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Brake friction coefficient differences #5322059 01/13/20 09:34 PM
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ledslinger Online Content OP
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Say you put a pad set on the back with high friction coefficient, and one on the front with low. How does the system handle changes like this? Are the friction coefficients just not that wide of a range, or is the system tolerant of a range of friction coefficients? Ever heard of mixing pad types front and rear (organic, ceramic, semi metallic) on a vehicle causing problems? I would think that front/rear proportioning is a delicate balance, but maybe is surprisingly tolerant to variables.

Maybe the effect is less than where payload is placed in a vehicle, and perfect front/rear proportioning is rarely achieved.

Re: Brake friction coefficient differences [Re: ledslinger] #5322121 01/14/20 12:23 AM
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CR94 Offline
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With or without ABS?


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Re: Brake friction coefficient differences [Re: ledslinger] #5322223 01/14/20 07:18 AM
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krismoriah72 Offline
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I would say most independent garages dont even know what a brake coefficient even is... so there are millions of cars on the road with mismatched brakes. In my shop i have put the 'cheapest' pads on an axle due to customers requests.. and also put the 'best' pads on an axle.

Used Car lots probably have the cheapest pads on an axle versus OEM on the other axle.

Re: Brake friction coefficient differences [Re: ledslinger] #5322341 01/14/20 11:09 AM
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porterdog Offline
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Racecar types adjust their brake balance by mixing pads front to rear on the regular. ABS will prevent single-axle lockup, but on the street you may have increased braking distances.

Re: Brake friction coefficient differences [Re: ledslinger] #5322350 01/14/20 11:23 AM
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WyrTwister Offline
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Never thought about it . I always buy a set for the front or a set for the back , or both if both need it .

I purchase the cheapest lifetime pads , from a local parts store . Never need to purchase , for that vehicle , again .

But I am an old man and drive like an old man . Not like a teenage would be race car driver .


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Re: Brake friction coefficient differences [Re: ledslinger] #5322355 01/14/20 11:30 AM
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EBC specifically has an article on this topic, and essentially says, if you do this you're a fool (slight artistic license taken on my part). Brake systems in general, believe it or not, are engineered to pretty exacting standards, even if there's not alot of actual brake force going on (think Fiat 500 vs. Bugatti Chiron). Most pad manufacturers use identical or "calibrated" pad coefficients to ensure the systems retain similar characteristics to OEM dynamics, even if they do provide greater stopping power.

It's all about balance.

Re: Brake friction coefficient differences [Re: ledslinger] #5322395 01/14/20 12:02 PM
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Pew Online Content
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The system won't change what it came out of the factory with. But with a high coefficient in the rear and a low coefficient in the front, the end result is you changed the balance (bias) of the brakes towards the rear.

Most people wouldn't be able to tell a difference other than 'it's better or worse.' Race cars are an exclusion, some with manual brake proportioning valves, different tires, and other stuff you wouldn't find on a road car. Like SubieRubyRoo said, it's a balance at that point.

Re: Brake friction coefficient differences [Re: SubieRubyRoo] #5322454 01/14/20 01:05 PM
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doitmyself Offline
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Originally Posted by SubieRubyRoo
EBC specifically has an article on this topic, and essentially says, if you do this you're a fool (slight artistic license taken on my part). Brake systems in general, believe it or not, are engineered to pretty exacting standards, even if there's not alot of actual brake force going on (think Fiat 500 vs. Bugatti Chiron). Most pad manufacturers use identical or "calibrated" pad coefficients to ensure the systems retain similar characteristics to OEM dynamics, even if they do provide greater stopping power.

It's all about balance.

My ABS equipped car came with FF pads on front and EE shoes on the back. shrug On my first front change last fall, I put EBC Ultramax2 (GG) on the front and cannot notice any difference with somewhat severe brake testing on a deserted road. When I asked here ahead of time, the consensus was that it didn't matter that much, as long as you don't do what Pew mentioned above.

Re: Brake friction coefficient differences [Re: ledslinger] #5322541 01/14/20 02:52 PM
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HangFire Online Content
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Keep in mind that pad ratings like EE and FF are NOT friction coefficients. They are ratings of friction and falloff due to heat. Meaning you can have a lower rated pad that is more grabby than a higher rated pad, at least if not overheated.


Various musings: http://hangfire.net
Re: Brake friction coefficient differences [Re: ledslinger] #5322699 01/14/20 05:08 PM
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DIM, I've got Ultimax 2s on my Outback as well... and if you take a look at EBCs page for the Ultimax, it says they are designed to work with stock pads on the opposite axle. It also says once you are above the Ultimax pads in coefficients, you must use the same grade pads on both axles; no mixing stock, ultimax, RYGBs with any other pad except its own color.

Re: Brake friction coefficient differences [Re: HangFire] #5323038 01/15/20 12:42 AM
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bbhero Offline
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The friction ratings are indeed coefficient of friction..

The first letter is for "cold" braking performance...250°F

Second letter for "hot" braking performance... 600°F

A brake pad rated GG will have a higher coefficient of friction vs a EE rated pad... I have a table showing be the coefficient of friction ratings... I am going to try and find it.

And the coefficient of friction is clearly listed in the second part of the table below. .

Ohh and EE is basically steel on steel coefficient of friction... No where near as good at stopping say as a pad rated FF and way, way less performance vs a GG rated brake pad. [Linked Image]

Last edited by bbhero; 01/15/20 01:00 AM.

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Re: Brake friction coefficient differences [Re: ledslinger] #5323060 01/15/20 01:49 AM
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I think for most vehicles and the average driver, they’d never be able to tell. On a vehicle like my 300 which can vary it’s brake bias, you might upset the system.


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Re: Brake friction coefficient differences [Re: ledslinger] #5325068 01/17/20 08:49 AM
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A coefficient is a number with an associated temperature.

Edge codes are an attempt to capture a group of coefficients and temperatures.


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Re: Brake friction coefficient differences [Re: ledslinger] #5325877 01/17/20 11:44 PM
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bbhero Offline
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True... GG brakes pads do stop better "cold" 250 degrees and "hot" 600 degrees vs EE rather brake pads...

And there is very, very little chance of fading at high temps with GG rated brake pads... Vs EE rated pads which will be guaranteed to fade hot...

FG rated pads will not be as good at "cold" 250 temp braking however will be better hot at 600 degrees...

I have had GG rated brakes pads by akebono and there was a very noticeable difference "cold" braking performance vs FF rated brake pads... I did not get them too super hot because I did not practice track braking at Virginia Motor Sports Park smile


Last edited by bbhero; 01/17/20 11:45 PM.

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"Treat your family like your friends and treat your friends like your family."
Re: Brake friction coefficient differences [Re: ledslinger] #5326045 01/18/20 08:11 AM
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I'm pretty sure the last owner of my car did a pad swap on the front, which had a different coefficient than the rear. When I changed everything, it felt very different. Matched pads felt much more balanced, the car stops more solidly, less drama. It's hard to explain, but it's better!


2007 BMW 335i n54 210,000 miles, lubricated by whatever is on sale
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