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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 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 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...)

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 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?
(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?

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