Hard or soft braking

On Sat, 14 Mar 2020 07:18:42 -0000 (UTC), Arlen Holder wrote:

> It's shocking, actually, how long the rear brake shoes lasted on that SUV,
> where I replaced the clutch twice in the time that I did the shoes just
> once, and that rear drum had plenty of meat left for another 180K miles.

BTW, is this about right for what you might think under "normal use" where
I know there's no such thing as a defined normal use... but anyway...

a. The clutch lasted less than 100K miles (say, oh, about 80 or 90K).
b. The rear shoes lasted less than 200K miles (say, about 180K or so).
c. The front pads lasted less than 50K miles (say, oh, about 30 or 40K).
d. The front rotors went about double the pads (about 75K miles or so).
e. The rear drums are gonna last about double the shoes (about 350K).

While every "normal" is different, how do those estimates sound if someone
were to ask you "how long" do these things last under normal use?
--
It matters for what you plan your maintenance and parts stocking for.

Arlen Holder wrote:
> On Sat, 14 Mar 2020 07:18:42 -0000 (UTC), Arlen Holder wrote:
>
>> It's shocking, actually, how long the rear brake shoes lasted on that SUV,
>> where I replaced the clutch twice in the time that I did the shoes just
>> once, and that rear drum had plenty of meat left for another 180K miles.
>
> BTW, is this about right for what you might think under "normal use" where
> I know there's no such thing as a defined normal use... but anyway...
>
> a. The clutch lasted less than 100K miles (say, oh, about 80 or 90K).
> b. The rear shoes lasted less than 200K miles (say, about 180K or so).
> c. The front pads lasted less than 50K miles (say, oh, about 30 or 40K).
> d. The front rotors went about double the pads (about 75K miles or so).
> e. The rear drums are gonna last about double the shoes (about 350K).
>
> While every "normal" is different, how do those estimates sound if someone
> were to ask you "how long" do these things last under normal use?

That depends entirely on how the person operates the vehicle and what
the vehicle is.
In city stop and go, you are going to use up the brakes and clutch
faster than highway driving, usually by a large margin. However if you
drive like one of my relatives you will wipe out the brakes far faster.
She likes to drive fast, then climb on the brakes rather than down shift
or use any engine braking at all. She goes through at least one full set
of pads and rotors in about 30K or so. Calipers at every second swap.

Then there are cars like my wife has, it's AWD and has a VERY balanced
braking system. It had all new brakes put on by the dealer when we
bought it at 60K and it has 140K on it and the pads and rotors still
look new. I'm going to change out the pads because the caliper pins
stuck on one front and the inner pads in the rear hung up and let the
rotor rust. All related to installer error.

With the description you have given of your driving style and road
conditions you have I would say you did pretty good.
However it wouldn't be hard to double the clutch life and front brakes
on flatter terrain.


--
Steve W.

On Sat, 14 Mar 2020 16:31:56 -0400, Steve W. wrote:

> That depends entirely on how the person operates the vehicle and what
> the vehicle is.

Understood.
It's a 2WD suv driven by a relative as a daily drive on these roads:
<https://i.postimg.cc/wxf5CyS6/mount42.jpg>

Rough estimates for that 2wd SUV are (in increasing miles):
o Tires <30K miles
o Front pads <50K miles
o Front rotors <75K miles
o Clutch <90K miles
o Rear shoes <200K miles
o Rear drums <350K miles

> However it wouldn't be hard to double the clutch life and front brakes
> on flatter terrain.

Yes. The problem for the clutch is the terrain, and, this particular driver
doesn't comprehend the concept of being gentle on the clutch either.

Even so, the hills eat the tires:
<https://i.postimg.cc/G3HWPtQg/mount39.jpg>

Xeno explained why in the past as 'camber scrub':
<https://i.postimg.cc/8zVxVHVx/mount40.jpg>

Which is an amazingly complicated set of affairs:
<https://i.postimg.cc/YqHVb5gY/mount33.jpg>

Resulting in wear of the front inside edge that you can't believe:
<https://i.postimg.cc/g004XCLW/mount37.jpg>

Which is palpable after even as little as a few hundred miles:
<https://i.postimg.cc/pT71cQZG/mount41.jpg>
--
Usenet helps all of us improve our technical skills by sharing with others.

On Sat, 14 Mar 2020 19:57:50 +1100, Xeno wrote:

> The second is to replace the drum rather than machining it. In fact, a
> lot of manufacturers don't recommend drum machining these days.

Hi Xeno,
I love that you brought up points of additional points of finesse, which
is, after all, what learning on rec.autos.tech is all about!

One thing I have observed, which I'm sure you'll understand, is that living
in the Silicon Valley, where shop rates are commonly around $200 an hour,
_any_ machining of basic parts isn't going to ever be cost effective.

As an example, when I replaced the flywheel of the SUV, the cost for
machining it was almost the price of a brand new flywheel at the auto parts
stores (but far less than a brand new dealer-supplied flywheel).

Even though the flywheel could have been machined, it wasn't worth it given
the cost of labor here in the Silicon Valley.

I suspect machining shoes and drums would have the same economics, unless
we bought the tools to do ourselves.

I think throwing away parts instead of machining them is kind of sad
because we throw out a lot of useful parts simply because they're cheaper
to replace than to machine.

On 15/3/20 10:14 pm, Arlen Holder wrote:
> On Sat, 14 Mar 2020 19:57:50 +1100, Xeno wrote:
>
>> The second is to replace the drum rather than machining it. In fact, a
>> lot of manufacturers don't recommend drum machining these days.
>
> Hi Xeno,
> I love that you brought up points of additional points of finesse, which
> is, after all, what learning on rec.autos.tech is all about!
>
> One thing I have observed, which I'm sure you'll understand, is that living
> in the Silicon Valley, where shop rates are commonly around $200 an hour,
> _any_ machining of basic parts isn't going to ever be cost effective.

Given that, on many cars, the disc is considered a wearing component
just as much as the pads, machining is likely not intended. For sure,
there are some marques where you cannot machine the discs at all. But
then, replacement discs are inexpensive.
>
> As an example, when I replaced the flywheel of the SUV, the cost for
> machining it was almost the price of a brand new flywheel at the auto parts
> stores (but far less than a brand new dealer-supplied flywheel).

If the flywheel has hard spots, machining is not always successful. The
cutting tool rides over the hard spots leaving high points. In these
cases, surface grinding is the better/only option.
>
> Even though the flywheel could have been machined, it wasn't worth it given
> the cost of labor here in the Silicon Valley.

Yes, costs always figure into the equation.
>
> I suspect machining shoes and drums would have the same economics, unless
> we bought the tools to do ourselves.

If you have, or have access to, a lathe, you can do most machining
yourself. It won't be as *efficient* as a dedicated brake machining tool
but it will get the job done. I used to use these;

https://www.youtube.com/watch?v=ICRRIUhwOJE

Very quick and efficient. Even at $200 per hour, I could make machining
operations cost effective with this machine. If you had ever used one,
you would know why.
>
> I think throwing away parts instead of machining them is kind of sad
> because we throw out a lot of useful parts simply because they're cheaper
> to replace than to machine.
>
That is the way of the world.

--

Xeno


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

The only issue with 'stab' breaking is it makes any passengers
do the 'funky chicken' as you're breaking.

An old friend of mine told me to stab slightly, rather than ride the
brakes, not just to minimize wear, but also to cause a slight nose
dive over traffic sensors near intersections, so as to speed up
the red-to-green cycle.