Vibration When Braking (Problem and Fix)

[jodakid69]

DISCLOSURE:
Before I proceed, in full disclosure I am not a mechanic. I am providing a few limited data points, reporting on my vehicle's performance, and providing my personal analysis regarding the performance of my vehicle's brake system performance. The braking system of your vehicle is a very important safety system and I am NOT providing guidance regarding how you should maintain the braking system of your vehicle. GM which is the OEM of Cadillac CT4V-BW and CT5V-BW vehicles does not recommend the use of "non-GM approved" brake pads or rotors for your vehicle.

BRAKE VIBRATION ISSUE:
My CT4V-BW developed moderate vibration during light to moderate braking at the steering wheel. This situation started after the vehicle had about 4250 miles. During the prior 1000 miles, the vehicle had been used in 4 track day sessions that included heavy braking from speeds of 125MPH to 135MPH. After 3 track days using the stock pads, the front braking had developed a pulsation/vibration at the steering wheel during light to moderate braking. The vibration increased after my 4th track day which was only a half day. The vibration remained after I installed two new front tires - both street driving and during my 5th track day session. In total, I had the stock brake pads in use for 5700 miles which included 5 track days.

Upon inquiry, I was informed by two Cadillac dealers, and the Chevy Dealer that performed a brake pad replacement, that I likely needed new rotors. My intent was to replace the rotors after a total of 10 track days.
View attachment 20010 View attachment 20011

BRAKE PERFORMANCE REPORT:
After having EBC metallic sintered track brake pads installed in my CT4V-BW and using them for 1 track day - (5) 20-minute sessions, the brake vibration that I was experiencing after my prior last track sessions with the stock pads has gone away.

It appears that the demise of my stock rotors has been inaccurately and prematurely predicted!

I am now back to experiencing normal braking performance under light, moderate, and heavy brake pressure. My assessment is that since EBC brake track brake pads are metallic sintered brake pads that work off of straight pad surface-to-rotor friction rather than pad-to-rotor film, use of the EBC brake pads in multiple high-speed brake applications cleared off the surface film that was causing the vibration. Reference information provided in posting #7 of the "I've Found the Secret Sauce(track pads)" thread by ALMAZING regarding metallic sintered brake pads.

I am speculating that repeated hard braking which engages the anti-lock at 135-140MPH down to 80MPH using stock CT4V-BW pads, causes uneven surface deposits to form which in turn causes the brake vibration that is felt at the steering wheel. With the switch to the metallic sintered brake pads, the surface deposits quickly were worn away and the vibration problem went away. I cannot comment on steel or carbon rotor performance for CT5V-BW.

It is interesting that the brake tech that installed the EBC brake pads noted that there were minimal rotor surface problems when he installed the EBC track brake pads, but the braking vibration continued to occur after installing the EBC track brake pads. Note that simply installing new brake pads did not "fix" the brake vibration. Therefore, their assessment was that the vibration was caused by warped rotors. The metallic sintered brake pads need to be used in multiple high-speed braking sessions to wear off the old brake pad coating. My analysis is that if you installed the stock pad or other pads that are not metallic sintered pads to "fix" the vibration problem, the new pads would not correct the problem. In fact, the brake vibration problem would persist and the dealer's solution to the brake vibration issue would be to install new rotors.

I like the solution that I stumbled upon better!

In summary, my analysis is that CT4V-BW vehicles that have stock brake pads installed and experience repeated heavy braking from 120+ MPH will likely develop uneven brake pad deposits on rotors that will cause braking vibrations. The solution to this issue is to continue to use stock pads and replace rotors or use metallic sintered brake pads. It is also possible that there are other methods to clean off uneven brake pad deposits other than using metallic sintered brake pads.

A final note is that you will be trading rotor life when using metallic sintered brake pads for street driving. So you will need to determine the amount of track use versus street use for your vehicle when selecting brake pads for your vehicle, as well as guidance provided by the OEM and professional mechanics and repair shops.

 

[FLYARMY]

We were told at Spring Mountain , that if you are going to be doing track days, that you should drain the factory brake fluid and install another brake fluid that has a higher "boiling point". I don't know what brand or part # they were referring to.

 

[almazing]

Rotor warpage is a myth from the olden days when rotors were thin and not vented. Nowadays with thicker vented rotors, it's practically impossible to 'warp' them since stock street pads will never make enough friction for the rotors to reach the temperatures needed to physically warp them. We're talking well over 1000C, which is what real racing brakes operate in. And even at 1000C, race brakes rarely 'warp'.

What you've experienced are pad deposits through repeated ABS use. Sintered pads do not leave any deposits since it uses straight metal to metal friction compared to the stock pads that leave a thin film on the rotor surface to aid in generating friction. The sintered metal 'grinded' off those uneven stock pad deposits and now you have a freshly surfaced rotor every time you're hard on the brakes. Enjoy.

Dealers and mechanics telling customers they have a 'warped' rotor are full of shit and it's just an excuse to sell new rotors. They'll take your old rotors, refinish the surface, and resell them for profit. Double money for them, less money for you.

 

[jodakid69]

Correct. When I had the EBC track brake pads installed, I had the mechanic perform a brake system flush and installed CASTROL ESF Brake Fluid.

 

[Tall Steve]

I guess I don't understand... What is wrong with the OEM brakes?

 

[jodakid69]

Rotor warpage is a myth from the olden days when rotors were thin and not vented. Nowadays with thicker vented rotors, it's practically impossible to 'warp' them since stock street pads will never make enough friction for the rotors to reach the temperatures needed to physically warp them. We're talking well over 1000C, which is what real racing brakes operate in. And even at 1000C, race brakes rarely 'warp'.

What you've experienced are pad deposits through repeated ABS use. Sintered pads do not leave any deposits since it uses straight metal to metal friction compared to the stock pads that leave a thin film on the rotor surface to aid in generating friction. The sintered metal 'grinded' off those uneven stock pad deposits and now you have a freshly surfaced rotor every time you're hard on the brakes. Enjoy.

Dealers and mechanics telling customers they have a 'warped' rotor are full of shit and it's just an excuse to sell new rotors. They'll take your old rotors, refinish the surface, and resell them for profit. Double money for them, less money for you.

You are correct in the dealer's misdiagnosis of the vibration problem. However, they might simply not know the facts. I am faily confident that if the "word" do not get out, many Cadillac owners are likely going to be buying new rotors. My question is that this brake vibration issue cannot be a "new" issue. Did brake pad buildup occur on ATS-V / CTS-V vehicles? Are the CT4V-BW brake pads the same as the ATS-V or just the size/shape?

There is a Cadillac V-Club Tech Talk with Brembo scheduled for next week and I have submitted this issue for discussion - "brake pad buildup causing vibration for CT4V-BW."

 

[almazing]

You are correct in the dealer's misdiagnosis of the vibration problem. However, they might simply not know the facts. I am faily confident that if the "word" do not get out, many Cadillac owners are likely going to be buying new rotors. My question is that this brake vibration issue cannot be a "new" issue. Did brake pad buildup occur on ATS-V / CTS-V vehicles? Are the CT4V-BW brake pads the same as the ATS-V or just the size/shape?

There is a Cadillac V-Club Tech Talk with Brembo scheduled for next week and I have submitted this issue for discussion - "brake pad buildup causing vibration for CT4V-BW."

View attachment 20014

The brake judder(what you refer to as 'warp') is common in all street based and street/track organic pads. Pads that leave a friction film on rotors. Which is practically all cars today. I can't think of any car that comes with sintered pads from the factory. There are not a lot of ATS-Vs in the wild, and even less that are being tracked, so finding information specific the the 4BW/ATS-V braking system is futile. But every performance car that has Brembos with stock pads and is driven very hard on track can come across brake judder. Physically, the stock brakes just cannot reach temperatures that could cause rotors to warp with reasonable and competent track usage, unless you make the ridiculous and tremendous effort to do so on purpose.

 

[almazing]

I guess I don't understand... What is wrong with the OEM brakes?

Nothing. The stock brakes are perfectly fine for street and track use... to an extent. The problem begins when the driver becomes faster around a track and the pads start to overheat, fade, leave uneven deposits on the rotor face, and wear quickly. See, the stock pads are street pads and also track pads. Track-ish leaning, but still street biased. So they have to work in a wide range of temperatures. From cold to hot. But for a skilled, advanced, fast driver, the stock pads won't be able to handle harder and deeper braking, which would raise brake pad temperatures far beyond their design and purpose. Aftermarket track pads solve this by moving the effective temperature range higher. So track pads have an operating temperature range that is a lot higher than stock pads. At low temps, track pads will eat rotors and itself, make a ton of noise, and dust like hell. But get it up to temp on track and a competent driver would never have to worry about brake fade or rotor deposits. There is no 'magic' pad that works in all conditions hot and cold, doesn't make noise, nor leave dust. Sintered pads are the closest to it, but they haven't been readily available since the fed banned copper on all brake pads. And even sintered pads have drawbacks that may be unappealing for many people.

Not an issue if you never track your car.

 

[jodakid69]

I guess I don't understand... What is wrong with the OEM brakes?

My personal experience is that REPEATED hard braking appears to cause uneven buildup on rotors. This will likely occur if you are using your vehicle in HPDE track sessions. This situation will likely not occur if you are using your vehicle for street driving.

The brake pad buildup appears to cause a vibration when braking. The dealer's solution to the vibration problem is new rotors. My solution, which I stumbled upon, was using non-OEM brake pads, specifically "Metallic Sintered" brake pads from EBC. I found the attached article that provides an overview of the different types of brake pads.

The other issue with the stock CT4V-BW braking system when engaging in HPDE driving is fluid overheating. This issue is solved by using a high-performance brake fluid and changing it on a yearly basis.

 

[Tall Steve]

Nothing. The stock brakes are perfectly fine for street and track use... to an extent. The problem begins when the driver becomes faster around a track and the pads start to overheat, fade, leave uneven deposits on the rotor face, and wear quickly. See, the stock pads are street pads and also track pads. Track-ish leaning, but still street biased. So they have to work in a wide range of temperatures. From cold to hot. But for a skilled, advanced, fast driver, the stock pads won't be able to handle harder and deeper braking, which would raise brake pad temperatures far beyond their design and purpose. Aftermarket track pads solve this by moving the effective temperature range higher. So track pads have an operating temperature range that is a lot higher than stock pads. At low temps, track pads will eat rotors and itself, make a ton of noise, and dust like hell. But get it up to temp on track and a competent driver would never have to worry about brake fade or rotor deposits. There is no 'magic' pad that works in all conditions hot and cold, doesn't make noise, nor leave dust. Sintered pads are the closest to it, but they haven't been readily available since the fed banned copper on all brake pads. And even sintered pads have drawbacks that may be unappealing for many people.

Not an issue if you never track your car.

Thank you for explaining it to me.... I only have one question, when Cadillac was doing the 24 hr testing on track with the Blackwings were the brakes/pads overheating and have brake fade? Didn't Cadillac have a professional drive behind the wheel during testing?

 

[almazing]

Thank you for explaining it to me.... I only have one question, when Cadillac was doing the 24 hr testing on track with the Blackwings were the brakes/pads overheating and have brake fade? Didn't Cadillac have a professional drive behind the wheel during testing?

I would think that they used actual track/race pads instead specifically for testing chassis and reliability on track. If a professional test driver takes a 4BW from the showroom floor on any given racetrack at actual pro-driver pace, the stock pads aren't gonna last longer than 3-6 laps before fading, depending on the track. Then they're gonna have to cool the brakes off, and then taking turns doing hot laps and cooldown laps for the remainder of the testing session. There's a lot of testing procedures that we aren't exactly privy to as well.

In addition, these are still street legal road cars that are track capable. But emphasis on the street part. I'm sure that at some point toward the end of reliability testing, their engineers decided on a pad compound that would do it all quite well for street and occasional track use.

Also, another thing I wanted to add is that the engineering team and bean counters are often at odds with each other. So what the engineering team WANTS to put on the car may not always make it on there because the bean counters say it's too expensive or it'll be hard to sell. It's a balancing act, but I feel that we've gotten the 4BW as good as the engineering team would want and as profitable as the bean counters would have liked.

 

[Tall Steve]

I would think that they used actual track/race pads instead specifically for testing chassis and reliability on track. If a professional test driver takes a 4BW from the showroom floor on any given racetrack at actual pro-driver pace, the stock pads aren't gonna last longer than 3-6 laps before fading, depending on the track. Then they're gonna have to cool the brakes off, and then taking turns doing hot laps and cooldown laps for the remainder of the testing session. There's a lot of testing procedures that we aren't exactly privy to as well.

In addition, these are still street legal road cars that are track capable. But emphasis on the street part. I'm sure that at some point toward the end of reliability testing, their engineers decided on a pad compound that would do it all quite well for street and occasional track use.

Ok, good enough, thanks for the info... I just drive the car and that's it.... Now I have to send an email to Mirza and ask him about it...

 

[jodakid69]

HAHAHA! .... 24hr track testing CT4V-BW on the stock production tires, brakes, and brake fluid?

If they did, they were not pushing the car. I am a novice driver that just moved up to intermediate HPDE sessions. I am getting passed by most drivers so yes I am driving the car hard, but not "really hard" and only for 20 minutes at a time. Then my next session is an hour and 20 minutes later. I just don't see how you can run a stock CT4V-BW all out on an HPDE session for an hour without overheating the tires or brakes. Unless you are running the test in cool weather like 50 degrees.

Continuous HPDE track driving will eat up tires, brake pads, brake rotors, and heat up the brake fluid. Obviously, a professional driver can drive to the edge by taking turns faster and using less brake, and or coasting into turns better so the tires do not heat up as much or wear out as fast.

Reference #1, for my 2nd session of the day I had 13 full laps plus an "out lap" and an "in lap". The total distance traveled in that 20 minute session was 22 miles. The front tires reached a temp of 180. Air temp was around 90 degrees. For a (6) 20 minute session track day, let's say the distance traveled was 120 track miles. The CT4v Manual says to replace the tires after 2 tanks of gas or 100 track miles. I have been using 1.25 to 1.5 tanks per track day since I cannot run all-out for most 20 minute sessions due to traffic. A track day = 2 hours of track time. So nominally, a 24 hour track day is the same as 12 track days or 1,400 track miles.

My left front tire needed replacement after 3 track days = 360 track miles / 6 hours of total track time. I wore out my front pads in 5 track days. I am not sure how much more stress continuous track time would put on tires and brake pads. At a minimum, I would say in 24 hours you would need at least 4 sets of tires, 3 sets of brake pads, and maybe 1 set of rotors.

Reference #2, last year I participated in an AMG Pro driving school at Laguna Seca. There was an incident where a student put an AMG E63 into the wall at the end of the front straight away because they lost their brakes. I believe it because we were red-flagged and pulled into the pit lane and my brakes were smoking. That session was scheduled for less than 20 minutes.

It is my analysis that production performance street cars are just not configured/equipped for heavy HPDE track duty, nor should we expect them to be, even "M", "AMG" or "V Cadillacs". In contrast, at the same class we also ran in AMG GT, they had ceramic brakes and had no brake problems.

CTV5V-BW with ceramic brakes is likely to be a different story, but the tires might be an issue.

 

[Tall Steve]

I'm only asking questions because I'm ignorant of the subject..... I'm not a "track" guy and don't plan to be..... I just think the Blackwing are great cars and a lot of work went into it by some very talented engineers and drivers.....

 

[Slick Blackwings]

Well, just back from the dealer I’ve got dreaded brake vibration feel it through the steering wheel. Funny thing is on hard breaking everything smooth, on lite braking from 50 MPH it vibrates. Dealers response rotors warped I can’t understand how they’re huge and we’re light on the brakes course there’s that occasional oh shit parachute moment, but this thing is designed for the track. I can’t imagine they’re warped. Anyway, full rotors and pads under warranty 7000 miles. Hopefully it’s a fluke. Also took measurements of rotor for GM minimal wear.

 

[PL69]

Well, just back from the dealer I’ve got to dreaded brake vibration feel it through the steering wheel. Funny thing is on hard breaking everything smooth, on lite braking from 50 MPH it vibrates. Dealers response rotors warped I can’t understand how they’re huge and we’re light on the brakes course there’s that occasional oh shit parachute moment, but this thing is designed for the track. I can’t imagine they’re warped. Anyway, full rotors and pads under warranty 7000 miles. Hopefully it’s a fluke. Also took measurements of rotor for GM minimal wear.

Pad deposit from the Street/Track OEM compound for sure.

What is your track experience, beginners or even sometimes experienced drivers who get a bad habit with a new car will overbrake and contribute to this problem.

 

[almazing]

Well, just back from the dealer I’ve got to dreaded brake vibration feel it through the steering wheel. Funny thing is on hard breaking everything smooth, on lite braking from 50 MPH it vibrates. Dealers response rotors warped I can’t understand how they’re huge and we’re light on the brakes course there’s that occasional oh shit parachute moment, but this thing is designed for the track. I can’t imagine they’re warped. Anyway, full rotors and pads under warranty 7000 miles. Hopefully it’s a fluke. Also took measurements of rotor for GM minimal wear.

You have 3 options here. Get sintered pads. Get the rotors resurfaced. Or find a quiet low key place where you can get to about 60 or 70 mph and do about 10 or so hard braking down to 30-40 mph to warm the brakes up. When the brakes are warm, do about 5-10 instances of 70-20 braking WITHOUT activating ABS, and hopefully that should get rid of the deposits. Or take it to the track and do your hard braking without activating ABS there.

 

[rdollie]

My closest track (Pacific Raceways), has a power-lunch hour event every couple of weeks. I've found it's the perfect and relatively cheapest way to fix brake rotor/pad issues and absolutely the best way to bed new pads!

 

[Slick Blackwings]

Pad deposit from the Street/Track OEM compound for sure.

What is your track experience, beginners or even sometimes experienced drivers who get a bad habit with a new car will overbrake and contribute to this problem.

Never tracked car, tried hard braking scenario as described above no change. There replacing rotors/pads warranty. Hard to believe after 7000 miles that everything was in heat cycled enough and set. Started out of the blue on our last road trip. Everything else is smooth before that.

 

[PL69]

Never tracked car, tried hard braking scenario as described above no change. There replacing rotors/pads warranty. Hard to believe after 7000 miles that everything was in heat cycled enough and set. Started out of the blue on our last road trip. Everything else is smooth before that.

That's pretty unusual, did someone drive your car and could of done something intense with it ?