Extending brake life- Stomp, or squeeze!

There are 198 turns and about 1600' of elevation change in the 13.4 miles from my cabin to the nearest town. Nearly every one of them is banked perfectly. It's a drivers paradise.

Unfortunately I am usually driving it in a truck that weighs nearly 9000 pounds. Sometimes I'm towing a trailer.

I know how to get through the turns the fastest- dive deep and stomp hard. Probably not the best idea in my truck.

I also know the best way to preserve the brakes is to slow down to about 15 mph. That's not gonna happen.

The ride is most comfortable when I break early and gently and squeeze the brakes, but it's easy to find myself with my foot riding the pedal.

So which would conserve the brakes the most? Diving a little deep and stomping medium hard, or breaking early and squeezing the brakes more gently?

My gut tells me they are probably about equal but I figure I'd ask the wisdom of the board.

probably a highly theoretical question, but at some point the same energy removed from your vehicles kinetic motion should have the same wear on the brakes.

does the wear rate increase or decrease with temperature? I have no idea.

To your point, slowing down will have the greatest effect on saving brakes. The more you push the gas, the more brake wear you incur (as almost all trips start and end with a non-moving vehicle). You could probably find bigger reduction in wear not by changing the braking method, but rather by finding the places where accelerating does not actually speed up your trip at all.

It would be just like a racetrack - if a long straight is ahead, make time by speeding up. If another turn is ahead, don't bother accelerating, as it will hardly hurt your overall travel time.

I'm thinking gentle squeeze and, without going too far down the rabbit hole, here's why:

We all know the job of the brakes is to basically convert kinetic energy to heat, then dissipate that heat. To shed a given amount of speed, you've got to generate the same amount of heat, regardless of the time interval. Dumping all that heat into the rotors/drums in a short interval (hard and late) gives it less time to dissipate that heat, thus they get hotter that way. Assuming more heat leads to faster wear, hard and late should wear them out quicker.

Now, that's neglecting to factor in how things like vehicle speed and temperature differential affect the heat transfer from the brakes to the air, but my theory seems to agree with practical experience.

I have the tendency to drop down a gear or two and use engine braking as much as possible. I tend to do that in traffic as well. That probably won't help the fuel economy though.

In an average 4 day weekend, I may make 5 round trips up and down that mountain.

That's nearly 2000 turns in 134 miles, and most of them are hairpins or switchbacks.

In reply to Toyman01:

Engine braking only helps the downhill.

Furious_E wrote: I'm thinking gentle squeeze and, without going too far down the rabbit hole, here's why: We all know the job of the brakes is to basically convert kinetic energy to heat, then dissipate that heat. To shed a given amount of speed, you've got to generate the same amount of heat, regardless of the time interval. Dumping all that heat into the rotors/drums in a short interval (hard and late) gives it less time to dissipate that heat, thus they get hotter that way. Assuming more heat leads to faster wear, hard and late should wear them out quicker. Now, that's neglecting to factor in how things like vehicle speed and temperature differential affect the heat transfer from the brakes to the air, but my theory seems to agree with practical experience.

You're actually completely opposite.

That's why race cars try to compress the braking zone as much as possible, so there is more time to dissipate the heat from the previous corner.

SVreX wrote: In reply to Toyman01: Engine braking only helps the downhill.

And letting off gas and letting the uphill grade slow you down works going uphill.

Do less braking with your service brakes, use engine braking more. It shouldn't have much effect on gas mileage. It may even help, since you are technically maintaining your cruising speed for less time between the corners. It will be slower. 9000lbs- diesel I'm guessing? Do you have an exhaust brake?

Boost_Crazy wrote: 9000lbs- diesel I'm guessing?

This is grm. More likely a Roadmaster or minivan when only towing 9k.

Use as much engine braking as possible and brake short and hard. This keeps the brakes cooler by giving them as much pads-off cooling time as possible...same as on the track. Remember during the Toyota runaway fiasco the advice was to brake hard if it happens? Same reason...lighter braking builds heat more steadily and eventually overheats something.

Keeping brakes cool doesn't necessarily mean less wear. The question is what leads to less wear...

And let's straighten something out here. Race cars brake late and hard because it is the fastest way around a track. No other reason.

Robbie wrote: And let's straighten something out here. Race cars brake late and hard because it is the fastest way around a track. No other reason.

This is the main reason and a good enough reason all by itself...but it's also the best way to keep the brakes cool:

http://www.motoiq.com/MagazineArticles/ID/2215/Modeling-Braking-Braking-Harder-Means-Less-Brake-Fade.aspx

Robbie wrote: Keeping brakes cool doesn't necessarily mean less wear. The question is what leads to less wear... And let's straighten something out here. Race cars brake late and hard because it is the fastest way around a track. No other reason.

Ah I didn't consider that, I was thinking about keeping the brakes from reaching some kind of overheat condition (whether in the fluid or pads or theoretically even the rotors). Overheated brakes can cause a crash which can cause severe wear to many different parts

I'd bet late & hard braking also causes the least wear through reduced temperatures. Pads last longer on cars with brake vent systems (to the point that they often have to be plugged for pad break-in). When pads get hot, you find a thin layer of pad material smeared across the rotor face...that can't be good for wear.

I think several of you jumped on "late and hard" because of race cars. I'm not convinced I agree with your logic.

I think Robbie was right in his first post- the math is equal on the heat and kinetic energy.

However, I also think the correct answer in this specific case is different. I think the right answer is light squeeze, for psychological reasons...

Braking hard and late makes me THINK I'm performance driving, which makes me want to give it more gas COMING OUT of every corner. That creates more energy which needs to be dissipated.

I don't think it's an engineering problem. I think it's a human psychology problem.

z31maniac wrote:

Furious_E wrote: I'm thinking gentle squeeze and, without going too far down the rabbit hole, here's why: We all know the job of the brakes is to basically convert kinetic energy to heat, then dissipate that heat. To shed a given amount of speed, you've got to generate the same amount of heat, regardless of the time interval. Dumping all that heat into the rotors/drums in a short interval (hard and late) gives it less time to dissipate that heat, thus they get hotter that way. Assuming more heat leads to faster wear, hard and late should wear them out quicker. Now, that's neglecting to factor in how things like vehicle speed and temperature differential affect the heat transfer from the brakes to the air, but my theory seems to agree with practical experience.

You're actually completely opposite. That's why race cars try to compress the braking zone as much as possible, so there is more time to dissipate the heat from the previous corner.

Figures

That makes more sense, though, same as not constantly braking on a long grade. I think my logic honed in on one singular braking event, while neglecting cumulative effects and cool down time between corners.

Ive got no secret technique. Downshifting during the downhill run, and managing vehicle speed uphill in anticipation of the turns. Have you considered ducting your front brakes? Pads and rotors are cheap and easy enough that, personally I wouldn't be so concerned with wear as I would ensuring the brakes are there, every time. Assuming rotor temperature significantly effects wear, it's win win.

On bicycles, there is a danger of hot wheels from braking causing the tire to blow. This happens when going slowly, as you get all of the kinetic energy and none of the cooling. If you want to preserve the brakes, use the force of cornering to slow you down where possible, and braking quickly and decisively where not.

Apples and oranges, of course, since you probably are going to be carrying a lot more kinetic energy than 200lb of bike/rider going 40-60mph. But the "slow is best" has been proven to be wrong in this environment.

'Course, bikes don't have engine braking.

In reply to Knurled:

Most bike don't have engine braking.

Fixies do.

In reply to Robbie:

Only if you're riding slowly! Besides, you're only supposed to ride a fixed-gear for the first 5000-6000miles in a season, to smooth out your cadence, before you hop on your real bike.

"Manage speed" is the obvious answer, but it's not really what I was asking.

I was actually interested in the technical question: is one form of braking more efficient at managing converting the kinetic energy to heat.

In other words, if I am entering a corner at 30 mph and need to reduce to 20, is it better to brake gently early (for a longer period), or wait a second and stab slightly later.

I think Robbie's answer was technically the closest to correct (no difference- same kinetic energy, same heat dissipation), but suspect there is a more nuanced correct answer, like the compound of the pads, the mass of the rotors, the effectiveness of the venting, etc. While all of these can obviously have an impact, I'm specifically curious about the driving technique.

I'm liking the stab later, because it leaves the disks unobstructed longer between braking events for cooling.

I like "stab later" because heavy application on cold rotors cleans the rust off.

this is interesting...

im no brake guru, but ive been told there are two types of braking

abrasive and adhesive.

abrasive is pad on rotor and is high wear braking

adhesive is the deposited friction material on the rotor vs the friction material on the pad.

what i was told is adhesive is what you want, better braking and lower wear. It is why you break in or burnish in pads.

Abrasive happens when the pads and rotors dont get to temp and all the deposited friction material is removed from the rotor, and it wears both components faster and is generally more noisy.

I have no idea if its true or bullE36 M3, and im sure it doesnt apply here (im sure you are getting your stuff hot enough), but its an interesting thing to consider when looking at a problem like this from a purely theoretical stand point. I always thought it had some truth to it, because after many years in the auto repair industry, i noticed we never got noise complaints from people who routinely worked their brakes hard and got them all the time from people who just putted around town and never got them to temp.

GameboyRMH wrote: This is the main reason and a good enough reason all by itself...but it's also the best way to keep the brakes cool: http://www.motoiq.com/MagazineArticles/ID/2215/Modeling-Braking-Braking-Harder-Means-Less-Brake-Fade.aspx

This is a good article, and I'm sure his math is right. But he missed the point of race tracks and ended up modeling off-ramps. Who on a racetrack comes up to speed and then quits accelerating with lots more straight to go?
Here is his graph:

He modeled braking from the same speed - but the point is if you are braking softer you would normally start braking from a slower speed, and therefore have less kinetic energy to dissipate. Therefore, his graph should not have flat tops. Imagine if the acceleration and braking lines kept going up until they intersected. The yellow would be going a heck of a lot faster before the braking zone than the blue. I would like to see him re-run the numbers based on racetracks rather than highway off ramps.

I do think however he may still be kinda right, albeit for the wrong reasons. Heat transfer is a function of transfer area (surface area of rotor, essentially) and temperature differential. When the rotor is hotter, it will drop 1 degree faster than when it is cooler assuming the same ambient conditions - I think you can see that in his other graphs. So if you are getting the rotors hotter, you are actually making them faster at cooling.

Edit: he DID do a really good job at modeling svrex's situation though. haha.

Toyman01 wrote: I have the tendency to drop down a gear or two and use engine braking as much as possible. I tend to do that in traffic as well. That probably won't help the fuel economy though.

Plus brakes are a lot cheaper to replace than engines..

frenchyd wrote:

Toyman01 wrote: I have the tendency to drop down a gear or two and use engine braking as much as possible. I tend to do that in traffic as well. That probably won't help the fuel economy though.

Plus brakes are a lot cheaper to replace than engines..

If engine braking hurts your engine, the engine deserved to die for being a weak POS.

"Brakes are cheaper" but it's very expensive to run out of deceleration ability when you need it.

Poorly thought out argument is poorly thought out.

Engine braking, incidentally, is one of the things I keep running up against when I think of getting a hybrid. I'd want to tow with it, and a lot of hybrids don't really "do" engine braking, just regenerative braking. Which makes sense, but it sucks for safety reasons. I'm not sure if it could be possible for the battery to get fully charged partway down a hill around HERE where the grades are relatively short and frequent, but I could see it happening elsewhere. This is a lot of why many/most hybrids have really low tow ratings, that and a lot of hybrids are electric only for Reverse.