[the duke]

I have seen several brake shudder TSB's for other vechicles but none for the 300. I have shudder when braking at speeds in excess of 80MPH. Anyone else have this problem?

 

[Northern Rider]

I have seen several brake shudder TSB's for other vechicles but none for the 300. I have shudder when braking at speeds in excess of 80MPH. Anyone else have this problem?

Duke, you might want to give this a try. I do it routinely on all of my vehicles - saves me lots of $$$:

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

 

[DanRealtor]

Shudder

Warped rotors perhaps?

 

[rmedina]

Is your steering wheel shaking when you are braking? If yes, you might want to get your rotors check. Sounds like warped rotors just like DanRealtor said.

Rmedina

 

[DZeckhausen]

Warped rotors perhaps?

Probably not. The diagnosis of "warped rotors" is almost always wrong, since the phenomenon rarely ever occurs. The vast majority of judder compaints are caused by a thickness variation in the rotors, which is the result of an uneven pad transfer layer. Brake judder can usually be avoided (and sometimes cured) by proper bedding. See: http://www.zeckhausen.com/bedding_in_brakes.htm for instructions. It's worth trying this technique before heading over to the dealer, since it's free and fun.

For those interested in the physics of what is actually going on, the following technical white paper may be of interest:
The "Warped" Brake Disc and Other Myths of the Braking System

 

[charlie D]

Bedding

I have seen several brake shudder TSB's for other vechicles but none for the 300. I have shudder when braking at speeds in excess of 80MPH. Anyone else have this problem?

Proper bedding wil eliminate this , as well as any ambiant squealing.

 

[DZeckhausen]

Proper bedding wil eliminate this , as well as any ambiant squealing.

Proper bedding will usually eliminate this unless the judder problem has gone unchecked for a while. The transition between bedded and unbedded portions of the rotor result in local hot spots that tend to accumulate more pad material and can eventually change the molecular structure of the rotor, resulting in cementite deposits. These deposits can't even be removed by turning, since the lathe's blade tends to skip over these hardened spots. When the problem has become this bad, rotor replacement is the solution of choice.

However, proactive bedding whenever you purchase a new car or install new rotors, should "inoculate" you from judder problems caused by transfer layer thickness variation.

Keep in mind that there are other root causes of judder that can be initiated by application of the brake pedal, but aren't directly caused by a brake problem. For example, the combination of old, weak shocks with worn control arm bushings and/or ball joints combined with a slight imbalance in the wheel/tire assembly can lead to a transient judder problem at certain speeds that is often triggered by a sharp input to the brakes. Diagnosis is often wrong, since attention naturally falls to the brakes as the culprit. Instead, it's the rhythmic input to a system (the car's suspension) that has a natural fundamental frequency. When the rhythmic input is a multiple (harmonic) of the suspension's fundamental frequency and the shocks are too weak to damp out oscillations, the "kick" from a sudden brake input may be enough to start an oscillation that continues until the vehicle speed falls outside a range of speeds. So, speeding up or slowing down may make the judder go away. And it's not necessarily the fault of the brakes. Most of the cars on this forum are too young for this to be happening yet.

 

[DanRealtor]

Warped Rotors

Proper bedding will usually eliminate this unless the judder problem has gone unchecked for a while. The transition between bedded and unbedded portions of the rotor result in local hot spots that tend to accumulate more pad material and can eventually change the molecular structure of the rotor, resulting in cementite deposits. These deposits can't even be removed by turning, since the lathe's blade tends to skip over these hardened spots. When the problem has become this bad, rotor replacement is the solution of choice.

However, proactive bedding whenever you purchase a new car or install new rotors, should "inoculate" you from judder problems caused by transfer layer thickness variation.

Keep in mind that there are other root causes of judder that can be initiated by application of the brake pedal, but aren't directly caused by a brake problem. For example, the combination of old, weak shocks with worn control arm bushings and/or ball joints combined with a slight imbalance in the wheel/tire assembly can lead to a transient judder problem at certain speeds that is often triggered by a sharp input to the brakes. Diagnosis is often wrong, since attention naturally falls to the brakes as the culprit. Instead, it's the rhythmic input to a system (the car's suspension) that has a natural fundamental frequency. When the rhythmic input is a multiple (harmonic) of the suspension's fundamental frequency and the shocks are too weak to damp out oscillations, the "kick" from a sudden brake input may be enough to start an oscillation that continues until the vehicle speed falls outside a range of speeds. So, speeding up or slowing down may make the judder go away. And it's not necessarily the fault of the brakes. Most of the cars on this forum are too young for this to be happening yet.

So, if I am turning my rotors and on the first cut, parts of the rotor are being cut and parts of the rotor (as in whole sections) are being completely skipped over, this is not a warped rotor?

My Q45: 154 mph, heavy car, stock brakes, had "Warped Rotors" on several occasions (also boiled the brake fluid numerous times). Each time I cut the rotors (until they got too thin, then new rotor time) whole sections were skipped over on the first cut.

The reason I ask is the article from stop tech you linked says that the author has never seen warped rotors, it's always a misdiagnosis!

Not arguing, just want to learn.


Dan

 

[DZeckhausen]

So, if I am turning my rotors and on the first cut, parts of the rotor are being cut and parts of the rotor (as in whole sections) are being completely skipped over, this is not a warped rotor?

My Q45: 154 mph, heavy car, stock brakes, had "Warped Rotors" on several occasions (also boiled the brake fluid numerous times). Each time I cut the rotors (until they got too thin, then new rotor time) whole sections were skipped over on the first cut.

The reason I ask is the article from stop tech you linked says that the author has never seen warped rotors, it's always a misdiagnosis!

Not arguing, just want to learn.

I totally understand why seasoned mechanics believe in warped rotors. Everything they see and do reinforces their misconception. For example, if they turn the rotors, the judder goes away. If they replace the rotors, the judder goes away. In both cases, if you believe the root cause to be warped rotors, the "fix" you just did will cure the problem. The catch is, the "fix" also cures pad deposition!

As for placing a rotor into a lathe and watching the blade cut into one section and not the other, that can also be explained. If you are making an aircraft quality part on a lathe, you don't use a cone shaped mounting fixture. Instead, you have a mounting surface that is completely perpendicular to the cut and you measure it with a dial indicator prior to mounting anything on it. If it's not within specification, you cut the mounting surface with your lathe. (Have you ever seen a Pep Boys employee measure and adjust a brake lathe?) And you use a 4-jaw chuck with a flat shoulder that holds the piece perfectly flat. If the piece has a section that is not going to be cut (analogous to the rotor's hat portion), you use a dial indicator to make sure the piece is being clamped perfectly flat. Only then do you begin to make the cut.

An automotive brake lathe is a terribly inaccurate device that, when used without meticulous setup technique, will usually induce several thousandths of an inch of runout into your rotor. This is runout that wasn't there to begin with. That perfectly flat rotor will appear warped because it isn't laying flat against the mounting fixture.

Back to diagnosis of warped rotors. Often, a mechanic will call and tell me he's just taken measurements of a rotor on the car and insists there is at least 8 or 9 thousandths of an inch of runout. So the diagnosis is warped rotors. I ask how the runout measurement was taken. Were the wheels simply removed and the dial indicator placed on the face of the rotors? If the only thing holding the rotor to the hub is a rotor retaining screw (or the metal clips on the 300C studs), you will get a false runout reading. You need to use washers and wheel nuts (or wheel bolts) torqued to the same setting (it doesn't have to be all the way to 100 lb-ft, you can torque them to 40 lb-ft as long as they are all the same) and only then will the dial indicator give you an accurate measure of rotor runout. If there is real runout on a newly installed rotors, I usually find a chunk of rust or debris (e.g., a metal shaving) between the hub and the rotor hat. Properly clean the hub mounting surface and reinstall the rotor and the runout goes away.

The problem is, the mechanic is expecting the rotors to be warped as an explanation for the customer's symptoms. So when he sees excessive runout during an on-car measurement, he doesn't question his measurment technique. And when he slaps the rotor onto his lathe and sees the blade only cut one section of the rotor on the 1st pass, he doesn't question his set-up. When you know the true cause of most judder problems to be pad deposition, you go back and question everything and that's when things start to make sense. For example, you can set up a fixture and take careful thickness measurements at about 20 evenly spaced locations around the rotor (same distance from hub) and you will find regions of thicker transfer layer in excess of four ten-thousandths of an inch.

If the problem was really warped rotors, then it wouldn't be cured by any of the following techniques:

1. Re-bed the brakes.
2. Install Hawk Blue race pads and drive around normally for 30 minutes of stop-and-go traffic.
3. Remove all pad transfer with a Flex-hone tool.

Once I've cured a "warped rotor" problem with brief use of an abrasive track pad, my customer becomes a true believer.

 

[DanRealtor]

Thanks

Thanks for the explanation. It does seem to make sense. Next time I have "Warped Rotors" I will be sure to carefully evaluate before turning them.

BTW: I know I am repeating myself somewhat but, in my Q45 I was able to boil the brake fluid and eventually have the pedal going down to the floor (a bit scary), in my 300C SRT-8 I tried really hard to get 'em to fade at Sears Point, 12 turns for 30-45 minutes a session 0-110mph down to 30 or 40 back to 110, all day long. NO Brake Fade, NONE! Aside from the squeal and dust, these brakes are amazing!


Thanks again for the explanations.



Dan

 

[Irwin]

warped rotor

In one of the past threads I stated I had warped rotors in my brand new rwdr "c" that the dealer replaced before I bought the car

 

[DZeckhausen]

My Q45: 154 mph, heavy car, stock brakes, had "Warped Rotors" on several occasions (also boiled the brake fluid numerous times).

Different brake pads have different failure modes when pushed way beyond their maximum operating temperature (MOT). For example, Pagid Orange race pads will be consumed rapidly when they exceed 1200 degrees F, but they last a long time at temperatures just below that. Other pads are notorious for laying down big blobs of transfer layer ("pad poop") on the rotors, resulting in judder problems. Likely that was the case with your Q45 pads.

Most street pads are not appropriate for heavy track use. The typical street pad has a MOT between 700 and 900 degrees F. The Performance Friction 01 race pads used by many of my customers and top race teams have a MOT of 2,000 degrees F.

Most track pads are not appropriate for street use because they are noisy and dusty until they reach at least 300 to 400 degrees F. Below that temperature, they are very abrasive and tend to chew up rotors. It's clear from the pad discussions on the SRT8 forum that DCX loaded up those Brembo calipers with pads more suited to the track than to the street.

You may find the following article I wrote on judder problems at the track to be interesting: http://www.zeckhausen.com/avoiding_brake_judder.htm

 

[DZeckhausen]

In one of the past threads I stated I had warped rotors in my brand new rwdr "c" that the dealer replaced before I bought the car

If the car had a judder problem right from the start, it's possible the rotor was manufactured out of tolerance. If the problem developed after driving some number of miles, then it was likely due to uneven pad transfer on the rotors. Had someone bedded the brakes properly, it might not have happened.

 

[tlim]

after trying the bedding process, it seemed to help my brake shudder at higher speeds for a short time, but did not last long. it seemed under more heat, the shudder comes back. then tried a higher performance brake pad to see if they would leave less deposits on the rotors under heat, but even after bedding, the shudder came back after heated braking. i finally broke down and changed my rotors, and so far they seem to holding off the shudder. it certainly brings the fun back to driving and braking. hard to conclude if the problem was brake deposits on the rotors due to bad pads, or rotors warping, but i have never had this problem (other than rotors wearing to below minimum thickness, and i rarely turn rotors) on any other vehicle i've owned.

 

[Americano]

That's the problem we've been having with our 300. You feel the brakes shutter & it only gets worse as you brake from higher speeds. I don't think that special pads & special break-ins would cure the problem. Especially since all 4 rotors have been turned & the current/stock pads are fine.

Has anyone else found a remedy for this problem?

 

[DZeckhausen]

That's the problem we've been having with our 300. You feel the brakes shutter & it only gets worse as you brake from higher speeds. I don't think that special pads & special break-ins would cure the problem.

Have you even tried the bedding process? It's not a "special" break-in. It's the normal break-in that's used to obtain optimum performance from any street or track pad, and it very often cures judder problems.

Especially since all 4 rotors have been turned & the current/stock pads are fine.

This may be a problem, since the very act of turning a rotor under the incorrect assumption that it was "warped" often introduces enough runout to cause significant judder that can not be fixed by bedding.

Has anyone else found a remedy for this problem?

Yes. Hundred of people have. It's right here: Instructions for bedding in your brakes

 

[stevesrt8]

thanks Dave

This may be a problem, since the very act of turning a rotor under the incorrect assumption that it was "warped" often introduces enough runout to cause significant judder that can not be fixed by bedding.

And I always wondered why my "nutcase" extreme machinist brother-in-law takes so long to turn a rotor. I've seen him take ten minutes just getting it all clamped down and turning true before he even begins a cut!

 

[Northern Rider]

As soon as you take ANY MAKE of car to a service department with brake shudder, they always seem to diagnose "warped rotors". They want to replace the rotors and pads. $$$$!

I have rarely ever seen any tech bed in brakes. It takes too much time and they usually don't have the open roads around their shop.

If you want to save money, follow Dave's advice. I run a fleet of vehicles in my business and the "bedding in" procedure has saved us thousands of dollars. It has also put a smile or two on the faces of my drivers.

 

[QABDJ]

2010- Brake Shudder Update! HELP!

As soon as you take ANY MAKE of car to a service department with brake shudder, they always seem to diagnose "warped rotors". They want to replace the rotors and pads. $$$$!

I have rarely ever seen any tech bed in brakes. It takes too much time and they usually don't have the open roads around their shop.

If you want to save money, follow Dave's advice. I run a fleet of vehicles in my business and the "bedding in" procedure has saved us thousands of dollars. It has also put a smile or two on the faces of my drivers.

Ok Guys... Just got my car back this morning from the dealership. All 4 rotors were replaced (Have been turned at my expense, now replaced at the dealerships expense) No pads have been replaced.

The problem was I had shudder at high speeds. Car shake, steering, etc. They said my brakes were overheating and my rotors needed to be replaced, as well as a brake line which took 2 days to get. All said and done, 50+ miles they drove it. I pick it up this morning, brakes feel like brand new (As they should now!). Get on the highway, going about 90, car swings out, I hit the brakes and bumm bumm bumm bumm, that familiar vibration is back in the car, as well as in the interior, like someone rolled a rear window down just a bit at high speeds.

I called the dealership and they said bring it back. It's all under warranty so I figure I'd allow the pads to form to the shape of the new rotors and put a 100 or so miles on it..

This happens at 80-60-40 Mphs. But not all the time.. I was going 60 and nothing, braked really well.. Another time at 60 it shook like an amusement ride, still slowed but that shake crap has to go!

I know they should've replaced the pads, my gut feeling and common sense tells me that.

Should I give it a bit longer for the brake pads to smooth out to the new rotor surface?

One more question; Slotted Rotors, is the slot directional or does it matter at all? Drivers side orientation looks correct, passenger side is opposite. Just a question. Slotted is more for cooling that I've read.

If anyone could help me out with a professional opinion it would be greatly appreciated! I'm so tired of this dealership but they are the closest and its all warrantied, OEM, etc..

Thanks everyone for the input and comments!

-D.J.

 

[Thorium]

I called the dealership and they said bring it back. It's all under warranty so I figure I'd allow the pads to form to the shape of the new rotors and put a 100 or so miles on it..

This happens at 80-60-40 Mphs. But not all the time.. I was going 60 and nothing, braked really well.. Another time at 60 it shook like an amusement ride, still slowed but that shake crap has to go!

That dealers are happy to replace all rotors, I learned. Strange they didn't take the oportunity to replace the pads also. Am I being insensitive to my dealer's needs?

The problem coming and going at the same speeds is an important clue. That would concern me.

- One possibility is that you have gotten deposits on your disk in between the time you noticed it had "gone" and by the time you noticed it had "returned", is this possible? Let say you have come to a complete stop with hot brakes, and got some residue stuck on the rotors (again)? I cleaned my rotors with new pads, but your rotors have just been turned, so you shouldn't have this problem.

- Could you have a resonance problem, so that what you notice at 60 might not be noticeable at 65, hence "coming and going"?

- Another possibility is that something is shifting, like wheel bolts not tight, bearing worn out, or something else moving when it shouldn't. Probably not, but I thought I would check.

- Front wheel alignment? Toe-in causing change in vehicle direction depending on what wheel has the most weight on it, leading to low frequency wobble. (Should feel very different/slow)

- Lastly, you can have ABS playing tricks on you. Never happened on my 300, but I have seen this on other vehicles. Any chance ABS thinks you are slipping when braking hard, and it starts pulsing the brakes?