Tech Q&A- Your Braking Questions Answered

Cone-Killing Camaro

Sam Withers; Hannibal, MO: As a longtime, Car Craft reader, I’m hoping you can help me sort out a simple question that’s driving me nuts. I have a 1999 Camaro SS with a six-speed transmission and Hugger Orange paint. As the third owner of the car, I’m really happy with the performance and the handling, but it needs a little help with the brakes. This is my daily driver, but I’ve taken it to the drags and recently competed in my first autocross. After a couple of hot practice laps, the car wouldn’t slow down quickly enough and I took out some cones. Some of the folks at the autocross said I need all-new brakes, but others said I could get way better stopping power with different pads at the cost of more noise and brake dust, which I don’t really want. After reading back issues of magazines, looking online, and reading the Camaro forums, I’m really confused. There are ceramic pads, carbon pads, semi-metallic, colored pads, street/race pads, and serious race pads, and they are all over the map price-wise, from $18 to $342! I’m not made of money, what is right choice?

Car Craft: Let’s see what we can do to improve the stopping power on that collectible Camaro while keeping you out of the poor house. First, the good news and the simple part of the answer: you will eventually end up with a high-quality ceramic pad. Now for the dose of reality: there is no unicorn brake pad that offers aggressive, no-fade stopping power with no dust and no noise at any price, let alone in the budget bin.

While you didn’t specify what went wrong when you unintentionally went cone hunting, beyond a mechanical failure like a caliper mounting bolt breaking, there are really only two common forms of braking failure, and the difference is easy to diagnose. If your pedal sank to the floor and required cooldown time or pumping to recover some braking effectiveness, you likely boiled the brake fluid. If the pedal stayed high and hard but the car wouldn’t slow, you likely experienced pad fade as the overheated binding materials and resins that hold the pad’s harder components together literally boil out the pad. This is known as outgassing, and the superheated material prevents the pad from fully engaging the rotor. You can confirm pad fade and outgassing by examining the pads after the event, and you’ll likely find cracking on the pad surface or even chunks of the pad material missing or deformed. If you ever tried to drive an original 1960s or 1970s muscle car hard with stock brakes, you’ll have experienced brake fade or what is actually pad fade. All factory cars are engineered to be able to panic-stop reasonably well at least once or twice, and as cars have gotten faster and heavier, the Detroit manufacturers have kept pace with at least that minimum standard. Beyond that, older factory brakes gave up the ghost pretty quickly. Your high-performance 1999 Camaro is far better at braking than its 1979 predecessor, but not nearly as good as a sixth-gen.

To check for boiled fluid, bleed out some of the fluid from the caliper’s bleeder into a clear tube and catch cup as if you were bleeding the brakes. It will likely be dark and may smell burnt. Regardless of your new pad choice, this is a good time to flush out all the blackened fluid from the system with fresh new fluid from a sealed container until it runs clear and clean. For cars that are driven hard, this is a good annual maintenance process, as boiled brake fluid will accelerate corrosion in the brake lines and generate air pockets much faster than fresh new fluid. As for the fluid, DOT 4 has a higher boiling point than DOT 3, but DOT 3 will hold up better if you don’t do the annual maintenance. If you progress to open-track events, you’ll want to replace the fluid before every event.

As for picking your new pads, a brake expert is going to walk you through how you use your car—how often you realistically autocross, drag race, or work the car hard on twisty roads—to confirm exactly which brake components you have behind the wheels. Many car crafters find that the “stock” car they bought has had cheaper parts installed over time, like remanufactured calipers, bargain-basement rotors, or even swaps to smaller brake components in a misguided effort to save weight or money. With that information, they’ll tell you that an aggressive pad will stop the car repeatedly without fade until you have pushed the brakes beyond their capacity to shed heat. Modern disc brakes convert the energy of the car’s moving mass into heat. That heat is properly absorbed into the rotor, not the caliper, and dissipated into the air. That is why simple brake ducts can really help lower brake temperatures. It is also why high-performance systems use thicker rotors and specify curved, directional vanes to further absorb and dissipate heat.

Better-quality pads have more sophisticated backing-plate materials and thermal isolators on the back of the pads that help keep heat out of the calipers, therefore reducing pad temperatures. Better-quality pads for your application will have a higher  (“mu”) factor or coefficient of friction. It also means the rotors will wear a little faster and, yes, you’ll have a bit more dust. Of the pad choices out there, the newest “carbon” pads are more expensive and will produce more dust. The term “semi-metallic” has become a broad catchall and won’t really help you decide. With an aggressive racing pad of any formulation, you will get squeal under some circumstances. The other alternative is a high-quality street pad like a Hawk HP+ or Baer Sport and then swap in a set of really aggressive autocross-specific pads like the Raybestos ST 38 for those occasional events. Just remember to bed each set in initially, according to the suppliers’ recommendation. Once that is done, you can swap pads back and forth without worry.

High Hard One

You have several options when converting to a manual brake system, with solutions coming from the aftermarket and original parts.

An adaptor plate, like this one from TRZ Motorsports, allows you to mount a manual brake master cylinder and significantly declutter your engine compartment.

Note the difference between these two Fox-body brake pedals. The manual brake pedal is on the right. The attachment point for the master-cylinder pushrod is closer to the pivot point.

Alex Rodriguez; Port Isabel, TX: I’m building a 1989 Mustang for some street/strip action and want to try out the Texas Mile one of these days. It has a strong 408 Windsor with a Comp 291 THR7 cam, Edelbrock Victor Jr. Heads and intake, 870 Holley carb, super T5 and an 8.8-inch posi rear end. My goals are to get the weight down, keep making more power, and get the car ready for more on-track duty. There is one problem my buddies and I haven’t solved yet: The car came to me with upgraded Cobra brakes, but it doesn’t stop as well as I expected. Sometimes it’s like there is hardly any braking at all. Our local speed-shop guy says it’s low vacuum and we should get an electric vacuum pump, retrofit a Hydroboost, or convert to manual brakes. The vacuum pumps are expensive, and a Hydroboost is big, heavy, and ugly. Going to manual brakes seems like a step backward, but I don’t have pro-baller money, so what is the right choice and how do I do it on a regular-guy salary?

Car Craft: Alex, you may not be the famous baseball player, but let’s see if we can hit your question out of the park. That Fox has hit the classic big-cam/low-vacuum threshold, and your experience fits the typical case. With a Ford booster in a stick car, the minimum recommended vacuum is 14 inches measured with the car idling in Neutral. With an automatic, test it in Drive with the brake depressed. For GM guys with Delco boosters, that number should be closer to 16 inches of vacuum at idle to have full braking performance.

Regarding power versus manual brakes, it’s important to remember that the brakes are the same in terms of stopping power, no matter what you have on the pedal side of the master cylinder. The power brakes in most U.S. cars are set up to require 100 pounds of force to panic-stop the car. With manual brakes, that rises to around 120 pounds. Power brakes typically react faster, which is what most folks are used to, but the car will not stop in a shorter distance if both systems are properly sized with the right pedal ratio. Those Cobra brakes were a common upgrade back in the day, and that same swap also allowed folks to go from four-lug to five-lug wheels if the original car was built that way.

Since the brake system has been modified, you also need to verify some things to be sure you go the right route for the least dough. First, does it have the original master cylinder? If it does, you’ll have an aluminum unit with a plastic brake fluid reservoir. The key identifier is a total of three ports on the master cylinder (MC) with one that goes down from the bottom side of the unit. If it is the original and appears to be in good shape, it has a 0.827-inch (21mm) bore. The good news is that the 0.827 bore MC will work on a manual brake setup as well. If you have a two-port aluminum MC with plastic reservoir, it’s likely the Cobra M2300 unit with a larger booster. It has a 15/16-inch bore, which will also work for a manual conversion. Then all you’ll need is a manual brake adapter plate, such as this one from TRZ, seen in the accompanying photos. Once in place, there is now much more room in the engine compartment, even with a tall-deck big-block. The other necessary change will be to install the brake pedal from a manual-transmission/manual-brake car sourced from a junkyard or available online. The manual brake pedal has a much higher pedal ratio, which is the distance from the brake-pedal pivot to the master-cylinder pushrod. On manual-brake cars, the distance between the two is shorter than with a power brake pedal. Expressed as a ratio, the power pedal is around a 3.5 to 4.25:1 ratio and the manual is closer to 6.5:1. Therefore, the manual brake pedal travel is going to be longer to get the same hydraulic pressure to the calipers.

Leaving everything you have in place, you can directly address the low-vacuum issue with an auxiliary electric vacuum pump like this one from MasterPower (photo). The large electric pump like those used on all electric vehicles like a Tesla or Nissan Leaf provides more than enough vacuum to operate the brakes at all speeds. You’ll need to add a 20-amp fused circuit set to operate whenever the vehicle is running, and you’ll have to find a good location to mount it near the existing power brake booster. Between the driver-side front fender and the sheetmetal foot well is a good spot. Expect some noise and vibration. You can also use a smaller electric-pump unit as a supplement to the engine’s meager vacuum, along with a vacuum canister to ensure you have enough to operate the current boosted system safely under all circumstances.

A Hydroboost unit gets its hydraulic oomph from the power-steering pump. If you still have power steering, you can get a complete kit from companies like CPP or MasterPower through Summit, Jegs, or other suppliers (photo). For a Hydroboost conversion, you’ll also need a 1-1/8-inch bore master cylinder as part of the kit or from another source. The reason is that the Hydroboost unit has a shorter throw than the stock booster and you need to make up the volume of fluid with the larger bore size. If you are running without power steering, the conversion is more involved because you’ll have to source the pump, bracketry, lines, and longer serpentine belt. You’ll need to decide if the weight and complexity is worth it in your hot rodded Ford.

If weight reduction, underhood room, and simplicity is your goal, the manual-brake route will work well and help with your overall power-to-weight ratio. If power brakes need to remain on the menu, you have the lower-price route with electric vacuum assist or the later model power-steering/power-brakes program with the Hydroboost approach. We hope this covers all the bases. Post your results on and show us what you decided.

Turned Around

The rotor shown on the right was used in World Challenge racing on the Paul Brown–driven, championship-winning car in 2014. It is still usable as-is, despite how it may look compared to the new rotor.

D. Morrison; Enterprise, AL: Both my 2008 Silverado and Marina Blue 1967 Chevelle 396 restomod need brakes, as the pads are getting thin and the rotors are no longer smooth. On one of the Chevelle forums, a guy I used to think knows what he’s talking about says nobody needs to turn rotors anymore. I like saving money, but that sounds wrong to me—what’s the real deal, CC?

Car Craft: Yo, D, this is a great question and the answers contain some serious myth-busting and a 180-degree bootleg turn from the conventional wisdom. Hang on while we show how brake maintenance has moved into the 21st century and we save you time, money, and aggravation.

Myth No. 1: When you get new drums or rotors, they need to be turned to ensure that they are straight and true.

False! For decades, this was a way for less scrupulous shops to add labor charges to a brake-replacement job. For folks salvaging used parts for their hooptie, this may have made sense 30 years ago, especially for drum-brake applications, but for almost all vehicles sold with disc brakes in the U.S. in the last five decades, inexpensive new rotors make that choice unnecessary and risky. For both your Chevelle and your truck, you have lots of stock or upgraded rotor options, including slotted and cross-drilled rotors or even lighter, higher-performance, two-piece rotors with aluminum hats and cooling features associated with big-brake kits from the major U.S. suppliers. New rotors from reputable suppliers will be more dimensionally accurate than the turning equipment at most shops can achieve.

One other fact to be aware of is that virtually all cast-iron brake rotors sold in the U.S. are poured overseas, primarily in China, India, and Malaysia. Cast iron continues to be the material of choice for brake rotors because it has far better heat-dissipation properties versus steel, stainless, or other alloys. More importantly, cast iron has the best coefficient of friction, known as  (“mu”) factor in the brake industry. Environmental and other local restrictions have resulted in the closure of all the large-scale foundries in the USA, so even Detroit’s Big Three source rotors offshore.

Myth No. 2: When performing a brake job on disk brakes, you always must turn the rotors.

False! If the rotors are so worn or damaged that you would think you would need to turn them, they need to be replaced. This includes rotors with small cracks and moderate grooves. The rotor pictured on the right can still be used. Simply put in new pads and drive easy for 100 miles and if high-performance driving or track use is part of the program, follow a normal pad bedding process with several sets of four progressively harder stops with cooldown periods in between ranging from 30 to 70 mph. The pads will quickly conform to the various ridges on the rotor—no machining necessary. You don’t need to replace the rotor unless a crack is fingernail thick. Well-used, cross-drilled rotors will always exhibit some hairline cracking around the holes. This is normal and does not warrant replacement.

Myth No. 3: “My rotors are warped they need to be turned” or “I got new rotors off the internet and they were warped out of the box!”

False! What most people think is a warped rotor is actually caused by pad transfer. Pad transfer is a normal part of brake-system usage where a nearly invisible portion of pad material is transferred by heat to the rotor surface. This is called the transfer layer. However, when the operating temperatures exceed the pad’s design capabilities, excess material sticks to the rotor, creating pad deposits that cause pedal pulsation or even a vibration that is felt through the steering wheel. The best way to identify excessive pad transfer is that the pulsation varies with ambient temperature and speed.

A truly warped rotor is extremely rare, but a rotor that has had excessive pad transfer over time can eventually have high and low spots, known as disk-thickness variation (DTV). Manufacturer specifications for DTV in new rotors are typically 0.0005 inch, far better than typical rotor-turning equipment can reliably achieve. The cure for pad transfer and that pulsating brake pedal is as easy as a new set of pads with a different formulation and using the proper pad-bedding process. Finally, on modern rotors with slots; if you still see slots, the rotor has plenty life left in it. After 0.100 of accumulated wear, it’s time for new ones. Maybe that guy on the Chevelle forum is still pretty sharp after all, right? He must read Car Craft.

More Info
Baer Brakes; (602) 233-1411;
TRZ Motorsports; (407) 933-7385;

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