Tracking the stock callipers

[rsevo6]

I agree ABSOLUTELY with you that you peak rotor temperatures will be higher in the Brake Late/Brake Hard scenario than when taking it easy.

But I DISAGREE with you about the 'same heat point'.
Assuming that you will be slowing down FROM the same speed TO the same speed using the brakes (from 140mph to 40mph for example) using the brakes, you WILL generate EXACTLY the same heat.
Your car's kinetic energy is transformed into heat. Transform the same kinetic energy will generate the same amount of heat. Period!. It is what is called the First law of Thermodynamics.
Mind you, this says nothing about your peak temperatures off course.

Funny, these discussions on brakes and braking technique
I fully agree with MvM on the energy aspect but think that when he states to agree on the the higher braketemps he is wrong.
Why?:
The statements of Stuntman comparing a proper racecar with racing quality brake materials glowing the brakes with average Joe not doing so when braking slower/longer on street braking materials, by this explaining that longer slower braking will cause less heat are flawed.

Average Joe will simply not be able to reach or brake from the same speeds as the racecar under the same conditions, on the same track. The comparison is flawed!

If the racecar would use the technique that Stuntman is promoting, he would destroy his brakes within a few rounds.

I race and know this from the beginning of racing when due to lack of experience/ not having the guts to brake late, I sometimes braked too soon and repeatedly before one corner or not hard and too long and burnt up a few brakes before I learned that the ONLY good way to be fast and get the max out of the brakes without destroying them is to brake as late as you dare and then as HARD as is possible.

And when you do still burn up the brakes when using this technique, it simply means that the brakes are not up to the speed of the car/driver and should be improved upon. However, when using the slow/long brake manner, the brakes would then have died even A LOT quicker.

 

[stuntman]

Funny, these discussions on brakes and braking technique
I fully agree with MvM on the energy aspect but think that when he states to agree on the the higher braketemps he is wrong.
Why?:
The statements of Stuntman comparing a proper racecar with racing quality brake materials glowing the brakes with average Joe not doing so when braking slower/longer on street braking materials, by this explaining that longer slower braking will cause less heat are flawed.

Average Joe will simply not be able to reach or brake from the same speeds as the racecar under the same conditions, on the same track. The comparison is flawed!

If the racecar would use the technique that Stuntman is promoting, he would destroy his brakes within a few rounds.

I race and know this from the beginning of racing when due to lack of experience/ not having the guts to brake late, I sometimes braked too soon and repeatedly before one corner or not hard and too long and burnt up a few brakes before I learned that the ONLY good way to be fast and get the max out of the brakes without destroying them is to brake as late as you dare and then as HARD as is possible.

And when you do still burn up the brakes when using this technique, it simply means that the brakes are not up to the speed of the car/driver and should be improved upon. However, when using the slow/long brake manner, the brakes would then have died even A LOT quicker.

The main concept is energy over time. Braking earlier and lighter results in less PEAK heat than later and harder. Peak heat causes more stress on rotor material (emphasis on cracking), pad heat soak and fade, and likely caliper heat soak.

With speed as a constant, decelerating a car will take the same amount of ENERGY regardless of how quick the stop is. Also keep in mind heat in the brakes is not the only way that energy is dispersed.

The streetcar vs. racecar analogy is not flawed but is also probably not the best example. A racecar on a racetrack with sticky slicks that is able to generate 1.7 G's of deceleration will tax the brake system to glow -generating a high peak temp when threshold braking (lets say from 140mph). Lets say the rotors get over 1,100*F. A street car on street pads cannot decelerate at the same rate as this racecar, so the rotors don't glow and it takes more time to slow the car. The street pads fade at a much lower temperature so the rotor dosn't get as hot and it takes more time to slow the car down.

Now Joe shmo in a street car with street pads is going 140mph (the location is irrelevant because the speed is constant) but for arguments sake, lets even say he's driving the exact same racecar but slows down by braking earlier and lighter and not threshold braking. Even though he's going the same speed, the lighter pedal effort and longer distance takes more TIME and thus expels the energy over a longer time resulting in lower PEAK temperatures.

Since the equation is energy over TIME, if you take a lot more time to slow the car down, the peak rotor temp will be lower. 140mph does not = 1,100*F rotor temps, otherwise everyone who has ever gone 140mph will have 1,100*F rotor temps.

In addition: As you brake longer over time there becomes more variables which expel the energy ranging from aerodynamic drag to engine/transmission drag to drag from the tires rolling on the road for a longer time. Let off the gas when you're driving on the freeway (or whenever for that point) - you slow down. Your rotors don't all of a sudden get hotter. As your braking distance increases, while small, some of the energy is dispersed through various means.


***A lot gets lost in translation through text and i'm sure you can pick through every word of every concept to continue the argument, but i'm not interested in that.


Main point:

I never said that I favored braking earlier or lighter. I simply stated that I no longer have the standpoint that braking later and harder results in lower temps and less fade than an amateur who brakes earlier and lighter. I now don't agree with those who say that i'm easier on brakes than they are because i'm a "pro" and I brake later and harder than them but rather I would be harder on the brakes then they are.

If you have shorter stopping distances, you will be faster (time wise) and harder on your brakes.

Thus - IMO the stock brake calipers and rotors with good pads and rotors (not ducted) are good enough for me and probably most everyone else with I/H/E, 235/275 top-level street tires, and suspension. Due to Ryneen's performance with R-compounds, if you are driving the car to its true potential, you might want to consider upgrading at least the front brakes.


0.02

 

[NSXDreamer2]

the flaw of the argument most people refering to their novice days or experiences, is not ONLY they stop earlier and dragging the brakes. They are over slowing into the corners.

Billy may as well braking at last cone from 140mph and turn in at 80mph while trailbraking into the apex.

I may have been braking at 3rd cone from 140mph and trun in at 70.

a novice could be starting to brake at 1st cone from 130mph but turn in at 50mph thus "killing" their brakes.

I also don't think 'braking' as hard and as late always work in every corner in favor of lower lap time either... There were few things about your car's aerodynamic, front tire grip as far as traction circle goes, and even the different lines due to the car set up.

However when you in wheel to wheel racing, you are braking to pass someone, then the as late and as you dare approach works everytime.

 

[MvM]

With speed as a constant, decelerating a car will take the same amount of ENERGY regardless of how quick the stop is.

This is exactly what I said before :smile:

The main concept is energy over time. Braking earlier and lighter results in less PEAK heat than later and harder. Peak heat causes more stress on rotor material (emphasis on cracking), pad heat soak and fade, and likely caliper heat soak.

Actually, purely speaking theoretically (emphasis), that statement is NOT correct. If we would NOT take into account heat lost through heat radiation (either to the air or by contact with your brake calipers, fluid, etc.).
If the same amount of energy is transformed into heat, the same amount of heat will be produced.
BUT, as we are not talking about theory here but about real life application, your statement is (almost) correct.

That is:
Braking Hard & short will GENERATE more heat in your rotors than braking Light(er) & longer.

This is actually rather obvious, since you are applying more force during a shorter time. So, actually, we are saying the same thing.

However, it seems that I have forgotten to bring up one point which seems to have eluded us in the previous posts.
When we are talking about peak rotor temperatures, we are actually referring to one time braking applications.
If Joe Shmo is braking his (street) car from 140mph just once, his peak rotor temperature will be higher if he slams on the brakes hard instead of taking it easy. Not because the heat generated is less, but more will have dissipated while braking.

On a race track however, we are constantly braking and accelerating.
Again, the same amount of heat will be generated, but every time we brake, the heat generated is added to the heat already stored in your brake rotors.

This is why, on a track, braking light & long will lead to higher rotor temperatures in the end, NOT because you generate more heat when braking before one corner, but because your brakes have less time to cool down and the heat generated adds up at every corner.
So, for example, when you start braking into corner 10 your rotors will already be hotter than the smart(er) guy who is braking hard & late.

 

[nsxtasy]

Unless you never use them, 99.9% of the time they will crack prematurely vs. a blank or slotted rotor.

Not true, in my experience. I've used blank-faced, slotted, and drilled rotors, and all three kinds lasted approximately the same number of actual track miles before cracking. (In all cases, I tossed them once radial cracks opened enough to feel them with the edge of your fingernail - when the cracks were roughly 1/2" long.) Yes, with drilled rotors, the cracks formed around the holes, but they lasted just as long as the slotted and blank-faced rotors did. Then again, the drilled didn't last any longer, either, so I'm not sure there's any advantage to them.

The one type of rotors I used that lasted significantly longer - anywhere from 50 to 100 percent longer - was two-piece rotors.

 

[e.pie]

MotoIQ just posted a good article about the heat with braking hard/short vs. long/soft. It reminded me of this thread

http://www.motoiq.com/magazine_arti...ing-braking-harder-means-less-brake-fade.aspx

 

[johnnymo]

Boiling the Honda brake fluid at the end of the front straight at Road Atlanta the first year I tracked the car left an impression on me. I distinctly recall the ungainly behind of the Porsche 911 coming at me when I the pedal went all the way to the floor with the resistance of a hot brick of butter at over 90mph.

I learned then and there if you continue to use the stock brakes at the track:
1) replace the Honda fluid with something good like Motul 600
2) drill out the goddamn splash guard to allow some air into the calipers
3) use better brake pads. I have used Porterfield R4S pads happily since.
4) buy the front brake scoop/deflector that attaches to a Porsche 993 lower A-arm and drill it right onto the laughable Honda deflector. Those suckers could scoop up a baby! Credit goes to the NSX guys in the Braselton Driving Club for that one.