Tom Wilson
March 1, 2003

Horse Sense:
Brakes really are impressive. Engines take the chemical energy in gasoline, convert it to heat energy, then mechanical energy via a bunch of monkey motion, and finally kinetic energy, which is what we all show up for in the first place. Brakes convert kinetic energy directly into heat. This streamlined energy path is a big reason brakes are about four times more powerful than an engine. If you don't think so, compare acceleration versus stopping times.

Braking has gone from ignored to celebrated in little more than a decade. From the pitiful '80s-era Fox-chassis brakes that had one good stop in them before fading and warping into uselessness, to the prized six-piston, 14-inch IndyCar brakes available in Mustang bolt-on kits today, braking power has finally been recognized as an integral part of automotive performance.

Part of the rush to better braking has brought brake pads to the fore. Perhaps still not the stuff of enthusiasts' dreams, selecting the right brake pad is at least acceptable banter among gearheads these days. After all, those huge-and hugely expensive-multipiston calipers and pizza pan-sized discs may have big-buck sex appeal, but everyone can at least afford performance brake pads. And, as we've found out, a performance brake pad can make a real difference.

To report on what is available in Mustang brakes, we took our open-track project car to Baer Brakes to sample a cross section of brake pads. Our "stripe car" wears Baer's Track Kit Plus brakes featuring PBR dual-piston sliding calipers essentially identical to those on a Mustang Cobra, and Baer's thick, massive Eradispeed rotors. This definitely gives us performance braking, but as the system fits inside a 17-inch wheel and shares its caliper design with most Mustang Cobras, it's also obtainable by us working-class folk and is thus found on many Mustangs.

The PBR caliper is one of the most popular performance calipers in the world. Its use by Chevy on the Corvette and Ford on the Mustang Cobras has engendered a wide range of brake pads, from all-around stockers to hot-shot track-only part numbers. This means there is a wide variety of pads available to try.

Furthermore, when we say sampled, we mean we ran through the bakery and barely smelled the stuff. Brake pads are a surprisingly complex subject. There are so many variables in the materials, usage, desired results, and drivers that the subject can become a morass of subjective claims and counterclaims. Our goal here is simply to raise awareness that there is more to selecting a brake pad than giving the counterman the make, model, and year. In addition, we want to give you some direction on what is available for and possible from current brakes.

Material Questions
What is available are several varieties of friction material. While a full description of what goes into pad material is far beyond the scope of this article, it's important to know some materials are better suited to certain types of driving than others. And as most of us do more than one type of driving, that means compromises are necessary. It's also necessary to understand that just as there is no such thing as the perfect camshaft, there is no perfect brake-pad material.

Major players in the brake materials game are organic, metallic, carbon, and ceramic compounds. Typically speaking, organic compounds are what's found in most production-car brake pads. They work at relatively low temperatures, fade at higher temperatures, are relatively soft, and tend to be quiet (not squeal).

Metallic compounds are just that-bits of metal embedded in the organic material. They raise the temperature range of the pad to resist fade better than a straight-organic pad. However, the more durable metallic bits can increase rotor (disc) wear and cause noise.

Carbon is heat resistant but not as harsh as metallic materials, while ceramic pads offer yet another heat resistant material. You'll also see dual-carbon, and carbon-ceramic labels. Such names illustrate how these common brake-pad materials are blended to varying degrees as the engineers cook up new pad recipes for specific appli-cations. This is especially true of high-performance or racing pads; endless varieties of pads can be dreamed up depending on the weight and speed of the vehicle (in other words the kinetic energy involved), and the environment where they'll be used.

Where and how the pad is used plays a tremendous role in how a pad reacts and therefore what characteristics the designing engineer will opt for. A heavy, aerodynamically sleek Winston Cup car needs a different brake pad than a flyweight formula car with high-drag wings. So does a daily driver Mustang compared to a track toy brought out to the dragstrip twice a month.

Brake-Pad Characteristics
So, just what things can a brake pad affect? Most obvious is braking torque, or simply, raw stopping force. Fade resistance is the next thing most of us consider in a pad, but there are other, more subtle characteristics you may have never thought a brake pad could affect. Pedal feel is one of these. Handling a brake pad fresh out of its box you'd swear it is about as compressible as a brick, but it isn't. Under 2,000 psi of hydraulic pressure a brake pad actually squishes some. This comes across as sponginess in the pedal under the heaviest braking.

There is also linearity, or how stable the pad is under varying pedal pressures and, especially, temperatures. The ideal brake pad would warm up to its working temperature, then provide the same amount of braking torque as it gets worked repeatedly. In other words, in a manner similar to a good street cam, a good pad has a flat torque curve. In practice such is not the case, but the better pads do offer consistent torque across a fairly wide temperature range.

A related idea is temperature resistance. Should a brake pad be taken over its working temperature range, does it fade right away, or does it hang in there the best it can and provide most of its braking torque well past optimum temperature? If it's the latter, it could be a big help to a racing driver locked into a run to the checker against a fierce opponent.

Brake engineers also like to talk about bite, or onset. This is shorthand for how the pad initially generates braking torque, right when the brake pedal goes down. A street car can use a fairly soft onset. Some race cars can use big initial bite, others much less.

At the other end, there are release characteristics, or how well the brake pad lets go of the rotor. This is important to pro race drivers in purpose-built race cars, but it's essentially a nonissue in street-driven Mustangs and is rarely mentioned, even in road-racing sedans.

Rotor wear is a major concern, as an aggressive pad can chew through brake rotors like so many potato chips. This can be a real shock if you're coming from street cars with their gentle ways with rotors and find your new high-dollar stoppers have tattered their rotors after only a weekend of track fun. Rotor wear is closely correlated to pad temperature too. Cold race pads munch on brake rotors like beered-up frat boys do pretzels.

A real street issue is noise. The occasional brake squeal from glazed street pads is no big deal, but try a set of rock-hard race brakes on the street and you'll have dogs howling for mercy and everyone at a red light staring daggers at you. Our track car is a perfect example. When we run hard-core race pads on the street-it doesn't matter the brand-they groan and squeal with excruciating volume. Believe us, noise can be a deal breaker on the street.

Dust is another street concern. All pads make some dust, but race pads can be like having coal mines in your wheelwells. Besides being a cosmetic pain, brake dust can combine with moisture to eat away at your fancy aluminum wheels.

What To Test
There are many brake pads avail-able for the PBR caliper used on the Baer/Mustang Cobra brakes, and we tried to sample a mix of street and race pads from various manufacturers. After the usual shambles of putting everything together, we ended up with more race pads than street pads. Considering the racy nature of our track car, we suppose that's appropriate anyway.

Brands tested include Hawk, Performance Friction, and SBS (Scandinavian Brake Systems). We also tried a set of stock PBR pads as used in Mustang Cobras. Please understand that we did not test a full line of pads from any of these companies, and some of them sent more street pads than race pads, and vice versa. That's of no concern, as this is in no way a brake-pad shootout. There are no winners or losers, rather these pads merely illustrate the range of possibilities in pads today.

Furthermore, we did not do a comprehensive audit of noise, dust, pedal feel, rotor wear, or many other things. In fact, we really didn't test any of those parameters, other than incidentally. What we did test was ultimate braking torque, as measured in stopping distance, and fade resistance, as measured through repeated stopping. Along the way we got some idea of pedal feel-although not the same nuances one would get in lapping practice at a road-racing course-as well as noise level and ABS action.

All in-car testing was done using our track car during a two-day period at Baer Brakes. The same testing surface and procedures were used for all pads. This began with a bedding procedure to introduce the pads to the rotors, followed by a cooldown. Then a series of five stops from 60 mph were run, followed by another cooldown. Next, we repeated the five 60-mph stop sequences, along with the cooldown. Finally, we made five 100-mph-to-0 stops.

All stopping sequences were run back-to-back, with speed regained after each stop almost as fast as the car would accelerate back up to speed. Given the short time spent motionless to allow the test gear to reset and enter the results manually in a laptop, the brakes-and the engine-got little rest.

As a brake torture chamber our Mustang did quite well. Weighing 3,555 pounds empty, our track car, with two big guys on board, along with some fuel and test equipment, weighed in somewhere around 4,100 pounds during the tests. Ugh! Given the 3.73 rear-axle gears and 250 rwhp, acceleration back to speed didn't take long either. Con-sidering our car does not have brake ducts, there was no rest for the wicked on this one.

For test gear Baer set us up with its radar-gun rig. It sped the testing, as speed readings are given in real time, and it is quite accurate. A laptop with proprietary software gave us the distance and drew graphs using the speed data from the radar gun.

A couple of test notes are worth mentioning. For one, our stripe car carries a full Maximum Motorsports suspension. This means we had a torque-arm, which noticeably reduces brake dive and goes a long way to calming the braking experience. So, don't try to compare our stopping distances to yours unless you have a full-on torque arm suspension too. Even with stock pads, our setup stops shorter than a stock Mustang because the vehicle weight is better distributed among the four tires.

Next, our tires. We used our usual 275/40ZR-17 Nitto 555R track tires in this test. They were at about half tread depth, so tread squirm was not a factor, and we benefited from the higher grip afforded by these sticky compound tires (tread wear rating of 100). Durable, high-traction, DOT-legal road-racing tires, these Nittos give far more traction than regular street rubber.

Counteracting our car's superior traction was a pebbly pavement on the testing surface. There were excessive marbles from time to time, but nothing that didn't average out given our multiple-stop test regimen. But if you're gee-whizzing at the raw stopping distances, be advised they could be a touch shorter on ideal pavement. Temperature and wind were not factors during the tests.

Finally, to reduce workload (tremendously), we tested only the front brake pads. The rear brake pads for all tests were the stock PBR units. These street pads therefore provided some stopping, but they really put the emphasis on the front pads where it belonged for this test.

And What Happened?
Well, to state the obvious, race pads stopped the car quicker than street pads, but with more violence and noise. The street pads seemed softer and certainly didn't generate as much braking torque as the race pads, but they were quieter and gentler.

It's the rare enthusiast who gets to participate in a test such as this, and we were surprised at how noticeable some of the differences were under these back-to-back conditions.

Let's begin with plain, old braking torque. It's something how a warmed-up racing pad will really lay you into the belts compared to the street stoppers. In the same way you can feel a 150hp nitrous shot, you can feel grippy brakes in the seat of the pants. We've noticed this with our stripe car when running race pads on the street. Their ability to lift you up and out of the seat is amazing compared to stock braking. Simply put, they are more powerful binders-something you might miss due to all the noise.

Another example is ABS violence. All our stops were simulated panic stops-we used nearly full-on pedal stabs (just barely enough ramping up of pedal effort so we could hope to feel braking onset), followed by clamping down the brake pedal as if we were in danger of driving over the edge of Pikes Peak. This produced plenty of ABS action, especially in the 50-mph-and-under speed range.

All the pads ratcheted the pedal as the ABS came into play, but the street pads did so with numerous small bites, while the race pads tore out big chunks, like a great white thrashing a seal. Call it bite, onset, aggressiveness, violence, or whatever, but the high-torque race pads obviously grab into and release from the brake disk with tenacity. Clearly this is most noticeable when invoking the ABS, but it is indicative of how a more aggressive pad comes on faster to light pedal application than a stock pad. It's sort of like adding a touch more power assist to the braking system.

Temperature is such an important part of braking that it will show in any test. In our examination the street pads came up to temperature quickly, about halfway through the first 60-mph stop, then plateaued for several stops before falling off, usually fairly rapidly. In the 60-mph stops, almost all the street pads were good for the two five-stop sequences with noticeable, but not disqualifying, fade. But when it came time to hammer through the 100-mph stops, the street pads just rolled over and died.

The specifics of each pad have been grouped in the sidebars. All stopping distances listed are in feet, and we've listed all the stops. There is slight varia-bility in the data due to test-track surface variations, driver technique, and occasionally where we made more than one stop to check repeatability or just to see if the pad was fading. The trends are readily apparent, however.

ABS-Don't Leave The Garage Without It
With brake testing accomplished using full-on ABS stops, imagine our chagrin when we showed up at Baer with inoperative ABS. The ABS warning light had been coming on and off for a while before the test, and we had figured a cleaning of the ABS sensors at the wheels would do the trick. Not.

Our left rear ABS exciter ring had come loose from the axle-it's a simple press fit-and chewed up the sending unit. A new sending unit, a Hail Mary tack-weld of the exciter ring to the axle-not recommended due to weakening the axle but no new parts were available in our short time in Phoenix-and we were back testing. The ABS provides extremely consistent stops, reducing the driver workload tremendously and yielding good test data. It's also how panic stops are made on the street, although we only occasionally invoke ABS at the racetrack. But when you do, it really helps, both with car control and on the stopwatch.

PBR OEM
If you have a Mustang Cobra with PBR brakes, then this is your brake pad. It's quiet, relatively good on dust, and able to hang tough in the slower stops expected of a hot street car, but it's not exactly the last word in repeatedly hauling down from triple-digit speeds. The gain of 100 feet in stopping distance between the first and fourth 100-mph stop is a real eye-opener when you're behind the wheel.

Note, however, that the first 325-foot stop from 100 mph is just acceptable from even racy pads. The difference is, with this stock pad you get one of those stops, while with the race pads you get stop after stop at these short distances or better.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
29.79 121.12 325.74
30.96 123.22 383.01
30.02 120.79 403.86
31.45 126.39 424.16
30.72 128.27 not tested, fade

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
27.05 117.56
27.14 109.15
29.39 113.86
29.93 120.62
30.54 120.48

Hawk HPS
We've open-tracked our test car quite a bit on Hawk's most aggressive race offering, the Blue pad, and found it powerful, fade resistant, a bit dusty, and noisy on the street. A good race pad, in other words.

For this article, we sampled Hawk's street (HPS) and street/track (HP Plus) pads. The HPS was smooth on the ABS and offered a nicely firm, consistent pedal when working in its heat range. Our brutal stopping trials were too much for it, however, and both the pedal and stopping power went away when worked hard.

When used as intended (the 60-mph stops) as a step-up-from-stock pad, the HPS lived up to its claims. It offered more braking torque (shorter distances) than the stock Mustang Cobra pad in a street-friendly package. Hawk says the HPS offers much better than OEM pad life, great rotor life, good cold performance, and extremely low dust.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
30.91 121.27 316.54
29.22 112.47 380.94
31.18 125.10 343.34
30.92 125.42 404.94
30.03 127.00 not tested, fade
30.58 127.93  

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
28.31 111.06
26.70 105.17
26.70 107.60
28.98 113.78

Hawk HP Plus
In feel, the Hawk HP Plus street/ track pad was nearly identical to its lower-performance HPS sibling. The HP Plus did offer more fade resistance than the HPS, but not the outright torque of some of the more aggressive pads sampled here. Hawk says the HP Plus is race-worthy for autocross or club events, so we'd think of it as sports pad and not a race pad.

Hawk says to expect a bit more noise, dust, and rotor wear compared to the HPS pad, which sounds perfectly reasonable.

We've seen HP Plus pads do well at open-tracks on moderately driven Mustangs, so if you're not absolutely hammering the brakes, this smooth pad should do fine. If you're driving harder, Hawk offers its moderate-duty race pad (Black) and the all-out Blue pads. Working temperatures for these pads are 100-900 degrees pad (not disk) temperature for the Blacks and 250-1,000 degrees for the Blues.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
30.22 114.91 322.56
28.02 108.42 340.03
29.01 111.41 332.24
29.61 117.10 347.45
29.20 117.38 not tested
31.45 125.94

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
26.96 106.50
28.17 103.78
28.01 105.25
29.98 109.91
31.36 116.32

Performance Friction 93
These racing pads are no longer offered by Performance Friction, but they are a favorite of Baer's, and are what our car was set up with for race-track duty a couple of months prior to this pad test. We've enjoyed these pads in several open-track events, where they've proven to be about bulletproof.

This is a high-torque pad (with rotor wear to match), enough so that Baer says it is too much pad for the rear of a Mustang. This either locks up the rears or requires invasive amounts of ABS. A data glitch kept us from presenting more of the stellar 100-0 mph stops; expect a rise into the 300-foot territory by the fifth stop.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
25.95 106.95 284.81
27.03 104.45 283.58
28.18 111.38
27.08 108.17
26.14 106.29

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
29.08 103.35
30.47 106.71
26.26 102.38
26.55 105.49
28.33 107.57

Performance Friction 97
This race pad is currently available from Performance Friction and should offer reduced rotor wear compared to the superceded 93 compound. As with the other race pads in this article, the second 100-0 mph test is typically the best of the string because the brake system temperature is optimal. This is noticeable on the road-racing track where the second or third lap is magical due to brake and tire temps and heat-sinking in the various systems. Then the tires and brakes back off a half notch and stay there quite a while. There was moderate pedal fluctuation when these pads warmed up in these trials.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
25.26 100.04 316.84
25.71 103.59 304.99
26.64 103.45 324.27
28.11 106.06 301.58
26.34 105.10 316.84

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
26.38 104.63
26.44 103.49
26.33 106.74
26.48 105.87
27.35 105.50
26.89 102.09
26.14 105.33

Performance Friction 01
Another noisy, violent pad from PF. Again, these Indy car, Winston Cup, and so on, derived pads are able to take anything we can toss their way with a mere Mustang. We sensed good onset with this pad, with a bit of pedal pulsation creeping in at the end of the 100-0 mph trials.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
28.05 106.55 324.81
25.46 104.66 310.51
26.88 103.91 299.25
26.97 101.91 303.97
26.55 104.43 312.91

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
25.96 105.53
26.06 104.60
27.00 103.83
26.54 104.90
27.35 105.50

SBS Ceramic
Baer is hot to trot on Scandinavian Brake Systems pads and has just now taken them on as the standard pad across the entire Baer line. SBS is a huge, international company with a first-cabin reputation in motorcycling, industrial, and some automotive applications. You'll be seeing more of this company as it addresses the performance and replacement aftermarket in the United States.

The ceramic pad is SBS' street or touring offering designed to work up to 1,022-degree disk temperature. Thus it's quiet and low on dust, yet it offers good performance. It also breaks in quickly, in just three pedal applications (this was true with all three SBS pads sampled here, so their prebedding procedure must be good). Under hard braking, though, the SBS pads offer a soft pedal, almost as if the pad was giving up. The performance remained strong, however.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
25.62 102.80 316.35
24.71 97.59 318.35
26.06 105.33 301.11
25.88 104.62 313.38
26.06 98.82 323.73

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
25.73 99.27
25.68 100.17
25.71 102.80
25.34 100.96
25.84 99.82
25.62 100.93
26.16 102.84

SBS Carbon Ceramic
SBS offers its carbon-ceramic pad as a high-performance street, or light-duty racing pad, at up to 1,292 degrees. It thus sounds worth considering for a street Mustang that sees the occasional track day, as then it would not be necessary to change pads.

These pads are designed to work through a wide temperature range. The pads broke in quickly, were a tad soft on the pedal, and were smooth with the ABS. They obviously offered great stopping torque and fade resistance.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
25.63 105.08 298.91
27.44 106.34 292.55
25.82 102.84 286.31
25.43 99.86 308.80
25.65 99.29 306.93

Second Trials
30-0 mph 60-0 mph
(feet) (feet)
25.35 102.61
24.69 99.61
25.53 102.89
26.48 104.88
26.98 102.92
25.75 103.21

SBS Dual Carbon
Top of the line at SBS is its dual-carbon, full-race pad, good up to 1,472 degrees disk temperature. This pad is supposed to work without a transfer film at low temperatures and with a film at higher temps, so again, it's designed to have a wide temperature range. It sailed through our fade tests with minimal dropoff. We noted a good initial bite from this more aggressive pad. We've since run this pad two days at racetracks during the Open Track Challenge and found it quite durable. It did fade slightly on tight, brake-killing tracks (our car has no brake ducts and will overheat any pad), but the pad came back when allowed to cool slightly. So far, it has been fairly quiet too. This pad does produce plenty of dust, though.

First Trials
30-0 mph 60-0 mph 100-0 mph
(feet) (feet) (feet)
26.53 101.88 299.16
32.65 110.00 309.55
26.47 103.21 312.61
26.65 108.93 309.11
26.01 105.54 319.15

Second Trials
(feet) (feet)
26.15 101.76
24.84 101.11
26.54 104.11
26.33 101.97
27.49 106.58
27.41 106.96