drilled vs. slotted...or maybe both?

[v1c10us]

lol..
I stand by everything I said with one backpedal for the sake of the argument.
The caliper is not changing, nothing is changing other than the area of the 2 mating surfaces and the dispersion of pressure, that has been clear the entire time.
Forget the point of increasing surface area to increase friction, we'll just pretend that Rsx-s brake swaps are completely pointless(and dont say anything about the caliper, its still 1 piston and the brake booster is still the same, aint a damn ounce more pressure being applied, just dispersed over more AREA!)
I dont care what you say or how the fuck you say it and i'm sick of trying to get through to you here.
The fact remains that if you take a brick the size of a sugar cube and put a brick ontop of it and slide it across a surface laterally, it will be easier to slide than a brick sized brick with a sugar cube sized brick on top if it..
The fact also remains that when you have bigger tires there is more friction and your gas mileage will decrease.
The fact remains that if you take one finger and slide it across a book and then take your entire hand and slide it across a book you will feel more resistance.
The fact remains that if you provide the same amount of pressure on on a smaller surface area the friction will decrease, the pressure per unit increases, and this increase decreases the amount of friction shared by the two surfaces.
i'll repeat it bolder and bigger, just for you.
If you apply the same amount of pressure on a smaller surface area the friction decreases, the pressure per unit increases because it has less area to disperse over and this increase in pressure causes a decrease in friction, as you said, and as your article said. Now stop arguing a mute point.
and if you honestly believe what you're saying then go drill half inch holes in your rotors and drive around, i promise you, when you apply the brakes you wont even feel them let go when the pads hits the big empty spot =]


edit: me saying if you increase the pressure while increasing the surface area was me quoting your article; your article said

If you were to increase the force as you increased the area to keep PRESSURE the same, then increasing the area WOULD increase the frictional force between the two surfaces.

[Zzyzx]

your original argument was that friction was subject to surface area, where it is clearly not (as shown in the sentence you quote). You seem to be confusing where this increase in pressure is coming form. as with out increasing the clamping force of the caliper, as you increase surface area, Pressure would decrease. (pressure equals force divided by the area of contact) the force coming from the caliper squeezing the pad against the rotors surface. I.e. as you increase pad/rotor contact, Pressure decreases.


the simplest response

- on a macroscopic level, surface area has no significant effect on friction. Only the force pushing 2 surfaces together and their materials (listed as their coefficient of friction against each other) matter. For instance, a 100 lbs block of steel will slide with the same difficulty no matter how you change its surface area in contact with the ground. This is because decreasing the surface area decreases the area that covalent bonding between the block and the ground (decreases friction), but it increases the force-per-area that supports the weight (increases friction), and the two friction methods cancel each other out.

So, that brick you talked about... doesn't matter how large or small of a contact patch it has. its still going to take the same amount of energy to get moving.

So you can keep believing that a larger pad & rotor some how magically increases the amount of brake power they can produce. Physics states other wise.

Now there are other factors that can be useful in generating more brake torque. For one, a larger rotor requires you to move the caliper farther from the center of rotation, which increases the mechanical advantage the caliper has on the rotor. (increasing brake torque output). But as physics states (seriously look it up) Just increasing pad/rotor interface size with out moving the caliper yields no significant difference in brake torque output.

As far as brake swaps I never said they were pointless, they just dont do what you think they do.... Think about it, you change the caliper(different pressure output per pedal input)... and move that caliper farther away from the center of rotation (greater amount of Torque multiplication).

The only advantage increasing the pad/rotor interface would give you would be a reduction in temperature across the pad's surface. as each square cm of pad would be under less pressure then the smaller pad.... and therefor less heat will be generated per cm2.

[dofu2]

So, that brick you talked about... doesn't matter how large or small of a contact patch it has. its still going to take the same amount of energy to get moving.

A bit off the main topic of the thread, but would this apply to stickier substances like tires too? Hypermilers like to fill their tires up to the max so they can get as small of a contact patch of tire to the ground as possible because they claim it'll help move or keep the car moving with less power. But this article you just quoted is saying that contact patch size does not matter...

[Lucid Moments]

There is more stuff going on with tires too though. Sidewall flex for one. I know that I've seen somewhere in this thread information regarding how the coefficient of friction on tire compounds grows at a decreasing rate as pressure is increased.

[Zzyzx]

A bit off the main topic of the thread, but would this apply to stickier substances like tires too? Hypermilers like to fill their tires up to the max so they can get as small of a contact patch of tire to the ground as possible because they claim it'll help move or keep the car moving with less power. But this article you just quoted is saying that contact patch size does not matter...

Your looking at rolling resistance, different forces to overcome.
http://en.wikipedia.org/wiki/Rolling_friction




Woo... tons of articles on google..
http://wiki.answers.com/Q/Does_frict..._or_indirectly
http://zebu.uoregon.edu/1999/ph161/friction.html (pictures as well)
a reply form the DOE http://www.newton.dep.anl.gov/askasc...9/phy99449.htm

[meetthenewguy]

I went with power slot crypos with hawk pads and ss lines and flush with DOT 4 while I was at it, what a difference! installed myself in about 4 hours with a buddy and some beer cost about 600

[v1c10us]

fair enough, I still have a few points i disagree on but I'm through arguing.
tires however are a completely different subject, rolling friction and sliding friction are very different things, although they are both forms of kinetic friction forces act on them differently.
edit: you said quite a few times that an increase in pressure causes a decrease in friction, so under that principle would you not say that by removing area of the rotor, you are increasing the pressure and thus decreasing friction =\

[Zzyzx]

you said quite a few times that an increase in pressure causes a decrease in friction

could you quote that, because i dont recall having ever said that, aside with tires. and you are dealing with the properties of rubber in that instance.

[v1c10us]

I suppose you never said it
I called my physics professor this morning over all this mess and he informed me as to where I was making my error.
The issue is that friction gives off so much energy as heat(and at this point he started on a tirade about how innefficient brakes are on a car and how we should be ussing eddy currents)the energy given off from friction is dependent on the distance the object was sliding against. The longer(or in my feeble mind, i assumed this meant the amount of area) the path the object takes, the more slowly it loses its energy provided it used the same amount of force as a shorter path.. he said it more complex and it made sense when he said it, but basically what I took from it is that the entire reason a bigger rotor works better is because its spinning in a circle, thus making it a longer path of travel, meaning that less energy is wasted under the same amount of force or something =\
so you lose less energy to heat, Im going to give up on this whole thing because he made me more confused, but I guess I can understand it as this. if you slide an icecube across one inch of table you expended all of the force over a shorter distance, so it lost more energy to heat than if you had moved it a longer distance....that also sounded much better in my head and i will give up now..

[dofu2]

Your looking at rolling resistance, different forces to overcome.

OK, thanks.