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Mad Roger Mad Roger is offline
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Default Need help INTERPRETING these test results police cruiser SAE J866a Chase Test

On Mon, 15 Jan 2018 15:02:37 -0500,
Clare Snyder wrote:

The tests were limited - addressing the use a cruiser puts the brakes
to. If you know how to read the information, it tells you a LOT about
the brakes - but you are correct - there is no "best" brake material -
it depends onthe use they are being put to, and what YOU want from
them. There may well , however, be " WORST" brakes.

Exactly. You've been right all along while I was hoping beyond hope that
there is an intelligent way to select a good/better/best brake pad.

You were right. I was wrong.

If you have two pads in your hands, or two on the net, you can't make an
intelligent choice between them, other than to know if they're the same or
not, and to know who made them, and to know what their cold and hot
friction coefficients are.

That's it.

Each pad can be different - but you have no way of knowing that from the
pad itself.

If brakes require higher pedal pressure to stop in a longer distance
(and decellerate at a lower rate) both when cold and at normal
temperature, and fade significantly on the second and third
application - they are pretty crappy brakes.

Nobody complained about fade in that one report we have, did they?
I don't think we have any better "fade" test than the Chase value for hot
friction (which was E or F depending on the pads tested).

So, while fade is important - it's a useless criteria since we have no way
of knowing the fade.

It's just silly to bring up all the things that *can* happen if you have no
way of choosing between them when the pads are in your very hands.

I don't disagree with you that two pads can be vastly different, but you
have no way of knowing anything other than their tested friction, their
manufacturer, and whether two pads are exactly the same material.

That's all you've got since brands are almost meaningless (e.g., PBR, Axxis
and Metalmasters are the same company) and semi-metallic/metalic/ceramic
marketing is even more meaningless.

If they require low pedal pressure to decellerate quickly to a stop in
a short distance when both cold and at normaltemperatures, AND do not
fade appreciably on the second and third (panic) stop - they are
pretty darn good brakes - anlness they squeal like a stuck pig, only
last for a month of driving, and/or destroy brake rotors - and/or coat
the wheels with nasty corrosive brake dust - - -

All well and good, but it's like predicting that a baby will become the
president of the United States.

No, not at all - you are TOTALLY missing the point.
The different brake PAD materials are mission specific.
A ceramic pad will outstop a economy organic pad when hot - hands
down. Every time.

Let's just agree to disagree since you don't seem to realize what I know
from talking to the Axxis marketing guy that the word 'ceramic' is a
bull**** marketing term.

Do you think I don't call these marketing guys up?
Do I seem like someone who doesn't ask pointed questions?

Ceramic is complete and total marketing bull****.
The marketing guy told me himself.

(Yes, I see the difficulty of position that puts me in.)

A metallic pad will usually stop better after several panic stops, or
when towing a heavy trailer down a longhill - than either the organic
or the ceramic. Both the semi metallic and the organic will stop
better on a cold stop than a ceramic.

Let's agree to disagree.
You believe in marketing.
I don't.

I believe in specifications.
No. a $85 Thermoquiet Ceramic will stop better than a $20 no-name
organic pad - and you can be pretty well assured you will not get a
$20 ceramic pad unless Rock Auto has something on clearout.

Let's agree to disagree.

You think price has some impact on performance.
I will prove to you that I can show exact same products with different
branding but the exact same price.

Everyone loves a number-line decision, whether it's good/better/best of
metallic/semi-metallic/ceramic or $10/$20/$30 or 3-year/4-year-/5-year
warranty, but none of that indicates a better or worse object.

Only specifications do, and we just don't know much about the spec other
than who made the pad, the code for the exact formulation, and the

Everything else is bull****.

Price is not a sure predictor of quality - but can be a pretty darn
good indicator.

Price is an indicator of demand only. Demand is influenced by a ****load of
factors. You know that. I know that. Let's not argue it. That's what
Economics 101 was for, and I already took that and passed it.

Also, a high iron semi metallic WILL wear out your rotors faster than
either the organic or the ceramic unless the organic causes the rotor
to blister because of uneven pad material transfer, and abuse.

If you truly know the "hardness", then of course it matters.
But you have no way of knowing the hardness.
Do you?

What you TOTALLY do NOT understand is how disc brakes, in particular,
work - and how the co-efficient of friction changes.

I think I do understand how disc brakes work, but we can discuss what you
think I don't understand.

What I know is that your energy of movement has to be converted into
something else, most notably heat. Lots and lots of heat.

When you "bed in" pads, you are burnishiung a thin coating of pad
material into the finish of the rotor..

Yup. Pad deposition. Something about covalent bonds making and breaking
under the heat of braking, where the breaking of the bonds elicits heat.

It gets complex HOW the heat is generated (it's not just 'friction'), but
the end result is heat. Lots and lots of heat.

The stopping power of the
brake depends on the co-efficient of friction between this burnished
in friction material and the pad - not between the pad and bare metal.

The Ameca engineer already explained the burnished pads that the Michegan
study used where he said it was to get rid of the volatile gases that come
out of the first few heat cycles.

How this coating is applied, and maintained, dictated the braking
charachteristics of a disc brake as much as anything.

Yup. We all know how to property bed our brakes.
I doubt many shops do it though, because it requires a lot of room and a
few very hard almost stops where, if there is traffic, it ain't easy to do.

I'll wager that few, if any, shops properly bed the pads.
But you'd have that experience because I've never been to a mechanic.

If you stop hard
and fast and keep your foot onthe pedal at a stop untill the brake
cooles,there will be a heavier deposit on the rotor at that point -
UNLESS the padmaterial deposited on the rotor does not adhere properly
and it pulls away with the pad. Either way you will end up with uneven
braking - either a "thump" or a "skip" on the next brake application.

NEVER, and I mean NEVER leave your foot on the pedal after a hard stop!
Everyone knows this, so I know you know this.
It's the worst thing you can do, unless you love to have judder every few
thousand miles as that ped deposition collects more pad over time.

I never understood why, but once a pad print, always a pad print.
And it only gets worse.

Unless you re-bed the brakes - which everyone knows - so you're preaching
to the choir on even brake pad deposition techniques.

A "quality": pad will transfer evenly and bond reliably to the rotor
during the perscribed "bed-in" and will not cause uneven transfer
under "normal" driving conditions. It will also not cause or promote
corrosion between that pad mnaterial and the rotor steel (which causes
"scabbies" and pitted rotors (often mistaken for the less common, but
sometimes "real" "warped rotor".

Yes. But. I have no good way of knowing a quality pad from a not quality
pad. So it's moot.

It's like me picking out the best students in a class based on whether they
wear glasses or not.

Total bull****. The friction rating doesn't tell you much, but the
difference in required pedal pressure, and the difference in stopping
distance - notto mention the difference in pad temperature between the
best and worst in the test is VERY significant.

It's significant in one thing. Pedal pressure.
If pedal pressure is your gig - then it's significant.
If pedal pressure isn't your gig, then it's not significant.

The pedal pressure changed about 100%, from roughly less than ten foot
pounds to less than twenty foot pounds in the lower-speed tests for

What's 10 foot pounds?
Dunno when it's pressing on a pedal, but if that's important, then you have
to buy a police cruiser and put those pads on it - because it doesn't tell
you anything about your car unless it's a police cruiser.

What is NOT significant is the predictabiklity of the results based
on the frictionrating of the pads under test. (almost totally useless)

Yup. We agree. There is no useful data other than the AMECA code and even
that isn't meant for the consumer.

And do your friend a favour and send them to a REAL mechanic to have
their brake work done. I fear you are DANGEROUS.

Knowledge is dangerous.
Logic is dangerous.
Thinking is dangerous.

Having someone else do all that for you, is dangerous.
The mechanic doesn't give a **** about you or your brake pads.

All the mechanic cares about is your money, and getting as much of that as
possible, in the least time possible, so he'll skip steps like you can't

I'm on car forums where there are complaints galore about mechanics
skipping half the steps in anything because they don't give a **** about
anything but money.

The only way to do it right is to do it yourself, is my motto.

You can disagree (and you almost certainly will), but you can't disagree
that I'm trying to make an intelligent decision on which brake shoes to
buy, and that I probably know them as well as any mechanic who *thinks* he
knows them - but he doesn't - because he can't.

Nobody can but the guy who submitted them for their Chase test.