i was talking to my buddy and we came to an impasse. he said that slooted rotors are supposed to spiral in when you go forward, i think they are supposed to spiral out. whats the proper way? does anyone know for sure?

spiral out I believe, if Im reading you correctly. You want the heat to leave the rotors

The spirals are not there for heat.

When your pads touch the rotor they transform mechanical motion into heat. When this happens there is a huge ammount of friction and heat, enough to cause powder and gasses. The slots and dimples are there for theese gasses.

If you want to get rid of heat , you would want more metal.

the real and only "spirals" that matter are the internal ones. You ever look at your front rotors from the side? it has slots for the air to go through em and cool things down.

Originally posted by Chamuko
The spirals are not there for heat. When your pads touch the rotor they transform mechanical motion into heat. When this happens there is a huge ammount of friction and heat, enough to cause powder and gasses. The slots and dimples are there for theese gasses. If you want to get rid of heat , you would want more metal. the real and only "spirals" that matter are the internal ones. You ever look at your front rotors from the side? it has slots for the air to go through em and cool things down.

ditto. slots are there for better pad "bite" and to give powder/gases some place to go. the direction is irrelevant. the only reason rotors hafta be mounted a certain way is if the internal vanes are directional.

Yes the real prupose of the slots is not to dissipate heat it's to vent the gasses from between the pad and rotor helping to keep contact between the two surfaces. If you have ever driven/braked hard on solid surface rotors you know what it feels like when those gasses get trapped between the 2 surfaces (for the life of me I can't remember the term we use to describe this happening). Basically you will feel the brakes become uneffective very quickly. The Slots expell the gasses from between the surfaces keeping your pads in contact with the rotor surface. This is why slotted rotors are used on GT Race cars. If you have ever watched a night race you can and will see the rotors glowing cherry red from heat but they are still working properly due to the gas being expelled from between the surfaces. Ok I'm Done going on and on.

-Kevin

Originally posted by shazow1969
(for the life of me I can't remember the term we use to describe this happening

Isn't it called a "boundry layer"?

Brian

Originally posted by ForceFed420a

Originally posted by shazow1969 (for the life of me I can't remember the term we use to describe this happening

Isn't it called a "boundry layer"? Brian

It's commonly refferred to as "glazing". The "glue" that holds cheap organic pads together will melt when you ask too much of the brakes. This creates a gas that will effectively act as a lubricant between your brake pads and your rotor. I had it happen a few times with the stock brake system on my Eclipse. It scared the shit out of me since I came about a foot and a half from rear ending somebody on the highway in a sudden stop situation. I knew that upgrading to better pads can reduce the chances of that happening, but I decided to splurge a little and replace my fairly scored rotors with new cross drilled ones instead of having them turned. I've yet to feel the slightest bit of glazing with my new brakes, and I've given them a 125-25mph test.

Id also like to add I go thru semi metalic pad in about 8 months cause of the slotted rotors. I also do a lot of mountian driving and brake hard in corners. Good thing for lifetime warrenty... lol

Originally posted by Silv Blt

Originally posted by ForceFed420a

Originally posted by shazow1969 (for the life of me I can't remember the term we use to describe this happening

Isn't it called a "boundry layer"? Brian

It's commonly refferred to as "glazing". The "glue" that holds cheap organic pads together will melt when you ask too much of the brakes. This creates a gas that will effectively act as a lubricant between your brake pads and your rotor. I had it happen a few times with the stock brake system on my Eclipse. It scared the shit out of me since I came about a foot and a half from rear ending somebody on the highway in a sudden stop situation. I knew that upgrading to better pads can reduce the chances of that happening, but I decided to splurge a little and replace my fairly scored rotors with new cross drilled ones instead of having them turned. I've yet to feel the slightest bit of glazing with my new brakes, and I've given them a 125-25mph test.

Hmm, interesting. I guess it was my understanding that everytime you have heavy braking you create gases. However, these are not huge amounts of gas, and are evacuated by the slots (if you are equipped as such) and thus not a problem. If you don't have slots, the gases have the potential to create this "layer" between the rotor and the pad effectively "aquaplaning" for lack of a better term. This creates pad fade as the pad reaches beyond its thermal capacity and creates gases from the binding agents in the pad. I understood this to be the first "stage". However, if you continue to use the brakes for extended periods of high duress, then they glaze as you described above. Am I incorrect in anything?


Brian

Originally posted by ForceFed420a
Hmm, interesting. I guess it was my understanding that everytime you have heavy braking you create gases. However, these are not huge amounts of gas, and are evacuated by the slots (if you are equipped as such) and thus not a problem. If you don't have slots, the gases have the potential to create this "layer" between the rotor and the pad effectively "aquaplaning" for lack of a better term. This creates pad fade as the pad reaches beyond its thermal capacity and creates gases from the binding agents in the pad. I understood this to be the first "stage". However, if you continue to use the brakes for extended periods of high duress, then they glaze as you described above. Am I incorrect in anything? Brian

It's true...everytime you use the brakes, some gases are created. Even without slots or holes, once you let off the brakes, the gases are released. When you hold the brakes for a long period of time or use them heavily, the gases build up and sit between the pad and rotor, and thats called glazing or pad fade. Holes and slots relieve that build up of gas. And as somebody else said, you do use your pads a little faster with holes or slots because there is more biting surfaces that cause friction. More braking forces, but shorter pad life.

Originally posted by Silv Blt

Originally posted by ForceFed420a Hmm, interesting. I guess it was my understanding that everytime you have heavy braking you create gases. However, these are not huge amounts of gas, and are evacuated by the slots (if you are equipped as such) and thus not a problem. If you don't have slots, the gases have the potential to create this "layer" between the rotor and the pad effectively "aquaplaning" for lack of a better term. This creates pad fade as the pad reaches beyond its thermal capacity and creates gases from the binding agents in the pad. I understood this to be the first "stage". However, if you continue to use the brakes for extended periods of high duress, then they glaze as you described above. Am I incorrect in anything? Brian

glazing or pad fade

So these terms are used interchangably? I thought pad fade was the gases, and glazing was the actual melting of the binding agents.

Thanks for your patience,
Brian

Originally posted by ForceFed420a

Originally posted by Silv Blt

Originally posted by ForceFed420a Hmm, interesting. I guess it was my understanding that everytime you have heavy braking you create gases. However, these are not huge amounts of gas, and are evacuated by the slots (if you are equipped as such) and thus not a problem. If you don't have slots, the gases have the potential to create this "layer" between the rotor and the pad effectively "aquaplaning" for lack of a better term. This creates pad fade as the pad reaches beyond its thermal capacity and creates gases from the binding agents in the pad. I understood this to be the first "stage". However, if you continue to use the brakes for extended periods of high duress, then they glaze as you described above. Am I incorrect in anything? Brian

glazing or pad fade

So these terms are used interchangably? I thought pad fade was the gases, and glazing was the actual melting of the binding agents. Thanks for your patience, Brian

I've heard them used interchangably, but I think you're probably correct that pad fade is the build up of gases and glazing the melting of the pad. Whether there's an actual difference or not, they're both bad and upgrading to better pads and slotted or drilled rotors will alleviate the problem.

Originally posted by Silv Blt

Originally posted by ForceFed420a

Originally posted by Silv Blt

Originally posted by ForceFed420a Hmm, interesting. I guess it was my understanding that everytime you have heavy braking you create gases. However, these are not huge amounts of gas, and are evacuated by the slots (if you are equipped as such) and thus not a problem. If you don't have slots, the gases have the potential to create this "layer" between the rotor and the pad effectively "aquaplaning" for lack of a better term. This creates pad fade as the pad reaches beyond its thermal capacity and creates gases from the binding agents in the pad. I understood this to be the first "stage". However, if you continue to use the brakes for extended periods of high duress, then they glaze as you described above. Am I incorrect in anything? Brian

glazing or pad fade

So these terms are used interchangably? I thought pad fade was the gases, and glazing was the actual melting of the binding agents. Thanks for your patience, Brian

I've heard them used interchangably, but I think you're probably correct that pad fade is the build up of gases and glazing the melting of the pad. Whether there's an actual difference or not, they're both bad and upgrading to better pads and slotted or drilled rotors will alleviate the problem.

Cool. Thanks man

Brian

TY guys Brake Fade or Pad Fade was the term I was thinking of. and to better describe Glazing it's not so much the pad bonding agents melting as it is the result of the Excessive brake fade and those gasses being trapped between the pad and rotor for long periods of time, resulting in them being forced to bond with the rotor instead of being expelled. that's why you can just drive glazing off of your rotors by using them properly for a while instead of hard braking.

I agree that cross drilled/slotted rotors will reduce pad life but I would rather have 30% less pad life than 30% less stopping power (of course that's an estimate on both numbers so don't quote me on those figures). Suggestion use good slotted rotors and Ceremic Pads and you shouldn't have to worry about brake fade.

Well, I did a little research. Found that "boundry layer" (as I said a while ago) is an acceptable term when it comes to describing the layer of gases that can exist between rotor and pad:

"While grooved, drilled and slotted rotors offer an enhanced appearance and add some resistance to the boundary layer of gasses that can build up between the pad and rotor, they are not designed to withstand the extreme temperatures that are produced on the racetrack. "

http://www.tirerack.com/brakes/tech/techpage.jsp?techid=78¤tpage=85




What causes brake pad glazing?
Brake pad glazing is caused when the brake pad friction material is overheated.
This results in crystallized friction material on the pad surface and the brake disc.
Typical symptoms of glazed brake pads include: Poor stopping performance, vibration or brake judder, and cracks or fissures in the brake pad material.
Pad glazing is typically caused by operating the brake pads at a temperature above the specified temperature range of the friction material or not properly following the 'Bedding-in' instructions for the brake pads. Always follow the manufacturers brake pad bedding-in instructions and use a brake pad that has a temperature range that is sufficient for its intended use.



http://www.raceshopper.com/tech.shtml



Resist the urge to immediately go out and hammer on the brakes with high speed, tire smoking stops. This will likely lead to pad glazing, a condition where the resins in the pad crystalize on the friction surface, resulting in poor stopping performance and excessive noise

http://www.ducatigarage.netfirms.com/brakepads.html


As I read this, I get a visual that it's not the gases bonding to the rotor, it's the fiction material (pad material) crystallizing.



Brian

Very good research Brian. Very Informative. Yes the Glazing is from the crystalizing of the pad material on the rotor this is correct. The Pad material Becomes Gaseous when it exceeds it's operating temperature. This is when you get your Brake fade the harder you push your brakes the More of the material that becomes gaseous. Then Just like you said the material Crystalizes onto the rotor and pad surfaces this is most commonly Referred to as Glazing (what we have been talking about). I was Mearly Simplifying my explanation of Glazing earlier. I have taken pleanty of brakes apart to see the Fissures you referred to in the pads caused by the material overheating, these pads also tend to have glazing on their surfaces. this is most commonly seen when brakes that were not intended for this level of performance are pushed well past their limits for long periods of time.

However I would have to remind a few people that Slotted rotors do not share the same tendencies to stress fracture as drilled rotors do. Which makes them better for racing than drilled or combo drilled/slotted. There is no real heat dissepation benetits of having slotted or drilled rotors, that is achieved by having More rotor material to soak up the heat. The only purpose of drilled or slotted rotors is to evacuate gas from between the pads and rotors. And that my friends is what we want to accomplish anyways.

Originally posted by shazow1969
However I would have to remind a few people that Slotted rotors do not share the same tendencies to stress fracture as drilled rotors do. Which makes them better for racing than drilled or combo drilled/slotted. There is no real heat dissepation benetits of having slotted or drilled rotors, that is achieved by having More rotor material to soak up the heat. The only purpose of drilled or slotted rotors is to evacuate gas from between the pads and rotors. And that my friends is what we want to accomplish anyways.

Excellent point. Sounds like we're all talking about the same thing, just using slightly different words.


Brian