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The Myth Of The Big Brake Kit – Stop Lying To Yourself!

Big Brake Kit

But what are the actual advantages of a big brake kit, and why do you really need one for your car? As you add power and performance to any car, the demand for better stopping power increases as well.  One thing is for sure, if you are traveling at a high velocity, you want to be able to throw the anchor out and bleed speed as fast as possible. Otherwise, bad things happen.  On the race track, being able to stop faster than the other guys gives you a major competitive advantage. 

BMW Big Brake Kit

Big Brake Kit Aesthetics

Let’s be honest with ourselves, the main reason we like big brake kits is that they look cool.  It’s the same reason we like the look of a lowered car.  Fender gap is the indicator of a boring stock car, the sure sign of a pleb that has no interest in the joy of driving.  A low car looks like a race car, and from a very early age, we’ve been conditioned to think race cars are cool.  Race cars, of course, are always lower to help the center of gravity, but for the street, you’re not trying to shave fractions of a second off your lap time, so the benefit is simply looking. Usually, to get an actual handling advantage on an otherwise OEM car, much more work has to be done than simply lowering.

Volvo Big Brake Kit
If wheels are a centerpiece, small wimpy brakes will look out of place, regardless of performance is important.

Race cars have huge brakes. They often fill up the wheels and look really aggressive. They also look expensive, and that’s something that always helps aesthetics. The bigger brakes on higher trim models are usually to cope with the extra weight of options, with some marketing aesthetics sprinkled in. If you drop the extra cash on the bigger engine model, you want to look down and see the bigger brakes. But really, when does upgrading the size of your brake discs actually make sense?

Stopping Friction

The common myth of a big brake kit is that your car will stop faster with larger pads and rotors because you have more surface area (thus more friction).  The truth of the matter is that most likely, you already have more stopping friction in your stock brakes that you can use.  If you are doing 60mph and hit the brakes as hard as you can, you will notice your ABS kicking in due to your street tires not being able to put the grip to the road.  Without ABS, most likely you will find your tires locked up and skidding across the pavement.  Your braking force is ultimately limited by tire grip.  If you are able to lock up your tires, then you don’t need any more friction.

Now, at the end of that emergency stop, you will feel your pedal get a little mushy. That’s because your stock brake pads and old brake fluid is starting to overheat.  When this happens, the rapid outgassing pad material forms an extremely thin layer of gasses between the pad and rotor, reducing friction. Simultaneously the brake fluid inside the caliper is boiling, and when you have air in your brake fluid your braking force is severely reduced and there’s nothing you can do.

Heat Dissipation

The main reason brakes get big on streetcars is not to increase friction, but to provide a larger area and more mass to dissipate heat.  Heat, due to the reasons listed above, is the biggest contributing factor to brake fade.  If you are finding yourself coming across heat faded brakes, here are the three steps you can take before resorting to dropping thousands on that big brake kit you’ve been shopping for (unless you just want it for looks, and nobody will blame you for that).

  1.  Flush your brake fluid.  When was the last time you bled your brakes? Brake fluid is extremely hygroscopic, which means it absorbs water naturally. Every molecule of water that is absorbed into your brake fluid reduces the boiling point.  It also starts corroding the interior of your brake system into a rusty mess from the inside out.  We recommend a brake bleed with every single brake job, for a max of around 3 years. Flushing your brake system with high-performance DOT4 brake fluid and doing NOTHING ELSE will substantially raise the effectiveness of your brakes when hot.
  2. Upgrade your brake pads.  There are three instances where you can move on to step 2.  The first is if you drive like a total crazy person on the street, doing canyon runs and top speed tests on the highway (which you should never do on public roads, ever).  The second is if you are towing in hilly areas, and find the pedal on your car or SUV getting really sketchy towards the bottom of some of the longer hills.  The third is if you are racing or doing track days. If this sounds like you, then your next point of focus is to upgrading your brake compound. Your brake compound is the material that the brakes are made of, is the single most influential variable when it comes to braking performance.  Here’s an article regarding the key features of brake pads made for heavy-duty use.  Most high-temperature sport and racing brake pads are designed to be able to clamp down on the end of the front straight at 100+mph to make turn one, and then be able to hard brake again in a few seconds for turn 2 and so on.

    Most OE brake compounds will be able to do that first part alright, but then as you continue your lap, the pad will overheat and then you have no brakes.  No Bueno. Finding the right brake pad compound is a long process that requires a lot of research, but in general putting the time in here to find the best pad for your application will be the biggest single change you can make, and generally the only one really necessary.
  3. BMW Brake Duct
    Some OEM’s like BMW have basic factory ducts already installed.

    Add Brake Cooling. If you’ve made it step 3, you’re probably racing.  Overheating a racing brake pad isn’t easy to do, as their temperature ranges are often knocking on 1000+F degrees, which is hot enough to get a rotor glowing.  However, when they get too hot, the pad life will suffer. One important thing to keep in mind is that poor braking technique, rather than the wrong brake pad, is a significant contributor to overheated brakes. The proper braking technique is a racing school fundamental.

    If you are braking deep, you have to stay off the brakes until the moment it really matters, then you stand on it.  What you DON’T want to do is start braking too far in advance with less pressure.  Hovering on the brakes like this will cause temperatures to skyrocket, leading to overheating when you need it the most.  Stab brakes, don’t hover.  If you are towing, this might not be possible.

    Running a hose from the front of the car into the brake ducts will get them precious fresh air, removing excess heat and keeping the pads in their happy range for longer.  Sometimes even a small tube is adequate to get enough air to the brake rotors to get temperatures back into specification.  For optimum cooling, the brake dust shield should have a hole cut in it, then the cooling duct would be mounted directly to the back.

How Big Brakes Can Hurt Performance

The rotors in a big brake kit are bigger in order to absorb and dissipate heat more effectively, they are also usually heavier.  Because they are mounted inside the wheel you are adding unsprung weight, which is a cardinal sin when it comes to overall performance.  Unsprung weight is the worst kind of weight to put on because the suspension can’t control it (hence unsprung).  It contributes to an overall sluggish response, which is why real race cars have extremely light wheels and brakes. Click here to learn more about unsprung weight.

If the big brake kit you are looking at comes with two-piece floating rotors and high-performance racing calipers, then this probably won’t apply much (also look to spend around $3-5k).  More often I see people adding the top OEM trim level brakes to their car, which are usually extremely heavy.  You will not see any performance increases by adding large rotors and big cast iron calipers, in fact, it might feel worse!  Something to consider when adding those big 9000 Aero brakes onto your classic Saab 900.

Nearly every grassroots racing team I know (and trust me there are a lot) run OEM brakes with upgraded pads, high temp DOT4 fluid, and a little bit of cooling.  Even in the most extreme amateur endurance racing applications, this is generally enough to spend an entire day (sometimes two) of thrashing on track without a hint of brake fade.  Now, if you are running 12in wide racing slicks with planet stopping grip and are bleeding 80mph into turns, then I can safely say that getting that big brake kit is a great idea.  Just don’t lie to yourself and think that larger diameter brake discs are going to help you stop any faster on street tires.

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