Vibration When Braking (Problem and Fix)

[Slick Blackwings]

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

Nope, started returning from long weekend.
And nobody else drives it, keys kept in safe LOL

 

[Carguyshu]

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.

100% stock cumulative 24 hours of testing not 24 hours straight. If you go to spring mountain they’ll tell you some interesting stories about them testing out different stuff fir the BW like various dive plan designs on the 4. https://gmauthority.com/blog/2021/0...llac-blackwing-sedans-in-24-hour-testing/amp/

A novice or intermediate driver can be a lot harder on tires/brakes than a more experienced one. Riding the brakes, over driving the tires, & coming into corners too fast are all common.

Most factory M cars, AMG, & RS cars (with steel brakes) are nowhere near as capable as a blackwing on track for extended use. I can only go 2 laps in my RS6 before the brakes are overheated. Never have gotten even the first brake warning light on my blackwing and I’ve run it all out for 40 minutes at a time. The blackwing can handle heavy hpde use without issue if driven properly.

Your brake issues are likely due to abs engagement causing uneven pad deposits. If you brake smoothly you won’t engage the ABS & often can stop faster that way too. As mentioned in other threads other people are getting way more life out of their consumables like tires & pads

 

[Carguyshu]

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.

They tested over 20 compounds before arriving at the ones that are on the production car. We Drive the 668-HP 2022 Cadillac CT5-V Blackwing, and It's Bombastic Fantastic

It seems highly unlikely the bean counters had anything to do with the pads chosen. Have you priced them? You don’t make CCB available either if you’re worrying about bean counters.

The main obstacle was making it cooper free & brake by wire. There are a lot of additional efficiencies that went into the design of this system bc of those compromises. Watch the savagegeese video. Lots of good brake info as they relay info given to them by Tony as well as brembo.

Per my last post the 24 hour validation was done with 100% stock components (other than fluid) and clearly was not done for 24 hours straight without stopping. Instructors at spring mountain (who give some big name racers instruction) can drive really well. That’s in addition to GM’s engineering & testing teams that must work their way up certification wise to be able to push certain vehicles. There’s a lot of info out there on how the cars were tested. They can take a lot more than you think.

 

[jodakid69]

Yes folks, I am obviously guilty here:

"A novice or intermediate driver can be a lot harder on tires/brakes than a more experienced one. Riding the brakes, overdriving the tires, & coming into corners too fast are all common."

I am getting over-confident, driving over my skill level/experience. In so doing, I am also beating on the vehicle hardware. Specifically, I am killing the brakes doing hard ABS stops @ 130+ off the front straight and then destroying the tires going all out at turns 3-5 and again on 9.

I promise to be less aggressive at my next track session on Monday.

 

[Carguyshu]

Yes folks, I am obviously guilty here:

"A novice or intermediate driver can be a lot harder on tires/brakes than a more experienced one. Riding the brakes, overdriving the tires, & coming into corners too fast are all common."

I am getting over-confident, driving over my skill level/experience. In so doing, I am also beating on the vehicle hardware. Specifically, I am killing the brakes doing hard ABS stops @ 130+ off the front straight and then destroying the tires going all out at turns 3-5 and again on 9.

View attachment 20320

I promise to be less aggressive at my next track session on Monday.

Focus on getting on the gas (usually you’ll want to roll in and not mash it) as soon as possible in a corner and exiting with as much speed as you can rather than entering with as much speed as you can and braking as late as possible. You’ll be surprised how much time you pick up focusing on exiting fast rather than entering fast and braking late. Often when you enter fast and brake late the car will be or few more out of control and you’ll lose out on valuable speed going through the corner and exiting it. It’s hard to fight the urge & most of us have all been there & make that mistake. I still do from time to time if I’m trying to push too much

 

[Jim2000]

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

I had a 2017 ATS-V and I had various issues with a vibration from the front brakes. After replacing the pads and rotors, the vibration returned and after extensive research and input from brake specialists, everything points to a problem with the quality of the GM replacement rotors. You can guess where they are made. It is interesting that I have never had issues with brakes on any of my past performance cars. I have had M cars, AMG cars, and S cars. Also, I don't track my cars.

 

[jodakid69]

Focus on getting on the gas (usually you’ll want to roll in and not mash it) as soon as possible in a corner and exiting with as much speed as you can rather than entering with as much speed as you can and braking as late as possible. You’ll be surprised how much time you pick up focusing on exiting fast rather than entering fast and braking late. Often when you enter fast and brake late the car will be or few more out of control and you’ll lose out on valuable speed going through the corner and exiting it. It’s hard to fight the urge & most of us have all been there & make that mistake. I still do from time to time if I’m trying to push too much

Thanks for the coaching. You are quite correct. I will need to adjust.

 

[jodakid69]

JUL 17 Track Session update.

The brake pad/rotor vibration issue seems to be resolved with the use of the EBC brack pads. After track season I will probably change back to stock pads.