More braking power out of stock brakes?

[jamesrw]

Well said, i concur

[oxbrain]

the more mass a brake disc has the more heat energy it can store. The speed at which it can shed heat is entirely dependant on the surface area. The only benefit gained from lower mass is that there is less rotating mass and less unsprung weight.

Think of the brakes like they were a barrel, they hold heat the same way a barrel holds water. The bigger the contact surface area with your brake pad, the bigger the water inlet to the barrel is. The more surface area, the bigger the water outlet is. The more mass, the bigger the barrel. When you step on the brakes you expend a certain amount of heat stopping the car. The rotor has to suck that heat up and either store it or expell it. If it cant take any more heat then it gets hotter, thats where your pads can glaze, rotor can warp.

Slotting and drilling rotors creates weakspots which can lead to sudden failure of the rotor. If you want more braking than is available with the stock brakes, get bigger rotors. The aspire rotors are larger diameter, aren't solid. They have vents in the middle. They weight almost the same, but have about 50% more surface area and more area for the pads, thats why you stop faster.

[FB71]

mostly true. Mass does have a direct correlation energy exchange, however. the more dense an object is, the more mass it is said to have. So, two items of equal size and shape made from different materials will have different mass. Lets consider a part made from steel, and an identical one made from aluminum. Steel is much more dense than aluminum, so the steel part will have greater mass. The greater the mass, the more difficult it is for energy to travel through it. Don't look at this as a barrel (energy stores very poorly, unless at a state of rest, then its only potential energy) but more like a roadway. Energy needs to travel from point A to B. The number of lanes would be equal to the size of the object, and the amount of traffic would be equal to the density of the object. A single lane road with no traffic can handle a moderate amount of energy travel before becoming overwhelmed, and causing the transfer rate to slow. More traffic on that roadway (higher density) means a slower transfer along the route. One solution is to increase the size of the route. Even with the density remaining the swame, say 50% traffic volume, the greater size of the roadway offers more opportunities for the energy to pass. The next solution is to reduce the traffic (mass), which gives the energy a less restricted path by which to pass. So the best solution is to reduce the traffic flow AND increase the number of lanes (less mass and greater size/volume). Keep in mind, energy is dynamic until it reaches a point of entropy, a state at which the energy cannot change forms again. Energy cannot be held in stasis indefinitely. The decay rate can be significantly slowed, but not stopped. A marble will not stop rolling until it reaches the lowest point in travel. It can be slowed by friction (energy transfer), momentarily held in place by an obstacle (impact w/ that obstacle is a transfer of energy), but it will not stop until the energy stored within the marble has reached a state of entropy, or a point at which the energy cannot be used.

"Entropy is energy
energy that can't be used
to state it more specifically
Take an egg
and drop it on the floor
you see it break
You go get a mop
so you can clean up
your mistake
Consider
for a moment
why we know its true
If you drop
a broken egg on the floor
you will not get an egg thats new"

MC Hawking, Prof Steven Hawking's Gangsta Rappa alter ego...

[FB71]

oh, and I do agree that slotting and drilling the rotor decreases its useful life. They create stress points as a result of heat cycling.

And your example of the Aspire rotor... very good, except...

the fact that rotor is ventilated does mean that it presents more surface area, true, but that also means it has lower mass than if it were solid like the Festiva rotor, given the two rotor were the same size.

The Aspire rotor keeps the traffic flow percentage the same, but has more lanes, and because of the increased surface area from vents, more "on and off" ramps, allowing the energy to escape more quickly

The last thing you want to do with brakes is store that heat energy. Just ask anyone thats ever raced a car with 4 wheel drum brakes...

[Gro Harlem]

meh, i doubt many ppl care to read all that physics jibberish


Plain an simple GET FRIGGIN DECENT PADS IF YOU WANT YOUR CAR TO STOP WELL!

And properly installing them is another key point. If you just slap the pads on all half-assed it still won't be as effective as it could be.

You ALWAYS need to regrease the sliders in your caliper every time you remove them for service.

You also ALWAYS need to resurface your rotors and drums any time you replace the pads or shoes with new friction material. AND you ALWAYS need to break-in the new pads or shoes by "burnishing" them which basically means transferring some of the pad material over to the newly surface rotor/drum so the friction action of the brakes actually does its work.

I have a procedure written up on my site about brake break-in procedure if anyone cares to click my site link

[FB71]

well said, Wil. elegantly simple...

[Safety Guy]

Okay let's talk about brake cooling ducts!

I eventually want a front air dam, somewhat "tamed" for street use. I'd like to add brake cooling ducts for better...uh...brake cooling!

I should think those ducts, if efficiently done, would work better for the Aspire vented discs than for the tiny Festiva solids. Am I right?

Thoughts, physics monographs, hallucinations?


Karl

[Eccentric]

Correct the tires stop the car, I read Grassroots motorsports too.
:wink:
Chris Rummel

Right you knew where I was going. I just wanted to get a little side topic going there.

actually, if youre car had no tyres, or wheels for that matter, it would still stop pretty damn good.

so in a nutshell, i would say friction stops a car.

Friction on what though. The reason tires make you faster is the same reason they make you slower. :wink:

What stops a car? when pressure is applied to rotor or drum by pads or shoes, the resulting friction causes the kinetic energy of the rotating mass to be converted into heat energy. The efficiency with which that heat energy can be dissipated determines how much energy can be transfer ed, thus determining the mean effective braking power. Therefore, the less mass the heat sink (rotor or drum) has, the faster it will dissipate heat. So, drilled/slotted/dimpled/grooved rotors present more surface area and less mass, therefore increase heat dissipation. And, modern pads and shoes DO out-gas, just not as dramatically as older asbestos compounds. And, also correct, that tires stop a car. Without the friction of the tire on the road surface, the only effect the energy exchange of braking would have is the loss of directional control of the vehicle. The mass of the vehicle exerts force on the tires, which, in trying to transfer that energy, cause the wheel on which they're mounted to rotate about its shaft. And that takes us back to the pads or shoes attempting to convert that rotating mass to heat energy. Ah, the wonderful world of physics...

Overall it's better to have more mass. If surface area was the key, rotors would be cast differently. For repeat stopping mass will delay it and dissipation will not be able to keep up.

They give off gas but they don't gas-out in the traditional meaning. By gas-out I mean the heat causes vaporization creating a film that drops the mu down to Fred Flintstone braking level. At the temps that pads would do enough to create problems you be more concerned about the tires melting, the fire shooting out of the front rims, and why the middle pedal is on the floor and that curve is coming up very fast.

... If it cant take any more heat then it gets hotter, thats where your pads can glaze, rotor can warp.

Slotting and drilling rotors creates weakspots which can lead to sudden failure of the rotor. If you want more braking than is available with the stock brakes, get bigger rotors. The aspire rotors are larger diameter, aren't solid. They have vents in the middle. They weight almost the same, but have about 50% more surface area and more area for the pads, thats why you stop faster.

Remember rotors don't warp :wink: GRM thing again.

Or do you stop faster because you now have 4x100 and get new tires for those cool Miata rims? I'm just poking the bear. Brakes do make a difference.

Now lets talk about brake cooling ducts.

[EVOGUN]

NO! lets talk about titanium and ceramic!

Thanks :wink:

[Eccentric]

NO! lets talk about titanium and ceramic!

Thanks :wink:

Wet or dry?

[oxbrain]

I want retro-thrusters.

you could get about 200lb thrust out of two 2" nozzles with a H/O fuel. That would ad about .1G to your braking. It would be just enough to offset the extra weight added by the tanks.




hmm, now that got my brain thinking. To hell with a rwd festy, I want a rocket festiva.

[ChrisDrives121DA]

I drove dominick's B6 car with some kind of german brake pads on the front & that thing was ridiculous. (didnt' have aspire brake swap either).

What german Brand? Textar?
is ridiculous positive or negative?

I got surprisingly good results with consciously brake-cleaning my rotors, proper maintenance of my calipers and a set of OEM Kia Pride pads I took from a donor car.

I did it due to laziness intending to delay the brake-job until I got new rotors as well, but the car stopped very nice!


-Chris-

[Gro Harlem]

i have no idea what brand, but they stopped well.


And I agree. I honestly think EVERY person who posts "My brakes suck" just don't maintain their cars.

If you keep your caliper sliders freely moving, keep the pad linings in good order and keep your rotors turned then your car should brake fine.

Cooling won't become an issue on the festiva unless you are running a track day. The fact the stock front 7.9" rotors are so friggin small makes the fact tehy are solid less of a problem. Even autocrossing you can run the car, let it cool off 10 mins between runs and not have any real fading problems. (at least on my car i didn't)

[oxbrain]

When I bought my car the guy had just paid someone to do the brakes. New rotors, new pads, and they actually didn't mess up bleeding them.
I don't have any problem stopping in a hurry, even when carrying 2 50 gallon drums of water in the back I could stop faster than most full-size cars.

If you haven't worked on brakes before, bring the car to a shop and have them do it. The life you save could be mine.
If you want to learn, do the front brakes first. Then wait a week to make sure the brakes are in good shape before doing the rear.

[Eccentric]

I don't have any problem stopping in a hurry, even when carrying 2 50 gallon drums of water in the back I could stop faster than most full-size cars.

Why would you carry around 2 50gal water drums? That's like 800lbs of water :shock: