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Discussion Starter #1
I've been meaning to write this tech tip up for a long time and finally found some free time to do it. This is a technique for avoiding the dreaded brake shimmy monster that I have been explaining to people again and again. Now I can just point them to a link.

I hope some of you find this useful!

http://www.zeckhausen.com/avoiding_brake_judder.htm

If anyone has ideas for improved readability, notices a spelling error, or has any other suggestion for improvement, I would love to hear it.
 

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Dave,

Thanks for the excellent article and great advice as you always provide.

I have always heard that it's best to stay in the same family if one is using track and street pads. I.e. Performance Friction street and track or Hawk street and track. Is this a myth or does it have any bearing? It seems to me that using your technique, it should not matter.

Best,

Najeeb
 

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One other question:

You state, "This "transfer layer" forms molecular bonds to the pads when you apply the brakes. As the rotors rotate underneath the pads, these bonds are torn apart. The resistance of the bonds to being broken yields additional friction above and beyond the abrasive action of the pads and rotors scraping against each other."

As the bonds are torn apart, does it help to rebed the brakes to get new bonds. I have frequently experienced that brakes don't feel as "sticky" after driving for a while as they did when new. Could this be the reason?
 

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Discussion Starter #4
01M5 said:
As the bonds are torn apart, does it help to rebed the brakes to get new bonds. I have frequently experienced that brakes don't feel as "sticky" after driving for a while as they did when new. Could this be the reason?
New bonds are formed as quickly as the old bonds are broken. This is an ongoing process that continues as long as there is a transfer layer remaining on the rotor. Hard braking refreshes the transfer layer. So if you drive like a granny for a few months, you may need to re-bed the brakes. But with agressive driving and late braking, such as what one normally does with an M5, the transfer layer should be maintained.

The first hint that your brakes might need rebedding is that they begin to squeal under light brake pedal pressure.
 

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Discussion Starter #5
01M5 said:
I have always heard that it's best to stay in the same family if one is using track and street pads. I.e. Performance Friction street and track or Hawk street and track. Is this a myth or does it have any bearing? It seems to me that using your technique, it should not matter.
Certain pad formulations are more compatible than others when you swap back and forth without without cleaning off the rotors first. But with this technique, you don't need to worry about compatibility, since you end up with clean rotors each time.
 

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Hi, Dave -

Great article - I think it will be very helpful to people.

I would suggest adding the following:

"Note that coming to a full stop and leaving the brake pads in contact with very hot rotors causes transfer of additional pad material -but only in one spot. The next time the brakes are applied, this spot, having different friction characteristics than the rest of the rotor, will generate more heat, which in turn causes more (uneven) material transfer. The result is a perpetually uneven surface that can cause severe judder. Always cool the brakes as evenly as possible, and roll to your final stop in the pits - release the brake before you stop if possible, or immediately upon stopping. Do not set the parking brake either. Use a wheel chock to prevent the car from rolling."
 

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Discussion Starter #7
greg said:
Hi, Dave -

Great article - I think it will be very helpful to people.

I would suggest adding the following:

"Note that coming to a full stop and leaving the brake pads in contact with very hot rotors causes transfer of additional pad material -but only in one spot. The next time the brakes are applied, this spot, having different friction characteristics than the rest of the rotor, will generate more heat, which in turn causes more (uneven) material transfer. The result is a perpetually uneven surface that can cause severe judder. Always cool the brakes as evenly as possible, and roll to your final stop in the pits - release the brake before you stop if possible, or immediately upon stopping. Do not set the parking brake either. Use a wheel chock to prevent the car from rolling."
While reading your (excellent) comments, I realized there was a disconnect between the title of my article and the original intent. I did not start out for it to be a comprehensive guide to avoiding judder at the track. I intended it to be a guide to switching back and forth between street and track pads without causing judder.

After a few moments of reflection, I decided against changing the title and in favor of expanding the scope of the article. When I get another batch of free time, I will incorporate the points raised in your post. My mindset had been that the tips you suggested were already pretty much common knowledge and that the track pad being used as a rotor cleaning tool was less well understood. But there are always new people coming into the world of track events and having a single article comprehensively address the care and feeding of brake rotors to avoid judder is a good idea.

Thank you very much for your comments! :cheers:
 

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Discussion Starter #8
The article is updated. Thanks again, Greg!
 

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Excellent write-up Dave. Thanks for contributing. Jeff :cheers:
 

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DZeckhausen said:
New bonds are formed as quickly as the old bonds are broken. This is an ongoing process that continues as long as there is a transfer layer remaining on the rotor. Hard braking refreshes the transfer layer. So if you drive like a granny for a few months, you may need to re-bed the brakes. But with agressive driving and late braking, such as what one normally does with an M5, the transfer layer should be maintained.

The first hint that your brakes might need rebedding is that they begin to squeal under light brake pedal pressure.
It is currently happening on my wife's Land Cruiser which is driven like a granny (especially when the baby is traveling). And it the brake do squeal like crazy. Thanks for the tip and I'll sneak it out and rebed the brakes.
 

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Discussion Starter #11
01M5 said:
It is currently happening on my wife's Land Cruiser which is driven like a granny (especially when the baby is traveling). And it the brake do squeal like crazy. Thanks for the tip and I'll sneak it out and rebed the brakes.
The Land Cruiser/Lexus LX470 is notorious for this problem and it has to do wtih the factory pad selection. If the bedding doesn't work, you may need to have your dealer turn the rotors on the car. Removing rotors from the Land Cruiser is not straight forward.
 

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DZeckhausen said:
The Land Cruiser/Lexus LX470 is notorious for this problem and it has to do wtih the factory pad selection. If the bedding doesn't work, you may need to have your dealer turn the rotors on the car. Removing rotors from the Land Cruiser is not straight forward.
David,

Great improvement after re-bedding the pads. Thanks for your great advice and for your teachings.

Najeeb
 

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i agree with the article but will continue to swap my front rotors with the pads, it takes 10 additional minutes to swap the StopTech rotors when swapping pads which is less time than bedding takes

it's hard for me to find a good place to bed brakes on the street, and i don't like to waste a track session bedding the track pads (if you do the math, and extra set of rotors is cheap compared to using up track sessions bedding)
 

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stever said:
i agree with the article but will continue to swap my front rotors with the pads, it takes 10 additional minutes to swap the StopTech rotors when swapping pads which is less time than bedding takes

it's hard for me to find a good place to bed brakes on the street, and i don't like to waste a track session bedding the track pads (if you do the math, and extra set of rotors is cheap compared to using up track sessions bedding)
I was cool with that philosophy, since I already bought a spare set of StopTech rotors. And then I learned that another set of AeroHats and hardware would cost another $500+! And then, without even starting, I went back to my old way of doing it! :)

Luckily, most of the tracks I frequent are out in the country, so public bedding is less of a concern. Some of the local farmers must know what time of year it is by the Carbon Black beast that keeps flooring it and slamming on the brakes in a seemingly endless cycle. Crazy city folk! At least the cattle seemed entertained....

BTW, driving to DEs on my PF-01s does seem to polish those rotors quite well. And leaving them on for a day or two afterwards has the same effect. That is only half of the equation (polishing/cleaning), however. I did not sufficiently bed my street pads after the last track event, and am experiencing judder on the street. Looks like it's time for a good ole' Zeckhausen bedding!

Great write-up, as always, Dave! Thanks for taking the time.

And great prices on the 4-wheel StopTech setup!! If I hadn't already taken the plunge, that would have been enough to reel me in.

-Dave
 

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Good article Dave, here I thought it was just my driving style, and cruddy EBC pads.
 

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"Some of the local farmers must know what time of year it is by the Carbon Black beast that keeps flooring it and slamming on the brakes in a seemingly endless cycle. Crazy city folk! At least the cattle seemed entertained...."

THAT IS HILARIOUS TEUTONADDICT!!
:cheers:
 

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Discussion Starter #17
6spd said:
Good article Dave, here I thought it was just my driving style, and cruddy EBC pads.
Don't blame yourself in this case! The EBC pads (assuming they are Greenstuff) are the most notorious pads in the world for developing brake judder problems. Even following my instructions, it's likely the EBC pads will give you trouble.
 

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Dave,

Thanks for the article, very informative as ever.

However, I would like to comment on your firm believe that discs do not warp (Entirely based on facts, no doubt). I have a set of 3 month old OEM BMW floating discs laying in the garage, to prove you wrong. After a long day at the Nurburgring (with minimal cooling down, I have to add, but no parking on handbrake or holding the pedal) they were shuddering as hell, as they always did, but this time it didn't go away after a couple of days. After checking everything out, I noticed that the distance between the brake anchor and the disc varied while spinning the disc around. Even after thouroughly cleaning the hub and the disc, it was noticeable to the naked eye. And surely, after measuring them, I can conclude they are warped by about 2 mm. This is on a E36 M3 GT with Ferodo DS2500 pads.

No problem really, as BMW was kind enough to give me another set under warranty, and I will try to get these discs turned so I'll have a spare set.

Anyhoo, just thought I'd add some more rumours to the whole "warping" myth.. :3:

Regards,

Gerrit
 

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Dave yes they are, but they will never be on it again.
I have a set of PDR/axxis and vented rotors.
I've had these rotors for sometime now. Bought them for regular rotor price as they were miss labeled in the store.
 
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