General question: Why are bigger brakes better?

Jeffblue

one thing to take home from this is that bigger brakes are better, and tires with more grip are better, however the ability of the car to stop is limited whichever is the weak link. all things being equal, same tires, same car, same conditions etc, the car with bigger brakes is going to stop better. The ability of a car to stop is limited by a lot of things, tire compound is just one of them. weight of the car (even number of passengers affects the weight), speed at which it is traveling, road conditions (wet/dry, hot/cold). all things being equal, bigger brakes (assuming kits being compared are of equal quality) are going to stop the car better. end of story. if you want to put those brakes on a minivan going 100mph in the snow down a hill or on grandma's carolla going 20mph down main street, obviously they are going to perform differently, but that is because of other variables, not the brakes themselves.

Red__Zed

I came in here to say most of that, except the last part. Friction is independent of surface area, at least with most materials.

Besides the heat dissipation, bigger rotors allow for bigger calipers, with bigger components that are usually more easily modulated.

axeman71

Wow, big discussion for one evening. I don't understand the sarcasm in the first 3 or 4 posts, I was asking a serious question. Just saying "duh, bigger brakes are better" doesn't tell me why which is what I was asking. The misspelling was just me not paying attention (I am a bad speller though). I maybe didn't ask the question in a clear enough way.

Taking our Z's as an example: I expect the larger sport brakes to stop the car from 60mph to 0mph in a shorter distance than the standard brakes (btw, I have not yet read any reviews testing the standard brakes, they all test sport packages). I know from experience that the standard brakes produce enough friction on the rotor to completely stop the tire from rotating making the tire skid over the pavement (or, well the ABS come on but you know what I mean). So, why do the larger sport brakes stop the car in a shorter distance? Yes, the sport brakes have a larger surface area in contact with the rotor and produce more friction but there is already enough friction with the standard brakes to lock up the wheels. The only answer I can gather (both from this discussion and my own imagination) is the larger brakes allow greater control over the stopping force allowing the driver to push the brakes closer to the point of locking up the wheel without crossing over the point where the tire starts to skid.

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ChrisSlicks

The sport package tires are wider than the base model tires, that is the only real difference. Put the sports wheels on the base car and the base wheels on the sports model car and the results should reverse.

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Red__Zed

I think heat is like 90% of the reason for the move to bigger brakes in most applications. Some people will find examples where that is not true, but the added absorption and dissipation area provides a huge benefit.

I don't think that a comparison in stopping distance between base and sport would do much good, as they sport different size/weight rims, as well as different stock tires in notably different sizes. I believe that the stopping distance would likely be very close.

I know I kept stock size brakes on my s2000, and despite the (relatively ) large rims I had on the thing, the stopping distance was in line with other s2k's sporting BBK's. On a track or in the twisties though, my rotors would heat up to the point where they were glowing red, while the rotors on said BBK's were still much cooler.

Contrary to the belief many will have, for the contact between brake pads and the rotor, surface area is irrelevant. The reason that surface area plays a role in other situations (notably tires) is due to adhesion (pieces of the tire bond to the road).

AP - Chris_B

I'll keep this as brief as I can (despite my reputation...). For a ONE TIME PANIC STOP, the tires are the limitation as long as there is enough braking torque to activate the ABS. Any model currently sold by Nissan (as well as most car manufacturers) makes that grade.

The big difference with a properly designed and built BBK is that you can do high-speed panic stops repeatedly without significant changes in stopping distance or pedal feel. While most people don't drive down the highway doing repeated 80-0mph braking, I've been though many a mountain pass when I didn't have enough brakes to keep them from fading. Some cars give you some warning before the pedal goes to the floor, but a few of them can give the driver quite an unwelcome surprise.

It's not the pad surface area that creates the extra friction. However, a larger pad will run at lower temperatures, which is very good for it and the rotor. Lower pad temperatures mean easier pad selection, better modulation (for many compounds), lower chance of boiling the brake fluid, more consistent and repeatable performance and increased pad and rotor life.

One of the added benefits of a BBK for regular street driving is the fantastic pedal feel. At least when you hit the off-ramp at speed to find that cars are back up around a blind curve, you know that you can bring the car down with confidence and control. Just keep an eye on those mirrors!

Chris

370Zsteve

"Braking is tire limited" is a very misleading statement.

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ChrisSlicks

Not really. Chris - AP covered it pretty well. Braking is initially tire limited, as any modern car can exceed tire to road friction with rotor to pad friction. Tire is the weakest link. Once you take repeated stops into consideration then many other factors come into play, and that is where the quality after-market brakes show their strength in resisting fade, consistent pedal feel, and durability.

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RCZ

Not really that misleading. Just saying that the original poster is not as wrong as you guys made it seem.

Now that you guys mentioned it, friction factors are pressure and mu, not SA. Sorry its been a while since highschool haha.

Mike

And our Sport Brakes give you very little warning when they go! Before the BBK, I got a soft pedal in one turn and slowed it way down and coasted into the pits, and took about 100 yards to stop from 20mph.

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AP - Chris_B

It's pretty difficult to describe that sort of "excitement" without experiencing it yourself!!!

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