Braking Bad: A Deep Dive on All Things Brakes

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Braking System Deep Dive

There’s a right way and a wrong way to do anything, and through the fog of relentless marketing hype, that line can get a little hazy. Every brake pad, rotor, and kit says that they’re the best, and that they’re an upgrade from whatever you already have. However this is the real world, and not everyone gets a first place trophy. Brake rotors, and pads are not a one size fits all kind of part. What works for a soccer mom isn’t going to cut it for someone’s truck brakes towing a boat or doing weekend track days.

I think a lot of this is a result of there being a lot of confusion and misunderstanding on how exactly the brakes on our cars actually work. It’s a simple concept at a high level, but things get complicated quick once you start getting in to the finer details.

Braking system overview:

TL;DR: On the simplest level, your brakes work by using hydraulic force to press a fixed friction pad (brake pad) against a rotating assembly (brake rotor or drum), converting kinetic energy into heat through friction. This slows that rotating assembly to a stop, and with it, you and your vehicle.

Going deeper:

Being a hydraulic system, your car’s brakes take advantage of Pascal’s law of fluid dynamics as its means of force amplification. Pascal’s law basically states that any pressure change enacted on an incompressible fluid will be transmitted equally throughout the fluid in every direction. That makes sense, right? But how do we use this principle to our advantage in a brake kit?

Pascal's Law Diagram
Image courtesy of Wikipedia

In the diagram above, basically what we have is a U-shaped tube with a piston on each side. The tube is filled airtight with incompressible fluid, so any pressure applied to the one side will be transmitted through the fluid to push the piston on the other side. By making the surface area of the right piston 10 times the surface area of the left piston, 10 times the pressure will be transmitted to the left piston. 100 pounds of downwards pressure on the right piston results in 1000 pounds of upwards pressure on the left.

So to apply this concept for use in vehicle braking (generally speaking), we apply that pressure via the brake pedal as it pushes against smaller surface area pistons in the master cylinder, through the brake lines to the pistons in the calipers, which collectively make up the larger surface area side of the equation.

Foot on brake pedalThere are also a few other tricks manufacturers use to give the driver a mechanical advantage. For instance the brake pedal itself is on a lever arm to multiply the force applied to it similar to how a breaker bar gives you an advantage on tough bolts. Most car or truck brakes these days will have a pedal ratio between 3.2:1 and 4:1. In practical terms, this means that 70 pounds of force on the brake pedal from the driver will translate to 210 or 280 pounds respectively.

After that, manufacturers use brake boosters to give drivers a further advantage. Brake boosters work by pulling vacuum from the engine as an assist in pushing a large diaphragm before the master cylinder, which then in turn pushes the brake fluid out to the calipers. A 7″ diameter with -8 PSI of vacuum from the engine will result in over 300 added pounds of pressure going into the master cylinder.

The result of adding these systems together results in thousands of pounds of clamping force at the calipers. So much so that anti-lock brakes became an invention of necessity in order to prevent complete lock-up of the wheels, resulting in loss of control of the vehicle.

Brake Pads and Rotors:

Changing brake pads and rotors

Now that we’ve established a general idea of how your brakes work, let’s take a look at the components you’ll be dealing with the most: Your brake pads and rotors.

Your brakes work by way of two forms of friction – abrasive and adherent:

Abrasive friction: When the pads are pressed against the spinning rotor or drum, the crystalline structure of the pad material and even the cast iron disc break down, converting kinetic energy into heat, bringing the disc (hopefully) to a stop. Being that the brake pad is the softer of the two materials, this wears down the pads more quickly than it wears down the rotors.

Adherent friction: As pressure is applied to squeeze the pad to the rotor, some of the pad material breaks apart and reforms, bonding to the surface of the rotor. This process saps energy away from the turning of the disc, spending it to create that bond (along with as heat). This is the method of friction that is used to bed your pads to the rotor.

All modern brake pads use both types of friction, just to varying degrees depending on the application. Semi-metallic pads lean more towards abrasive friction, and therefore are tougher on rotors and create more dust in a trade-off that results in the ability to operate effectively at temperatures. Organic and ceramic pads lean more on the side of adherent friction, the trade-off being that they’re easier on rotors, have better cold performance, and are quieter, though sometimes that is at cost of high temperature performance (depending on the formula).

In order to ensure normal, and even brake wear between your pads an rotors, manufacturers recommend perform the process of bedding in your brakes. This is a process to “mate” your pads to your rotors with gradually increased heat cycles to create a thin, even film of brake pad material on the surface of your rotor. If the rotors and pads are not properly mated with each other, you could end up with brake shudder, squealing brakes, and uneven wear.

How does bedding in your pads pertain to the brake judder you’re feeling in your brakes?

Brake bedding procedure

If your rotors have not been bedded-in properly, or they were pushed too hard and lost that bedding, you can end up with uneven pad deposits on the surface of the rotor. At first, this just means uneven grip across the surface, causing the pads to grip, then slip, then grip, then slip, etc, and that’s an early stage of the judder you’re feeling as you brake. At the extremes, if this is not corrected, this can result in uneven rotor wear, and ultimately a “warped” rotor. I use quotes there because the term is a bit of a misnomer (more on that later).

Why are my new brakes squealing?

There tends to be a lot of confusion here due to the fact that that most brake pads come with a metal tab that will sound against the surface of your rotor to indicate that your brake pads have worn down to a certain point. So now when most people hear their brakes squeal, they think that they already need to be replaced, but that is often not the case.

What’s happening here is that the conditions are just right for your rotors to vibrate as they pass through the clamping pads, not unlike how a bow being dragged across the strings of a violin work — the main difference being that a violin is a lovely sounding instrument in the right hands, while a squealing brake rotor tends to scream in the key of “ouch.” Not pleasant.

Proper bedding of your rotors can go a long way in reducing this effect, but there are a few other factors that can contribute here. For instance, a layer of rust on your hubs when you install your brake rotors can let them sit against the hubs slightly unevenly, or with some wiggle room, allowing them to vibrate as they turn. Another reason could be your brake pads shifting and allowing play in the contact between the rotor and caliper, allowing the vibration. This can be solved using brake pad shims or some of that brake pad lube they always try to sell you at your local auto parts store (though anti-seize works just as well).

What to look for when shopping brakes:

So let’s get into what you need to know in order to see past those flashing neon “BUY ME NOW” signs and actually find what works best for your specific needs. Hint: it’s probably not the most expensive thing on the market. A takeaway theme here will be to not spend more than you actually need, as those high end, fancy race brakes are can actually be a real headache for normal street driving.

Narrow down brake pads by how you drive, not by price.

Brake pad choice is similar to choosing a tire. There’s no glory in getting something outside of your driving style. All you end up with is an expensive compromise.

This works both ways, too. You might think you’ll be doing yourself a favor and be safer buying expensive heavy duty pads for daily driving, but what you could end up with is loud, annoying pads that dust like crazy and have worse cold bite than your stock pads. By the same token, if you’re doing a lot of towing or track days/autocross, you’ll be let down by a light duty pad that will fade after the first round of hard braking — to the point of being dangerous.

So let’s break this down by use case:

Daily driver:

OEM replacement level is generally all you’ll really need. If brake dust and noise are pet peeves of yours, look into some ceramic pads, as they tend to have better street manners as far as that’s concerned.

Staff picks:
Posi Quiet Ceramic Brake Pads – Hard to beat for a basic OEM replacement pad. These are quiet, last a while, and are all around a safe bet for a commuter.

EBC Green Stuff padsEBC Green Stuff – If you’ve got a daily driver that’s a little more sporty, or that you might load up and haul things with on the weekend, this is a great pad for someone who works their vehicles a little harder than the average Joe, but are still mostly relegated to daily driving duty.

Spirited street/track use or towing:

Here’s where heat resistance starts to become a priority over street manners. Still, with the recommended picks below, you’ll be fine with day to day, but just know everything is a trade-off. Brake pad requirements tend to be pretty similar between towing and track driving. Both need to stand up to high heat over repeated cycles without fading.

EBC Yellow Stuff – This pad is an easy recommendation for anyone looking to take their car to a track day, autocross, or who tows heavy loads in mountainous areas. You don’t want to have to find out the hard way why they line the walls of the track with tires or how effective those gravel run-away-truck ramps are.

Hawk HPS Performance brake padsHawk HPS – Generally a little more expensive, but feature Hawk’s own ferro-carbon composite pad material that offers a higher coefficient of friction, fights brake fade, and can be relied on to maintain grip and pedal feel lap after lap.

Let’s Talk Brake Rotors:

Next to calipers, rotors get all the glory. What shows people your car is serious better than some massive brake rotors that are the size of most people’s entire wheels. That look brings us to the elephant in the room, though. Those big brake rotors you’re picturing are drilled and mean looking aren’t they? Well unfortunately that’s not exactly ideal if you’re looking to get the most out of your car. Let’s get into why:

Drilled and slotted rotors look awesome. They just do. They look like the Jason Statham of brake rotors, for serious drivers who want to do serious things with their cars. The difference is J. Stathe doesn’t crack under pressure, but drilled rotors do. Want an easy way to prove they’re more for looks than actual performance? Google around and look at any real race car’s brakes. IMSA, NASCAR, F1, WRC, you name it. You’ll see slotted rotors sometimes (especially in rally), but never drilled in anything that is competing at a high level.

So why do these serious performance cars like the Mustang GT350R, Porsches, or Ferraris have drilled rotors? The simple answer is that they’re for looks, and that they’re still strong enough that they won’t be a big problem for most drivers on the street. However, if you really push them to their limits, they will crack long before straight rotors will. If they are pushed hard, but not to the extreme, you get some pretty interesting wear patterns as well (more on that below).

So where did drilled rotors come from then?

They actually did come from legitimate racing needs, in fact. Way back in the day of asbestos brake pads (ignorance isn’t always bliss), there was an issue of outgassing with the pads under high heat. The issue is that the bonding agents in the pad would evaporate and create a layer of gas that Drilled brake rotors big brake kitprevented good contact between the pad and the rotor. The rather rudimentary solution at the time was to just drill a bunch of holes in those suckers and go racing — and that worked pretty well for the time.

The issue is that these days, we no longer use asbestos in our brake pads (no, not even Raybestos pads, despite the name), and with how far material science has advanced in this industry, outgassing is no longer as big of an issue as it once was. Also, pad manufacturers began putting slots down the center of their pads, reducing the need for those holes anway.

But drilled rotors cool run cooler too, right?

Yes, drilled rotors do indeed tend to run a little cooler than straight faced rotors, but here are two caveats to that fact:

The face of drilled rotor might have a reduced surface area of up to 10%-12%, which means there is overall less surface area for the pad to grip onto, meaning less friction applied in total, and not as much heat generated as a result. The cooling provided by those holes being there do make a slight difference, however, but that can be a bit of an issue in itself.

Due to those drilled holes catching air, the surface in those areas cool more than others, leading to cracks. Cast iron rotors expand and contract with heat, and the metal around those holes cools faster than the solid surfaces around them. This means that as the rotors cool, they are contracting at different rates around the surface of the rotor. What’s even worse is that the areas of the rotor that experience the biggest heat differentials are the narrow spaces between the holes of the rotor, where there is less material to spread the stress out across by their very design. It’s a viscious cycle.

That’s how you get cracked rotors as seen above. That cooling is a double edged sword that, unfortunately, is sharper on the side facing you in the case of drilled rotors. Oh, and that uneven wear pattern I mentioned earlier, check out the rotors on this Porsche I saw at a stoplight just the other day:

So what about slotted rotors then?

Like I mentioned, slotted rotors are in fact found quite often in motorsports, even among serious race teams. There are a few reasons for that, namely the ability to provide runout for water, dust, and other debris (hence their popularity in rally). On top of this, they provide a way to wipe the pad’s surface to help with things like glazing, and to maintain a properly bedded StopTech Slotted Rotorspad and rotor. This is in addition to maintaining structural rigidity in the rotor over drilled (though they can still crack before straight rotors).

Everything is a trade-off, however. The (relatively minor) disadvantages of slotted rotors is that they tend to wear out pads a little more quickly, and in a daily driver, they can result in some noise when coming to a stop in a quiet car. Depending on the slotting pattern, this can be sort of a growling sound, or with some, under really hard braking, a quick thumping not unlike ABS lockup.

So why do all of these brands put drilled rotors on their performance cars?

Because they look cool (marketing), and because most drivers generally won’t find the limits of those fancy looking drilled rotors — even in their 500+ horsepower speed machines. Doesn’t that just kind of make you sad to know? All those ponies under the hood and they never get to gallop.

Are my brake rotors warped?

Short answer: No, they have just worn unevenly.

Long answer:
So going back to that adhesive friction stuff, if a pad is not properly broken in (yes, this is a thing), the material that transfers between the pad and the disc can do so in a seemingly random, uneven fashion creating islands of deposits that keep growing, leaving high and low spots on the disc. Another problem is if you hold the pad against the rotor after intense braking or coming down from a high speed, the pad can literally leave a print of material on the disc like the image from StopTech above shows.

The other way your rotors can feel warped happens when your discs develop heat spots. Modern cast iron rotors are an alloy of iron and silicon mixed with particles of carbon. At high temperatures, spots of silicon carbides form and create uneven hot spots, growing in temperature faster than the iron around it. Once this temperature reaches up around 1300 degrees Fahrenheit, the cast iron around that area begins to form cementite, or iron carbide which is very dense, abrasive, susceptible to cracks, and conducts much more heat than the cast iron around it. Once the cementite forms, continued use will just heat up those spots, causing them to heat the iron around them and form even more cementite. It’s a vicious cycle.

Resurfacing your rotors can remove the cementite if you catch it early enough, but it’s very unlikely and most times you’ll be back in the shop after a few months getting them replaced all together. It’s a band aid fix for a larger issue, and honestly isn’t even really all that cost effective over a set of decent replacement rotors and the knowledge of how to keep this from happening again.

Brake fade and you:

We all know what brake fade is, and have likely experienced it in one form or another, but what isn’t always clear is what exactly is happening to make our brakes less effective after hard use. I’ve covered a bit of this already, but I’m going to go into more detail.

There are three reasons why your brakes fade, and they are not necessarily mutually exclusive. I already covered why the more “average consumer” friendly pads lose their abrasiveness after being overheated, but I’d like to talk about pad glazing and the effects of overheating your brake fluid. More specifically, why some brake fade leaves your pedal feeling healthy and firm, but with decreased effectiveness — and why other times your pedal will feel squishy and soft, forcing you to pump the pedal to get any performance out of the system. (Feel free to add your own innuendos to the previous few sentences, I’ll wait.)

Glazed Pads:
Pad glazing is when the surface of the brake pad literally melts and hardens, leaving a dense, smooth material that slides easily across the rotor. This will result in a normal pedal feel, but requiring much more effort to achieve adequate braking. A glazed pad has lost its porous, almost flaky surface and instead is left with an almost glassy, hard face for it to slide on. Properly bedding in your pads to the manufacturer’s spec can prevent this. Most performance oriented aftermarket pads will come with a guide, but a broad one can be found here.

Last but certainly not least, we find ourselves on possibly the most neglected and ignored item on any car, possibly only losing out to the blinkers on your average BMW (now an optional extra!):

And now for your poor, neglected brake fluid:

Importance of bleeding your brakes

Some people are surprised to hear this, but you can easily boil your brake fluid if you overwork your brakes. Why is that bad? Brake fluid boiling results in air bubbles in the brake lines. While brake fluid itself is not compressible, as we all know from the lovely world of forced induction, air is very easily compressible.

Those bubbles result in a squishy brake pedal and a reduced squeezing force on the rotors. It can even get so bad
that you can push the pedal to the floor and still not be able to stop your car. That’s not what you want mid-corner at Laguna Seca, and that certainly isn’t what you want coming down a mountain pass with your family in the truck.

Another reason to change your fluid, is that brake fluid is highly hygroscopic, which means it absorbs water. This absorption can occur through the rubber brake lines, various seals around the system, or if you open the reservoir to add fluid. This happens less than it used to with modern brake lines, but it still happens. That’s why fluid manufacturers list two boiling temperatures for their fluids. A dry boiling point and a wet boiling point:

StopTech STR Dot 4 Brake FluidDot 3:
Dry boiling point: 401 degrees
Wet boiling point: 284 degrees

Dot 4:
Dry boiling point: 446 degrees
Wet boiling point: 311 degrees

Dot 5 and 5.1 (more on these later):
Dry boiling point: 500 degrees
Wet boiling point: 356 degrees

It seems strange to call a fluid wet or dry, but basically, dry fluid is fresh stuff right from the container, and wet is fluid that has been contaminated with 3.7-percent water or more. According to Amsoil, DOT 3 fluid can absorb up to two-percent water content in a year. You read that correctly. With just 3.7-percent total water content, your high-performance DOT 4 or 5.1 fluid turned into something worse than the DOT 3 that comes in your neighbor’s Accord.

Once you boil your fluid, you might be able to pump your brakes to regain some pedal feel in the moment, but your brakes will need to be bled to get that air out, and it’s likely a sign that it’s time to change out your fluid completely.

When To Change Your Brake Fluid:

Temperature resistance isn’t the only reason to change your fluid. Too much water in the system can lead to corrosion of metal components (like the iron in your calipers). That build-up of corrosion leads to interference with moving parts — possibly to the point of leading to a seizing a caliper. Even worse, the included anti-corrosive compounds in the fluid break down over time, compounding the issue.

That’s why shops will offer to test your brake fluid for water and copper content. Copper seems like a strange thing to make its way into your brake lines, but copper content in your brakes is an indicator of corrosion. If you’ve done enough work on your cars, you’ll know that copper crush washers are used in fittings in the brake system, and those are some of the first components to corrode.

The Automotive Maintenance and Repair Association (AMRA) recommends changing your brake fluid when its copper content reaches 200 parts per million (PPM). We would take that number with a grain of salt, though, because that organization is made up of companies who have a financial interest in you flushing your brake fluid often. Either way, save that little fact in your head as an interesting little fact at the next social event of your choice. That will be sure to keep people riveted.

Otherwise, changing your fluid every two years is a good cadence to go by for a daily driver.

Calipers and other non-wear items:

Disk brake component diagram

Here’s the other side of that glamor equation. If you don’t have big, gleaming red calipers to show off behind your wheels, then what is even the point? Calipers are simple things, really. They’re big chunks of cast iron with 1-6 pistons inside, and they’re basically maintenance free, as opposed to pads, rotors, and fluid.

But there is a misconception about brake calipers, that more pistons means more squeezing force, but that simply isn’t true. The real determining factor is total surface area, not the amount of pistons. The advantage for more pistons comes from more equal pressure across the entire pad, and to spread out the heat bearing areas in the hopes of transferring less heat to the calipers and the brake fluid inside.

Brake lines:

These are often considered a lifetime part of the vehicle, but in older cars they can start to degrade and leak. Brake lines are generally hard lines up until the wheel wells, where they need to flex with the suspension, so they switch to rubber lines from there. A common upgrade that people do is to StopTech Stainless Steel braided brakelinesinstall braided steel lines, but a lot of people don’t really know why it’s done.

Braided brake lines aren’t just thrown on because they’re more durable, they actually are meant to cut down on brake line swelling under pressure. That’s right, your brakes can generate so much force, that the rubber expands and stretches, sapping braking power away from the calipers, and giving you a squishier pedal feel.


So like I mentioned earlier, every brand insists that they’re the best, but we know that just can’t be true. So how do you filter out who is worth spending your money with? Well being that this is such a competitive market, the good news is there are a lot of companies doing a lot of great things. Different brands standout in certain areas or price brackets, so I thought I would take you through some of the best companies we work with, and include some of my personal insights into the products I personally use.

EBC Brakes:

EBC is one of those rare companies that lets their products and their reputation speak louder than marketing campaigns. Even their website is stripped down and focused on the details that matter over extravagant marketing copy. This kind of no nonsense approach to their business shows in their products as well.

EBC Stage 5 Brake KitFor instance, they’re one of the few brakes manufacturers that doesn’t offer drilled rotors, and to me that makes a statement that they’re more focused on performance than flashy looks pick up those sales from people looking for that look over whether or not a drilled rotor is a design that will stand up to the kind of abuse that would meet their standards.

EBC brake kits become an easy recommendation around here for anyone looking to get more out of their brakes. EBC’s Yellow Stuff pads are one of the best compromises between being able to handle track use and heavy towing, while still maintaining good enough street manners to keep most people happy. Combine those with a set of Sport or BSD rotors, and you’re in good shape to knock out some track days.

StopTech Performance Brake Systems:

Not only does StopTech make seriously great parts, but they are an absolute wealth of information. They publish their white papers of their findings in their product development and insight into the industry, giving the public more information than almost any other company would ever even think Stoptech Big Brake Kitto. Being Centric’s performance branch, they have deep roots in this industry and a proven motorsports record to back it up.

StopTech are also one of the best performance deals in the game right now as well. I have run their slotted rotors for years because of how well priced they are compared to other comparable disks, and the fact that their quality is so consistent. They’re also have probably the widest vehicle coverage in the industry to braided brake lines, and offer everything from your pads and rotors to calipers and fluid, to full brake kits.

Power Stop Brakes:

Remember what I said before about different companies shining in different areas? Well Power Stop is the king of budget performance. Their pads and rotors punch above their weight to give you performance for a Power Stop Z36 Truck and Tow Brake Kitprice that wasn’t really possible even 15 years ago.

The Power Stop Z23 brake kit is one of our most popular kits period, not just for performance. They’re a great choice for someone carving canyons on the weekends or looking to try their hand at autocross. Oh, and for towing your car out there, the Z36 Truck and Tow kit is meant to hold up to repeated heat cycles like your rig might see in stop and go traffic or coming down a winding mountain road Power Stop is also a great supplier of performance brake calipers, which come with a temperature resistant red powder coating that looks good and will last as many heat cycles as you can throw at them.

Brembo Brakes:

This is one of those names that transcends their industry and becomes a household name — even if those people don’t have any real experience with Brembo Brake Kitthe products themselves. When your brand is used as the factory upgrade for new performance cars, you know you’ve done something right.

Brembo Big Brake Kits have become the defacto standard for anyone looking to get the most out of their cars on a track. And when I say “get the most out of their cars” I really mean it, because these are not cheap kits. To take the leap with Brembo, you’ve got to be dedicated to what you’re doing, and it truly pays off. With that many F1 championship wins with their parts, you know they’re doing something right.

MGP Caliper Covers:

Gotta fake it till you make it, right? Well if you’re up front about it, there’s nothing to ashamed of, I suppose. If you want that big brake kit look, but MGP Caliper covers customizabledon’t want to pay big brake kit prices, then these can get you most of the way there for a whole lot less than what you’d pay otherwise.

They’re available in different colors to match the look you’re going for, and also can be had with your car’s logo lasered into the side. They’re hydraulically formed out of 6061-T6 aluminum, and bolt on in under 10 minutes per wheel. Easy as cake.

Centric Brakes:

Centric is one of those brands that people might not know the name of, but probably have their parts on their cars right now, as they are one of the largest OEM suppliers in the business. They’ve become the gold standard in Centric Posi Quiet Brake Kitthe aftermarket for OEM replacement parts that can be relied on to be solid, and manage to get these things done at a price that undercuts a lot of brands that unfortunately don’t match the Centric’s quality.

Namely, their premium ceramic brake pads are a serious bargain for a ceramic pad of that quality. Hard to do better for your daily than that.


Brakes really are the unsung hero of any good car. It’s always entertaining to see the look on someone’s face when I tell them the first thing they need to do to go faster on the track is to upgrade their brakes. That gets some confused looks sometimes, but it makes sense when you really get into things like we did here today.

So what do you think? If there is something you’d like me to cover, or have questions about your own setup, drop a comment below!

3 COMMENTS

  1. Excellent overview! I’d be interested in knowing your opinion on pad material, rotor vane design, and brake cooling options. Thanks!

    • Thanks, Steve! That’s a great idea, those are good topics that I would love to get into. Going to take a lot of research for those, but they’re on my list!

      Cheers,
      Garrett

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