Hard or soft braking

Arlen Holder > wrote in
:

> On Tue, 10 Mar 2020 16:26:47 -0000 (UTC), Arlen Holder wrote:
>
>> o Wear due to friction in the transmission, versus
>> o Wear due to friction in the engine
>
> 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.

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.
>
> 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...

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

>
> 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.

to reiterate it is not a trany vers the brake wear the only thing at
issue here. KB
>
> I _love_ facts; so if folks have more facts, please let us all know.

On 11/3/20 9:47 am, Kevin Bottorff wrote:
> Arlen Holder > wrote in
> :
>
>> On Tue, 10 Mar 2020 16:26:47 -0000 (UTC), Arlen Holder wrote:
>>
>>> o Wear due to friction in the transmission, versus
>>> o Wear due to friction in the engine
>>
>> 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.
>
> 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.

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.
>>
>> 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...
>
> again accel is not the only reason to have the vehicle always in gear.
>
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.
>>
>> 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.
>
> to reiterate it is not a trany vers the brake wear the only thing at
> issue here. KB

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


--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On Tue, 10 Mar 2020 22:47:14 +0000 (UTC), Kevin Bottorff wrote:

> so you are ignoring the friction of the entire drive train not just the
> trany friction.

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?

> also consistant drag of the drive train/transmission can
> make keeping control more consistant than in neutral.

Hmmmm... take a look at just _one_ of these curves on this road:
<https://i.postimg.cc/kGhZh80q/mount44.jpg>

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).

> 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.

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.
--
Usenet is so much more valuable, and pleasant, when people share ideas.

On Wed, 11 Mar 2020 11:08:33 +1100, Xeno wrote:

> The transmission has been designed with ablative technology in mind.

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 <https://www.merriam-webster.com/dictionary/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 <https://www.merriam-webster.com/dictionary/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?

> 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.

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.

> 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.

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

> 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.

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?

> 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.

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.

> 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.

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.
<https://i.postimg.cc/kGhZh80q/mount44.jpg>

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?
--
Together we can understand far more than any one of us can being all alone.

On 11/3/20 5:36 pm, Arlen Holder wrote:
> On Tue, 10 Mar 2020 22:47:14 +0000 (UTC), Kevin Bottorff wrote:
>
>> so you are ignoring the friction of the entire drive train not just the
>> trany friction.
>
> 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.,).

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.
>
> 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?
>
>> also consistant drag of the drive train/transmission can
>> make keeping control more consistant than in neutral.
>
> Hmmmm... take a look at just _one_ of these curves on this road:
> <https://i.postimg.cc/kGhZh80q/mount44.jpg>
>
> 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).

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

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.
>
> 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.

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.
>
> 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).

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.
>
> 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).

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

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

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

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 11/3/20 6:13 pm, Arlen Holder wrote:
> On Wed, 11 Mar 2020 11:08:33 +1100, Xeno wrote:
>
>> The transmission has been designed with ablative technology in mind.
>
> 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 <https://www.merriam-webster.com/dictionary/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 <https://www.merriam-webster.com/dictionary/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?
>
>> 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.
>
> 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.
>
>> 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.
>
> 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
>
>> 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.
>
> 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?

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

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*.
>
> 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.

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.
>
> 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).

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.
>
> 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 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.
>
> 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).

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

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.
>
> 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.
> <https://i.postimg.cc/kGhZh80q/mount44.jpg>

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

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On Wed, 11 Mar 2020 18:48:24 +1100, Xeno wrote:

> 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.

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.

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

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
<https://groups.google.com/d/msg/alt.home.repair/YvubIh8oBwY/-utBXsHDAAAJ>

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.
<http://www.bild.me/bild.php?file=5199382clutch03.jpg>

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:
<http://www.bild.me/bild.php?file=2998436clutch02.jpg>

> 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.

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.

> 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.

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.

> Indeed, there will be moments where you need to slow down more for a
> sharp corner.

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.

> 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.

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.

> 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.

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).

> It is all in
> the interests of maintaining a *safe* speed and preserving the brakes
> for when they are needed.

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.

> 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.

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.

> 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.

> I was relying
> 100% on my brakes and, at the critical moment, they were ineffective -
> full pedal but zero stopping power.

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.

> 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.

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

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

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

> I beg to differ. The golden rule of driving is to come down a hill in
> the same gear you go up it.

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!
--
Usenet allows purposefully helpful adults to exchange useful information.

On Wed, 11 Mar 2020 19:54:24 +1100, Xeno wrote:

> 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.

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.

> The more you use the brakes, the hotter they will get.

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.

> The trans, on the other hand, has a trans oil cooler.

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).

> But which gear will they be in? That is the $64 question here.

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.

> Most people leave their
> trans in D which *forces* (over)use of, and reliance on, the brakes.

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.

> 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.

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.

> Now if they had selected a lock ratio, they could use engine braking
> initially.

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

> In fact, I think you will find a car's handling *improves* when you
> accelerate through/out of a corner.

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.

> Again, they are designed this way
> because of tyre slip angles. You will find this difficult if you are in
> neutral.

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.

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

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

> Under engine braking you can brake much more softly at the curves
> thereby minimising brake use.

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!
--
Together we can understand far more than any one of us can being all alone.

On 12/3/20 1:25 am, Arlen Holder wrote:
> On Wed, 11 Mar 2020 18:48:24 +1100, Xeno wrote:
>
>> 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.
>
> 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.
>
>> Given the nature of your road, and the requirement to constantly change
>> speeds, you should be using engine braking *all the time*.
>
> 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
> <https://groups.google.com/d/msg/alt.home.repair/YvubIh8oBwY/-utBXsHDAAAJ>
>
> 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.
> <http://www.bild.me/bild.php?file=5199382clutch03.jpg>
>
> 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:
> <http://www.bild.me/bild.php?file=2998436clutch02.jpg>
>
>> 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.
>
> 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.
>
>> 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.
>
> 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.
>
>> Indeed, there will be moments where you need to slow down more for a
>> sharp corner.
>
> 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.
>
>> 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.
>
> 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.
>
>> 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.
>
> 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).
>
>> It is all in
>> the interests of maintaining a *safe* speed and preserving the brakes
>> for when they are needed.
>
> 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.
>
>> 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.
>
> 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.
>
>> 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.
>
>> I was relying
>> 100% on my brakes and, at the critical moment, they were ineffective -
>> full pedal but zero stopping power.
>
> 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.

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

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.
>
>> 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.
>
> This speed is about 25mph on about a 9% grade.
>
>> Doesn't need to be miles long.
>> Repeated braking will have a similar effect.
>
> Understood. I think the speeds are slow enough and the braking intermittent
> enough that brake fade isn't going to happen under those circumstance.

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.
>
>> I beg to differ. The golden rule of driving is to come down a hill in
>> the same gear you go up it.
>
> 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.

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


--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On Thu, 12 Mar 2020 12:17:16 +1100, Xeno wrote:

> 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.

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.
<http://www.bild.me/bild.php?file=9428041drum_brakes_3.jpg>

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.
<http://www.bild.me/bild.php?file=9335528drum_brakes_2.jpg>

>> It's impossible to be in any gear higher than 2nd on the way up.
>
> So, given that level of steepness, the *rule* informs the gear you
> should engage on the way down.

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:
<https://i.postimg.cc/qMj0ZFMh/pskill00.jpg>

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!
--
Usenet is so much more valuable, and pleasant, when people share ideas.