Hard or soft braking

Hi Xeno,

Thanks for that additional advice on heat dissipation, where you were the only one who understood the "extreme conditions" for tire wear on this type of road, which I appreciate. o How would you run a lateral acceleration test in a vehicle on twisty roads at no more than 40mph?

Bear in mind, I do all my own service (including both clutches on the manuals, and brakes for all the vehicles) for my entire family, and even the tire mounting and balancing, as you're well aware. o Just mounted & static balanced my 30th tire in about five years

Brakes are completely trivial and clutches aren't that much of a big deal. o Why can't people figure out warp versus runout versus disc thickness variation

I'm not sure how difficult automatic transmissions are to repair as I've only had to deal with BMW limp-mode issues which I can program my way out of on the ZF five speed GM transmission.

If wear must be had, I'd trade brake wear for transmission wear any day of the week. :)

Experimentation. But why would you want to?

Yeah, that bugs me too but, hey, I'm retired now. The *tests* done to differentiate are simple. You just need appropriate tools.

Highly complex. The mechanicals aren't too bad. Getting your head around

*power flows* can be a headache though. The hydraulics, quite complex. As for control, two new layers have been added, electrical (servos) and electronics (ECU, sensors, etc). Without an understanding of the *systems* involved, any attempts at diagnostics are, at best, guesswork.

Arlen Holder snipped-for-privacy@is.invalid wrote in news:r45ra7$qd7$ snipped-for-privacy@news.mixmin.net:

The amount of wear would be unnoticeabe in the life of the car. As stated being out of gear on a down hill drive would be foolish for any number of reasons. One being not using free engine braking. (on a auto, manual could be a different set of wear factors.) KB

Long ago hubby shifted the monsterhome into reverse at ~50mph (mistake, of course). Problems ensued. Arkansas liquor store (open on Saturday night) called his pal the Dodge dealer who made arrangements with HIS friend the transmission shop guy to open up Sunday morning to get us going. Asked woman at gas station for directions -- she decided it would be easier to lead us there than to explain how to get there and didn't even stick around for thanks. People in Fort Smith are just DIFFERENT.

Anyway, the old guy took the trans apart and put it back together while we watched. He had Parkinson's, but not a single tremor while he was working. Most amazing thing I've ever seen. Moved like a robot -- absolutely sure of every single movement.

REALLY DIFFERENT.

Indeed.

Hi Xeno, You and I have a mind that distinguishes between fact and intuition; but a _lot_ of people have very strongly held opinions that are based purely on intuition, e.g., that brake rotors "warp" in normal everyday use.

They don't even _question_ their intuition, in the least, Xeno.

To them, it's instantly "intuitive" that the thick steel rotor melted such that it's shaped like a potato chip, as that would "explain" (in their mind) why they feel brake-related pulsations at highway speeds.

And yet, they _never_ test for warp (which is simple to test for). o They based their opinions _purely_ on intuition and nothing else.

Unfortunately, a _lot_ of people seem to own belief systems that are not based on any facts that I can tease out of them, which is why I very much appreciate that you've provided _many_ facts to help explain what I've been observing, particularly on the inside edge extreme wear of our tires:

Which is visible on multiple vehicles even after only a few hundred miles:

I'm seeking similar facts for how to trade wear when a vehicle is incessantly driving constantly decelerating for miles every day between: o Engine braking o Brake-system braking

The facts are that brakes are made for this task; where it's not as clear to me that transmissions are designed for incessant engine braking tasks.

Personally, if it's 1:1 on wear, then I'll take brake system braking repairs any day over transmission repairs, simply because brakes are made to be easily repaired for wear.

I don't disagree.

Something has to absorb (in heat) the potential energy of incessant almost constant braking daily for miles on end on steep twisty mountain roads.

If wear must be had, I'd trade brake wear for transmission wear any day.

Hi Kevin, I appreciate your input as I'm trying to obtain comparative facts on o Wear due to friction in the transmission, versus o Wear due to friction in the engine given there is no other way to slow down on long mountain roads.

So we only have two possible choices: a. transmission friction b. brake system friction And, I argue, the need for sudden acceleration isn't even remotely an issue on these single-lane roads that have almost zero traffic on them, and where acceleration would put you instantly at the bottom of a cliff, if not into a tree.

Hence the question is only of the relative wear tradeoff between: a. transmission friction b. brake system friction

To that end, thanks for the observation that the wear of the friction on the transmission necessary to reduce the potential energy of the car traveling on a 9% grade for miles on end would be insignificant during the life of the transmission.

Likewise, I've noted that the wear on the pads is also insignificant, given how trivially simple & inexpensive it is to replace brake pads on today's vehicles (about twenty five to thirty bucks every few years on average).

Given I can't even envision a situation where you'd need to accelerate (as, even if you did accelerate, you'd end up at the bottom of a cliff), and given the logic of the _last_ reason to "obey a law" is because "it's the law", then it seems to be a simple tossup. o Trade transmission-based engine braking for brake-system braking, versus o Trade brake-system braking for transmission-based engine braking.

It seems, to me, based on those facts, that it's a tossup between the two given in both cases, the impact of friction-related wear is negligible. a. transmission friction b. brake system friction

As always, I'm wide open to facts since I can change my mind in an instant if and when compelling facts are introduced, since my belief systems are always based on facts as much as humanly possible - and not on intuition.

This is _excellent_ information, Xeno, which I appreciate since I love facts.

Facts are what drive my decisions, not intuition (which is often wrong).

Thanks.

Ooooops. That last sentence was a thinko...

The facts seem to be we only have two exactly equal choices: o dissipating potential energy via friction in the _transmission_ o dissipating potential energy via friction in the _brake system_

We have no other choices given I start in neutral so there is zero acceleration other than that due to the potential energy of mg sin theta.

Either via brakes or the transmission... "something" must dissipate the potential energy of a few thousand pounds on a 9% grade for miles on end.

In both cases, transmission or braking system, the potential energy has to be turned into friction which itself results in heat dissipation.

The question is which is damaged more by the same amount of heat dissipation, the braking system or the transmission.

If the wear is negligible in both cases, and if the safety is, as I argue, not in the least an issue (given you likely can't accelerate even if you had wanted to as you'd end up against a cliff or at the bottom of one if you did).... then...

It seems to be a tossup between the inherent wear of... a. Dissipating potential energy as heat in the braking system, versus b. Dissipating potential energy as heat in the transmission system.

I _love_ facts; so if folks have more facts, please let us all know.

Arlen Holder snipped-for-privacy@is.invalid wrote in news:r48flc$gq1$ snipped-for-privacy@news.mixmin.net:

so you are ignoring the friction of the entire drive train not just the trany friction. also consistant drag of the drive train/transmission can make keeping control more consistant than in neutral. also miles long brake drag is NOT designed into most systems, and glazing of the pads can lower the brake efficiency which is a safety issue not just a wear factor.

again accel is not the only reason to have the vehicle always in gear.

to reiterate it is not a trany vers the brake wear the only thing at issue here. KB

The transmission has been designed with ablative technology in mind. The bands and clutches *do not slip* in normal use. What happens is that as the bands or clutches apply, they are cushioned by *fluid*. While rotating at different speeds, it is fluid friction that matches the speeds of the two components. Once the speeds match, the last of the fluid is squeezed out and full clamping takes place. At no time should there be abrasive friction wear of clutch or band facings. Therefore, unlike with brake pads or shoes, there is no friction surface wear of any consequence and heat buidup is removed by the fluid and dissipated elsewhere. This is all due to the special characteristics of the trans fluid used and why trans fluid should be *changed* according to schedule or, more importantly, severity of use.

Indeed. My primary reasons for using engine braking are keeping the brakes cool and maintaining *control* of the vehicle. I taught my wife the same practice.

If, in the event of an accident, the vehicle was found to be operated in

*Angel's Gear*, the driver will be charged with failing to maintain control of the vehicle - regardless of whatever the actual cause, indeterminate or otherwise, might have been.

Hmmmmm.... this question is a basic philosophical technical question, where you bring up a good point about friction in the drive train.

I readily admit I had not priori considered what you're calling the "drive train" (e.g., the differential in a RWD car, the U joints, the wheel bearings, etc.,).

However, thinking about the "drive train" for a moment, if we keep our thinking hats on, and stick to facts, my first question to you is how is the action of the drive train any _different_ with or without engine braking?

Hmmmm... take a look at just _one_ of these curves on this road:

Again, you bring up a good point, where you don't know that the speeds attainable on this road are never going to ever be greater than about 35 to

40 mph at the absolute fastest - where once you brake hard on these turns (many of which are 180 degree hairpins) - you're almost down to walking speeds, and by the time you're at the next hairpin - you're only at around 20 to 25mph (give or take).

So, while you're correct that you go from about 25 mph entering each turn down to around 5 or 10 mph at the apex of the turn, we're not talking huge changes in speed.

Although I do agree, we go from walking speed to 25mph back to walking speed back to 25mph to walking speed back to 25 mph, constantly, instead of going a steady 10 mph (which nobody does).

Thinking about it a bit (I hadn't considered the constant-speed issue prior), I don't think _anyone_ would _ever_ go at a constant speed, simply because the only constant speed possible would be either too slow or too fast.

So you're gonna be braking no matter what, with or without engine braking (which I've said prior but I hadn't considered that constant speed is likely nearly impossible until you just made me think about it).

Do you really feel constant speed is even possible at any speed other than about walking speed (which is just far too slow to be practicable).

Not gonna happen.

I flatly state that if you think there is miles long brake drag, then I didn't explain the situation properly.

Nobody is gonna be on the brakes the whole way down. Nobody. o If you were, you'd never make it to the bottom except at walking speed.

You brake when you enter the turn. o Then you coast to the next turn, gradually picking up speed.

If anyone thinks there's gonna be constant brake drag, then it's my fault for not explaining the situation properly.

It's just never going to happen, even with the most sophomoric of drivers.

But I do appreciate the questions and comments because the whole point is to figure out, intelligently, whether it's a viable tradeoff of... o dissipating potential energy via friction in engine braking, or, o dissipating potential energy via friction in the brake system.

The amount of heat dissipated will be the same in either case: o The question is which system is best designed to slow down the car.

It seems to me. logically, that it's a no brainer which system is designed to slow down the car, where, using the engine to brake the vehicle seems almost like abuse, in that the whole purpose of the braking system is to slow the vehicle down - but the purpose of the transmission is NOT that purpose.

But folks here seem to feel the transmission is designed to slow down the car, which is why I ask the question to flesh out why they think that.

THANK YOU for making me think of these additional details! o I love taking apart a system to make informed pragmatic decisions.

Thanks Xeno for your technical advice since the question is a sincere question of which system is best designed to brake the car: a. The transmission, or, b. The braking system.

I must admit, when you first wrote "ablation" and "ablative technology", I inferred you meant "heat dissipation", but I decided to look up the word, where, now I'm more confused than before I looked it up:

Since I'm in the USA, I use Merriam-Webster almost exclusively, which says: o ablative

"of, relating to, or constituting a grammatical case expressing typically the relations of separation and source and also frequently such relations as cause or instrument" o ablation "a: surgical removal b: loss of a part (such as ice from a glacier or the outside of a nose cone) by melting or vaporization"

Of those definitions, the only one which comes remotely close is: "the loss of a part" But I don't think, from the context, that you meant that.

Did you?

Thanks for that explanation, where I admit you know this stuff better than I do, but where I will let you know if I don't follow your train of thought.

As we stated, I agree with you that there's no way "friction" isn't involved, where that friction must turn into heat, whether we use the braking system as a braking system to turn friction into heat, or whether we use the transmission as a braking system to turn friction into heat.

I think you're saying the couple of liters of automatic transmission fluid is capable of handling the heat, which I don't doubt. The question in my mind is whether the automatic transmission is better designed to be a braking system than the braking system is, which is what you're implying it is the case and which is why I ask these logical questions.

Hmmmmmmm.... we all took physics in high school & college. There's no way that friction isn't involved, and there's no way heat isn't the result of turning the potential energy of a vehicle a few thousand feet in the air into a vehicle at sea level in the span of a handful of miles.

Assuming we only used either the transmission or the braking system to dissipate that heat via friction, the amount of heat is exactly the same.

However, you just made me think of another good point which I had _not_ thought about prior, which is that _sharing_ this heat might be a "good thing" for the vehicle.

That is, if we dissipate _half_ the heat via the braking system friction, and the other half of the heat via the transmission system friction, that might be, in the final analysis, the best course in terms of overall wear to the vehicle components.

As I already stated multiple times, no matter what, we're gonna be braking, where the only difference, practically, are the speeds between curves:

That is, instead of going from, oh, say: a. Coasting 25mph between curves to 10mph in a curve & then slowly to 25 With engine braking, we'd go from, oh, say: b. Idling 15mph between curves to about 10mph in a curve & then to 15

In situation (a) the transmission doesn't dissipate the heat of slowing the vehicle down, while in situation (b) the transmission dissipates the heat, but a far slower speed will be attained (assuming no acceleration between curves).

In reality, nobody wants to go the speed that an idling engine will put them while in gear, so people will almost certainly hit the gas pedal between turns, which makes it situation (c) below being most likely: c. acceleration to 25mph between curves & braking to 10mph in each curve

Thinking about these three situations, the question is which is best for the vehicle? a. 25mph between curves to about 10mph in a curve & then slowly back to 25 b. 15mph between curves to about 10mph in a curve & then slowly back to 15 c. acceleration to 25mph between curves & braking to 10mph in each curve

Hmmmmm... that statement indicates there _is_ wear due to the constant incessant daily use of the transmission to do the job of the braking system, does it not?

I really think I didn't explain this road well enough, as nobody is going to be "riding the brakes". They're just not.

Most people, of course, will be in gear the entire time with their automatic transmission, which means that they'll brake at each turn down to walking speeds, and then they'll _accelerate_ to about 25 mph between curves.

Every day, for miles on end, they will alternate between acceleration and braking, acceleration and braking, acceleration and braking, acceleration and braking, acceleration and braking, acceleration and braking, acceleration and braking, acceleration and braking (ad infinitum).

What I do, instead, is alternate between coasting and braking, coasting and braking, coasting and braking, coasting and braking, coasting and braking, coasting and braking, coasting and braking, coasting and braking (ad infinitum).

Those are the only two choices, since if the transmission is in gear, and if you do not accelerate between curves, you'll go at walking speeds which almost nobody is going to do.

So there are really only two choices on this type of 9% curvy grade: a. Either you accelerate constantly and brake harder repeatedly, or, b. You coast gradually and then brake much more softly repeatedly.

Notice that I didn't realize until I thought more about this that I'm braking much _less_ than everyone else, since there's no way they're not accelerating between turns, which means they are almost certainly going into each turn at about twice the speed that I'm entering these turns (give or take a few mph as I hadn't thought about this aspect until now).

THANK YOU for making me think of these additional details! o I love taking apart a system to make informed pragmatic decisions.

As I stated a few times, I was well aware of the blanket law well before this thread, where the technical problem has nothing to do with a blanket legal stipulation.

On this road, I'd be shocked if anyone would ever need to accelerate any more than to just get back up to speed after having braked to walking speeds on each and every hairpin.

While I can't say the chance of needing to accelerate is not zero, it's so close to zero as to be negligible. If you accelerated appreciably, you'd smash into a tree or into the upside cliff, or worse, you'd careen off the down slope cliff.

I'm more worried about an asteroid hitting earth than the need to accelerate on this road. Seriously. I must not have explained how curvy this thing is, where this curve is typical and the distance between them is only about 500 to 750 feet or so on average.

Ignoring the blanket laws, the question is one of techical interest, where I thank you and others for allowing me to think through this technical question in more detail than I had before.

The fundamental question is which of these is best for the vehicle? a. Either you accelerate between curves & brake (harder) at the curves, b. Or, you gradually coast up to speed & then brake (softer) at the curves.

The question is which of those two choices are the best for the vehicle?

Anything in the drive train connected to the transmission output main shaft, and being rotated by it even in neutral, will be a friction drag at *all times*, even under cruise or acceleration.

Given the nature of your road, and the requirement to constantly change speeds, you should be using engine braking *all the time*.

So, use engine braking to maintain a relatively constant speed *between* slow points, short jab on the brakes or press on the accelerator at all other times.

There are a lot of places where I am desirous of maintaining a constant speed on a long downhill run. Engine braking makes it easier to maintain a constant speed with selection of an appropriate gear.

Indeed, there will be moments where you need to slow down more for a sharp corner. There will be straight points between those slow points where your car will naturally want to increase speed on the descent. You should be using engine braking for those straight bits thus requiring only the lightest touch of the brakes at the slow points, if at all. The brakes don't overheat and you don't experience brake fade.

Why is it, do you think, that trucks are required to halt at the top of a steep hill and engage low gear before making the descent. It is all in the interests of maintaining a *safe* speed and preserving the brakes for when they are needed. At the speeds you are travelling, your brakes likely will have insufficient time to cool between bends so you will be getting a lot of heat soak into wheel hubs, bearings, hydraulics and the like. Long term, that may well be detrimental to your brakes. On that point, you only need to experience brake fade once to really appreciate keeping the brakes cool. Brake fade happened to me just once, way back in the first couple of years of driving and in a car and at a point where I didn't think the brakes were even getting hot. I was lucky that time as there was a run-off conveniently located on the bend I was about to negotiate - or should I say *attempted* to negotiate since I had no option but to go straight at the speed I was travelling. I was relying

100% on my brakes and, at the critical moment, they were ineffective - full pedal but zero stopping power. I survived unscathed and learnt a valuable lesson that day. Been an advocate of effective engine braking ever since. Never assume your brakes will always be there.

Engine braking in top gear on my car drops off below 60kph. To maintain engine braking at a lower speed than that requires selection of a lower gear. That gear will depend on the speed required.

Doesn't need to be miles long. Repeated braking will have a similar effect.

Both have their purpose. Overuse your brakes at your peril.

I beg to differ. The golden rule of driving is to come down a hill in the same gear you go up it. In driving, the transmission is designed so you can keep the engine RPM at a level where it produces maximum torque and the transmission will multiply that torque as required. When coasting, ie. on the overrun, the trans acts as a brake. It is a

*feature* of gearing and one that proves very useful downhill as much as going uphill.

No. Transmission fluid degrades over time. Its friction modifying characteristics, which are required by the clutches and bands, are given by the *additives* and these will degrade through excessive heat. It is the *additives* which degrade. The only time large amounts of heat are generated in an auto trans are *under acceleration* and it is generated in the torque converter proportionate to the speed disparity between impeller and turbine. The greater the speed disparity, the greater the heat generation. The heat generated under engine braking is miniscule.

The more you use the brakes, the hotter they will get. At low roads speeds, there will be insufficient cooling. Think about where your brakes are with regard to *airflow*. Not a lot of airflow around the nave of a roadwheel until you get up to speed.

The trans, on the other hand, has a trans oil cooler. In fact, the trans oil cooler is typically located in the torque converter return line. Ever wonder why transmissions generally have large oil pans. You guessed it, located in the airflow under the vehicle for *cooling*.

But which gear will they be in? That is the $64 question here. If they are in D (Drive), and are coasting under no engine load, the car will automatically default to the *highest gear available*. In most that will be overdrive where engine braking effectiveness is at a bare minimum. To get any engine braking you need to get out of overdrive and select Lock 3, lock 2, or if called for, Lock L. BTW, those numbers indicating ratios other than drive are called *lock ratios* since selecting any one of them will *disable* any overrunning clutches so that you can have engine braking. It is a *design feature* so that the operator can select a ratio for the purpose of engine braking and/or hold a gear longer under acceleration. By selecting a ratio *other than drive*, you are locking out any *overrun clutches* in the transmission that will be active when D is selected.

Yes and that is considered *safe driving* if the transmission remains locked to an appropriate ratio using engine braking that gives you a safe descent with minimal use of the brakes. Most people leave their trans in D which *forces* (over)use of, and reliance on, the brakes. My wife is surprised at the number of passengers riding in her car who ask why she shifts to Lock 3 or lock 2 on hill descents around here.

So that is why you select an appropriate Lock ratio, accelerate out, engine brake up to the corner, brake (if required) at the corner, then accelerate out of the corner. It's what *I* do.

Now if they had selected a lock ratio, they could use engine braking initially. BTW, diesel trucks have much more aggressive engine braking but then, they need it.

In fact, I think you will find a car's handling *improves* when you accelerate through/out of a corner. Again, they are designed this way because of tyre slip angles. You will find this difficult if you are in neutral.

Yes, I live in a mountainous region here and have roads similar or much worse. Some are gravel. I *still* push engine braking.

Under engine braking you can brake much more softly at the curves thereby minimising brake use. The vehicle is *designed* to be driven this way. If it were not, there would be no need for the lock ratios under D.

Hi Xeno,

Thank you very much for edifying me on the particulars, which I appreciate.

Thanks for reaffirming what I had thought on the drive train friction, although I readily admit I hadn't thought about it prior to the discussion here.

Even on the manuals, I coast in neutral 'cuz I'd rather replace brakes than the clutch any day of the week. o Woo hoo. Just got my first clutch kit - for replacing my first clutch

As you know, I do all my own work lately, where I admit the clutch has only been replaced about every 80 or 90K miles on the SUV that is a daily drive.

My thought process was that I'd rather replace brake pads than clutches is the same though on both the automatic and the manual transmissions:

Understood. Agreed. Instead of drive on the automatics, use the appropriate lock ratio for the most engine braking, and then short jabs on the brakes at the hairpins.

Much appreciated your advice on finesse and wear and tear.

I should clarify that the 9% downhill road is long, but there are so many turns that I'd estimate over a hundred of them in a few miles, so the distance between hairpins is not much more than a few hundred feet. At no point is there ever a straightaway.

Absolutely. These are 180 degree turns where you have to assume there is a truck coming up the other way which is taking up the entire width of the road. Or bicyclists. Of course, 999 times out of 1,000 there will be nothing on the other side, but you can never assume that so you have to brake at every turn no matter what method you use. There's no other way.

I don't think this happens on this road with the people in drive because they are _accelerating_ in the distances between curves.

Otherwise, they'd be going too slowly. (It's rare to have a car behind me but it happens mostly in the morning and evening at the beginning and end of a work day, where I pull over and let them pass.) Even then, if I can help it, I leave the vehicle in neutral, but it does take a few extra seconds to get the car rolling at speed again. :)

I completely understand this concept where safety is their concern given their brakes overheat (personally, I've seen a truck inside tire explode from the heat after the driver pulled over and got out of the vehicle because it exploded as I passed by it parked on the side of the road so I stopped to see if my vehicle was damanged, which I can explain if you want more information).

There is no way anyone is going to overheat their brakes on this road. I'm sure if they really tried (e.g., riding the brakes the whole way), they might, but as I said, most people are accelerating between turns so they're not riding the brakes. Neither am I. I tap them as needed.

Understood. However, we're braking at no greater than about 25mph speeds to start with, so it's not like a 60-to-0 stop at the bottom of an exit ramp, which, as I've noted, I also shift into neutral if I'm at the bottom for a while (e.g., at a light) and I make sure the pad footprint doesn't stay in one place on the rotor.

This happened to me once, long ago, in an old 1970 Dodge Dart.

The damn brakes just didn't work on a steep short hill at an intersection in the city.

I don't know why. They just had no friction. I was pressing as hard as I could, but there was just no friction. It's as if the power brakes gave up instantly, but, get this ... the engine didn't quit so afterward it was fine and it never happened again on that vehicle.

To this day I don't know what had happened, but luckily, the city traffic just honked their horns angrily as I mowed into the intersection, and mosied on down to the next one.

To this day, I don't know what happened, as the engine was running the whole time so I don't know what happened to the brakes at that moment.

This speed is about 25mph on about a 9% grade.

Understood. I think the speeds are slow enough and the braking intermittent enough that brake fade isn't going to happen under those circumstance.

That's an interesting rule I've never heard, but on the manual 2WD SUV, we generally are in first and second the whole way up. Obviously we're in first on the curves, and second for a short time in between curves.

It's impossible to be in any gear higher than 2nd on the way up.

For a manual though, things are easier, but I like that rule of matching the uphill gears to the downhill gears. I have another grandkid to teach how to drive in about six months, where I hope you don't mind that I steal your advice and use it as if it was my own! :)

("Grandpa, do you know everything" she used to ask me when she was younger, to which I said "Why yes. I do, and if keep an open mind, you will too!".

:)

In summary, I very much will keep an open mind, and try to learn from my fellow Grandpa Xeno's advice!

Hi Xeno,

Much appreciated the technical response, as that's what this is about.

Thanks for this reminder that heat via friction isn't gonna be generated except under acceleration, which, as we've said, is just not gonna happen.

Yes indeed. However, you're gonna use the brakes no matter what.

At every curve. There's just no way around it since you must go at walking speeds at the curves, which is too slow otherwise for most people.

For me, I tap the brakes periodically to regulate speed on the longer stretches between curves if the vehicle approaches 25 mph (or so).

Rarely do we meet another on this road, but usually during the morning and afternoon, those going to and from work are going at the same time, where I've noticed my coasting-and-brake method has me going slower than those who use the accelerate-and-brake method.

So they're definitely braking harder than I am braking, which means they're generating more heat in the brakes than I am - but - they get down faster too.

Yup. In the bimmer it's the bottom chunk of the "radiator", as I recall (it has its own separate lines but it's integral otherwise).

That's interesting about the "lock ratio", which, also, I hadn't considered (although I certainly know about it as my bimmer even has a semi-manual automatic transmission that nobody ever uses and I don't blame them).

Likewise, while I would agree that not leaving the auto in "Drive" is what people might want to consider, trust me when I say nobody does that, for sure (or, maybe 1 out of 1,000).

Still, I get your point, which is to select the appropriate lock ratio, which I appreciate as "finesse" is what this is also about, in addition to wear and tear.

Exactly. As I said above, 1 out of 1,000 is gonna be using finesse, where I much appreciate your advice, as finesse (and wear) is what this is about.

Thank you Xeno for bringing this up, as even I don't do this, as I generally consider the "manual" function of the bimmer to be unused.

I understand and don't disagree with your point that these 'lower gears' should be used instead of "Drive" for "finesse" with style. :)

Makes sense. Much appreciated the advice on using the lock ratio.

I ride a K1200. I have taken the classes. I know all about accelerating out of the turn. While it's the same on a car, all that doesn't apply as much to such low speed 180 degree turns where you can't select the apex because you can't see a damn thing around the curve, as much as you look ahead and try.

While I agree on the accelerating out of a turn, you have to look at what a

180 degree means in terms of speed. You're basically almost stopped since you can never trust that a vehicle isn't coming the other way. 999 out of 1,000 times there will not be another vehicle, but you can't risk it, so you have to stay on your side of the road.

This road is so narrow it doesn't even meet California regulations for a divided line, so there's no line in the middle either.

This is good to know as the whole point was finesse and wear. Thanks for your advice!

Yes. If the appropriate lock ratio is chosen. Understood. Appreciated. Agreed.

In summary, I appreciate your advice, where I had not thought of many of the things you brought up, which I very much appreciate the chance to discuss and learn from you.

Usenet is difficult to carry on a conversation, particularly because everything has to be described, so I appreciate even more your patience and candor.

Thanks!

Proves that you don't need to be doing high speeds. It's all about the heat absorption rate versus the heat dissipation rate.

If the booster had failed, for any reason, you would still have brakes but very high pedal pressures. With brake fade, you have *no brakes* regardless of the pedal pressure. That's because the pads are gassing and the gas builds up in a layer between the pads and the disc. Hence, zero friction. When the pads cool down below gassing point, the gas dissipates and brake function returns to normal. Now you know that it takes very little braking at city speeds to cause brake fade. The same applies to your longish downhill run. It simply amounts to more heat building up in a given time than can be dissipated. Whilst on that topic, the thinner the disc (through wear or machining) the less it is able to hold heat and the sooner it will reach the point of brake fade.

Intermittent braking can also overheat brakes because the intervening periods of time are to short to allow adequate cooling as are the minimal air flows available to the disc.

So, given that level of steepness, the *rule* informs the gear you should engage on the way down.

Hi Xeno, Much appreciated all your kind help & advice! o I'll pass it on to one of my granddaughters who will be driving soon!

On that topic of the amount of metal, I'm one of the (apparently rare) shade-tree mechanics who owns calipers and dial gauges such that I check rotor thickness, runout, and brake drum diameter. :)

I do realize a lot of people on Usenet "talk" that they check rotors and drums, but IMHO, without pictures, it didn't happen (most don't seem to even own the proper tools with which to check them, particularly those who spout that their brake rotors 'warped').

I replace a rotor or drum when it's due, but not before it's due.

As I said, I _love_ your "golden rule" of being in the same gear in both directions, which I will steal (with your permission) to use with my upcoming driving lessons for one of my grandkids.

I thank you for your advice, where today I ran a tracking program:

On the way downhill, the average speed was 21.81 mph which is a bit lower than the 25mph I would have guessed, and the maximum speed, surprisingly, was a bit higher than I would have guessed, where it was 35.48 mph.

Thanks for all your helpful advice over the years, where I'm a sponge for facts, and hence, I love when others deal with logic, sense, and facts!

I hope that isn't the caliper you use to measure drums. The jaws are not long enough to reach the friction areas inside the drum for a good measurement of wear. Same thing with a set of rotors, you need to check thickness in at least three areas on the friction surface and to do that you need longer jaws on the calipers to reach to the depth of the hat.