Give me tech on brakes...

[DSC]

I've never heard really good definitive information on brakes. Everybody wants 13" 30mm slotted cross drilled rotors with massive 6 pot calipers but was does it all do?

So tell me what each of these does:
Larger rotor diameter
Larger rotor width
Slotted rotors
Cross drilled rotors
Calipers with more pistons
And anything else you've got...

I already know the function of a few of those, but I thought I'd put up a more complete list for other people to see as well...and not answer them myself incase I'm wrong.

Also, where do more brakes not matter in relation to the tires ability to stop the car?

[AceInHole]

post whore time: answer one part at a time:
Larger rotor diameter = more braking power as you have more "leverage".  torque is a product of force times length.  increasing the radius of the rotor places the brake pad farther out, thus increasing length and obtaning more torque for the same amount of force.  this ends in more stopping power without necessarily more caliper force, and will then reduce brake fade as there is less frictional force needed between the pad and rotor.  brake fade is also slightly overcome by the sheer power of the additional torque, so in the end you get more consistent and powerful braking.

[AceInHole]

slotted and cross drilled rotors serve the same purpose: cooling. brake fade is caused by heat, so keeping the rotors cool will prevent brake fade. the slots and holes serve the purpose of cooling and channeling gasses produced by the brake pads away from the rotor face.

baah. TNord was supposed to get in the middle of these posts but he biach'ed out or something.

so... i'll take on the pistons too:
more pistons = more braking force and more even distribution of that force on the brake pads.
with more pistons, you effectively get more piston volume.  since we all understand engines, we know that more displacement = more torque = more power, thus a piston that you can more easily pump brake fluid into (as you have a greater change in volume per movement of the piston) you get more power using more brake fluid.
as stated before, it helps to be able to clamp on the rotor even harder to help fight brake fade, even after the brakes are hot.

[tnord]

one thing that wasn't mentioned was tires.  tires are the most important part on your car. each tire has a limit on the force it can bear in any direction.  when you exceed that limit, the tire stops rotating and you lock em up in braking, or spin em when accelerating, whatever.  so obviously, if you get a tire that has a higher limit on force, the more braking power that can be applied, the shorter your stopping distance.  don't be surprised to cut 60-0 stopping distances by 10 ft or more by adding some really good tires.  nice big brakes are good to have, but good tires should be everybody's first upgrade, they do everything.

bridgestone rules.

[JpS]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (AceInHole @ May 09 2002,12:05)</td></tr><tr><td id="QUOTE">so... i'll take on the pistons too:
more pistons = more braking force and more even distribution of that force on the brake pads.
with more pistons, you effectively get more piston volume. since we all understand engines, we know that more displacement = more torque = more power, thus a piston that you can more easily pump brake fluid into (as you have a greater change in volume per movement of the piston) you get more power using more brake fluid.</td></tr></table><span id='postcolor'>
with more pistons on the caliper wouldnt you need a larger master cylinder? &nbsp;that would be my guess anyway... because more displacment means more force to compress them am i even close? or am i in left field with yastrzemski?

[tnord]

no, i think you're right. certain brake upgrades do require new master cylinders iirc.

[HippoSleek]

0o - I want to play too!

one more thing about larger rotors - heat dissipation! &nbsp;If you have ever seen any type of air cooled engine (e.g., lawnmower), you will notice that it has fins for cooling. &nbsp;Why - b/c a larger area dissipates more heat. &nbsp;Ditto w/ brakes (that's also why front rotors are always vented). &nbsp;Ditto width - more area to absorb heat (which your brakes need to a point), but also, more area in the vent area = more surface area for cooling.

As for slotted and drilled... well... Ace has made two of the worst errors in why these exist - gassing a cooling. &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>
1. &nbsp;Out gassing - back when Mario Andretti was racing for the world championship (i.e., F1), the material brake pads were constructed out of emitted a gas when heated. &nbsp;This gas would hang around the pad/rotor interface and disrupt performance. &nbsp;x-drills were designed to force these gasses away from the pad/rotor interface. &nbsp;Modern pads (post 1987) - of ALL types - do not emit such gasses and x-drilling is not longer necessary for this.

2. &nbsp;Cooling - some people think that slots and drilling are for cooling the brakes, but this is not really accurate either. &nbsp;Slots are designed to wear away at pads so that "fresh" pad is available for the brakes. &nbsp;Better cooling *might* be provided in some small amount, depending on whether the increase in surface area for heat dissipation from the slots or drills offsets the extra heat generated by the increased force needed after the necessary reduction in surface friction (b/c you are taking away part of the pad/rotor interface by cutting holes in it). &nbsp;

3. &nbsp;What is well settled is this: 1) drills and slots look cool; 2) drills and slots are more prone to both surface and catastrophic cracks; and 3) drills cost a lot more.

4. &nbsp;Don't give me this what about Porsche sh!t either b/c those rotors aren't even metal. &nbsp;Ditto the "but they run slots on race cars" b/c those are carbon rotors.

Now, my question for you is How much do you really want to learn about brakes? &nbsp;This link: Brakes thread (http://www.altimas.net/forum/showthread.php?threadid=32327) has more infomation on brakes than you will EVER need. &nbsp;BUT, it is mixed with flames, smackdowns, and about 25 pages (IIRC) of jibber jabber. &nbsp;Basically, if you follow Cobra and a few others, you will be a brake expert in no time. &nbsp;BTW: most of the outsiders that participated in that thread are local VA/MD racers that you will see out at the track when you come out.

... and about that master-cyl. question that I just noticed Tnad answer - Yeah... some would say that z32 fronts should have an MC updrade so the first inch or so of pedal doesn't feel like I stepped in a pile of sh!t.

[tnord]

pretty interesting mark, although being the skeptic i am, i'm not willing to give up what i believe and have been told just yet (although it looks like i'm going down that path). i'm somewhat confident that porsche had x-drilled rotors before they went with the ceramic brakes thing.

also, when pad material is worn out, it has to go somewhere. maybe it just all turns to brake dust, i don't know. but i'm guessing that with all that heat some of it does turn to gas. does that gas hang around and cause problems? i don't know. but i don't think that it's debateable on whether or not the slots/x-drills do their job in getting rid of it.

so yeah, mark you've ignited some curiosity i am going to have to look into further.

EDIT: after reading 5 pages (i'll finish later) from the link mark provided i have come to 2 conclusions.
1) the guy that bought the brakes, is an idiot, he said tires don't help braking
2) altimas.net is much worse off for having him as a moderator

[bbp]

Let me add .02 to this.

By Importance:

Tires: &nbsp;Ultimate factor. &nbsp;No matter what kind of bite your brakes have, the tires are the ulimate contact between car and road. &nbsp;If you tires suck, your brakes will suck too.

Pads / Fluid: &nbsp;I put these together because it is really resistance to heat we are dealing with. &nbsp;I like Ford DOT3 &nbsp;brake fluid, it's cheap and performs as well as the expensive stuff (FOR REAL). &nbsp;Good brake fluid will handle the heat and prevent boiling of the fluid. &nbsp;

Now Pads, Pads are equally important. &nbsp;Modern brake pads do not tend to "gas" like mentioned above. &nbsp;It is the organic compounds in brake pads that tend to burn and create this gas layer. &nbsp;When people have brake "fade" there is a layer of gas forming between the brake pad and the rotor, almost like a pnuematic lock. &nbsp;Race pads do not have this problem due to the material they are made of (carbon and metal). &nbsp;You may notice that these pads may have the word "burnished" on them. &nbsp;They do not require "breaking in" which some people do to new pads, they are trying to burn the gasses out of the pads before using them (usually by making several 50-0 stops in short order) &nbsp;I have used both Performance Friction and Hawk. &nbsp;I prefer Hawk because I think it has a better wear and feel to them.

Now Rotors: &nbsp;Cross drilled rotors do dissapate heat better than conventional rotors, but at a price, longevity. &nbsp;They will begin to crack much sooner than non drilled. &nbsp;Yes, Porsche uses cross drilled rotors (non carbon), money isn't an issue. &nbsp;Contrary to some peoples belief, the rotor is not meant to retain or absorb heat, it is meant to disperse and get rid of it. &nbsp; Slotted rotors: haven't been around them too much, doesn't seem to do much for me. &nbsp;Regular old vented disks are probably adeqaute for any of our cars, if your are having problems with these try running some brake ducts to the center of the back of the hub, or YOU ARE USING THE BRAKES TOO MUCH!

I love discussions about brakes. &nbsp;When I instruct at these driving schools the participants always tell you how much they have done to the motor, how fast there car is....ya know what? &nbsp;I really don't care about that... tell me how fast your car can stop? &nbsp;Thats the important part, &nbsp;that's what will make them a faster driver.

Learn how to use the most powerful part of the car...the brakes.

[bbp]

As for larger calipers, &nbsp;I would match the master cylinder to the calipers. &nbsp;Not always needed, but worth the insurance.

[AceInHole]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (HippoSleek @ May 08 2002,10:51)</td></tr><tr><td id="QUOTE">As for slotted and drilled... well... Ace has made two of the worst errors in why these exist - gassing a cooling. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>
1. Out gassing - back when Mario Andretti was racing for the world championship (i.e., F1), the material brake pads were constructed out of emitted a gas when heated. This gas would hang around the pad/rotor interface and disrupt performance. x-drills were designed to force these gasses away from the pad/rotor interface. Modern pads (post 1987) - of ALL types - do not emit such gasses and x-drilling is not longer necessary for this.

2. Cooling - some people think that slots and drilling are for cooling the brakes, but this is not really accurate either. Slots are designed to wear away at pads so that "fresh" pad is available for the brakes. Better cooling *might* be provided in some small amount, depending on whether the increase in surface area for heat dissipation from the slots or drills offsets the extra heat generated by the increased force needed after the necessary reduction in surface friction (b/c you are taking away part of the pad/rotor interface by cutting holes in it).

3. What is well settled is this: 1) drills and slots look cool; 2) drills and slots are more prone to both surface and catastrophic cracks; and 3) drills cost a lot more.</td></tr></table><span id='postcolor'>
doh... i feel old fashioned now.

i'm still pretty sure that slotting/ crossdrilling still helps with cooling, as without them you aren't channeling cool air (which is a gas itself) to the brake pad surface and channeling hot air out. &nbsp;i guess i'll have to look it up a bit more. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>

good info though <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>