Hot Tips for Building a Braking System

Oct 13, 2010

The days when hot rodders could consider brakes secondary to straight-line performance are clearly over. For one thing, modern traffic conditions simply don’t allow for that kind of thinking.

“On today’s highly congested highways, we should embrace the issue of safety,” said Ed Rodriguez of ABS Power Brakes in Orange, California. “It’s amazing that people will spend $10,000 on an engine and then go bargain-hunting for a brake system. The brakes are the most important component on any vehicle. Think what it would cost you if you were unable to stop your vehicle in time.”

Hot rodders are focusing more on all-around performance rather than single components. Today’s cars have more-sophisticated chassis and suspensions, which means they also need better brakes. Taking a cue from the sport compact crowd, hot rodders have discovered that big, flashy brakes complement big, flashy wheels.

Mike Jonas, president of SSBC (Stainless Steel Brake Corp.) in Clarence, New York, pointed out how brakes have become an important consideration in both safety and cosmetics. When building a hot rod, he said, you need to look not only at a brake system that will stop a car, but also one that will allow you to go ahead with optional colors and finishes.

“Make sure you have the opportunity to pick and choose what you want,” he said.

We took a detailed look at building hot rod and muscle car brakes in our October 2009 issue. In this issue we offer a somewhat shorter summary and update to keep you on the leading edge of this rapidly developing technology.

Sizing the System

“What we have witnessed [in the past year] is a steady evolution in processes and metallurgy that have resulted in continuous product improvements,” noted Ken Hale of Wilwood Engineering in Camarillo, California. “For example, by adapting new computer CAD programs, including Finite Element Analysis (FEA), four of our mainstay caliper lines have been subtly redesigned for improved performance. The same is true for our rotors. We are constantly developing and testing new metallurgy formulas and vane design to improve rotor performance for the street and at the track.”

Better brakes are just part of the trend toward more-solid and sophisticated engineering of the entire vehicle, especially at the high end of the hobby, according to Jonas of SSBC.

“Instead of subframes, they have full frames, which are lighter and stronger,” he said. “Instead of Mustang II components, they are using C5 and C6 Corvette [components]. They have independent rear suspension, or a Ford 9-inch, and the brakes and suspension are very much interrelated.”

One of the biggest specific advantages of a C5 of C6 front end over a Mustang II is that the spindles are taller, accommodating bigger wheels and tires, which in turn provides more room for larger, more sophisticated brakes.

“We’re mounting eight-piston calipers on 14-inch rotors” for the Corvette suspensions, Jonas added.

Wheel size is critical when selecting brake components.

“First you look at the wheel size, then at the weight of the vehicle,” Jonas advised.

“You have to approach brake selection with a complete-system mentality,” added Hale of Wilwood. “Your first consideration is going to be the demand on the system. Is it for street use, racing, or a combination of the two? And if it’s for racing, then what kind of racing? Autocross, for example, will not place the same demands on a system as road racing.”

“The next consideration would be the weight of the vehicle and the size and type of tires,” he added.

Bigger rotors are better for two reasons: braking torque is proportional to the diameter of the rotor, and heat dissipation increases with area.

“A larger rotor is like a larger radiator,” Hale noted.

But, of course, bigger also means heavier, so Hale recommends the lightest rotor that will meet the application’s demands.

“A lighter rotor reduces unsprung weight and rotational mass,” he added. “To maximize stopping power you need the largest rotor that will fit within the wheels,” said Todd McClure of The Right Stuff Detailing in Westerville, Ohio.

Usually an 11-inch stock size rotor is the largest that will fit under a 15-inch wheel; popular 13-inch aftermarket rotors require 17-inch or larger wheels, McClure added.

When selecting calipers, said Jonas, don’t assume that more pistons necessarily translate into more stopping power.

“You can put six-piston calipers on 17-inch wheels, but the pistons won’t be very big,” he said. “And keep in mind that a lot of multi-piston calipers hang out beyond the rotor,” requiring additional clearance inside the wheel. More pistons will spread braking force more evenly over the total area of a larger brake pad, but it’s total piston area that translates directly into more braking force. It’s a simple mathematical equation: force = pressure x area.

“It’s like comparing a Ferrari V-12 to a big-block Chevrolet V-8,” Jonas continued. The Chevy has eight bigger pistons, “and you know it can smoke the Ferrari.”

“One of the biggest changes we’ve seen is the move toward larger, multi-piston calipers,” Rodriguez confirmed. “The thought process [is] the more pistons the calipers have, the more power they will create. The problem with that type of thinking is that they’re still using yesterday’s technology to generate [the] power for these calipers. If you are unable to supply the pressure to utilize all those pistons, then the calipers are just for show.”

At the opposite extreme, Jonas noted how “on some cars we’ve seen small four-piston drag-race calipers. People put them on Mustang II front ends because they fit really well. They’re great for going straight, but for street driving they’re just barely good enough.”

So how should you select calipers for a 3,500-pound muscle car?

“Single-piston calipers work great on a basic car with a 350 and 17-inch wheels,” Jonas answered. “Now take that same car, and instead of a 350, drop an LS7 in it. It can do 0-“60 in four seconds, and the same caliper won’t stop it so well, so you want three-strokers in there, like our TriPower calipers, which fit very much like single-piston units. You want a more-aggressive caliper for a more-aggressive motor.”

Your choice of a master cylinder and pedal ratio will be governed by the same mathematics, except that now you’ll want to translate the force on the brake pedal into pressure in the brake lines. If the force = pressure x area, then it follows that     pressure = force / area.

“Master cylinder size depends on the caliper piston size, brake pedal ratio, and if the system is boosted or not,” said Hale. “Contrary to intuition, the smaller the master cylinder bore, the more pressure it generates. A mistake we see a lot is too large a bore, resulting in a hard pedal with very little stopping power.”

McClure cited 5⁄16- or 1-inch as an appropriate bore with non-assisted or four-wheel disc brakes. He also emphasized the importance of replacing the single-chamber master cylinder in pre-1967 vehicles with a modern dual-chamber unit.

With the OEM system, “if the one line coming off the master cylinder breaks or loses pressure, you are without your hydraulic brakes,” he said.

Kits including a dual master cylinder, brake block, and brake line set are available from The Right Stuff. If you’re installing a servo, McClure recommends using the largest unit that will fit.

“A common issue with boosters is interference with taller-than-stock valve covers,” he said. “This can be fixed by using a smaller-diameter, dual-diaphragm booster.”

Still, some customers who switch to a 7-inch single or even a 7-inch dual booster are often unhappy with the smaller amount of power assist, he said, adding that a booster that can pull 16 inches of vacuum at idle is ideal.

Yet another variable is pad compound. Wilwood offers 12 different compounds for everything from normal street use to extreme racing, said Hale.

“It’s critical that you pick the right pad for the way the vehicle will be used,” he said. “While our street pads can work well for light track days, they will nevertheless be a compromise.”

Rodriguez of ABS Brakes described the entire process as “very tricky, because of all the variables that come into play. What type of vehicle?  What is the weight of the vehicle? Is it a disc/disc or disc/drum system? What is the size and type of the calipers-or the size of the rotors customers want versus the size of the wheels they already have? The best advice we can give is to consult an experienced professional.”

Comparing Components

Totally Stainless of Gettysburg, Pennsylvania, supplies some of the hardware that can make the job easier, including brake line tubing and line clamps. The bright-finished clamps are U.S.-made from 13-gauge (.092) 18-8 stainless and are bored with 13⁄64-inch holes for No. 10 screws.

“We also carry universal flex-line clips in stainless,” noted the company’s president Doc Hammett. “We wholesale thousands of these parts every year.”

As Hale mentioned, Wilwood has made major improvements to some of its most-popular brake components and kits, including the Dynalite Pro Series front hub kits. The forged billet hub assemblies have been revised to minimize or eliminate any change to the OEM track width and the resulting tire-to-fender clearances.

“This is a key feature for anyone who has already mounted the largest tires and/or maximum-offset wheels that will fit within the stock fenders,” Hale noted.

And the rotor size has been increased from 10.75 to 11 inches to provide additional brake torque and cooling capacity. Coverage will include all of the popular muscle car and hot rod front spindles covered previously by the company’s earlier-style Pro Series kits, according to Hale.

This includes most of the popular cars from GM, Ford and Chrysler. Wilwood offers 12.19-inch Dynalite rear disc brake kits for the popular muscle car rear axles, plus new kits covering the OEM 1955-1957 Chevy passenger car rear axles.

“Base-model kits are shipped with smooth-faced HP Series rotors and Platinum-E electro-coated calipers,” Hale said. “For customized applications, kits can be ordered with SRP Series drilled and slotted black eCoat discs.”

Meanwhile, Wilwood’s new DynaPro 11-inch Rear Disc Parking Brake Kits have been specially designed for tight wheel clearance situations such as deep-backspacing, wide-width 15-inch wheels, many popular OEM-type 14-inch and 15-inch disc-brake-offset wheel styles.

“Using our popular Dynalite 12.19-inch rotor parking brake kits as the base, these new DynaPro kits feature the same internal parking brake shoe assemblies as the larger kits, but mounted within a specially machined 11-inch OD one-piece integral-drum iron rotor,” said Hale.

The Right Stuff has introduced new backing plates for 1955-1964 full-size Chevys with disc-brake conversions.

“These plates protect the brakes from debris while giving the system a more- original look, and they’re compatible with most aftermarket kits,” said McClure.

SSBC supplies calipers, rotors and complete braking systems for hot rods, muscle cars and other performance vehicles. The company’s aluminum calipers feature pistons made from 300-series stainless to resist corrosion. A clear anodized finish is standard, but powdercoated and polished finishes are also available, as are configurations from one- to eight-piston.

ABS offers the Electronic High Pressure Master cylinder (EHPM), which, according to Rodriguez, addresses major issues that hot rodders have been dealing with for generations, specifically the low manifold vacuum and limited space that come with big, high-performance engines.

“This is a self-contained unit that does not depend on engine vacuum, the power steering pump or any other engine component that may fail,” he said. “The EHPM can generate up to 2,500 psi and has a large enough bore to feed multi-piston calipers, while giving the driver a good, solid feel in normal or panic situations.”

Common Mistakes

We asked our experts to list additional common mistakes they’ve seen in custom-built hot rod and muscle car brake systems.

One common thing that Wilwood’s Hale sees builders do wrong is to put in too much rear brake. He added that proper balance should be designed into the system.

“Balance bars and a proportioning valve should be used for fine-tuning, not for overcoming a poorly designed system,” he said.

Another common mistake that builders make is to use rotors and calipers that are larger than necessary, said Hale.

“Having said that, however, there is an aesthetic component to brake selection,” he said. “Nothing looks better to my eye than a wheel-full of slotted rotor with a red caliper.”

“The most-common mistake is not doing enough research,” said Rodriguez of ABS Brakes. “After the system is installed and doesn’t work properly, that’s when [customers] become frustrated because no one can give them a simple answer that will correct the problem. They may have to start over, and that’s when the costs escalate.”

SSBC’s Jonas added another caution. “We’ve seen an influx of Chinese products on the market that are sub-par in quality,” he said. “The parts coming in from overseas are not the same quality as the parts that are made here.”

At the same time, Jonas said, “we’re dealing with an economy that’s soft,” tempting consumers to “buy on the cheap. But you don’t get a second opportunity to do it right. You can’t return what you’ve already mounted.”

Caliper brackets, particularly, require careful examination, according to Jonas.

“Factory original brackets are always stamped or cast in one piece,” whereas some imported imitations are welded from two pieces. “That’s a safety issue. No one has gotten hurt”-”as far as Jonas knows-””but I’ve seen some pretty badly damaged vehicles because of improperly manufactured products.”

“A lot of brake kits and systems on the market are cobbled together haphazardly,” added Hale. “Make sure you know exactly what the customer needs, then buy your components from a reputable manufacturer who has a history of delivering a quality product backed by excellent customer support and service.”