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Mention performance to an automotive enthusiast with any amount of octane in their blood, their mind’s eye will likely go straight to horsepower numbers and burning rubber. But there is another aspect of making a car perform that is far more important than making one go fast – the brakes! While stopping better is always a plus, there are numerous reasons why a brake upgrade is a valuable investment.
To help understand why drilling, slotting, and adding more clamping force are worthy performance modifications, we went to the knowledgeable folks at Classic Performance Products (CPP) to find out more. CPP has been providing enthusiasts with affordable steering, suspension, and brake upgrade components since 1991. Along the way, the company has amassed a broad catalog of parts for all makes and models of classic autos and vintage muscle cars.
Why A Brake Upgrade?
Of course, the obvious reason for upgrading a classic car or truck’s brakes is for – wait for it – better braking. Sure, carving canyons and chasing cones around a parking lot are a lot more fun when your brakes are up to the task. Also consider that many cars and trucks left the factory with drum brakes, making the upgrade to a modern disc brake system a no-brainer. And let’s be honest, they’re likely due for a rebuild by now anyway. Add on a power brake booster, and the benefits become exponential.
Converting to disc brakes eliminates fade, improves wet-weather performance, and reduces the need for constant adjustment. – Sadie Reis, CPP
There are many personal opinions as to why a brake upgrade is a necessity. As mentioned, more performance forward is almost always a good thing, unless you can’t control it. For that, your brakes need to be able to rein in those moments when that tall, skinny pedal gets a little frisky. Stock brake systems were designed for totally stock cars back in the day. Add power or today’s traffic into the mix, and those OEM binders are already at a disadvantage.
When it comes to brakes, there are plenty of options. Knowing which option is the best one for your ride is key to getting all the fun each time you turn the key. Read on to find out which brake upgrade is best for your driving style.
Another reason enthusiasts will make the upgrade is for pure aesthetics. Those OEM 13-, 14-, and 15-inch rims helped roll millions of cars and trucks off the production line, but on today’s show field, bigger rolling stock catches the hearts and minds of enthusiasts. A larger, cool-looking set of brakes does a lot for filling in those gaps between the hubs and hoops. And, if you still need more of a reason, those upgraded brakes will help slow the larger tires you’ve installed to fill in those cavernous wheel openings.
Connecting The DOTs
One of the most misunderstood components of our car’s braking system is the fluid we fill it with. The oft-forgotten workhorse of the braking system, choosing the right fluid for the job is key to any braking system’s success. When it comes to picking the right brake fluid, you need to connect the DOTs.
Each brake fluid is classified by its DOT rating. DOT 3 and DOT 4 fluids are glycol-based and compatible with each other; they are interchangeable. DOT 4 has a higher wet and dry boiling point than DOT 3, which makes it a good choice for high-performance or heavy-duty use, where the brakes will see more heat. DOT 3 is still quite suitable for lighter-duty, daily driving duties, but is more prone to boiling under repeated hard stops. DOT 3 and DOT 4 brake fluid are hygroscopic, meaning they absorb water voraciously, right out of the air. That is why it is recommended to only use fluid from a freshly opened container and keep the lid (or master cylinder cap) sealed.
DOT 5, on the other hand, is silicone-based and does not absorb moisture. The downside is that it does not play well with either DOT 3 or DOT 4 fluid. Converting to DOT 5 fluid can only safely be done if the entire brake system is replaced or thoroughly cleaned, as even trace amounts of DOT 3 or DOT 4 fluid will contaminate a DOT 5 system.
DOT 5 is also not as responsive as DOT 3 or DOT 4 fluid, and is generally not recommended for performance braking systems. It does work well in vehicles that sit inactive for long periods of time, where moisture absorption and corrosion are the bigger concerns. DOT 3 and DOT 4 are the preferred fluids for daily drivers, with DOT 4 getting the nod when extra heat resistance is a consideration.
Drilled, Slotted, & Multiple Pistons
Chances are, we’re all guilty of peering into a wheel with an impish smirk when we notice a set of cool-looking drilled or slotted rotors doing the deceleration duties. Let’s face it, they look cool, and all the big names are running them. But understanding their purpose is paramount in determining if they are right for your application. “Drilled or slotted rotors can help with cooling and pad bite, but they don’t increase stopping power,” CPP’s Sadie Reis confirms. “Rotor diameter and caliper clamping force remain unchanged”.
These drilled and slotted rotors would make a great brake upgrade from drum brakes. They don’t enjoy all the leverage of those massive rotors, but they still fit under many factory-sized rally wheels of the muscle car era.
And what about those multi-piston brake calipers? More is better, right? Sadie cuts through the show field superstar marketing and explains, “Dual-piston calipers that bolt in place of a single piston caliper usually use much smaller pistons, so the total clamping area is not much greater than stock.”
There's more than just adding the number of pistons to a caliper. Notice how these dual-piston calipers clamp only from one side while these six-piston monsters clamp down on both sides of the rotor for a better, more even bite.
But, Sadie explained, “OEM single-piston calipers apply all their force in the center of the pad. Under hard braking, this can flex the pad, creating uneven contact with the rotor. The result is uneven wear, less effective use of the pad surface, and reduced consistency under repeated stopping.”
Dual-piston calipers spread the clamping force over more of the pad, making the most of the entire brake pad’s surface, and those super-cool, four-piston calipers go even further, balancing all that pressure on both sides of the rotor. Both two- and four-piston calipers help reduce pad taper, improve heat distribution, and provide a firmer, more consistent pedal under hard use. Reis goes on to explain they still have their limitations, “These types of upgrades can improve feel, but won’t overcome the limits of a factory-sized system.
To get the most leverage possible, you need bigger rotors. Of course, swapping out to larger rotors means the wheels need a large enough opening to accommodate these super-stoppers. Many wheel manufacturers have templates to help determine if a brake kit will fit.
And therein is the key, “factory-sized” brakes. No pun intended, but it all breaks down to leverage. A big-brake kit will use simple physics to exceed those factory-sized stoppers by adding larger rotors for more leverage and heat capacity, along with much larger calipers that deliver significantly more clamping force across the pad. And with that, a big-brake upgrade wrangles in the trophy-trawling trifecta – great looks, a wheel’s worth of braking value, and much better braking ability than those OEM engineers ever dreamed.
Beyond The Discs
Just like a finely tuned performance engine, a proper performance brake system is a sum of all its parts. That means trying to harness all that power with a single-reservoir master cylinder is like trying to bilge out the Titanic with a Slurpee straw. Just like rotors, when it comes to pumping fluid to those calipers, size does matter.
For many vintage muscle cars, a dual-circuit master cylinder is a great brake upgrade. Adding a vacuum-actuated power brake booster, or even a hydro-boost-style assist system can greatly improve pedal feel and brake performance.
A properly tailored braking system is a blend of clamping force, line pressures, and pedal effort. The best way to bring all of these hydraulic entities into harmony is by adjusting the bore size of the master cylinder. A smaller bore creates a higher line-pressure with less effort, but if it’s too small, the result is excessive pedal travel. A larger bore reduces pedal travel, but takes more effort to achieve the same pressure in the system.
Thankfully, upgrading to a power-assisted brake system can help press the whoa pedal when the going needs stopping, but even still, balance is paramount. “The key is to match the master cylinder bore size to the calipers, booster, and pedal ratio so the system feels balanced and consistent,” Sadie concedes.
CPP offers master cylinders in a variety of bore sizes to suit the many different driving styles and brake needs of its customers. There are units for manual and power-assisted applications, as well as kits for disc/disc or disc/drum combinations. Speaking with a CPP representative is a sure-fire way to get the best pedal feel and stopping performance for your specific setup.
All The Feels
Delving deeper into the braking system, there are several other factors that help create the perfect pedal feel for any application. One of the most common upgrades beyond bore and brake sizing is the switch to braided, stainless steel brake hoses. More than just a pretty face, these braided beauties encapsulate a PTFE inner liner that greatly limits brake line expansion, like you would see with an OEM rubber hose. The result is a firmer, more consistent pedal with a greater service life and reliability.
In emergencies, every fraction of an inch matters. That’s why a properly designed braking system also includes residual valves. What is a residual valve? As its name states, it is a pressure valve that maintains a small amount of (residual) pressure in the braking system’s lines when the pedal is released. Beyond helping prevent leaks by keeping seals expanded, a residual valve keeps the brake pads or shoes closer to the accompanying rotor or drum. This can greatly reduce brake pedal travel, a benefit you (and your front bumper) will enjoy in those instant “both-feet-in” braking exercises.
Many OEM drum/drum applications were designed with 10-pound residual valves built into the factory master cylinder to overcome the springs used on the drum brake shoes. Disc brake systems typically only require a two-pound residual valve, which holds just enough pressure to keep the pads close to the rotor without having to fight any spring forces.
The distribution block on the far left is great for systems already designed for disc, or disc/drum brakes. It doesn't have an internal residual valve. The proportioning valve (middle left) and the adjustable proportioning valve (middle right) both include residual valves. On the far right is an inline residual valve. These can be ordered to tailor line pressure for either disc or drum brakes.
Most aftermarket master cylinders do not have residual valves, so tailoring your brakes to your build is again vital for proper pedal feel. If you’re running a drum/drum brake setup, Sadie strongly recommends installing inline 10-pound residual valves. If you are using either a two- or four-wheel disc brake proportioning valve, separate residual valves are not required, since the proportioning valve already manages the fluid pressure in the system.
Braking It All Down
We all enjoy driving our cars, or at least we should. With all of the technology at our fingertips, there’s no reason why our vintage or classic cars should be a chore to drive regularly. Technical gizmos such as fuel injection, overdrive transmissions, and more modern steering systems get the lion’s share of the spotlight. That said, there’s no reason why a brake upgrade using that same modern technology can’t put the same level of enjoyment in dealing with the daily drive and safely slowing down.
