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Discussion Starter · #1 ·
What do you believe is achieved by "bedding" brakes?

I am an engineer so I want an engineering and/or physics discussion of just exactly what people think bedding means or achieves. I don't want any hokey BS. If you can't tell me what physical characteristics change then don't even bother.

I'd especially appreciate hearing an explanation of how this relates to disc warping, given what I just read. An engineering description, not "my grandad told me that on his old international harvester...".

To me a lot of what I hear sounds like the way some people polish rifle barrels... which will void your warranty with the McMillan brothers (vendors of ultimate quality sniper, tactical and competition rifles).

Why do I ask? Because in the UK, where I only once experienced warped discs and that was on a used car so I have no idea how they did it, I never heard any discussion of bedding brakes or resurfacing them. In 500,000 miles of unreasonably hard driving, we're talking 12-14000 miles for a set of tires and 25k for brakes, I never managed to warp them myself once.
 
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Bedding brake pads has a couple of important effects. The friction material in semi-metallic pads is held together by an organic binder, usually a type of phenolic material. As the pads get hot, the binder boils, and burns, from the top surface of the pad. Once this burning or “Bedding” takes place the friction material makes proper contact with the rotor.

Some race/performance pads, like the Performance Friction’s line of pads, are designated as “pre-burnished” from the manufacturer. In our experience these pads still benefit from“bedding”. “Bedding” pads establishes a wear pattern between the pads and rotor. Some pads, like the Performance Friction pads, deposit a layer of carbon in the surface of the rotor. They need that layer of carbon to perform at peak efficiency.
 

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Quoting Pagid brakes site http://www.pagidusa.com/Pagidusapassenger.htm

"To ensure maximum performance and customer satisfaction, new brake pads must be bedded in upon installation. Correct bedding guarantees that new brake pads and new rotors work flawlessly together. In order to function optimally, organic brake pads must develop friction coal on its surface. This friction coal develops at a temperature of approximately 280°C (537°F). It is very important that this temperature is reached continuously and slowly. This gradual process generates temperatures that not only penetrate the surface of the brake discs and pads, but also distribute evenly through the whole disc and pad material. This is essential when using new brake discs, since the disc often shows signs of stress (due to the casting process and fast cooling) in the materials. A steady and careful warming and cooling process guarantees a good release of both materials"

Hope that this can be helpfull
 

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Discussion Starter · #5 ·
Cool!

Any correlation with warping?

Never mind, I was replying during the second post. OK, I can buy that and will do the right thing when I swap all four corners in a few weeks. I wonder where I'm going to find enough road to do it right in the bay area?
 

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geordie said:
Cool!

I wonder where I'm going to find enough road to do it right in the bay area?
:lol: I will live 120 years more, but still I will not understand where they find such waste space for bedding with no colisions.
 

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On warped rotors and bedding: these are two distinct issues. A warped rotor "could" be due to improper "Seasoning" of a rotor. This is nothing more than heat cycling the rotors to essentially prevent warping them when it comes time to really heat them up in say a 75mph to zero stop.

Somehwhat like heat treating metal, you want the internal molecules of the iron to setup in a pattern that will make them stronger. Cyrogentically treating them (www.frozenrotors.com) is like doing the same thing only from the other end of the spectrum.

I guess it's like the differnce between a cast aluminum wheel and true "foged" aluminum rim. The molecules on a forged wheel setups up in a directional pattern to make them stronger. I believe this is what seasoning the rotors does to some extent.

If I sounded like an idiot, my aplologies in advance. Maybe I'll learn something here. :)
 

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Whoa, it looks like everyone jumped in before I got a chance.. Everyone made excellent points!!

The 20VVillian really hit on a good point concerning pads that are "pre-burnished". If proper bedding doesn't take place, then it's possible that excess heat can build up during those first initial brake applications which causes resins used to bind the pad material to stick to the rotor surface. The purpose of rotor bedding is to create even pad contact throughout the surface of the rotor, and to slightly temper the rotor over time. In some cases brake-pads don't make flush contact to the rotor which can cause uneven pad wear and leave material on the rotor surface. When pad material is left on the rotor surface in certain spots or the pad surface is glazed due to those first initial applications when slight fading has occured, it can lead to uneven and premature rotor wear. Once that uneven spot is worn in the rotors, you get the famous vibration during braking and your rotors are warped.

Now I will admit that some brake pad compounds and rotors are a little more difficult to bed-in than others. Some compounds will allow you to "re-bed" if you notice slight vibration. Bedding in some racing circles is also called Rotor Seasoning, so in many cases folks are using different terminology for the same process.

HermanH, also hit on a good point. I use a company called Diversified Cryogenics to temper my rotors by dropping them to -300F and slowly bringing them back to room temperature. I did this process only on cross-drilled/slotted rotors as a way to resist cracking. When a BBK is available for my W8, I will send rotors off to get treated in this manner.

Here's an excellent technical write-up on bedding-in new brakepads.
 

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Discussion Starter · #12 ·
Well, I'm glad I asked. The Stoptech article is very good and answers most if not all of my questions. It also explains the almost soft and furry feel of some well used pads. Now I'll be sure to fry my brakes when I get them... slowly of course.
 

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Should bedding pads then be part of the break-in period on a new car? Or is bedding mostly targeted at performance replacement pads and rotors?

If it is required or at least preferable on a new car, is there a point where it is just too late, or should you do it anyway irrespective of accumulated mileage?
 

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g2, excellent question. Yes, you should bed-in your pads on your new Volkswagen. The stock Pagid and Jurid OEM pads used by Audi/VW are very difficult to bed-in. Use the method described in David Zeckhausen's write-up and you should be alright.

Folks, please don't forget to flush your brake-fluid every 2 years no matter how many miles are on your Passat!! :thumbup:
 

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Nenad said:
Quoting Pagid brakes site http://www.pagidusa.com/Pagidusapassenger.htm

"To ensure maximum performance and customer satisfaction, new brake pads must be bedded in upon installation. Correct bedding guarantees that new brake pads and new rotors work flawlessly together. In order to function optimally, organic brake pads must develop friction coal on its surface. This friction coal develops at a temperature of approximately 280°C (537°F). It is very important that this temperature is reached continuously and slowly. This gradual process generates temperatures that not only penetrate the surface of the brake discs and pads, but also distribute evenly through the whole disc and pad material. This is essential when using new brake discs, since the disc often shows signs of stress (due to the casting process and fast cooling) in the materials. A steady and careful warming and cooling process guarantees a good release of both materials"

Hope that this can be helpfull
This method emphasizes the delta T be reached continuously and slowly.
This is what I have always done in the past and NEVER had 'warping' issues.
It runs counter to the stoptech article which is widely accepted on this website.
I have always been skeptical of the stoptech method for street cars.
Any insights or comments?
 

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What the hell is all this hair splitting about?

You treat your brakes bad, they are going to get lumpy. Who gives a flying crap if the lumpiness is deposits or actually a "warped" rotor?

As for bedding on a new VW, if the dealer tech is worth anything (insert joke here), they are already bedded.

If you have a brake job done with resurfaced or new rotors and the tech worth anything, they're already bedded.

What the hell is the big deal here?
 

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Sharky said:
What the hell is all this hair splitting about?

You treat your brakes bad, they are going to get lumpy. Who gives a flying crap if the lumpiness is deposits or actually a "warped" rotor?

As for bedding on a new VW, if the dealer tech is worth anything (insert joke here), they are already bedded.

If you have a brake job done with resurfaced or new rotors and the tech worth anything, they're already bedded.

What the hell is the big deal here?
Hey, we're not all VW Gods around here. :poke:
 
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