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Weigh in on a bar discussion... Braking

BoldlyGoing

TJ Enthusiast
Oct 9, 2017
494
Atlanta, GA, United States
So my buddy and I were discussing proper braking (like you do) over a few beers this week.

He is the opinion that braking early and over a long period of time is the proper method for applying the brakes under normal conditions. In other words, begin braking as soon as you know you will have to stop.

My position is that a harder, but shorter braking duration stop is the best technique (not a panic stop, just basically not braking until you’re at the minimum distance needed to stop safely).

His argument is that a slower “lighter” application reduces shock on braking / suspension components thus increasing their useful life.

My argument is that the shorter time the brakes are engaged, the less time material is being removed from the pads/rotors thusincreasing the life. The suspension is irrelevant in this discussion.

What say you (besides “Ya’ll need better drinking topics”). Am I right? Is he? Are we both retarded?

Idk how to tag people, but someone tag Blaine. I feel like he has some thoughts on the topic.
 

rasband

LJR
Supporting Member
Sep 11, 2018
654
Denver, CO
I think it’s a function of heat generation (friction). Long and light would, I believe, have more friction over the period thus wearing pads more.

You guys forgot the third option: lock up your brakes, save all the pads, but buy tires every month. :qmeparto:
 

Mr. Bills

TJ Addict
Nov 24, 2017
1,546
Area Code 530
I think the correct answer to "What is the "best" braking technique?" is a resounding "It depends."

Some brake pads require "braking with enthusiasm" for optimum performance (think Black Magic Brakes). Other pads are more "consumer friendly" and do not suffer much noticeable degradation in performance from a longterm pattern of long, steady "limousine stops."

Like the hub height thread, does this mean that we're supposed to report the thickness of our brake pads, how long they've been installed and how enthusiastically we brake? ;)
 
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BoldlyGoing

BoldlyGoing

TJ Enthusiast
Oct 9, 2017
494
Atlanta, GA, United States
Like the hub height thread, does this mean that we're supposed to report the thickness of our brake pads, how long they've been installed and how enthusiastically we brake? ;)
Dude... this is the Supreme Court of Bar where the only evidence accepted is anecdotal and even better if you heard it from your sister’s husband’s cousin.

Pure conjecture reigns supreme!
 
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Equilibrium31

TJ Enthusiast
Supporting Member
Apr 7, 2018
931
Burnsville, MN, USA
I did some google searches on this and was actually surprised to see a lot of "how to reduce wear on your brake" type articles that didn't say either way on this. There were a few posts from random people that were answered by other people arguing both ways.

While I couldn't find anything stating that sharp vs smooth braking generates less/more wear, everywhere agrees that coasting as early as possible will reduce wear. Also, it's worth noting that sudden braking can be a danger and even if it would, technically, reduce wear, having someone rear-end you would cost a lot more than some new brake pads.
 

Equilibrium31

TJ Enthusiast
Supporting Member
Apr 7, 2018
931
Burnsville, MN, USA
Actually, if you look at the formula for kinetic to thermal energy associated with friction braking, it doesn't seem to make a difference since less distance would mean more force and more force would mean more distance. Both would still have the same result:

Ethermal = Ff × d where,

• Ff is the force of friction in newtons (N).

• dd is the stopping distance in meters (m).

• Ethermal is the thermal energy produced by the brakes in Joules.
https://energyeducation.ca/encyclopedia/Braking
 
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BoldlyGoing

BoldlyGoing

TJ Enthusiast
Oct 9, 2017
494
Atlanta, GA, United States
I did some google searches on this and was actually surprised to see a lot of "how to reduce wear on your brake" type articles that didn't say either way on this. There were a few posts from random people that were answered by other people arguing both ways.

While I couldn't find anything stating that sharp vs smooth braking generates less/more wear, everywhere agrees that coasting as early as possible will reduce wear. Also, it's worth noting that sudden braking can be a danger and even if it would, technically, reduce wear, having someone rear-end you would cost a lot more than some new brake pads.
Well of course coasting early is best. But that’s slowing. We were specifically drunk arguing about braking.

Clearly abrupt stops are a bad idea, we agreed on that. But there is a difference between “quick” braking and abrupt.
 

Equilibrium31

TJ Enthusiast
Supporting Member
Apr 7, 2018
931
Burnsville, MN, USA
Well of course coasting early is best. But that’s slowing. We were specifically drunk arguing about braking.

Clearly abrupt stops are a bad idea, we agreed on that. But there is a difference between “quick” braking and abrupt.
As best as I can tell, it just doesn't make a difference from a brake wear standpoint. Although, braking sharply does have some safety issues if done really suddenly and you could potentially see some warping or tire wear if you go really extreme on it.
 

Mike_H

Rust Belt Heavyweight
Supporting Member
Feb 28, 2017
4,424
Grand Rapids, MI, United States
It shouldn't really matter. The 1st law of thermodynamics is the conservation of energy, which means that energy cannot be created or destroyed...only converted. When you stop, you are converting your kinetic energy to heat. Its the same amount of heat regardless if that is over a long amount of time or a short amount of time...what matters is the starting energy.

Now that the physics are out of the way...Pad material and composition, rotor material and composition, tires, etc all have an affect on braking performance and which is better. So the correct answer is....It depends.
 
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BoldlyGoing

BoldlyGoing

TJ Enthusiast
Oct 9, 2017
494
Atlanta, GA, United States
Actually, if you look at the formula for kinetic to thermal energy associated with friction braking, it doesn't seem to make a difference since less distance would mean more force and more force would mean more distance. Both would still have the same result:



https://energyeducation.ca/encyclopedia/Braking
That seems like common sense... just like if you raise 1g 1m 10 times, you use the same energy as 10g 1m 1 time. (If I am remembering my physics correctly. It’s been a while)

But then the question is is there any difference in the pads if they absorb say 100° for 10 second vs 400° for 2 seconds. (No idea what’s temperatures brakes actually experience- just pulled those numbers out of my butt)
 
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BoldlyGoing

BoldlyGoing

TJ Enthusiast
Oct 9, 2017
494
Atlanta, GA, United States
It shouldn't really matter. The 1st law of thermodynamics is the conservation of energy, which means that energy cannot be created or destroyed...only converted. When you stop, you are converting your kinetic energy to heat. Its the same amount of heat regardless if that is over a long amount of time or a short amount of time...what matters is the starting energy.

Now that the physics are out of the way...Pad material and composition, rotor material and composition, tires, etc all have an affect on braking performance and which is better. So the correct answer is....It depends.
“It depends” is exactly the type of thing that leads to great bar conversation.
 
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RubiconMike

TJ Enthusiast
Supporting Member
Oct 25, 2018
298
Santa Cruz, CA
I've always followed the Jackie Stewart theory of "smooth inputs for acceleration/braking upset the chassis less" which is really designed to optimize handling, not necessarily brake life (your buddy's answer seems to agree to this). Then, when I went to the Panoz racing school, the instructors there said to wait until the last minute and hammer the brakes hard, so I don't think there is an obviously correct answer to the question.

For everyday driving, if you follow the "hammer the brakes at the last minute" theory, you may find people are less likely to want to ride with you.... :)
 

RubiconMike

TJ Enthusiast
Supporting Member
Oct 25, 2018
298
Santa Cruz, CA
Actually, if you look at the formula for kinetic to thermal energy associated with friction braking, it doesn't seem to make a difference since less distance would mean more force and more force would mean more distance. Both would still have the same result:



https://energyeducation.ca/encyclopedia/Braking
To get even nerdier, it would seem that lightly applying the brakes over a longer period of time would generate the same amount of heat as hard application over a shorter period (since you are losing the same amount of kinetic energy), but the rotors would be trying to shed heat at the same time, so would lightly applying the brakes end up cooler due to the longer time spent shedding heat?
DISCLAIMER: I have no training or special knowledge of physics, just the usual "the world looks flat, so it must be flat" type of logical thought.

Maybe Blaine can comment here with some results of testing he's done on his brakes.
 
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Equilibrium31

TJ Enthusiast
Supporting Member
Apr 7, 2018
931
Burnsville, MN, USA
That seems like common sense... just like if you raise 1g 1m 10 times, you use the same energy as 10g 1m 1 time. (If I am remembering my physics correctly. It’s been a while)

But then the question is is there any difference in the pads if they absorb say 100° for 10 second vs 400° for 2 seconds. (No idea what’s temperatures brakes actually experience- just pulled those numbers out of my butt)
Yea, that's a good point. I couldn't find anything specific to that. Seems like this would be a good question for Mythbusters.
 

Equilibrium31

TJ Enthusiast
Supporting Member
Apr 7, 2018
931
Burnsville, MN, USA
Ha! I found a smart guy that answered this question!

David Starks - MS Mechanical Engineering - Iowa State University said:
In point of fact, gradual braking will result in longer wearing lifespan of the braking components. However, what you will find is that there's very little difference in the impact it will make to your life. Whether your brakes last 50,000 miles or 60,000 miles will likely concern you less than whether it is going to rain next weekend, as you will likely only require brake service a very small number of times over the course of your vehicle ownership.

Now for the semi-technical explanation: The force at which you press down brakes has a mild effect on how much material is scrubbed during braking. However, each time you brake, only micrograms of material are being removed - so the impact can't really be seen on a per-braking metric. However, even though the lower force is longer duration, the total mechanical stress is lower for the braking components under lighter loads.
Source: https://www.quora.com/If-you-brake-hard-and-sharply-does-this-cause-worse-brake-pad-wear-Or-if-you-brake-smoothly-does-the-longer-braking-time-outweigh-the-friction-intensity-and-cause-overall-worse-brake-pad-wear
 

tworley

TJ Addict
Supporting Member
Ride of the Month Winner
May 23, 2018
2,257
Morrison, CO
I downshift as much as I can until I use the brakes. I put on BMB pads/rotors back in August and it was a little difficult at first trying to brake enthusiastically vs slower stopping. I had to break them in a couple times after installing due to the way I stop. I would lean towards more aggressive stopping vs riding them.
 
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BoldlyGoing

BoldlyGoing

TJ Enthusiast
Oct 9, 2017
494
Atlanta, GA, United States
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