Ceramic v Metallic

[Maeztro]

Getting my car serviced made me wonder...they replaced my front brakes with ceramic...What are the pluses and minuses of ceramic v metallic?

TIA
M

[crystal_red]

Ceramic vs Metallic Pads

There are many rumors about ceramic pads causing excessive abrasive wear on the rotors or not holding up at high temperature. I conducted tests on 10 different metallic and ceramic pads to compare performance and wear characteristics.

The products included Hawk, Performance Friction, Raybestos, Power Stop, EBC, Akebono, Morse, and a widely used economy pad from China. There were five ceramic and 5 metallic pads. All data was performed using the test protocol in ISO NWI 2560 on a Chevy Tahoe front axle corner. The tests were run by Link Testing in Detroit. This is an aggressive test that pushes the pad to more than 1200 Fahrenheit, and conducts high speed stops, fade snubs and panic stops. One popular ceramic name brand pad did not make it through the test as it was completely consumed before the test ended. Therefore, I was only able to compare four ceramic and five metallic pads.

I measured and recorded the following:
. Rotor wear
. Pad wear
. Green friction coefficient (mu) - before the burnish or cure on the vehicle
. Fade snub friction coefficient (mu) - 15 consecutive stops without cooling
. Hot stop friction coefficient (mu) - above 1100 Fahrenheit
. Speed sensitivity - the percent change in mu at 160 kph vs 80 kph
. Pre-fade pedal pressure sensitivity - % change in mu
. Post fade pedal pressure sensitivity - % change in mu

Background:
About 25 years ago, we were using asbestos as the binding fiber for the friction compound. It was the ideal product to resist high temperature, and the barbs along the fiber captured various elements and contained it in a nice homogenous mix. When asbestos was phased out in the late 80's and early 90's, compounders had to find a good substitution for asbestos such as iron fibers, chopped kevlar or fiberglass. Development focused on a non-asbestos organic variety and a metallic type pad. That is, until Akebono developed the first ceramic pad. It was a giant leap in brake formulations because it provided outstanding noise, vibration and harshness (NVH) properties with stable mu over a wide temperature range. A true ceramic pad contains no ferrous metal, so there is no metal to metal contact between the pad and the rotor. However, the SAE has no definition of a ceramic pad to specify minimum contents of various elements. So a manufacturer could take a low metallic pad, sprinkle some ceramic stuff in the mix and call it ceramic. This has led to a wide variation in brake performance from brand to brand.
Are ceramic pads bad for your rotor?
Friction works primarily with two mechanisms: 1) abrasion and 2) adherence. Abrasive friction consumes the pad and/or the rotor with a cutting action. Adherent friction is when the pad material is deposited on the rotor, and a friction force is produced from the breaking of chemical bonds as material in this deposition layer is sheared. Abrasive pads will cause higher rotor wear (normally less than .002") and decrease rotor mass. Adherent type pads can actually increase rotor mass. At higher temperatures, adherent friction is the primary mode of producing a friction force.

In analyzing the test results, I found no correlation to make a general claim that ceramic pads are hard on rotors. In fact, it is clear that some metallic pads are more abrasive than some ceramic pads. The pads that were easiest on rotors were Akebono ceramic, Power Stop Z26 metallic and Performance Friction metallic.
Do metallic pads perform better than ceramic?
Under cold conditions, brake torque was not significantly different between ceramic and metallic pads. What I find interesting is what happens as temperature gets up to 1000 degrees. This is where metallic pads have the edge. Ceramic mu tends to drop at extreme conditions.
In summary, the general statement that all ceramic pads are hard on the rotor is false. There are advantages to ceramic pads in terms of uniform pedal pressure characteristics, low noise and low dust. Ceramic pads are a great street compound and can give better performance than some metallic pads. The advantage of metallic pads is improved high temperature performance. I recommend metallic pads for extreme performance such as hauling loads, track racing, towing trucks or traveling in mountains. Our Z36 series has super stopping power even at extreme temperatures. Power Stop offers Evolution ceramic with a nice compromise between pad bite and stability. Of all the products tested, Power Stop Evolution operates close to Akebono (the OE pad) in performance. ...

[MoFex]

For what it is worth.
My previous car, Nissan Murano had ceramic pads. Fronts were in good shape after 94k miles. Rear were replaced with Akebono ceramic at 50k miles.

My wife car, FX35 needs brake pads replacement every 30k miles. It uses also ceramic pads. I have used Akebono and they seem to perform very well. Right now the FX has 82k miles and there is no noticeable wear on brake rotors.

My experience: ceramic brakes pads are very good for street driving, are very quiet, there is no visible dust to talk about. It is my understanding that after the TSB I have ceramic rear pads on the CTS as well. They seem to be quiet and do not produce much dust. At front I have still the OEM’s as my replacement ceramic pads were taken off before dealer visit. I may put them back.

For all who are still not sure ceramic pads are working – just try. You will not regret.

[Maeztro]

Wow..thanks for the great info!