Brake Rotors

[sn8kbit]

ok, i think i see what tone's sayin.

from 150-50 regardless of when you brake, it takes the same amount of energy, thus generates the same amount of heat. starting the braking earlier gets the rotors in the cooling process sooner. 700 degrees at a spike, versus 700 degrees on metal already cooling would equal cooler brakes going to the next corner. of course, i probably just screwed it up even worse...LOL

also, i think you've got a point there on that TA shugg. my car with the IRS is going to brake completely different than your stick axle car since the two setups are completely different. i wonder how you'd try to reduce brake dive with an IRS...

ya'll keep goin, i think i might actually be learning something here...

[thomasmoran1]

Originally posted by Dean95CobraR
That analogy really doesn't relate to the discussion about braking technique though. Everyone agrees that more speed will generate more heat.

Sorry Dean for not being clear. The point I was trying to make was that the extra heat generated by hard braking is what wears pads and rotors out. Not costing them into the brake zone which I believe increase’s brake life.

Thomas

[b_tone]

Are you saying that if the end temp of the rotors equal 700F, the amount of time it takes to cool off is related to how the heat was generated - long/soft vs short/hard?

not really. If you take 500ft to stop from 150 your rotor temp will be much less than if you do it in 300ft. You still generate the same amount of energy based on the Kinetic Energy (i misspoke before it's not PE, it's KE) equation but you allow some of that heat to dissapated into the air rather than being retained in the rotor.

The heat generated is the byproduct of the work done on the rotor (force x distance = work). When braking over a long distance vs a short distance you will do the same amount of work, you will just have to have higher or lower force to do the same amount of work.

Doing that work over a short distance is what caused the high temperature spike and this is what hurts the rotors.

Is this any better?

Personally I tend not to come into a corner and wait until that last minute, I tend to brake just under limit for a little longer. This keeps the heat down and usually keeps me under control coming into the corner. I don't know about you guys but I never enter a corner perfect enough to wait until the last second to brake. I always need a bit of a cushion.

EDIT: if you want to reduce brake dive in an IRS you should really start at the front of the car with the geometery(sp?) because it's easier than changin it in the back. a poor mans way is to increase the spring rate in front as well, but this has other effects.

I am also saying that the temp will not be as high when you brake froma greater distance vs a shorter one.

Shugg did you get my email?
Tom Lewis, shoot me an email: btone@ford.com

[tgentry]

I've been giving this a lot of thought and here are the factoids that I've come up with. I'm comparing late, hard braking to earlier, lighter braking. Feel free to poke holes in any or all of them.

Early braking allows a greater percentage of the braking to be done by other factors than the brakes. Engine drag, rolling resistance, aero resistance all become larger (if only slightly) factors in the energy dissipation calculation. This obviously can lead to lower brake temps.

Early braking means less time spent accelerating, and therefore less braking is necessary. The simple fact is, if I brake 100ft earlier, I'm NOT going as fast. Again, obvious implications to the brake temperatures.

Early braking allows more time for rotor heat to soak into the pads/calipers/fluid. Boiling fluid is a bad thing! This may even mean that while rotor temps are lower, pad/caliper/fluid temps are as high or higher for the early braker.

Early braking means more rotor surface area contacting the pads. The rotor will turn more revolutions during the braking process. Again, I'm not sure what effect this has, but it's something no one has mentioned.

To keep it on topic, does anyone have a recommendation for where to get rotor on hat rotors for the stock PBR setup? I'm interested in going that route if the replacement rotors are reasonable in price.

[sn8kbit]

tom, back up a couple of pages. (i thought you saw mine at RA this year) replacements for mine are right at 140 each, solid disc.


looking at the late/early braking, there's a lot of things i think that come into play also. (thanks tom for turning that light on for me, pads, fluid etc...) tires, level of experience ect, but i think the basic pad/rotor life pretty much rests on how soon/late you brake. also, i think there should be some basic techniques everyone should be able to do, then there would be what i call a braking style, which is how different drivers use those basics.
i've ridden with Dean, Kevin, and the illustrious mr Groth ,(next RA, i'm gonna try to con tone into a ride... ) and all three of them approach a corner completely different (which has helped immensley in adapting my own approach) how soon or how late comes with experience, what i'd like to know is what the "fundamentals" would be i guess is what i'm asking....

hopefully i'm going in the right direction with the frontend. i'm avoiding coil-overs for the moment to improve my driving first. the H&R race springs should help. i'm still trying to work up a urethane bushing setup for the rear....

[98banana]

Originally posted by thomasmoran1
Tom, think of when your at the track and think of how when someone is out there for their first time they can get away with a stock setup in most cases because they are not braking hard enough to generate more heat then the stock setup can handle. But then as they start getting faster they need to upgrade their brakes to cope with the extra heat which increases wear.

Thomas

But, that's the key, "they're getting faster". I'm not arguing with you though because I'm starting to agree. It's just that the newbie won't wear brakes as much because he or she is driving slower which means less energy from braking.

Good conversation here...

[Dean95CobraR]

Originally posted by 98banana
But, that's the key, "they're getting faster". I'm not arguing with you though because I'm starting to agree. It's just that the newbie won't wear brakes as much because he or she is driving slower which means less energy from braking.

Good conversation here...

Maybe that's why I didn't have a wear problem - I brake like a girl!!

[tgentry]

Originally posted by sn8kbit
tom, back up a couple of pages. (i thought you saw mine at RA this year) replacements for mine are right at 140 each, solid disc.

Steve, am I mis-remembering? I thought you had the one piece Eradispeeds, not rotor and hat. If I am, forgive me, it's the sometimers setting in again.

If those are rotor on hat, what is the weight difference from the stock one piece rotors?

At $140 each, that's over twice what I pay now. You really think I'll get over double the life? I was thinking that rotor on hat would be a big initial investment but that the rotor part would be less expensive in the long run (in addition to any performance/reliability/wear gains). And don't rule out the pimp factor

[tgentry]

Originally posted by Dean95CobraR
Maybe that's why I didn't have a wear problem - I brake like a girl!!

That's understandable, kart brakes look a little wimpy! Thinking of joining GGR?

[sn8kbit]

Originally posted by tgentry
Steve, am I mis-remembering? I thought you had the one piece Eradispeeds, not rotor and hat. If I am, forgive me, it's the sometimers setting in again.
If those are rotor on hat, what is the weight difference from the stock one piece rotors?
At $140 each, that's over twice what I pay now. You really think I'll get over double the life? I was thinking that rotor on hat would be a big initial investment but that the rotor part would be less expensive in the long run

i can't testify to life yet. you're much quicker than i am on track. i do however have right at 20k miles on them, with no problems as yet. i didn't think to weigh them when i put them on, unsprung weight in this particular area was new to me. the only thing i can say is there is a difference. (wow, real tech huh?)
the 140 each replacement price was for the zinc washed, i'm shying away from that due to some things i've heard about it reduces the ability of the rotor to absorb heat as it should. key word being heard. if you paying 70 a rotor, are you using the brembo or the KH style? (that is durn cheap)
now that i officially have a business license, i'm looking into a way to reduce that price some. if anything results from that, you guys'll be the first to know.

(ok, here's a pimpy shot... )

[b_tone]

Early braking allows more time for rotor heat to soak into the pads/calipers/fluid. Boiling fluid is a bad thing! This may even mean that while rotor temps are lower, pad/caliper/fluid temps are as high or higher for the early braker.

Why do you think this?

Don't forget that for every second you are accelerating you are adding the energy not in a linear fashion but as a square of the velocity. this means that if you are on the gas until the very last second you have that much more speed to scrub off. speed through the corner and the exit speed is more important than your ultimate velocity on the straight. They are directly connected and a function of eachother but I am willing to give up 100ft of on throttle at the end of the straight for a nice clean corner entry/exit allowing me to accelerate at a greater rate than if I muff the entry.

Boil it down to seat time and figure out what makes your car fast and how to drive it fast. Doing that will benefit you more than listening to the slowpokes like me.

Brian

[tgentry]

Steve, very pimpy indeed! I still can't understand why the rotor, without hat, should cost so much.

I've been using Bendix rotors in the directional style. Word way back in '98 was that the Bendix rotors were a bit better than the actual KH ones. I tried Brembos and didn't feel there was any real benefit over my tried and true Bendix rotors. YMMV.

BTW, I also tried the Bendix non-directional and have decided that the directionals are worth a few extra dollars.

Tone, I'm basing that theory on the fact that the rotors and pads are in contact for a longer period. It's my belief that the rotor temps won't vary enough to make up for the duration. Am I making sense?

Your technique sounds like a good way to save brakes, tires, and gas. In our universe you might even be right, nailing the corner is probably more important than that last 100 ft of acceleration. Even so, I'd be willing to bet that if you're name was Schumaker you'd be standing on the gas until you saw God and STILL nailing the turn.

[sn8kbit]

these were prices quoted last year, when i first picked them up. i have no clue if they've gone up or down, since i've noticed they have more options now. one piece, and the +1 kits which are new brackets and rotors 1 inch larger than stock. i may give em a ring tomorrow while not doing anything and find out....

[97whitevert]

Originally posted by 98banana


Good conversation here...

very good!! i am reading, thinking and hopefully learning!!

[97whitevert]

Originally posted by Dean95CobraR
Maybe that's why I didn't have a wear problem - I brake like a girl!!

DEAN!!!!!!!!

that was uncalled for!!!!!!