed, a valve system releases the vacuum from the rear chamber. This pressure difference multiplies the force applied by your pedal to the master cylinder. When you release the brake pedal, a spring returns the diaphragm to center.

Many Booster Choices

Like the hot rods at your local car show, brake boosters are equally varied. Tuff Stuff offers many different options ranging from those desiring an OEM replacement with improved looks to a custom booster for those building the ultimate hot rod.

There is an additional twist to your choice of boosters. Tuff Stuff offers a booster with either a single or dual-diaphragm configuration inside the chamber. Unlike the basic single-diaphragm design we mentioned earlier, the dual-diaphragm booster holds two diaphragms and a different valving system that applies even greater pedal assistance, thanks to having two sections pulling vacuum.

Used mostly in OEM replacements, the dual-diaphragm units can offer better braking when compared to a stock single-diaphragm unit. A double-diaphragm design is also especially effective when you need to use a booster with a smaller overall diameter.

We directly compare Tuff Stuff's stealth black powder-coated 7-inch boosters. The left contains a single diaphragm, while the booster on the right illustrates the unique shape and a longer length required to include dual diaphragms.

The smaller diameter brake booster is a big help when working around clearance problems in a custom application. Stasko explains, “Our most popular booster is probably the 9-inch dual because they’re used in many Corvettes. We have specific ones for specific-year Corvettes. We also just added a mounting feature that is pretty popular for people who are converting over from manual brakes.”

In assembled form, Tuff Stuff can put together a complete brake booster, master cylinder, and bracket assembly for many popular vehicles. These can mount to original firewalls that once utilized manual brakes. Oliver adds, “The number one mistake people make when going from manual brakes to power is they don’t think about the pedal assembly.”

Making sure your brake-pedal geometry is correct, especially when converting from manual to power brakes, is crucial. Tuff Stuff offers a variety of mounting brackets and brake rod components for your retrofit or custom project.

Brake System Geometry

Oliver continues, “Considerations need to be made in regard to pedal geometry when updating from a manual system. If you do not think about this, the pedal ratio will be a mess. The angle at which the booster rod enters the booster is not going to be right. I often answer questions related to necessary modifications when installing a universal brake booster. Our boosters’ bolt pattern is General Motors-based, so if you’re working on a GM vehicle, the odds of having to do any modifications are very low.”

… a 1-inch bore is recommended for disc-drum or drum-drum brake combination while our 1-1/8-inch bore is recommended for most disc-disc arrangements. – Mike Stasko

The professionals at Tuff Stuff also field questions when customers are converting to power brakes concerning the proportioning valve that follows the master cylinder. Since Tuff Stuff offers master cylinder options specifically designed for different combinations of discs and drums. They recommend their master cylinders that do not require proportioning valves in many cases. According to Mike, “a 1-inch bore is recommended for disc-drum or drum-drum brake combination while our 1-1/8-inch bore is recommended for most disc-disc arrangements.”

Tuff Stuff offers many pages of bracketry, brake rods, and connectors along with specialized master cylinders in their online and paper catalogs. They also provide many tips and informative diagrams concerning brakes along the way.

“Many people will put their brake system together with our specific disc- or drum-matched master cylinders without a proportioning valve,” clarifies Oliver. “They see how it feels and if it is right for them. If they decide the brakes require a proportioning valve, we match up master cylinders and proportioning valves designed for each other.”

Many hardcore enthusiasts who use a very radical camshaft will attest to the lack of vacuum to properly operate a brake booster. Though the smaller diameter boosters require a little less volume, in that situation, the best cure for your brake booster is having a vacuum reservoir canister such as those offered by Holley Performance/Mr. Gasket or Moroso Performance connected to your vacuum feed to the booster. They provide a vacuum “reserve” to assist booster function.

Like all of their products, the boosters are manufactured from new components at their Cleveland, Ohio, plant. Tuff Stuff's high-quality chrome and gold-zinc plating are also performed in-house. Their master cylinders, boosters, and brackets can be powder-coated in various colors as well.

As another option for a vacuum canister, there are also 12-volt-powered vacuum pumps that can supply the booster with vacuum, eliminating the engine from the equation altogether. Oliver and Stasko agree that these pumps can be quite noisy.

Look Good, Brake Better

Though there are different ways to power assist your brakes, the vacuum/canister system has been the automotive standard for more than 50-years. Custom boosters, like those from Tuff Stuff Performance, offer the braking power you want without detracting from the appearance of your car’s engine bay.

With complete kits available for a wealth of popular muscle cars and trucks, plus unrivaled plating and color options, they make it easy to create a brake system that adds functionality and good looks. All it takes is a quick call or email to get a recommendation to ensure you have the right braking parts for your ride.

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About the author

Todd Silvey

Todd has been a hardcore drag racing journalist since 1987. He is constantly on both sides of the guardwall from racing photography and editorship to drag racing cars of every shape and class.
Read My Articles

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