Hard or soft braking

On 10/3/20 10:11 am, Arlen Holder wrote:
> On Mon, 09 Mar 2020 15:15:14 -0400, Steve W. wrote:
>
>>> There is no value in selecting neutral when stopped at traffic lights.
>>>
>>
>> It's illegal in many US states for the same reason.
>
> There is value in _not_ imprinting the pad footprint on a hot rotor.
> o How you go about _not_ depositing the footprint is what we can debate.
>
Predictive driving works for me.

--

Xeno


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

On Tue, 10 Mar 2020 11:13:53 +1100, Xeno wrote:

> The trans is better able to dissipate heat than the brakes under low
> speed decel.
>
> Also, on your road, I wouldn't be on the brakes much at all. I would
> just manually select an appropriate lower gear. I like to preserve the
> brakes as much as possible and the trans is designed with ablative
> technologies in mind.

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?
<https://groups.google.com/d/msg/rec.autos.tech/x7pwhNCqlCo/o-zmIvu-CwAJ>

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
<https://groups.google.com/d/msg/rec.autos.tech/ameCXs0Smdw/QPyAN4DwAgAJ>

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
<https://groups.google.com/d/msg/rec.autos.tech/F-ptM5J_huQ/78GEP86pCAAJ>

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.

On 10/3/20 12:08 pm, Arlen Holder wrote:
> On Tue, 10 Mar 2020 11:13:53 +1100, Xeno wrote:
>
>> The trans is better able to dissipate heat than the brakes under low
>> speed decel.
>>
>> Also, on your road, I wouldn't be on the brakes much at all. I would
>> just manually select an appropriate lower gear. I like to preserve the
>> brakes as much as possible and the trans is designed with ablative
>> technologies in mind.
>
> 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?
> <https://groups.google.com/d/msg/rec.autos.tech/x7pwhNCqlCo/o-zmIvu-CwAJ>

Experimentation. But why would you want to?
>
> 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
> <https://groups.google.com/d/msg/rec.autos.tech/ameCXs0Smdw/QPyAN4DwAgAJ>
>
> 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
> <https://groups.google.com/d/msg/rec.autos.tech/F-ptM5J_huQ/78GEP86pCAAJ>

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

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


--

Xeno


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

Arlen Holder > wrote in
:

> On Mon, 9 Mar 2020 17:38:35 +1100, Xeno wrote:
>
>> Transmissions will do that without complaint. What is at issue is
>> whether it is a good idea to be in neutral whilst on the highway. My
>> viewpoint is that it is not - whether the trans is a manual or an
>> automatic. The issue here is *safety*, not trans damage.
>
> Hi Xeno,
> I very much appreciate your technical acumen.
>
> I would like to ask that we ignore the "danger" factor to humans, as
> that isn't my technical question in the least.
>
> You've made your point on the "danger factor" so that _others_ will be
> scared enough to have second thoughts - but the "danger factor" isn't
> even on my list of the least of my worries (I've explained why in the
> other post).
>
> My key _technical_ question I would love to know the answer of is
> this: Q: *Does constant daily prolonged engine braking cause
> transmission wear*?

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

On 03/09/2020 06:45 PM, Xeno wrote:
> On 10/3/20 12:08 pm, Arlen Holder wrote:

>> 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.
>
> 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.

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.

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

Indeed.


--
Cheers, Bev
Teamwork: A bunch of people running around doing what I tell them.

On Tue, 10 Mar 2020 12:45:43 +1100, Xeno wrote:

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

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:
<https://i.postimg.cc/g004XCLW/mount37.jpg>

Which is visible on multiple vehicles even after only a few hundred miles:
<https://i.postimg.cc/pT71cQZG/mount41.jpg>

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'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.
>
> 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.

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.
--
Adults are supposed to be able to form their belief systems based on facts!

On Tue, 10 Mar 2020 15:47:55 +0000 (UTC), Kevin Bottorff wrote:

> 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

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.
--
Those who trust their intuition more than they trust the facts, scare me.

On Tue, 10 Mar 2020 15:57:16 -0000 (UTC), Arlen Holder wrote:

> 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 belatedly saw your post on transmission wear being mostly upon
acceleration, and almost negligable on engine braking.

Given that datapoint, it seems to me to be a coin toss, since the wear on
brakes is also insignificant (bearing in mind that pads/shoes are trivial
to replace).

Given the apparent fact that the wear is insignificant in _both_ cases, it
would seem to me to fall to _other_ factors.

Given you can't accelerate without running off a cliff, the "safety" factor
is not in the least a concern of mine, while I hold that _others_ may do
things just because "it's the law", I teach my kids and grandkids that
there are a lot of stupid laws (e.g., sodomy laws, as one obvious example)
such that if the _only_ reason for following a law is because "it's the
law", then it's a de-facto stupid law (like many of the four-way STOP signs
used in California as "speed-limit" signs).

In summary, it seems to be a tossup between turning the potential energy
into braking friction heat or transmission friction heat.

Me?

If it's truly a tossup...
o I'd prefer to replace brakes than transmissions any day of the week.
--
People desperately want to _feel_ safe, even when they're not ever safe.

On Tue, 10 Mar 2020 11:33:44 +1100, Xeno wrote:

> As far as gear wear is concerned, in the overrun you are using the coast
> (back) side of the gear teeth so the relatively *unworn* part. As well,
> one single full throttle acceleration would apply the wear of a thousand
> engine braking instances. Under acceleration, you are applying the *full
> power* of the engine. Under engine braking you are only applying
> friction and engine pumping losses. If you are concerned about
> transmission wear, it's not engine braking you should be concerned about
> as most wear occurs under acceleration.

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.

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.

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.
--
My belief systems are based on facts which is why I ask facts of you.