Best way to brake for long brake life

Maintenance/Repairs
1

Ok we were slow last night and this question was asked… What is better for the longevity of your brake pads.
You are driving along at 50 MPH you see a red light up ahead, do you:
A) Slowly apply the brakes, and gently slow the car down… This will have the brakes engaged for the longest amount of time.
or
B) Wait a little longer and hit the brakes harder for a shorter amont of time.

I know that prolonged long brake application builds heat and can cause fade, and rotor warpage… However slamming on the brakes harder for a shorter amount of time dont seem like a good idea eather.

Is there a “right” answer??

2

Step 1 get off the gas immediately and coast.

Step 2 apply brakes lightly to scrub off some speed, then coast a bit more.

Step 3 apply brakes for a smooth stop.

The little bit of coasting allows some heat to dissapate. Theoretically the amount of heat generated by converting the energy of motion into heat will be the same. Wear on brake pads in theory is the same as well. In practice the key is to get off the gas as soon as possible, that is the best way to save your brake pads.

My guess based on experience is that lighter braking for a longer period is easier on the pads and brakes than harder braking for a shorter time to stop the same car from the same speed. Not sure if any actual test results are available to confirm my guess.

3

The best thing to do is get off the gas as early as possible and let the driveline slow you down. Use the brakes as needed to complete the stop. If you wait a little longer, you are utilizing the driveline less and the brakes more to stop the car,

4

Look ahead, anticipate the lights and adjust speed to allow the lights to change to green by the time you reach them.

5

Personally, I try to anticipate lights and coast as much as possible. Away from following traffic I may brake a little and let up, followed by braking again. The assumption would be that those pauses will get rid of some brake heat and this may have something to do with brake pad life. Generally speaking, I get a 100k miles or more out of a set of pads.

6

This is actually how the conversation came up we were talking about fuel milage, and how you should let off the gas as soon as you see the yellow/red light. However it was then debated on when to hit the brakes, coast as long as you can and hit them hard, or softly press them WAY back and come to a smooth long stop.

7

The earlier you start braking get off the gas, the more the drivetrain friction helps, reducing brake wear. I think the gentle approach is better, but I can’t prove it.

8

In the early days of home computers, I had a simple little simulation in which you had to bring your high-speed rocketship to a safe tail-first landing, using the minimum amount of fuel. Igniting the rocket engines was your only means of slowing down. And gravity is always trying to accelerate your fall.

A lot of trial and error showed that the solution was to wait until the last possible moment and then to hit the ‘gas’, applying maximum thrust for the shortest possible time. This solution can also be confirmed mathematically.

And my story bears absolutely no relation to ragtop’s situation. But it’s a slow day here too.

9

@stevef I remember that game… LOL

For memories sake
http://www.classicgamesarcade.com/game/21671/lunar-lander.html

Or very old school
http://seb.ly/games/moonlander/

10

@SteveF that moon landing game pre-dates home computers.
I first saw it in 1976 using a terminal in Madison WI that was tied to a time-shared mainframe at Dartmouth.

Before someone flags this a off-topic I think it’s better to brake lightly for the reason @texases gives plus there’s a lower temperature at the surfaces of the rotor and pad: less thermal gradient.

11

I’ve noticed a big difference in brake pad life since moving from a rural to urban area. It’s hard to wear out your brakes when there’s only one traffic light in town!

12

Apart from coasting as much as possible rather than using brakes, the lighter you apply the brakes, the better, even if it means longer application time

Why?

Say your car weighs 1000 kg and you’re traveling 20 m/s. Your car has 0.5* 10002020 = 200 kJ of kinetic energy. If you’re going to slow down to a stop, you have to eliminate that energy somehow. If, for a second, we assume you don’t lock your brakes and they make NO noise, all of that energy is going into heat in the brake pads and rotors. So now matter how you brake, you’ll end up with the same net amount of heat.

However, if you brake more slowly, your heat FLOW is slower, and while that is occuring, you do have convective, conductive, and radiative cooling of the brake parts. And this is crucial.

I’m going to grossly simplify things here, but all of those cooling methods are generally dependent upon the difference in temperature between the parts - so the difference in temperature between the brake rotor and the surrounding environment (again, simplifying things). They’re all roughly (again, simplifying, but a safe one) directly proportional to this difference, too.

So if you look at the system, you have a heat flow in, a heat flow out, and the difference must be accumulated heat energy (thus a temp increase) in the parts. Let’s again simplify things and say we brake until we reach a steady state temperature. So say you brake for 10 seconds or 5 seconds to bring your vehicle to a stop. Let’s pretend (making the number up), that the heat is dissipated entirely by convection, and the convection coefficient times the surface area of the rotor is equal to 1000 W/K

You then have :

Braking energy in = Heat energy out (at steady state)

So in the 10s case, using 293K as an ambient temp:

200000J/10s = 1000 J/s/K*(rotor temp - 293 K )
rotor temp = 313 K

In the 5s case, you get:
200000J/5s = 1000 J/s/K * (rotor temp - 293 K)
rotor temp = 333 K

Even if you don’t reach steady state heat transfer, you’re still going to reach higher temperatures if you brake harder…

And as in the cases of so many things automotive, temperature is your enemy. Therefore, since braking slower results in lower brake temperatures, you will end up with longer brake life.

Even better yet is to not even use your brakes when possible (ie, coasting) - you get ZERO heat buildup then. :slight_smile:

13

I agree with braking for a longer time and with an easy pedal application to extend brake life. That is what I have been doing. It may not feel like the right thing to do but it works. In summary, braking longer, for one thing, gives more cooling time to keep pad and rotor peak temperatures down. Cooling does not take place until there is heat generated when you begin to brake. The same method should also help to extend your tire tread life.

14

I also watch traffic conditions and when seeing a car in front of me slowing down or a traffic light coming up that is red I let off the gas and coast, many times never having to touch the brake pedal, because the other driver speeds back up or the light turns green prior to me getting to it. When I do have to use the brakes I use the least amount of pressure on the brakes as possible. As a normal rule I get in access of 100K miles out of a set of shoes/pads.

15

Does all this excellent advice work in downtown Boston ? Sometimes I feel like playing leapfrog just to keep from getting run over. Saving my brakes is the last thing I think about then. I guess my point is, like hyper milers, safety some times takes priority and I just hope I have enough pad left to get me home safety.

16

You all missed it:

What is better for the longevity of your brake pads.

<b>Let it coast to a stop! or stomp on them and skid to a stop</b>  

That is not the best choice, but it will reduce brake wear to near zero.   Of course you will be buying new tyres often and I doubt if the local police and other drivers will take kindly to your driving.
17

I agree generally with the low and slow technique, it’s the one I use, but strictly speaking it isn’t the correct answer to the question. If minimum brake wear is the goal the proper technique would be to wait until the last possible moment and lock the brakes. This wouldn’t do much for the tire wear but the brakes would last a lot longer. Everyone so far has focused on the heat generated by the brakes, but abrasion not heat is the primary wear mechanism. The number of revolutions the wheels turn counts. Ideally braking in the shortest distance without overheating the friction surfaces should result in the best wear.

Apparently it does take a rocket scientist to stop a car.

18

The cooler you keep your brakes, the longer they will last…It’s as simple as that…The best driver in the world seldom if ever uses his brakes…Most stops or the need to reduce speed can be anticipated and accomplished without the use of brakes…

19

To lock the brakes you’ll have to find the button (if your car has it) to disable the anti-lock braking system.

20

Of course, Uncle Turbo, your tires will wear out faster and get out of balance every time you lock 'em up. But, the brakes would certainly last!