Need help INTERPRETING these test results police cruiser SAE J866a Chase Test

The scientific question is how do we correctly interpret why EE pads seem
to outperform FF pads in this police cruiser study done in 2000?
formatting link
formatting link

In another thread today, the topic was discussed on how to intelligently
select friction materials for replacement brake pads and shoes.
formatting link

That discussion hinges on a scientifically valid interpretation and
understanding of the utility of the "friction codes" printed on every brake
pad and shoe in the USA:
AMECA Compliance List of Automotive Safety Devices:
Friction Material Edge Codes(TM), May 2011

A general summary of which is listed below:
formatting link
formatting link
formatting link
The scientific question is how do we correctly interpret why EE pads seem
to outperform FF pads in this police cruiser study done in 2000?
formatting link
Reply to
Mad Roger
On Thu, 11 Jan 2018 02:47:38 -0000 (UTC),
Here is the original response to that thread where it was said that SAE J866a Chase Test EE pads outperformed FF pads.
And those tests showed the EE pads CONSISTENTLY outperformed the FF brakes pretty well across the board - with the FF brakes SEVERELY underperforming in most cases.
The Dana Ceramic family was the only FF to outperform OEM, while HawkHead outperformed on both Chevy and Ford - and Raybestos and Carquest alsooutperformed on Ford in the panic stop test.
Across the board, EE brakes, on the whole, outperformed the FF and even the EE/GG combination - so what does your friction rating tell you????????????
What it tells ME is if I buy Raybestos, NAPA, CVarquest, or Dana (all major OEM suppliers) brakes, I will equal or excede OEM performance - doesn't make a bit of difference to me WHAT rating they have.
If I want slightly superior hot panic braking, at the expense of poorer cold and medium temperature braking I should buy ceramics - and this is STRICTLY for braking performance.
Now, from REAL WORLD experience, both myFord Aerostrs went through rotors like crazy - untill I put on NAPA's Carbon Metallics a set of pads destroyed a set of rotors at about half of pad life - and I mean TOTALLY DESTROYED, here in Southern Ontario. That came out at just over a year.
When I went to NAPA Carbon Metallics, the same rotors lasted for TWO FULL SETS of pads - and over 5 years - and I was able to actually lock the front wheels on dry pavement (rear ABS only) - which NONE of the other brakes were capable of doing.
Never looked at the friction rating - never needed to, because friction rating doesn't tell the whole story (as your reference so elegantly proved)
You can have 5 different FF pads - and one will be noisy as hell, one will eat rotors for lunch, onde will corrode as soon as it SMELLS salt, and another will turn to gravel the first time you get it hot - ALL FF rated (or ef, or ee. or FE )
The fact it met the test requirements ONCE in the lab means NOTHING about quality
Reply to
Mad Roger
The scientific results are back! You are certifiably insane!
Reply to
The engineer's enigma. 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 NECESSARILLY mean ANYTHING.
That's why I say buying known brand parts from a trusted supplier is the FIRST step in getting good parts.
Assuming coefficient of friction IS the main quality you want in brakes - which for me it most definitely is NOT.
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. I want brakes that do not fade excessively, and that willprovide more than adequate braking in real world conditions.
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 re-ballanced.
Reply to
Clare Snyder
On Wed, 10 Jan 2018 23:07:18 -0500,
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
formatting link
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?
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).
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...)
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 Curve).
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.)
Why wouldn't fade be covered in the SAE J866 Chase Test, which tests their friction coefficient at a variety of temperatures?
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 momentum.
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 reason).
Reply to
Mad Roger
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.
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 position.
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.
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 tests.
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.
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.
Failure of the testing/certification process to reflect real world conditions.
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 start.
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?????
Reply to
Clare Snyder
On Thu, 11 Jan 2018 11:44:01 -0500,
I agree with you that it's unlikely that the police in Michigan were testing counterfeit parts, especially as they apparently received the friction material directly from the manufacturer, according to their summary paper.
I'm not disagreeing with your contention that the EE pads, in those police tests, somehow worked better than the FF pads, even though E is a friction coefficient only marginally higher than steel on steel.
I'm only asking why.
I'm an electrical engineer; so I believe in friction, but if the lower friction coefficient pads are working better than the higher friction coefficient pads, the precise understanding of that is out of my league.
That's why I asked here, where I was hoping the s.e.r intelligentsia might help us rationalize a reason that stands the test of logical analysis.
I agreed with your assessment, and I even quoted the Michigan police cruiser test warning saying that the markings don't necessarily conform to real-world practice.
I'm only asking here WHY an E coefficient pad (which is basically no pad at all) performed better than an F coefficient pad (which has an appreciably higher cold & hot friction coefficient)?
I'm going to have to somewhat reluctantly agree with you, unless we get a good reason, that no pad at all (i.e., just metal on metal) is "just as good" and "maybe even better" than a high friction coefficient pad.
Pretty much that says "all pads work", does it not?
Again, I'm going to have to somewhat reluctantly agree with you, from a logical standpoint, that if essentially no pad at all (i.e., an E coefficient pad which has a coefficient of friction marginally better than steel on steel) is better or about as good as having a pad, then almost nothing printed on the side of the pad is going to make any difference.
It seems there *must* be other *major* factors in braking performance, other than the friction rating of the pads themselves.
That's a hard logical pill to swallow, for me, which is why I asked here, hoping the s.e.r folks can enlighten us as to why.
Well, the friction coefficient is a "real world" measurement.
It just doesn't seem to matter in braking performance, based on that police cruiser test I unearthed.
That's too bad, because it means you can't compare pads easily other than to note the material, type, and manufacturer, which the DOT CODES printed on each pad and shoe do tell you.
So at least we can tell three pads with three different marketing strategies (e.g, Axxis, PBR, & Metal Masters) are the exact *same* pad, and we can tell when a pad is rebranded (I think Centric only does rebranded pads, for example, but I'd have to check the numbers to be sure).
That indicates there is some utility in the mandated information that is printed on the side of each pad.
But it's just sad that the friction coefficient means so little to a friction material!
Friction is friction. It's a mathematical beast.
I don't think the SAE J866 Chase Tests lie about the friction of a 1" square piece of the friction material.
They just don't predict real-world performance, it seems. (As noted in the Police Cruiser report.)
Again, I must reluctantly agree with you, as hard a pill as it is to swallow, that friction coefficients are NOT an important factor in the performance of brake friction materials.
I just want to know WHY?
Well, as I said, the *numbers* printed on the side of every pad/shoe sold in the USA are *useful* in that they tell you the manufacturer, the material, and, the friction rating - so even if we discount the friction rating, it's nice to know when you can tell that two pads sold and marketed at two different prices, are the same pad.
I'm gonna have to reluctantly agree with you, yet again. I don't ever dispute fact.
It must be the case that friction isn't a *primary* determinant of brake performance, hard a pill as that is to swallow.
You'd think the SAE would know how to design a friction test though...
I know. I know. You don't have to rub it in. I apologize for chastening you for using EE pads and shoes.
I still think my Toyota OEM shoes are FF so I'm gonna get FF. Can you summarize again the short list of brands you'd recommend? I want to do the work for the owner this weekend.
Reply to
Mad Roger
Elementary, my dear Watson. There is a HECK of a lot more to brake pads than just the coefficient of friction - as Ihave been stating time and time again. Steel on steel is noisy. Steel on steel has no "feel". Steelon steel makes TERRIBLE brake dust, and steel on steel would have terrible pad and rotor or shoe and drum life.
The coefficient of friction isn't all that bad - and the difference between e and f, I would postulate, is not so "appreciable" as "measurable" and the difference in fade bertween ee and ff pads is laughable. At 600 degrees an ee can suffer from 0 to 25% fade, while the "appreciably better" FF suffers from 0-22% fade - which means there is EVERY possibility that an EE pad would hac WAY less fade than another FF pad.
The STUPID thing is an fe can suffer 2-44% fade - doesn't make ANY logical sense, but that's straight from
formatting link

Friction material consists of a cobination of the following components: Fibers, such as fiberglass, kevlar, arimid, stainless steel, and aluminum maintain the heat stability of the pad. These fibers have various binding strengths and can be organic or metallic. Friction Modifiers such as graphite adjust the friction level and fine tune the performance characteristics of the pad at specific cold and hot temperatures. Fillers take up dead space in the pad. These are generally organic materials with some low frictional effect such as sawdust. Finally, Resins are used to hold the elements of the pad together so they don't crumble apart.
All pads work at least once. The life of the pads is not taken into account
Dropping a railway tie into a post hole will stop you faster than a GG pad will = guaranteed!!!
Yes, but the assininely simple test procedure is FAR from "real world". The behavior of a 1 square inchchunk of friction material does not come CLOSE to the effect of 2 30 square inch arcs of pad material in a 3 inch wide enclosed drum, or 2 10 square inch pads rubbing on an open disk - simple things like pad vibration can reduce the EFFECTIVE friction of a disc pad SIGNIFICANTLY (by cutting the "duty cycle" of the pad basically in HALF (A vibrating pad is only in full contact with the rotor roughly half the time) An off-gassing pad only 1 inch square is not going to "float" on that gas layer like a 10 square inch patch is under the same pressure. The "micro-ball-bearings" of brake dust will have virtually no effect on a 1 inch piece of friction material, but may have a SIGNIFICANT effect on 10 inches of brake shoe (which is why , partly, a grooved pad can significantly outperform a solid pad.
There are WAY too many contributing factors that have WAY more influence on brake performance than the relatively SMALL difference between an e and an f pad. You could have an E pad at .34 and an f at .36. You tell me there is a quantifiable difference between the two???? Not in my world - where the rubber hits the road.
Well over half of the "brands" are rebrands - not manufacturers. particularly the "boutique" brands the enthusiasts and boy racers wet their pants over
VERY limited utility
"Figures don't lie, but liars figure" You can make math give you any answer you want - ask an accountant.
They don't lie, they just, by their very nature, CAN NOT tell the whole truth
Because the initial friction co-efficient, as measured by the test in question, is only one of a miriad factors involved in brake performance - and a relatively MINOR one in the grand scheme of things.
Well, if I was doing the job, I'd be heading over to my neighbourhood NAPA store and pickingup a set of their Napa Ultra Premium rear shoe kits for $57.28 CANADIAN (about $35 US??)and be done with it. Or possibly over to Canadian Tire for a set of Brembos if they have them 20% off (they did this week - but their coverage is limited - they might not have shoes for a 'runner) or Wagners.
Let's face it - they are REAR brakes - and they do less than 30% of the actual braking. A whole lot less in many cases due to the action of the load sensing brake proportioning valve that cuts preasure to the rear brakes when the rear axle us "unloaded" to prevent the rear brakes from locking and the ABS from activating.
ABB (Brakebond) and Dana are generally predictable performers as well.
Reply to
Clare Snyder
On Thu, 11 Jan 2018 09:37:21 -0800 (PST),
With respect to "stopping distance", in the Michigan Police Cruiser study, they controlled for identical deceleration (thus identical stopping distance) and measured pedal force.
This is a different test than applying a uniform pedal force and measuring stopping distance.
I'm not sure how to extrapolate that information to stopping distances.
Reply to
Mad Roger
On Thu, 11 Jan 2018 13:20:56 -0800 (PST),
Here's just one example to help answer that on-topic question bearing in mind that brake pads are highly marketed items.
If you are comparing three pads that fit your vehicle spec: a. $50 Axxis performance b. $30 PBR midline c. $20 Metal Masters economy
And you look at the code printed on the pads, you'll find they are *exactly* the same numbers (since they're all the same pads/shoes, just marketed differently).
In addition, the code printed on the pads tell you the material is exactly the same, even if they're not the same pads (so you can more easily compare across brands).
And it will tell you the coefficient of friction, even if those two things are different still, so you can compare across lines and brands for friction.
Why would you deny a vehicle owner that useful comparative information?
Reply to
Mad Roger
On Thu, 11 Jan 2018 16:55:12 -0500,
I found out the DOT Edge Code for the OE Toyota shoes which is NBK LN508 FF which is made by "Nisshinbo Automotive Manufacturing, Inc.".
It turns out that you were completely correct where I was hoping this number would be a "holy grail" where I could use it to better compare two brake shoes in my hands.
To get a better handle on how to interpret the numbers, I called the main number at AMECA.ORG in Maryland at 202-898-0145 and spoke to the engineer in charge of that "AMECA Edge Code Markings" cross reference.
It was a long discussion, the net of which is that this code isn't really for the consumer.
The engineer said it's kind of like the so-called "serial number" on a tire, or on a package of baked beans, where if something goes wrong, the government has a way of tracking down whose fault it is. In addition, he said that the SAE J866 Chase Test is really a quality metric, and not a performance metric, even though friction is an outcome of the Chase Test.
The engineer did give me all sorts of personal insight into how to buy brake pads but overall, he said you can't extrapolate very much real-world decision-making data from the DOT Edge Code.
Of course, if you miraculously find two pads with the same DOT Edge Code, then there's a 100% chance that it's the same friction material.
Or, if you find any pads with any of the 19 DOT edge codes that cross reference to the same AMECA registration number 160426 then they too are exactly the same friction material. NAC D9011 FF NAC LN508 FF NAC N2009 FF NBK D9011 FF NBK LN508 FF
Reply to
Mad Roger
On Sat, 13 Jan 2018 22:45:47 +1100,
Xeno the troll.
How much on-topic technical value have you added to *any* thread.
In your *entire* life?
Xeno the troll can't comprehend the topic. Nor can Xeno the troll add any technical value.
Xeno the troll is too stupid to add any value to any topic whatsoever.
Just watch. Xeno the troll proves he's incapable of even *comprehending* the technical topic by his every response.
Xeno the troll will respond with more non-technical worthless blather. Just watch.
Reply to
Mad Roger
Whats the stupid fixation with the coefficient of friction anyway?
As any fule kno, friction is notionally independent of contact area, and force due to friction is determined by the coefficient of friction *and the applied force* so if you want more frictional force, you just need to press the pedal harder, or have more servo assistance.
Simply ignoring all of the other (engineering) considerations which have been cited, relating to brake performance in the real world, will not help you be enlightened about anything. It just makes you look like a dumb fuck trying to be cleverer than your brain permits.
Reply to
Mary-Jane Rottencrotch
UNLESS it's counterfeit (admitedly likely less than 1% chance - until it is - - - -
Reply to
Clare Snyder
I guess we'll have to give the poor guy a break. I suspect he is a young graduate engineer who has yet to learn how little he knows.
Reply to
Clare Snyder

Site Timeline Threads

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.