http://www.essexparts.com/learning-center/cat/brake-pads/post/choose-brake-pads
by Jeff Ritter
Introduction
I'm going to share a little secret with you: As delivered from the
factory, the brakes on your car are not capable of handling repeated
lapping on a racetrack. They're also probably not very good for
Autocross, drifting, or rally racing. I don't care if your calipers are
painted red or gold, if you have gigantic carbon ceramic rotors, or if
your car is advertised as being optimized on the Nordschleife. Do you
know why your brakes are not up to the task of a serious thrashing as
delivered? It's the lowest common denominator rule.
In the US in particular, manufacturers try to make every car as
accessible to as many people as possible. That includes the guy who
probably has no business being behind the wheel. Despite the hardcore
enthusiast's wishes, that's why you don't see fixed-back race buckets in
a stock Corvette, and why stiff, manually adjustable coilovers aren't
standard issue on a 911. It's much easier to push a button in the
cockpit. The same is true of your car's brake system. If a
manufacturer delivered a 'track-day special' with an extremely noisy
brake pad, there would be countless complaints and warranty-related
service calls. The Nissan GT-R is a perfect example. The owner's
manual clearly states that the car has high-performance brakes, and that
they could make some noise. I was browsing one of the GT-R forums the
other day, and of course there were a number people complaining about
brake noise. Go figure.
So, how do manufacturers address this problem? They compromise, sometimes heavily.
The
fundamental dilemma of taking a street car on a racetrack is that it
was designed to do so many other things besides going as fast as
possible. A purpose-built racecar has no such identity crisis.
The brakes fitted to your car as standard are one of the most glaring
examples of this dilemma, and they're often the first vehicle system to
wilt when leaned upon under heavy use.
What we want and need from a street pad is completely different from
what we expect out of a race pad. For day-to-day street driving, we'd
all love to see our pads have the following attributes:
- Never make any noise
- No dust on our fancy wheels
- Good cold bite on the way to work
- Effective in the rain and snow
- Last 100,000+ miles
- Never wear out rotors
When the weekend rolls around however, our priorities shift. We want our pads to have the following traits:
- Enough heat capacity to never fade after repeated lapping on a racetrack
- Predictable torque response for precise brake pedal feel and modulation
- No required bed-in or preparation
- Low compressibility for a rock-hard brake pedal
- Immediate release from the discs when we let off of the brakes
- No uneven pad deposits or scoring of the rotors
- Little to no wear as heat increases
See any differences between those two lists?
Unfortunately, most manufacturers err on the side of caution, and
prefer to make the stock brake pads as docile as possible for the
street. They know that one day your girlfriend or wife will take your
Evo to the store, and she'll tell you that there's something wrong with
your "screechy brakes." For the hardcore enthusiast however, the
inherent performance compromises in OE brake pads are difficult to
accept.
Therefore, our currently available options are as follows:
- Accept the sub-par performance of the factory pads during aggressive driving, and enjoy their docile manners around town
- Try to find a 'happy medium' pad that contains some attributes of both street and race pads
- Install a harsh race pad that performs well in motorsports but has no 'street-friendliness'
So, we have some choices to make. We must define the most important
pad characteristics for the type of driving we'll be doing, and choose a
pad strategy with acceptable compromises. We try to get as close to
our happy medium as possible, based on how we use
our car. Every situation is different.
Basic Pad Composition
Before jumping into specific pad selection, let’s first take a step
back and look at the bigger picture. Understanding the material
composition of the four basic pad types, and how those materials behave
on our cars, will substantially narrow the sensible choices for any
given driving condition.
Brake pads for street cars typically fall into one of four
categories. These categories are defined by the pad’s fundamental
composition: organic, semi-metallic, ceramic, and sintered.
Organic
Organic pads are made of fibers mixed with fillers and binding resins
to hold them together. Some components commonly found in organic pad
are glass, Kevlar, and carbon. Organic pads have what enthusiasts
consider a ‘mild’ character. They tend to be softer, easier on rotors,
and they don’t make much noise. In the US, most OEM’s ship organic pads
in new cars because they don’t require a lot of heat to generate
friction, or bite. They are therefore safe for commuting in various
environments. While these pads offer comfort, their Achilles Heel is a
severely limited temperature range. Once they reach their maximum
operating temperature, they almost immediately lose their coefficient of
friction and burn up very quickly.
The materials used in these pads are the least costly to acquire, as
are the tools and processes to manufacture them. Therefore, organic
pads are typically the least expensive pad type.
Semi-metallic
Not surprisingly, semi-metallic pads get their name from their
composition. Each friction puck contains a substantial amount of metal.
Common ingredients are steel wool, iron, or copper, mixed with
fillers, friction modifiers, and lubricants such as graphite. On the
plus side, these pads have higher operating temperatures than organic
pads, draw heat out of the rotors, and do not wear as quickly. On the
other hand, they’re more abrasive and tend to wear rotors more quickly,
make more noise, produce heavier dust, and many times have very little
cold bite. Most race pads on the market today are semi-metallic.
Because the constituent materials, tools, and processes involved are
more expensive than those used to produce organic pads, semi-metallic
pads are more expensive.
Ceramic
The term ‘ceramic’ has been a hot marketing buzzword in brake pads
for the past decade. These pads are created by mixing ceramic fibers,
fillers, and bonding agents. The greatest benefits of ceramic pads are
their lack of dust and noise. They tend to wear a little longer than
organic compounds, and are also a bit more rotor-friendly. While they
may have a higher temperature threshold than some of the organic
compounds, they cannot compete with semi-metallic or sintered pads for
heavy duty use. Enthusiasts who spend a disproportionate amount of time
staring lovingly at their 6” polished rim lips may enjoy ceramic pads.
Those who prefer to actually drive their car hard may be disappointed
with the performance of ceramic pads.
Sintered
While sintered pads have been popular on motorcycles with steel
rotors, they remain an emerging technology for automotive use. Most
sintered pads are formed from a copper alloy powder. The powdered metal
is mixed with other lubricating and wear controlling constituents such
as graphite and carbon, formed into the required shape, and then brazed
to a backing plate at temperatures as high as 1800 degrees F. ]
Sintered pads have some unique characteristics vs. other pad types.
Their nearly pure metal content provides a stable coefficient of
friction from cold to hot, meaning they often need almost no warm-up
time to produce bite. Since they’re formed at extremely high temps,
they don’t fade under extreme use. They also don’t create as much of a
transfer layer on rotors, and therefore don’t require a lengthy,
traditional bed-in procedure. Since the pads are semi-porous, they can
be used in any weather condition: rain, snow, mud, etc.
Because they are mostly metal, the negatives traditionally associated
with sintered pads have been increased rotor wear, noise, and the
transmission of heat into the calipers.
The materials, tools, and processes involved with producing sintered pads are the most expensive of all current pad types.
The chart below provides a summary of expected pad characteristics
based on the material composition. There are exceptions, but these are
the general rules of thumb.
|
Organic
|
Semi-metallic
|
Ceramic
|
Sintered
|
Common Usage
|
Street
|
Race/Track
|
Street
|
Race/Track
|
Noise
|
Low
|
Moderate to High
|
Low
|
Low to High
|
Dust
|
Varies
|
High
|
Low
|
Varies
|
Judder
|
Varies
|
Varies
|
Varies
|
Low
|
Max operating temp.
|
Low
|
High
|
Low
|
High
|
Pad life
|
Varies
|
Varies
|
Varies
|
Varies
|
Rotor wear
|
Low
|
High
|
Low
|
Varies
|
Cold bite
|
Moderate
|
Low
|
Low
|
High
|
Judder/pad deposits
|
Varies
|
Varies
|
Varies
|
Low
|
Compressibility
|
High
|
Low
|
Moderate
|
Low
|
Cost
|
Low
|
High
|
Moderate
|
High
|
How Will You Drive Them?
Looking at the dissimilar ingredients in each pad type above, it
should be obvious that they'll perform quite differently as driving
conditions change. The underlying components dictate each pad's basic
operating parameters. If you ran a piece of chalk down the side of your
car, would you expect identical results when doing the same thing with
your house key? Of course not. It's not any more reasonable to expect
an organic pad to last forever at 1200 degrees F, or a semi-metallic pad
to run silently against an iron rotor.
Each pad has its ideal operating conditions, which may or may not fit
your driving style, habits, or requirements. So how do you choose the
pad that's right for your situation? You compromise, beginning with
your top priorities and working your way down to the traits that aren't
as important to you.
Let's take a look back out our initial bulleted list of desirable
characteristics for the street and track, except this time we're not
going to isolate the street from the track. Instead, we'll blend the
lists together into one abbreviated attribute list:
- No uneven pad deposits, judder, or vibration
- Low noise
- Low dust
- High max operating temperature (fade resistance)
- Good cold bite
- Long rotor life
- Effective in all weather conditions
- Good hot bite
- Long pad life
- Predictable brake torque response
- No bed-in
- Low compressibility
- Immediate release
Now we'll take a look at each of the scenarios you may encounter
behind the wheel, and examine which characteristics are the most
desirable or important for that type of driving. The goal of this
article is not to dictate the perfect pad choice to you. The objective
is to get you thinking about as many of the factors that go into pad
selection as possible for your unique situation, which should help you
make an informed purchase decision.
Daily driver shared vehicle
If you share your street/track car with a significant other, save
yourself some headaches and go with as mild of a pad as you can
stomach. Unless you can find a quiet sintered pad, organic or ceramic
pads are your only logical options. You'll have to accept the fact that
your favorite toy has become a glorified taxi and shopping cart. For
this situation, important attributes from our list above include:
- Good cold bite- When you hit the first stoplight on
the way to work in the morning, you want the car to actually stop.
Standing on the brake pedal and praying is a terrible way to start the
day, and it's even less fun for the person you just rear-ended.
- Effective in all weather conditions- Assuming you
don't live in Southern California, having a daily driver that can slog
through rain, snow, and dirt without compromising performance is
important.
- Low noise- If the pads on your shared vehicle are
noisy, you may be sleeping on the couch. When the average schmuck who
knows nothing about cars hears your S2000’s squealing brakes and asks,
“What’s wrong with your car,” you find it amusing. When they ask your
wife for the fifth time, she may lose her mind.
You could argue that long wear rates and predictable response are
both important to economical street driving. For the most part however,
appropriately handling the three issues above should keep all involved
parties relatively safe and happy.
The pads required to accomplish these feats very closely resemble the
OEM pads found in most US passenger cars. These are the issues on
manufacturers' minds when they decide on a pad compound. They want to
make the brake system as idiot-proof as possible, avoid all warranty
claims for noise and vibration, and ensure that even the most careless
won't hurt themselves while driving their mobile phone booths.
If you want to drive your shared car aggressively on country roads,
canyons, or in any type of motorsport event, buy a nice jack, ramps, and
some hand tools, because you're going to be frequently changing your
pads to get the performance you're after. Using a pad geared towards
solving the most basic transportation needs doesn't exactly provide a
broad performance envelope.
If you try to take this type of pad into an aggressive driving
situation, you'll encounter pad fade, lack of bite, poor modulation, and
accelerated pad wear as temperatures rise. You may even trash your
rotors with uneven pad deposits.
If your significant other isn't too vain, you may want to talk her
into an inexpensive beater for daily driving duties. For the price of a
nice set of wheels, you can buy a car that gets solid gas mileage,
provides reliable transportation for many miles, costs almost nothing to
insure, and you won't even have to worry about door dings. Implement
the beater lifestyle, and your newly converted track-only toy will thank
you.
Daily driver & Aggressive Street Driving
Many enthusiasts fall into this category. You drive your car on the
street to work each day, to run errands, and out to dinner when you feel
like stroking your ego a bit (although you rarely allow the valet to
touch your car...and you watch him like a hawk when he does). You take
every opportunity in the evenings and on weekends for a spirited drive
off the beaten path. You'd like to get into motorsports, but you're
either unsure how to do so, have a severely limited budget, or a
complete lack of time.
When we throw aggressive driving into the mix, we have to deal with
higher brake temperatures. While organic pads could be an option,
semi-metallic or sintered pads are the smarter choice.
- Good cold bite- Even though you use your car for
'fun' driving in addition to daily duties, your safety is the top
priority. It's still critical that your brakes bite cold on the way to
work each morning
- Effective in all weather conditions- As with cold
bite, you're again constrained by daily driving requirements. If you
live in Phoenix, enjoy that 'dry' July heat, and don't worry about this
issue. If you dwell where the sun doesn't shine...ahem, sintered pads
could be your best choice.
- High max operating temperature- If you ever hammer
your brakes on country roads or canyons in your spare time, it's
entirely possible to get pad fade (firm brake pedal, but the car doesn't
stop). See point #4 below if you only plan to get your brakes really
hot "once in a while."
- No pad deposits, judder, or vibration- The
propensity for uneven pad deposits, or what many people call "warped
rotors," increases dramatically when you plan to drive your car hard at
times, but err towards a milder pad compound for comfort. You think to
yourself, "Well I'm only going to get them really hot once in a while."
Whether done once or twenty times, organic compounds tend to smear on
the rotors when pushed towards their maximum operating temperature,
sometimes causing irreparable damage to both the rotors and pads. Yes,
you can ruin your rotors the first time this happens, a costly lapse in
judgment. Don't be the guy who says he'll only try crack once. If you
plan to bomb away on your pads once, you'll do it more than once. If
you think you'll ever
push your pads to a temperature above the recommended range for a given
compound (even once), go with a compound capable of handling those
higher temperatures.
You'll now have to decide if it's worth the additional noise, dust,
and possible loss of cold bite to step up to a semi-metallic pad. If
you go with semi-metallic's, research their cold bite before
purchasing. Or, if you can find a low noise sintered pad, that would be
acceptable as well, particularly if pad deposits are a concern. If you
stick with an organic compound for comfort reasons, you must be mindful
of brake temps. Backing off before you actually experience substantial
pad fade can mean the difference between a fun drive and ruining your
pads and rotors. If you have the experience to read the signals of an
impending problem, feel free to ignore this advice. Otherwise, suck it
up and deal with a little noise and dust you big baby.
Please keep in mind that there's almost always more than one solution
to the same problem. In the above scenario, rotors that flow more air
or brake ducting could both potentially lower pad temps enough for the
use of a milder compound. These solutions work towards the same
objective of lower overall brake system temperatures. To minimize
compromises, look for different routes to the same objective.
Weekend Warriors
Most serious enthusiasts begin with aggressive street driving, but
eventually make the leap to some form of motorsport on weekends. They
do so when they either have enough money to continually replace
consumables such as brakes and tires, or when they become frustrated
with the limited driving experience public roads offer. Because of the
prohibitively high costs of storing and transporting a dedicated track
car, the majority continue to drive their 'fun' car on the streets.
Although over time, the car gradually becomes a different creature, one
that is less comfortable, louder, faster, and much happier on a track
than on the street.
With some motorsport experience under your belt, you likely find
yourself driving slower and more sanely on public roads. You realize
that you'll never be able to replicate your track driving style without
killing yourself or someone else. Driving fast on the road just doesn't
do much for you anymore.
At this point, many enthusiasts adopt a multiple brake pad strategy,
one for the street, and one or more pad compounds for various motorsport
venues. The street pad choice is now geared mainly towards comfort,
although some still enjoy a quick blast down a deserted road. Most of
these customers know when to back off however, and can recognize when
damage to their limited street setup is imminent.
Let's take a look at the various motorsport venues for which dual-use
street and track cars are commonly used, and examine the brake pad
requirements for each.
Drag Racing
Unless your car is on the verge of needing a parachute at the end of a
run, any decent aftermarket pad should be able to handle one
substantial stop from a relatively high speed. That said, I'd place
good cold bite
as my highest priority, particularly if you're driving a sub 11 second
car like Vinnie Diesel. That means organic or sintered pads are your
best options. Waiting around for your pads to bite when doing 130mph+
at the end of the strip is a pucker-factor 13, so I'd steer clear of
ceramic pads, and be sure the semi-metallic's you're considering have
good cold bite.
Autocross
Autocross presents a unique challenge for your car's brakes.
Depending on the course layout, the amount of pad heat generated may not
be any greater than driving through stop-and-go traffic. Many times
you never get out of second gear, which means speeds are generally
limited to 60mph or less (yes, I know your Viper does well over 60mph in
second). Additionally, the flowing nature of a well-designed autocross
course means that you don't scrub off a tremendous amount of speed
entering each brake zone. More often than not, you're trail braking as
you approach the apex of the corner, rather than standing on the brakes
in a straight line. Therefore, precise control and feedback is what
you're looking for in a pad:
- Good Cold Bite- In autocross, you don't have many
chances for the perfect run. Just as with tires, you need immediate
response from your brakes when you approach the first turn on the
course. If the pads need heat to bite, you'll push your way into the
first turn, and stutter into turn six as the pad heat builds.
- Predictable brake torque response- Ideally, your
brakes will feel exactly the same on the first stop as they do on the
sixth stop, allowing you to smoothly enter each corner under braking.
- Effective in all weather conditions- Autocross
season usually starts in March, and in many areas of the country it's
not surprising to see a light snow or rain at the first few events.
Having pads that work in these conditions certainly won't hurt your
cause in the season point standings, and will certainly give you the
drop on fair weather competitors.
- No Bed-in- Properly bed-in pads and rotors add a
substantial amount of control, which is critically important in
Autocross. While driving your car around on the streets you're
gradually wearing off your pads' bed-in transfer layer. A pad that
doesn't require a complicated bed-in procedure could be a big time saver
and give you a competitive edge.
Due to the nature of the braking events, we don't really see many
heat-related brake problems at autocross. Therefore, fade and uneven
pad deposition can be eliminated from our requirement list. If winning
carries any weight with you, noise and wear should not be
considerations. If you're worried about dust on your wheels, wait until
you try getting all of the tiny shoe polish bits out of the corners of
your windows. Magnetic numbers are your friend.
Organic or ceramic pads could offer the desired results at Autocross,
but may not have enough response or feel to satisfy the discerning
driver. Additionally, most of these pads require a thorough bed-in and
constant maintenance of the transfer layer to operate at their peak
level. If you can find a semi-metallic with good cold bite, you'll
probably be happier. Even better, a good sintered pad could address all
of the critical requirements for a solid Autocross pad.
As mentioned earlier, you should explore various solutions when
setting up your brakes for autocross. With some organizations, slotted
or drilled rotors may not bump you to a different class, but they can
add additional pad bite and control when trail braking. Stainless steel
brake lines could also give you improved pedal response and feel.
Reduce compromises by exploring multiple solutions to the problem at
hand.
Gymkhana
Gymkhana is a timed event on a closed course, which most Americans
immediately liken to autocross. Similar to autocross, speeds tend to be
lower in Gymkhana, with a focus on car control and precision. Some
would argue that gymkhana events are even more technical however, as
they demand the mastery of a different set of car control skills such as
drifting, spins, etc. As we saw with drifting, the popularity of US
Gymkhana is being fed from Japan, where it has been popular and
competitive for many years.
Brake requirements for Gymkhana closely mimic Autocross needs, with
cold bite and predictable all-season response emerging as the most
important requirements. A semi-metallic pad with good cold bite, or a
sintered material would be the best pad options.
Drift
In the past few years a number of big brake kit manufacturers have
targeted the drift crowd for advertising. Let's clear something up.
The notion that fifteen inch rotors and twelve piston calipers will
improve your drifting is just plain foolish. Big brakes are required
when the primary objective is reducing brake system temperatures.
Adding a gigantic brake kit to a drift-specific car is akin to
perpetually having an import model riding shotgun. Your car will always
look better, but you'll be continually dragging around dead weight and
spending more money than you should. Tsuchiya-san would surely smack
you with his finger pointer if given the opportunity.
Many of the techniques used to initiate a drift have little to do
with the brake pedal. As such, brakes play a supporting role, rather
than a starring role in drifting (with the exception of the hand
brake). Controlling your car's weight transfer is crucial for effective
drifting. As such, control is a higher priority than heat capacity.
- Good Cold Bite- As with autocross and gymkhana, you
don't have many chances for the perfect run in competitive drifting,
and you don't have all day to wait for your brakes to warm up. The goal
is to shift weight quickly and smoothly, and a pad that bites hard cold
is a boon.
- Predictable brake torque response- As with road
racing, repeatability is critical in drifting. If the car enters a
drift the same way every time, your ability to get creative increases
dramatically. You know what the car will do in response to your
inputs. You want your brakes to feel exactly the same at all times when
making attitude adjustments to the car with the brake pedal.
- No Bed-in- Properly bed-in pads and rotors add a
substantial amount of control, which is paramount in drifting. While
driving your car on the street with cold brakes, you're continually
wearing off the pad transfer layer on the rotors. A pad that doesn't
require a complicated bed-in procedure saves time and provides a
competitive advantage.
Although you'll likely give your brakes more of a workout in drifting
than you would in autocross, you don't need the pad with the absolute
highest maximum operating temperature on the market. Then again, you
also don't want something that wilts as soon as the heat gets ratcheted
up. If you go with a mild organic pad, you do run the risk of fade and
uneven pad deposition. Wear isn't really a consideration unless you
have a BBK, in which case new pads and rotors may cost more than the
replacement value of your 240. If the dust on your Volks bothers you
that much, use more Zaino you pansy.
Organic or ceramic pads probably don't have enough feel to satisfy
the driver with a sensitive foot. Additionally, most of these pads
require a thorough bed-in and constant maintenance of the transfer layer
to perform optimally. A semi-metallic or sintered pad with good cold
bite would be the ideal choice.
As mentioned earlier, you could evaluate slotted, drilled, or dimpled
rotors to gain some additional pad bite and control. Some people like
the feel of these rotors, while others find the grittier feel through
the pedal distracting. Stainless steel brake lines offer improved feel,
and don't forget to regularly flush your brake fluid to maintain the
most solid pedal. Brake fluid constantly absorbs water over time, even
under ambient conditions.
Show
I threw this one in under motorsports for all of my show car friends,
because I didn't want them to feel slighted. Seriously though, you
really want my advice on which brake pads to use for your show car? How
about the ones with the chrome backing plates and Hello Kitty
stickers? Don't just sit there looking at it, play with it! Friends
don't let friends have cars that are all show and no go.
HPDE (High Performance Drivers Education)
Unless you flagrantly risk your life at every turn, you'll never put
the same amount of heat into your brake system on the street as you will
on a road course. HPDE is really the first venue I've mentioned thus
far where maximum operating temperature and fade resistance come to the
forefront as the critical brake pad requirements.
One of the most interesting aspects of HPDE is the wide range of
speeds and driver ability across run groups. As such, it's difficult to
recommend a blanket pad compound or type for HPDE. After countless
discussions with customers on this topic over the years, I believe there
a few key considerations when selecting a track pad: Driver experience,
track layout, vehicle configuration/modification, and tire choice. A
careful examination of these factors in your personal situation should
lead you towards an acceptable pad choice. Keep in mind that all of
these factors are related, and cannot be considered in isolation from
one another.
Driver experience
If you've never driven anywhere but the street, your first couple of
trips to the track will most likely not tax your brake system too
heavily, right? Not exactly. If you're driving a twin turbo Viper on R
compound tires at Road America, you're going to have some serious
problems with a bone stock brake setup. A blind chimp could obliterate
the brakes under those circumstances, so you being a complete track
newbie won't necessarily protect your brakes from destruction.
It's true that novice drivers tend to be easier on the brakes because
their corner exit speeds are lower, their terminal speeds entering
brake zones are therefore lower, and there's less kinetic energy being
transferred into heat during a given stop. That said, novice track
drivers also tend to stab wildly at the brakes, stay on the brakes too
long, oscillate between on and off brake, and do all sorts of other
things you never seem to expect from the passenger seat! The end result
can be some serious brake punishment. It's impossible to say that a
novice driver will be fine on stock brake pads based on track experience
alone.
Track layout
Long straights followed by tight turns mean your car is decelerating
from a very high speed to a very low speed, creating a high energy stop.
The distance between stops will also impact the heat retained in your
brakes. If a particular track layout has a steady succession of medium
straights and tight turns, your brakes don't have much time to cool
between stops. That means heat will continually build. Flowing tracks
with long sweepers are much easier on brakes (think Willow Springs).
Look closely at the track you'll be driving to determine how demanding it will be on your pads.
Vehicle configuration/modification
Power to weight ratio, drivetrain layout, and other brake system
components all factor into pad selection for track duty. All else held
equal, more massive, faster cars place a greater strain on the brake
system in a brake zone. An Audi Allroad will require a much larger
rotor as a heat sink than a Miata.
If you strip 200lbs. out of your car, you're placing less demand on
your pads in terms of mass, but you'll be hitting higher speeds entering
turns. For a given amount of power, lighter cars are easier to
accelerate, and will reach a higher speed at the end of a straight.
Front engine cars are much harder on front brakes than they are on
the rears. If you drive a 911 or NSX, your car uses comparatively more
rear brake than a Viper, which has a massive V10 sitting over the front
wheels.
If your car has large rotors and fixed (non-slider) calipers from the
factory, is fairly lightweight with lower power (think DC5 Integra Type
R), your pads will be much less stressed than on a heavy, powerful car
with undersized factory brakes (base model 350Z).
The interplay of vehicle power, mass, weight distribution and the
overall brake package will all substantially impact pad choice.
Tire choice
Tire choice is one of the single greatest factors in determining
which pad will work for you on the track. The stickier the tire, the
more brake you can use, and the more heat you will generate. More grip =
more heat. If you're running street tires, or if it rains at an event,
you won't be able to generate as much grip, and you won't tax your
brakes as much. Maybe you really don't have to pull off your wheels to
swap pads in that downpour!
So where does all of that leave us when choosing a pad for HPDE? The
critical point is, every modification you make to your car and the nut
behind the wheel will change the demands on your brake system, and you
must adjust accordingly. Just because you used a particular pad before,
doesn't mean it will work again after you've installed your new turbo
kit and Hoosiers. Chances are that after your 25
th event,
you'll be taxing your brakes very differently than you did during your
first event. You'll be hitting higher speeds, entering and exiting
corners faster and in a different way, and your car will likely have
more grip and power than it did when you started (you'll also be much
poorer). As such, you must constantly evaluate the overall condition of
your brake system, and not be afraid to try new pad compounds as both
you and your car evolve.
If you want to play
it safe and not risk damage to the major components of your brake
system, don't EVER drive an OEM pad on a road course. It may be more convenient and seem economical to run stock pads, but it
will cost
you time and money in the long run. There's also not much worse than
wasted track time. When you're sitting in the pits watching your buddy
rip down the front straight, and your stock pads are a steaming pile of
dust lying inside your wheels, you'll be wishing you took the hour on
Friday night to change your pads and bleed your fluid. I can assure you
that they weren't designed to cope with the stress of an HPDE event.
So, what pad attributes are
critical for HPDE?
- High max operating temperature- Pussyfooting around
a track while nursing fading brake pads is incredibly frustrating, but
slamming into a barrier after your brake pads have completely lost all
grip on the rotors is slightly more upsetting. Evaluate the parameters
of your situation as described above, and make sure you have pads that
will handle the heat you plan to throw at them.
- No uneven pad deposits, judder, or vibration-
Although some pads may have problems in this area at moderate
temperatures, this attribute often goes hand-in-hand with a High max
operating temperature. You do not want a pad that readily smears high
spots of material onto your rotors. Entering every turn with a
thump-thump-thump through the brake pedal and steering wheel is
extremely distracting, and could waste your hard-earned track time, your
rotors, and a sizeable stack of cash.
- Predictable brake torque response- If you want to
increase your driving skill and graduate to the next level, consistency
will take you there. Brake pads that feel the same in every brake zone
will go a long way towards improving your lap times and comfort on the
track, as your mind will be freed up to focus on other things.
Although not critical, these are some other important attributes for HPDE:
- Good hot bite- To a large extent, this is a matter
of personal preference. Most pads with an adequate Max Operating Temp
for the track have at least decent bite. That said, the coefficient of
friction of race pads is all over the map. I'll discuss this topic a
bit more in the next section, but most HPDE drivers enjoy a pad that
requires only a modest pedal effort to produce tangible results.
- Long pad life/Long rotor life- Your budget will
completely dictate the importance of this issue, but the bulk of my
customers don't have $500 to burn up during every 20 minute track
session. You'll have to find a pad that offers a balance of wear along
with the characteristics you're after. A milder pad may be gentler on
your rotors, but will burn up more quickly as the temps increase. A pad
with ultra high bite may feel great, but it may chew your rotors up
quickly. Tradeoffs, tradeoffs.
Good cold bite isn't really a huge issue in HPDE. Your warm-up
/recon lap under yellow flag conditions is the perfect time to bring
your pads up to temp, and in HPDE you're not running for a time on lap
number two.
While driving on the track in the cold, rain, and snow is definitely
entertaining, it's not the norm with HPDE's. Most sanctioning bodies
delay or postpone events for adverse track conditions, so all-weather
effectiveness isn't typically a prerequisite for a great HPDE pad.
When preparing your car for the track, you must take the time to
bed-in your pads. Assuming you've accepted this fact, a pad that
requires little or no bed-in would not be a critical performance
advantage. It would however be a tremendous convenience.
Low compressibility and immediate release are nice-to-have's, but probably outside the scope of many HPDE drivers' concerns.
If you're worried about noise and dust while tracking your car, maybe
you should just stick with knitting or coin collecting Sally. You're
probably the same guy that uses two full rolls of painter's tape on your
front bumper.
Semi-metallic and Sintered pads are the only reasonable choices for
track duty. Organic and ceramic pads will rapidly turn to dust or
melt, trash your rotors, and waste valuable track time.
Time Trial / Time Attack
If you're competitively driving your car against the clock on a road
course, you hopefully have a fairly solid handle on the capabilities of
both yourself and your car. As such, your priorities for brake pads may
shift above and beyond the critical necessities described in the HPDE
section. At this stage you begin to evaluate the nuances of a pad
compound.
I briefly touched on the generic topic of a pad's 'hot bite' in the last section. For the seasoned driver,
how
the pad bites when hot is a very personal and important attribute.
Some pads have a completely flat torque curve: as temperatures rise, the
pad's coefficient of friction remains constant and stable. During a
stop, you feel this through the pedal. As you progress through a given
braking event, you progressively push the brake pedal harder to slow the
car "more." For many people, it's the only logical and ideal response
out of a pad. They find it easier to adjust the car's cornering
attitude by modulating the brakes with a linear leg effort...pushing
harder means "go slower" or "stop!"
Others prefer a pad with a rising torque curve. As heat
progressively builds during a stop, the pad's coefficient of friction
ramps up as well. This type of pad requires a more constant, or even
diminished, leg effort as you progress into a turn. The pads bite
harder without much change to the force input.
The most obvious way to evaluate these characteristics prior to
purchase is via a compound's brake dyno plot. Unfortunately, most
manufacturers don't publish this data. Additionally, the methods used
to collect and display dyno data is non-standardized. Therefore, the
customer is presented with the classic dyno dilemma as witnessed in
countless message forum wars regarding engine power. Brake pad dyno
plots from different manufacturers should not be compared directly.
Instead, they should only be used to provide general guidance on the
shape of the Mu curve for a given pad compound, or to compare compounds
within a particular manufacturer's available range.
In addition to Mu, advanced drivers take notice of other pad
characteristics such as compressibility. Given the vast array of
materials used to create brake pads, it isn't at all surprising that
certain pad materials are more pliable, malleable, and compressible than
others. If the primary components of organic compound A are newt eye
and bat wing, it's going to feel a little more 'squishy' under foot than
pad B made from nearly pure iron. Again, this is a matter of personal
taste. Some drivers spit venom if they feel even the slightest bit of
slack through the brake pedal. As with Mu, there's no easy way to
identify a compressible pad prior to purchase. You'll have to rely on
personal experience or the experience of others for guidance. (Note: If
you bleed your aftermarket big brake kit six times and something still
doesn't feel sharp when braking hard on the track, don't overlook a
compressible pad material as a potential culprit.)
As with Mu and compressibility, release is a term you hear thrown
around quite a bit in race pad discussions. A pad with poor release
continues to ride the rotor after the brake pedal is released. The pads
feel 'sticky,' and won't let go of the rotors as you trail brake into a
turn. As with compressibility, you'll have to discover which pad
compound suits your taste in this regard through experience or
recommendation from a trusted source.
For the competitive time trial or time attack driver, experience and a
detailed analysis of the driving environment will be core determinants
in choosing the appropriate pad compound. It's obvious that a
semi-metallic or sintered compound with a high max operating temperature
and predictable response is critical. After that, it gets tricky.
Relying on the subjective opinion of friends, competitors, and experts
to describe the subtle nuances of a given pad can be helpful, but don't
be surprised if your reaction to the pads is completely different when
you try them for the first time.
Because of their format, certain time trial and time attack events do
offer the opportunity to exploit a competitive advantage through brake
pad selection. Some organizations run a format of one warm-up lap,
followed immediately by a very limited number of hot/timed laps (one to
three), culminating with a cool-down. Just as with autocross, a brake
pad that doesn't need a substantial amount of heat to provide stable
maximum friction can provide a great advantage. In this regard, a
sintered pad has the advantage over other pad types.
Wheel-to-wheel road course sprint & endurance racing
Only a select group of individuals have the intestinal fortitude to
rip a street car to pieces and turn it into a full-blown racecar. It
takes some serious courage to weld in a cage and go speeding around a
track six inches from a guy you've never met before. If you crash, you
lose a lot of money. If you ever try to sell the car, you lose a lot of
money. If you win, you lose a lot of money but you feel good about it.
Plenty of people in the PCA race their 911's and continue to drive
them on the street. Most of these individuals simply leave their race
pads in the car at all times, since the car is typically a weekend toy.
On the rare occasion the car sees street action, they're happy to deal
with the screeching, dusting, and complete lack of cold bite found in
many semi-metallic race pads. In many of these situations, the car is
even trailered to events, so there's not much concern about street
manners.
The critical requirements for a good full race pad mimic those for
time trials or time attack. The only notable exception would be the
need for superior pad wear when endurance racing.
Rally /Hill climbs/Rallycross
The variables and challenges in rally-related events are probably the
most complex across all motorsports, and the drivers who excel in these
venues are arguably the most versatile and talented. Most notably,
track conditions in these events are much less controlled vs. other
types of motorsports, and having a single solution for all occasions is
virtually impossible. Drivers may encounter tarmac, dirt, mud, snow,
ice, and water during these events. Each of these surface conditions
prevents unique grip levels and brake requirements, and these surfaces
are not always encountered in isolation from one another. For example, a
car may encounter split-mu conditions, such as braking with the
driver's side tires buried in loose gravel, while the passenger side
tires are clawing for grip on ice. The ramifications of these complex
conditions are outside the scope of this article, but there are some
basic desirable traits for brake pads if you plan to take your STi, Evo,
or 323 GTX to one of these events.
- Good Cold Bite- You need pads with high bite on the
first stop, and every stop thereafter. You may also have sizeable
distances between heavy brake applications, which allow the pads to cool
considerably. Good cold bite is a must for rally-type motorsports.
- Predictable brake torque response- With ever-changing track conditions, you always want to know what the car will do in response to your inputs.
- Effective in all weather conditions- A pad that can predictably perform when covered in water, snow, and mud is a huge advantage in rally events.
- No Bed-in- Not having to bed-in pads or maintain a transfer layer is a tremendous advantage as event conditions change.
While this list mimics the requirements for autocross, the speeds
associated with these types of events are normally higher. As such,
ensuring that the pad you choose has a
High Max Operating Temperature
is also critical. Organic and ceramic pads are not really appropriate
for these types of events. Some semi-metallic compounds may work well,
but sintered pads will provide the most driver advantages due to their
versatility during changing conditions.
It's extremely unfortunate that rally racing has never gained a
sizeable mainstream acceptance or following in the US. Even during its
Group B heyday of the early '80's, it never drew the audience that the
juggernauts of F1 and NASCAR do today. Regardless of past public
reception, if you've never watched Sebastian Loeb hit a jump, graze some
crazy spectators, and narrowly dodge four trees larger than telephone
poles all while sipping a latte, you really should. I still can't
figure out how that guy fits his gigantic brass pair into a standard
issue race bucket.
Overall most important vs. least important attributes
So now that we've combed through most of the ways in which we'll
potentially use our street/track car, which of the brake pad attributes
from our list repeatedly came to the surface as being critical? The
ones that allow us to go faster and enjoy our car more with less hassle
of course!
- Good cold bite
- Predictable brake torque response
- No uneven pad deposits, judder, or vibration
- High max operating temperature (fade resistance)
- No bed-in
- Effective in all weather conditions
As a serious enthusiast, you're likely the competitive type who wants
the best performance. Pads with the above performance attributes are
not the cheapest to manufacture, are quite often specialized in their
application, and probably aren't the best choice for your wife's car.
If performance is your priority, you'll have to compromise on comfort
and cost, which you'll notice rarely made it to the top of our priority
list. These attributes are only important to manufacturers making a pad
choice for the average Joe, and they likely hold little relevance to
the type of driving you most enjoy:
- Low noise
- Low dust
- Long rotor life
- Long pad life
The grids below summarizes the important pad attributes by driving venue.
Daily Driver
|
Canyons
|
Drag
|
AutoX/Gymkhana
|
Drift
|
Good cold bite
|
Good cold bite
|
Good cold bite
|
Good cold bite
|
Good cold bite
|
All weather
|
All weather
|
|
Predictable response
|
Predictable response
|
Low noise
|
High MOT
|
|
All weather
|
No bed-in
|
|
No Judder/deposits
|
|
No bed-in
|
|
|
|
|
|
|
|
|
|
|
|
HPDE
|
Time Attack
|
Wheel to wheel
|
Rally/Hill
|
High MOT
|
High MOT
|
High MOT
|
Good cold bite
|
No Judder/deposits
|
Good cold bite
|
Good cold bite
|
Predictable response
|
Predictable response
|
No Judder/deposits
|
No Judder/deposits
|
All weather
|
Good hot bite
|
Predictable response
|
Predictable response
|
No bed-in
|
|
Good hot bite
|
Good hot bite
|
|
If you try taking what appears to be the cheap and easy route of
using OEM or low cost aftermarket pads for performance driving, don't
expect a favorable experience. You'll have poor performance, and it
will probably cost you more money and time in the long run than if you
initially bought the proper tools to match your needs.
Ask yourself how much time you spend in each of the driving scenarios
we examined. Do you use your car 98% of the time for daily driving,
and only take the car to the track twice a year? In that case, it's
probably worth the time to swap pads for the rare motorsport event. A
good set of track pads is a great investment that will likely last you
multiple years in this scenario.
On the other hand, if you're competing in autocross twice a month,
time attack once a month, and canyon driving weekly, you'll either have
to buy dedicated pads optimized for each driving environment, or you'll
have to choose a pad that works fairly well for all of these scenarios.
Just accept the fact that you will have to make some compromises in
comfort, cost, convenience, or performance.
Closing comments
Every time I see a lazy newb on a car forum toss out the innocent,
"what's the best brake pad?" question without providing any information
about how they actually plan to drive their car, I brace myself for the
inevitable mind-numbing fanboy brand warfare that ensues. As you can
hopefully see, there is no one best pad or brand for all people in all
situations. Pads are largely a personal preference based on usage
requirements.
While you should now be able to quickly assess a pad's basic
performance envelope by knowing what it's made from, realize that there
are exceptions. Don't be too hasty to immediately eliminate an option
based on its composition alone, and please don't be afraid to experiment
and try something different. That's why God created eBay and the
message forum marketplace. What may not be ideal for your situation is
probably perfect for someone else. I feel bad for people who find
something that always stick to what "works well enough." How do you
know that something else won't suit you better?
Most serious enthusiasts have tried a wide range of compounds, and
have developed at least some sense of what they do or don't like in a
pad. This is where the real fun begins. Driving style and the
appropriate product characteristics converge, allowing the driver to
explore the car in new and different ways. At this stage you'll also be
able to put into words more clearly what you're feeling with a given
pad. Things like a rising torque curve or poor release will become more
obvious with a broader base of comparison under your belt. While these
terms will certainly confuse the hell out of your neighbor in a casual
conversation, they will help you gain better advice and guidance from
other drivers, racers, and industry professionals.
Take a serious look at your unique situation, assess your needs, and
be prepared to compromise if you plan to use your car in more than one
driving environment. The one-size-fits-all approach has never been a
viable option in the brake pad market, nor will it be with the current
technology in hand. Choosing 'the best' brake pad will be a unique
process for every enthusiast based on their unique wants and needs.
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