Why are expensive brakes better?
 

Seems like an obvious question, but I can't find the answer. Even if you have a very nice braking system, your car's stopping ability is limited by traction, right (tires, downforce, car weight, and weight distribution, suspension)?

If your brakes are too good for the rest of your car, I feel that all it's doing is making wheel lock easier (and activate ABS).

How do they improve stopping distance?

Thanks

It depends on how you would like to drive your car. If your doing daily driving on normal roads a new brake kit won't be too much better. If you are on the track you ride the brakes alot and the brake rotor heats up and essentially fails to perform so you will see loss in braking power. The better brakes will have larger surface area so that temperatures don't get as hot and better materials that withstand more heat before breaking down.

You can always adjust the braking power if the kit ends up locking up too much.

They don't improve stopping distance.

What they do is allow you to brake over and over and over, without overheating the system. Larger rotors offer more surface area for cooling, as well as more mass in the rotor itself to sink heat away from the pads. Larger opposed calipers offer more mass to sink heat away from the pads, and promote more even pad wear as opposed to the stock floating caliper.

Unless you're FI, the stock system with upgraded pads is generally "good enough". At least, in our experience it has been.

Here's a video of our BRZ braking over and over on sticky street tires; we suffered no fade, even running 5 laps back to back in 105+ ambient temps with race pads:

Turn 3: 129 to ~40
Turn 5: ~87 to ~45
Turn 8: ~100 to ~35
Turn 11: ~104 to ~45
[ame="http://www.youtube.com/watch?v=waCr19ZM640"]BRZ at Auto Club Speedway - YouTube[/ame]

Ummm, larger brakes can also can also improve stopping distance. More surface area = more friction.

Stopping distance is dictated by tires, not brakes (unless your brake bias is severely off). Can the stock brake calipers, rotors, and pads lock up the tires? Yes. That means that you have more braking power, than your tires have grip. Increasing braking power still doesn't address the lack of tire grip; the tire grip is the limiting factor in this case.

CSG Mike and Xanatos nailed it. Also, it comes down to driver preference. Usually when getting into aggressive street pads/ race pads you may find that a pad that is very expensive is the one that feels best to you, however you may also find that a very inexpensive pad is the right one for you, as it comes down to how you like the car set up and how you like it to feel.

Thanks,
Rick

What happens when tire grip exceeds brake force?

Quick replies with dead-nuts correct info, nice!

You simply run out of usable brake power and are required to apply excessive force, "standing on the pedal" comes to mind. This causes pads to overheat, glaze, break down and chunk off, uneven wear, fluid to overheat, boil, etc. Seals get damaged, too. Friction alone generates heat, but higher pressure allows that heat to transfer more quickly into the pistons and caliper body. Heat from the rotor can bleed into the steering knuckle and overheat the wheel bearings. Excessive heat is not good.

In addition to the benefits of hardcore track use mentioned above, another benefit of big brakes is lighter foot pressure and easier modulation.

edit- With extremely grippy tires and high power brakes, you eventually rreach a point of diminishing returns, where extra brake power doesn't really help, or the extra grip can't be utilized beyond a certain point. This is where aerodynamics come into play (read- downforce!) This changes everything and is really a topic for another discussion.

So, if you have more tire grip than brake power larger brakes don't equal more stopping power to take advantage of tire grip? I understand the larger surface areas do better with the heat. I'm just trying to understand, and as you can see I'm struggling.

Surface area has nothing to do with 'more friction'...mu is mu... Now thermal capacity/ability - that's already been mentioned.

You want as small a brake system as possible for the application you need it to do reliably. The stock system is very good on track with sticky tires - all it really needs is a better pad compound. If not running more power than stock, then there is no need to 'upgrade' to a 'Big Brake Kit' for track duty (HPDE) - all you will be doing is adding a noticeable amount of unsprung weight with a very minimal increase in braking performance... degrading your performance when not on the brakes in other words.

im not sure surface area has nothing to do with it. mu is a coeffecient

I should add that a BBK can contribute to a more consistent pedal feel... but at a rather high price.

In that unlikely scenario, getting a higher friction (mu) pad will get you the additional stopping power you need. However, if the tires really overpower the brakes, you'll likely overheat your braking system VERY quickly.

The formula for friction is: Ff = u * Fn

Ff = Friction force
u = Coefficient of friction
Fn = Normal force

There is no term for area. When the surface area is larger, the normal force is spread out over said larger area. Thus, each unit of area receives less force applied and the total force remains the same.

this is what you commonly find in the street scene with modified cars running fat grippy tires on 19 inch wheels and stock honda brakes.. the weight and grip of the wheels/tires will overheat the stock brakes and then you get super dorifto oh god cant stop rear-end a school bus kids on fire... so a BBK will help give the added pressure and heat management capabilities to slow down that extra rolling mass...

But even on those, a simple brake pad change can fix the problem 99% of the time as they are only seeing street use.

It's not the extra rolling mass of the wheel/tire combo that will overheat the brakes - 50 lbs vs 40 lbs is nothing. It's the increased frictional force from stickier tires that will increase the stress on the braking system.

It's worth restating that big brakes do nothing if you can lock up the tires. If you can lock up the tires, then upgrade the tires. If you are getting pad fade, upgrade the pads. Outside of the fast and furious crowd, a BBK is not really needed unless you are tracking the car.

For reference, Miata guys will downgrade their brakes from bigger to smaller just to save weight.

If you like the look of shiny new brakes, go nuts. But you won't get any performance advantage out of it.

correct, i should have added the caveat of "if not tracking the car, its really unnecessary"

just trying to generalize for people who may not be planning to take their car to the track what bbk could possibly be useful for..

Considering what you're buying .. are brake calipers not the most extravagantly over-priced aftermarket items? You'd think with the evolution of technology and manufacturing that someone hasn't figured out how to make a quality 4 pot upgrade for ~$1000. Think about this .. $1000 is a LOT of money to sink into making something as simple as a caliper on a mass scale.

That's like saying someone would have figured out how to make a set of quality forged rims for ~$1000...

Unfortunately, supply and demand gets us all :brokenheart:

I'm no expert but if size does nothing to help you stop then why wont a SUV with huge wheels and extra weight not stop with factory brakes?

I have a friend who builds demo cars and they put 26's on a Armada along with a ton of weight from a stereo. With the stock brakes the car would barely stop, to the point of being really dangerous.

They upgraded to a much larger brembo setup and all was well.

Because the heat generated from a 5000lbs+ SUV vs a 2700lbs sports car are not the same. There is a minimum amount of braking needed for each type, anything beyond that is overkill. The point being for the 86s, the stock brakes with upgraded pads will be more than good enough at its stock weight/power. Now up the power and/or weight and you have to recalculate that formula. Make sense?

The larger Brembo setup came with a much more aggressive set of brake pads, that is where the added stopping power is coming from. :happy0180:

Unless it is a dedicated track car, a set of Stainless lines, performance brake pads & high temp brake fluid should be more than good.

Never knew that. I was always under the impression if you add huge wheels with tons of rotational mass, and weight to an SUV larger brakes would be required.

If size makes no difference than why are there different brake rotor and caliper sizes? Wouldn't there be a standard small setup with different hardness of pads?

Not trying to argue, just understand.

SUV's only have larger brakes because the center hub is larger to accommodate a 6 or more bolt pattern and thicker driveshafts, etc. or a larger bolt pattern (such as a porsche.. 120X5)

sometimes it's the HAT that's larger, and subsequently the outer diameter grows..

if you measure the actual shiny part and brake pad area you'll be surprised how similar it is.. among most cars.

Think about it this way...

Flip a bicycle upside down. Spin the wheels. Squeeze the brakes. They stop instantly.

Now ride the bike at the same speed, the wheel is harder to brake because of the mass of the bike and rider.

You aren't stopping just the tire. You are stopping the entire vehicle. The wheel and tire weights have very little to do with stopping power.

Size DOES make a difference, it's just not always a positive one.

Brake torque is affected by piston area and rotor diameter, but pad size doesn't matter (other than lasting longer). This can be used to adjust brake bias or simply offer more "stopping power" (i realize that's not really the right word). Tires are almost always still the limiting factor in stopping distances, but it is possible to increase braking forces in a useful way for a system that has dramatically changed from stock (i.e. hoosiers on a car that started with seriously undersized brakes). But again, bias is very important in all cases. There are big brake kits that use larger rotors but send bias slightly rearwards by using smaller pistons...

The reason we don't just use super aggressive pads with small rotors is because the larger heat sink from the rotor is more useful than a very aggressive pad that eats through rotors quickly and takes a long time to get up to operating temp. Also, larger rotors operating at lower temps keeps other things around them from being cooked (hubs, hoses, etc.).

- Andrew

Super interesting. I love learning new things, especially about cars.

:respekt:

Larger brakes theoretically will provide the car with more stopping power, but there are a ton of factors that play in to how well the system will work, its much more than size. Too big and it will hurt the cars performance.

When upgrading the brake system these are some of the things we look at including but not limited too:

Tire size & compound
Suspension components & setup
F - R Bias
Brake pad size & compound
Brake fluid compound
Caliper size, piston diameter, piston count, piston bias.
Rotor compound, pad to rotor surface area.
Master cylinder size & pressures.
Plumbing

couple reasons I will be putting the Essex sprint brakes on my track car:

1. pedal feel - I'm not convinced my dissatisfaction with the stock system wasn't tread squirm of the RS3's.
2. heat capacity
3. unsprung weight - 2 piece rotors save a ton of weight. 8lbs/corner on the essex sprint kit
4. rotor life - stock rotors with upgraded pads worked ok on the track, but the rotors got really cooked. I am curious how long they will last before they crack.

The Essex AP Racing brakes seem like an excellent kit at a reasonable price.

And here's a note on what happens when you get a "cheap" big brake kit:

http://forums.evolutionm.net/evo-tir...-shacking.html

- Andrew

so it's up to 8lb per corner now? i thought it was only 4

which is a lot regardless considering how brakes are in general.

A simple test - find somewhere nice and quiet and try braking as hard as you can from 80mph to 20 mph repeatedly. :)

Chances are that you'll do excellently the first few times but notice that heat? Funky smells? Smoke? More heat? Glowing rotors? No more brakes?

I like to think of brakes as machines for converting kinetic energy into heat. Of course brakes aren't 'perfectly efficient' systems so after a certain equilibrium is reached their performance degrades as temperatures rise beyond their operating (thermal efficiency) evelope and various parts in the system begin to fail.

Why good (not necessarily big) brake kits cost what they do is because the good ones are are designed to perform consistently for much longer in an entirely different operating envelope than 'normal' brakes are required to. To do so they require more effort in terms of engineering, development, higher quality materials and tighter tolerances.

You can get pretty far by upgrading parts of the stock braking system but depending on your application you may well reach a point where you've already upgraded much of the system but it (the system) can't hold up well enough, i.e. too much performance degradation or component failure.

Matt Andrew's case os a prime example - a high level of driving skill and a requirement to run a large number of fast laps. He's already done pads, fluid and (I'm assuming) brake lines which has exposed the rotors as the next point of failure. The only thing after that is two piece rotors perhaps, but by this point the value/money equation logically begins to tilts towards an entirely different, higher end system since the stock calipers will be the next weak link in the chain.



TL;DR most people probably don't need 'em but it depends on the need. :)

i know the formula. notice how there is also no term for heat. do brakes never fade? im not saying that are absolutely does change things. im just saying that its very well possible

Your test might be easier just to pull the hand brake half way, and step on the gas half way and keep it there. The car should start to accelerate as the brakes start to overheat, although I've never done it before :)

I was told it was 8lbs a corner. If I'm wrong, Id like to know before they show up. I think the endurance package was only a couple lbs a corner?

You're correct, stickier tires can utilize more braking torque, but only if the braking system is capable of providing it. More braking power can be applied in any combination of the following three ways: more pressure, higher friction pads, or more leverage (larger rotors).

You're still slowing down the car's mass (converting kinetic energy into heat), the difference is how the brakes cope with it. Sticky tires can slow the car faster, which generates more heat, more quickly.

The point is (for the FRS/BRZ), the stock brakes are pretty damn good, mostly due to the car's light weight. For street use (even moderately aggressive driving), the stock pads are fine. For aggressive street use (like canyon carving) or track days, upgrade the pads to something rated for street & track use (not race pads, they require a lot of heat to work properly, and don't work so well on the street with lower operating temps). You don't need a BBK unless you're racing with really sticky tires or REALLY whoring at the local track. Constant hard laps (over time) can overwhelm almost any stock system.

http://www.zeckhausen.com/Testing_Brakes.htm
Ok a BBK can (if done right) increase stopping power? Same car same tires better stops with a BBK.

I think you will find that 90% of people get BBKs for looks.

same pads?

Stopping power and stopping distances are not the same. In that test they got shorter stopping distances by modifying the brake bias.

- Andrew