On Sun, 04 Mar 2012 14:02:21 -0600, Ignoramus28705
wrote:

On 2012-03-04, Pete C. wrote:

Ignoramus20398 wrote:

On 2012-03-04, Pete C. wrote:

The problem is not the brake fade, the problem is if you do not do your
downshift before you go over the crest of the hill, you have very poor
odds of being able to successfully complete the downshift on the
downgrade. What happens is you get it out of gear and then you are
unable to get it into the lower gear and often you can't get it back
into the previous gear as well. This leaves you on a downgrade in
neutral with *no* engine braking at all and your service brakes won't do
the job. It's runaway truck ramp time if you are lucky enough to find
one.

OK, I will bite, why would the service brakes not do the job and stop
the truck, at least once?

i

They might... if you have not picked up too much speed before you
realize you are in deep doo-doo and you apply them solidly in one
emergency stop.

OK, I think that I get the picture.

I now know one honest mobile truck mechanic (!), he will look and
adjust all my brakes, making whatever repairs may be necessary.

And he should be able to teach you the right way to treat them,
because he's the one that sees what people do wrong. If you ride the
brakes and pre-heat them, you might not even get the one full stop out
of them on a steep hill.

It's all in heat buildup and transfer - You can get that one good stop
out of the brakes because they were cold - but when you are done, the
drums and shoes (or front discs and pads if you've got them) are
pushing 500F to 700F - dull red hot to Bright red hot.

Look at today's NASCAR racing on TV, Darlington chews up brakes.
Beautiful In-Car-Camera shots of glowing red rotors through the wheel
spoke holes. And they already had a pileup from a driver losing the
front brakes,the rears locked up, and he pirouetted and backed it into
the wall HARD.

Once you release the brake pedal the drums start cooling slowly, but
the shoes are now sealed up inside the drum and backing plate, and
they release heat really even slower - and worse, starts radiating the
heat into the hubs and wheel bearings and wheels. The tires catch on
fire if the wheels get too hot, and the grease in the bearings too.

And above maybe 800F the friction materials of the shoes starts
glazing over and losing it's stopping abilities.

Get them REALLY hot (I'll guess over 1000 - 1200F) and the glue
bonding the lining to the shoe can fail and then you're truly screwed.
But this is mostly cars that have bonded linings, trucks usually use
riveted shoes.

If you can do it, ask the mechanic about converting the dump truck
and/or the Semi Tractor over to Air or Air/Hydraulic Disc Brakes -
they make them for all positions, but even the front axles would be a
great help. It's a good sized chunk of change for the pieces, but it
could easily save your life if you start running around in the
mountains a lot.

-- Bruce --