View Single Post
  #9   Report Post  
Posted to,,
Clare Snyder Clare Snyder is offline
external usenet poster
Posts: 4,564
Default Need help INTERPRETING these test results police cruiser SAE J866a Chase Test

On Thu, 11 Jan 2018 14:46:34 -0000 (UTC), Mad Roger

On Wed, 10 Jan 2018 23:07:18 -0500,
Clare Snyder wrote:

The engineer's enigma.

This is a difficult question to answer, where *Xeno the troll* clearly
isn't capable of answering it, but neither am I, which is why I asked for
scientific help.

We're talking about EE and FF pads as determined by the SAE J866 Chase Test

And, we're talking about EE/FF pads being tested in the *same vehicle*,
where one must note the friction coefficient of E is marginally above that
of steel on steel (i.e., no pad at all).

Hence it is an enigma if the EE lower-friction coefficient friction
materials can outperform FF higher-friction coefficient materials in
real-world tests.

However, it is true that the link above says, very clearly:
"Due to other factors that include brake system design and
operating environment, the friction codes obtained from this
document cannot reliably be used to predict brake system performance."

So the only scientific question here is why would EE outperperform FF?

And that's with "genuine" parts (we will "ass u me")

Now google "counterfeit brake parts" - or just "counterfeit auto
parts" - and you will see how big a problem parts counterfeiting is
world wide, and why those ratings stamped onthe brakers do not

While counterfeit parts "could" be the problem, do you really think that a
state-run test posted and published nationally, would fall prey to them?

I'm discounting conterfeit parts as being the problemin these tests -
just going back to your "trust" in "government mandated markings" from
your previous thread.

I think that fails Occam's Razor for logic (unless you have proof).

That's why I say buying known brand parts from a trusted supplier is
the FIRST step in getting good parts.

But we can assume the police did that - where it's just not reasonably
logical that they would fall prey to a plethora of counterfeit parts,
especially since the parts were *supplied* by the manufacturers, I believe.

(We could fall prey to "ringers" though...)

No, I'm just saying - again - that depending on the government
mandated friction rating markings will NOT get you the best brake -
which has been my thesis from the beginning and has been proven by TWO
law enforcement vehicle tests you have provided to support your

I'msorry, but your thesis does NOT stand the test of proof using the
scientific method. You are an engineer. What does that tell you???

If it was just a case of FF pads on a dodge undeperforming the same
pad on a Foprd, you could put it down to bake design - but that is not
the case here., There is NO LOGICAL EXPLANATION other than the FACT
that the markings are NOT a reliable predictor of brake performance -
muchless quality.

Assuming coefficient of friction IS the main quality you want in
brakes - which for me it most definitely is NOT.

I have to openly admit that I think the coefficient of friction is one of
the critical factors in brake friction materials, other than fit and
"reasonable" everything else (longevity, noise, dust, etc. in the Bell

I puit more weight on the other qualities,as they are readilly evident
- while the friction grade of the material is not - as proven by the

I want quiet brakes that respond smoothly both hot and cold, last for
a good length of time, and do not destroy my rotors/drums.
On disc brakes I want pads that don't dust excessively, and the dust
does not attack the finish on my alloy rims or wheel covers.

Everyone wants that, so we all agree (except trolls like Fox's Mercantile).

But how do you know that from the numbers printed on the pad?

You don't.

Now another thing that affects HOT braking is the attachment of the
lining to the shoe/pad. Does the "glue" adequately transmit the heat
or act as an insulator?? Personally,I'm a BIG fan of rivetted linings
and pads, rather than bonded.

They are generally quieter,and in my experience exhibit less fade.
They also generakky speaking have a smoother engagement.
(Rhetorical question - as I know there's no way to know that.)

I want brakes that do not fade excessively, and that willprovide more
than adequate braking in real world conditions.

Why wouldn't fade be covered in the SAE J866 Chase Test, which tests their
friction coefficient at a variety of temperatures?

Because the damned tests are either faulty or improerly performed
(the material does not meet the spec) OR the method of mounting does
not properly mitigate the heat.

When I installed oversized tires on my Ranger, brake effectiveness
deteriorated significantly - with the same brake pads and rotors.
I'm no engineer - but it was not hard to determine the problem was a
problem of leverage - the big wheels were exerting more foot-lbs of
torque to the brake - and the answer was bigger rotors - NOT different
brake pads - or even bigger brake pads. Just move the brake pads 10%
farther from the axle, like the larger wheels moved the road contact
area about 10% farther from the axle, and the brake force was

I agree that there are *many* factors in the act of slowing down a vehicle
with brake friction material heating up causing a loss of the energy of

However, the cold & hot friction coefficient, logically, must be a primary
factor, where there's a reason if lower coefficient EE pads (which have
just barely better a coefficient of friction than no pads at all) could
outperform FF pads (which have appreciably higher friction coefficients) in
the same vehicle under standard tests.

All I ask is how this can happen (where counterfeits are not logically the

Failure of the testing/certification process to reflect real world

Sorry, but you engineers devise the tests. There is definitely
SOMETHING wrong with either the design of the test, the implementation
of the test, (application) or the theory applied.

Which is why I put very limited weight on the stamped/published
friction ratings.

They have been proven time and again to be pretty close to useless.

Now, if you take a, for instance, BRakebond pad with ee, another of
their pads with ef, and another eith ff - there MIGHT be a displayable
progression between them - all other factors being the same (which
they seldom are). Or you may find an ee or ef pad or shoe STILL
outperforms an ff in the real world.

There is a lot more involved in brake performance - particularly hot
performance, than simple coefficent of friction.

gassing from the friction material, and how it is vented, being one
issue. Simply cross-cutting a pad, or chamfering the edge of the pad -
while marginally reducing the active braking area CAN improve hot stop
performance significantly.

In this case, the test using a one square inch sample of pad material
TOTALLY misses the mark - meaning the test design is faulty from the

I'm no engineer - but I know that much!!

When you combine government beaurocrats and engineers with no "real
world" experience to implement ANY program, the chances of failure to
perform get exponentially higher than tests performed under "real
world" conditions.

And as for not using EE friction materials - SOME of the cruisers
used in thase testa use ef or ff material in the
persuit special" vehicles, while civilian and even taxi (heavy duty)
use may have EE from the factory.

The whole CAFE situation, requiring the lightening of all components,
has resulted in a generation of vehicles that are (or have been)
SEVERELY underbraked - and this deficiency has been hidden by the
universalimplementation of antilock brakes - the small brakes canNOT
provide enough braking force to lock the wheels on dry pavement
because, by and large, they do not have to.

As long as the braking action of the brake assembly matches the
friction betweenthe tires and the road, it is accepted.

If I shut off the antilock function of my brakes, I want them to be
capable of throwing the vehicle into a complete slide - on command -
whether hot or cold.

With the oversized brakes (same pads as stock) with ee friction
material on my ranger- I CAN lock all 4 wheels - on command - with
antilock dissabled. - so why would I insist on FF pads, which, by the
results of the tests YOU provided, may very well underperform the "low
grade" ee pads I have installed?????