Brake friction coefficient differences

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1,200
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Missouri
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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.
 
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2,529
Location
wv
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.
 
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308
Location
Detroit (Rock City)
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.
 
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4,184
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Texas
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 .
 
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.
 

Pew

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1,016
Location
Illinois
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.
 
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7,663
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MI
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.
 
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4,001
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Central Maryland
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.
 
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.
 
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8,449
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Virginia
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]
 
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2,880
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Chicagoland
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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8,449
Location
Virginia
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
 
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1,032
Location
Minneapolis
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!
 
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16,002
Location
Silicon Valley
Originally Posted by ledslinger
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.
I had it like that once, because they wore out at different time. I had Axxis / PBR Ultimate at the back and some cheap Raybesto on the front, and the car bite the brake quite early instead of braking linearly on tapping. The rear also wear out much faster on that setup too.
 
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