old pads vs new rotors
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From: Longing for my ol' white '02 WRX :(
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old pads vs new rotors
I have that grooved stock rotor problem ('02 WRX). I've had my current pads on for about two months of city driving, about 2000mi total. I want to take my rotors in to get resurfaced today but change the pads tomorrow myself (as well as put in SS lines and Motul).
Would there be a problem with one day's worth of driving the old pads that probabaly have acclimated to the grooved rotors? Would they regroove the resurfaced rotors, in that short of a period of time?
jason
Would there be a problem with one day's worth of driving the old pads that probabaly have acclimated to the grooved rotors? Would they regroove the resurfaced rotors, in that short of a period of time?
jason
@Stoptech
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From: San Francisco, CA
Car Info: 2002 WRX Wagon
why don't you just take the rotors off, go get them surfaced while you wait, then change the pads and discs at the same time? i know it's not ideal to bed in new pads and discs at the same time, but IMO it can be done without any adverse effects. then you can just wait till tomorrow to put in the lines and fluid. i hope you have speed bleeders.
in regards to your second question, no the old pads would not groove the new rotors, especially if you drove mellow. it really doesn't matter though because in order to bed the new pads in, you'll have to remove the old pad material with the new pads and then apply the new pad material to the surface of the rotors by bedding them in.
before you do any of this, there are a couple things you MUST read. the first is http://www.stoptech.com/whitepapers/...otors_myth.htm and yes you have to read the WHOLE thing.
The second is in the following post because it contains WAY TOO MUCH GREAT FOCKING INFORMATION.
in regards to your second question, no the old pads would not groove the new rotors, especially if you drove mellow. it really doesn't matter though because in order to bed the new pads in, you'll have to remove the old pad material with the new pads and then apply the new pad material to the surface of the rotors by bedding them in.
before you do any of this, there are a couple things you MUST read. the first is http://www.stoptech.com/whitepapers/...otors_myth.htm and yes you have to read the WHOLE thing.
The second is in the following post because it contains WAY TOO MUCH GREAT FOCKING INFORMATION.
Last edited by Steppin Razor; Jul 3, 2003 at 10:50 AM.
@Stoptech
iTrader: (5)
Joined: Nov 2002
Posts: 2,416
From: San Francisco, CA
Car Info: 2002 WRX Wagon
I deal with 1-3 calls a day relating to pad transfer and vibration issues, and I'm pretty sure we have it right in terms of a general analysis. (I'm actually SURE we have it right, but don't have the energy for a full blown online brake pad Jihad today...)
All modern brake pads are what are referred to as an Adherent type of pad. The pad is designed to transfer a layer of pad material onto the rotor. When a sufficient and EVEN layer of pad material is adhered to the rotor face, the pad material on the rotor, interacting with the similar material on the pad creates the most efficient friction mechanism. These like materials, breaking against each other on a molecular level are what really stops the car well. To emphasize, there is supposed to be a layer of material on the rotor.
The problems occur if the pads are not properly bedded-in (an even layer of pad material on the rotor) and run aggressively, OR if the pads are overheated (street pads on the track like I tell 37 people a week NOT to do). The pad transfer occurs most efficiently at the pads optimal operating temperature. That means a higher temperature pad needs to be hotter to properly transfer material. If you have a high performance pad and never run it hot enough to get a nice layer of material onto the rotor, it will never be properly bedded-in. Then, even after 1000 miles of easy street driving, you blast your favorite canyon, heat the brakes and get uneven deposits on the rotor causing a vibration.
The other common scenario is over-heating the pads even if they are properly bedded-in. In this case, the pad material starts to break down and smear onto the rotor face, again causing the UN-EVEN deposits.
The other problem that occurs is if the system is really hot and you come to a complete stop and leave your foot on the brake pedal. In this instance, we get what we call "pad imprinting" where a small layer of material breaks off the surface of the pad and literally can be seen as an imprint of the pad on the rotor face. This can occur no matter the state of bed-in.
All these scenarios leave very small, uneven layers (we call it TV, Thickness Variation) of material on the rotor. We're talking a few 10/1000's of an inch, like a TV of 0.0003". It starts out almost imperceptibly, but as the pads start to skip over the high spots, more material is deposited on those areas, ever increasing the vibration until it becomes quite noticeable, even days after the event that started it occurs.
The best way to avoid these problems is proper bed-in of the system initially, and using the proper pads for your exact driving conditions. If you are planning on swapping pads for a track day, you need to re-bed them before the event (or dedicate the first session to bed-in). Remember, you have that layer of street pad material adhered to the rotor face, and if you don't remove and replace it with the track pad material, it is going to degrade from the heat and... yep, cause uneven pad deposits. Same goes when you put the street pads back in, you need to re-bed them for optimal street performance.
The article on the Technical page of our website referenced earlier in the thread is an excellent source of additional information. It’s titled “The Warped Brake Disc and Other Myths of the Braking System”. Here’s the link again:
http://www.stoptech.com/technical/
OK, now that we hopefully better understand why the steering wheel is shaking out of my hand, what can be done to cure it? Turning the rotors will take care of it, but you will be shortening the life of the rotor and decreasing its ability to absorb and control heat, as there will be less mass. Also, turning a 2-piece rotor that uses floating attachment hardware between the rotor and hat can be tricky. We have had very good success running an aggressive track pad at lower temperatures on the street in order to scrub off the rotor surface. We have found the Hawk Blue 9012 race pad to be very effective. At lower temperatures it is very Abrasive, not becoming Adherent until it reaches it’s optimal operating temperature. If it is used with a few firm stops at a time, not getting too hot (we want to remove material, not transfer more), it will often remove the source of vibration. A WARNING: Do not leave an abrasive pad in the caliper longer than necessary to solve the problem. We have had rotors destroyed in under a week by leaving the aggressive pads in on the street.
I hope this clarifies more than mystifies. The bottom line is proper bed-in and proper pads for the conditions will effectively keep pad deposition related vibrations from sidelining your car.
Please feel free to contact me if you have any questions-
Matt Weiss
StopTech
mweiss@stoptech.com
All modern brake pads are what are referred to as an Adherent type of pad. The pad is designed to transfer a layer of pad material onto the rotor. When a sufficient and EVEN layer of pad material is adhered to the rotor face, the pad material on the rotor, interacting with the similar material on the pad creates the most efficient friction mechanism. These like materials, breaking against each other on a molecular level are what really stops the car well. To emphasize, there is supposed to be a layer of material on the rotor.
The problems occur if the pads are not properly bedded-in (an even layer of pad material on the rotor) and run aggressively, OR if the pads are overheated (street pads on the track like I tell 37 people a week NOT to do). The pad transfer occurs most efficiently at the pads optimal operating temperature. That means a higher temperature pad needs to be hotter to properly transfer material. If you have a high performance pad and never run it hot enough to get a nice layer of material onto the rotor, it will never be properly bedded-in. Then, even after 1000 miles of easy street driving, you blast your favorite canyon, heat the brakes and get uneven deposits on the rotor causing a vibration.
The other common scenario is over-heating the pads even if they are properly bedded-in. In this case, the pad material starts to break down and smear onto the rotor face, again causing the UN-EVEN deposits.
The other problem that occurs is if the system is really hot and you come to a complete stop and leave your foot on the brake pedal. In this instance, we get what we call "pad imprinting" where a small layer of material breaks off the surface of the pad and literally can be seen as an imprint of the pad on the rotor face. This can occur no matter the state of bed-in.
All these scenarios leave very small, uneven layers (we call it TV, Thickness Variation) of material on the rotor. We're talking a few 10/1000's of an inch, like a TV of 0.0003". It starts out almost imperceptibly, but as the pads start to skip over the high spots, more material is deposited on those areas, ever increasing the vibration until it becomes quite noticeable, even days after the event that started it occurs.
The best way to avoid these problems is proper bed-in of the system initially, and using the proper pads for your exact driving conditions. If you are planning on swapping pads for a track day, you need to re-bed them before the event (or dedicate the first session to bed-in). Remember, you have that layer of street pad material adhered to the rotor face, and if you don't remove and replace it with the track pad material, it is going to degrade from the heat and... yep, cause uneven pad deposits. Same goes when you put the street pads back in, you need to re-bed them for optimal street performance.
The article on the Technical page of our website referenced earlier in the thread is an excellent source of additional information. It’s titled “The Warped Brake Disc and Other Myths of the Braking System”. Here’s the link again:
http://www.stoptech.com/technical/
OK, now that we hopefully better understand why the steering wheel is shaking out of my hand, what can be done to cure it? Turning the rotors will take care of it, but you will be shortening the life of the rotor and decreasing its ability to absorb and control heat, as there will be less mass. Also, turning a 2-piece rotor that uses floating attachment hardware between the rotor and hat can be tricky. We have had very good success running an aggressive track pad at lower temperatures on the street in order to scrub off the rotor surface. We have found the Hawk Blue 9012 race pad to be very effective. At lower temperatures it is very Abrasive, not becoming Adherent until it reaches it’s optimal operating temperature. If it is used with a few firm stops at a time, not getting too hot (we want to remove material, not transfer more), it will often remove the source of vibration. A WARNING: Do not leave an abrasive pad in the caliper longer than necessary to solve the problem. We have had rotors destroyed in under a week by leaving the aggressive pads in on the street.
I hope this clarifies more than mystifies. The bottom line is proper bed-in and proper pads for the conditions will effectively keep pad deposition related vibrations from sidelining your car.
Please feel free to contact me if you have any questions-
Matt Weiss
StopTech
mweiss@stoptech.com
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From: Plymouth, MN
Car Info: 94 T-Leg Sedan and a 00 M5
Excellent article. I now have another item in my "favorites". I wish I had known more about pad/rotor break-in a last weekend when I finished my upgrade. I did it wrong. Oh well, live and learn. I won't make the same mistake again.
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