General question: Why are bigger brakes better?

[axeman71]

I understand that bigger breaks (rotors and pads) stop a given car better than smaller breaks. What I don't understand is why. It seems to me that breaking is more about friction between the tire and the road. As long as a small break setup can squeeze the rotor hard enough to stop the wheel rotating (causing the tire to skid) then it seems that should be good enough. A bigger break gains no advantage from being able to squeeze harder.

I do think that larger breaks might give you more control of how hard the breaks squeeze allowing you better control over breaking force without locking up the wheels. Is this the difference?

My thoughts above don't take into account heat build-up during breaking or ABS. I realize bigger breaks would spread the heat out more and fade less and I don't really know what effects ABS might have.

[frost]

Originally Posted by axeman71

I understand that bigger breaks (rotors and pads) stop a given car better than smaller breaks. What I don't understand is why. It seems to me that breaking is more about friction between the tire and the road. As long as a small break setup can squeeze the rotor hard enough to stop the wheel rotating (causing the tire to skid) then it seems that should be good enough. A bigger break gains no advantage from being able to squeeze harder.

I do think that larger breaks might give you more control of how hard the breaks squeeze allowing you better control over breaking force without locking up the wheels. Is this the difference?

My thoughts above don't take into account heat build-up during breaking or ABS. I realize bigger breaks would spread the heat out more and fade less and I don't really know what effects ABS might have.

First off, it's "brakes," not "breaks."

"It seems to me that breaking is more about friction between the tire and the road" That's not correct. Braking is about the friction between the brake pad and rotor. Therefore, bigger brakes -> more surface area -> more friction = better stopping ability

[SmoothZ]

Damn, frost beat me to it.

More surface area = more friction and better stopping.

[kenchan]

higher capacity, improved consistency.

like playing a 1000watt stereo but only at 5-10% of its power.

[Trips]

Thats the kind of question someone asks when they don't show up to auto mechanics class?

[Cmike2780]

^^agree.

Bigger brakes also allow for less pressure for the same amount of torque given the same conditions as a standard brake set. For the most part, the increase surface area allows for a larger pad which results in more bite. The tires play a big part in stopping distance, but the brakes are doing most of the work. Bigger brakes, with the right material, also spread heat better and can withstand higher cycles before failing/fading.

Also, it would actually be easier to lock-up the brakes (tire looses traction) with bigger brakes, but thats a whole other topic.

[frost]

Friction Lesson:

*Friction is a measure of how hard it is to slide one object over another. Take a look at the figure below. Both of the blocks are made from the same material, but one is heavier. I think we all know which one will be harder for the bulldozer to push.



To understand why this is, let's take a close look at one of the blocks and the table:



Because friction exists at the microscopic level, the amount of force it takes to move a given block is proportional to that block's weight.

Even though the blocks look smooth to the naked eye, they are actually quite rough at the microscopic level. When you set the block down on the table, the little peaks and valleys get squished together, and some of them may actually weld together. The weight of the heavier block causes it to squish together more, so it is even harder to slide.

Different materials have different microscopic structures; for instance, it is harder to slide rubber against rubber than it is to slide steel against steel. The type of material determines the coefficient of friction, the ratio of the force required to slide the block to the block's weight. If the coefficient were 1.0 in our example, then it would take 100 pounds of force to slide the 100-pound (45 kg) block, or 400 pounds (180 kg) of force to slide the 400-pound block. If the coefficient were 0.1, then it would take 10 pounds of force to slide to the 100-pound block or 40 pounds of force to slide the 400-pound block.

So the amount of force it takes to move a given block is proportional to that block's weight. The more weight, the more force required. This concept applies for devices like brakes and clutches, where a pad is pressed against a spinning disc. The more force that presses on the pad, the greater the stopping force.

howstuffworks.com

[RCZ]

Actually... he is more right than you guys are. Braking is 100% limited by the grip of your tires. He is also right that the pressure is spread over a larger surface which makes braking modulation easier as well as heat dissipation. The materials used are also part of the mix, sport brakes tend to have less flex to them and are designed to transfer more of that pressure to the rotor.

Another thing to keep in mind axeman71 is that you're making an assumption that bigger = better and thats not true. AP Racing 6-pot brakes are better than a lot of those 8 pot show brakes that take up half the rotor.

Also, I dont want to repeat what everyone else already said, but more surface area to create friction with..

[SmoothZ]

Who invited the rocket scientist?

[Trips]

Originally Posted by SmoothZ

Who invited the rocket scientist?

Brakes? We don't need no stinking Brakes!!!

[frost]

Originally Posted by RCZ

Actually... he is more right than you guys are. Braking is 100% limited by the grip of your tires.

That's kind of an obvious statement, it's like saying braking is 100% affected by the speed you are going. But we wouldn't attribute good braking to slow speed, nor should we attribute good braking to contact between the tire and the road. If we hydroplane and can't stop, we don't blame the brakes themselves, right?

[TreeSemdyZee]

I'm convinced. I'm gonna put Shimano brakes on my Z.

[shabarivas]

LMAO poor guy

[cossie1600]

Originally Posted by frost

That's kind of an obvious statement, it's like saying braking is 100% affected by the speed you are going. But we wouldn't attribute good braking to slow speed, nor should we attribute good braking to contact between the tire and the road. If we hydroplane and can't stop, we don't blame the brakes themselves, right?

Nope, brakes too big are going to lock the tires.

[ChrisSlicks]

RCZ is right on. Braking is tire limited, the base brakes of any car are capable of locking the tire and hence have a sufficient coefficient of friction. Better brakes (not necessarily bigger) may improve pedal feel, modulation, but most importantly consistency.