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Mentioned I'd be at Watkins Glen, which I have been for the past three days.
First day, all four brand new rotors, pads, wheels free of "road marbles", road force balanced...
I've been tracking since 2018, so not a whole long time, but my previous car, 2017 C7 Z06, never had these issues, and I drive basically the same. I usually run in advanced groups, and with my 2017 C7 Z06, I was fine always running in sport track mode. Never felt the need for race 1 or race 2, I'm too old to be a Nascar driver, so not trying to set track records.
Sold the 2017 last year, got the 2024 Stingray in June last year, broke it in, had personal things / vacations, so started tracking this year in April.
Running again in sport mode, but finding my driving style or the car leads to very violent vibrations during hard braking that even continue through the turns / corner.
Here's what usually happens:
1. First lap or two, vibrations are at a minimum.
2. Next few laps, violent vibrations.
3. Final few laps, vibrations tend to revert to the first couple of laps.
I've replaced the wheel hubs, taken it to the dealership, have an MDI 2 and GM subscription, analyzed Cosworth PI toolbox data, nothing...
I have a a theory here, wondering if there's anything to this...
Sport mode in the C8 is much more aggressive and applying ESC / traction control more aggressively that the C7? I don't see the "esc" light go on when this happens though... I have had better luck in Race 2 mode, but when at a new track, i.e. Watkins Glen, I wanted a bit of "safety" first...
When I aggressively brake, i.e. trail braking, the vibration seems worse, if I do less than aggressive braking, the vibration seems to be less. However again, my braking style hasn't changed from my C7, which was much more powerful and faster, and never had vibration / braking issues.
For my C8, running Apex wheels, Front: 18x10” ET42, Rear: 19x11.5” ET48
Tires right now: Toyo R888R, Front: 275/35, Rear: 325/30
Brake rotors: EBC, same issue with Girodisc
Brake pads: Hawk DTC-70 front / DTC-60 rear, had same setup with my C7 Z06. Tried Carbotech XP-20's on all 4's with Girodisc, before changing to Hawk and EBC to see if that was the problem...
Did you mark your tires to see if they're spinning on the wheel? If they do, then your balance will be way off. Check if your wheels are currently out of balance (that'd be a clue), and if so rebalance them and this time put a line on the tire by the valvestem to see if it slips...
Did you mark your tires to see if they're spinning on the wheel? If they do, then your balance will be way off. Check if your wheels are currently out of balance (that'd be a clue), and if so rebalance them and this time put a line on the tire by the valvestem to see if it slips...
The C8 has a hybrid brake by wire system. Could you be simply exceeding the ABS threshold? Unlike other cars, the pedal will not be vibrating during ABS operation, so it'd be hard to know if ABS is engaging, short of wheel vibrations.
I've actually had this issue with CCB brake booster profile (which is part of this brake by wire system; brake booster seems to have a different tune/map per C8 model), and high bite pads. I had to switch to milder 'enduro' type pads with less initial bite to fix this issue.
The C8 has a hybrid brake by wire system. Could you be simply exceeding the ABS threshold? Unlike other cars, the pedal will not be vibrating during ABS operation, so it'd be hard to know if ABS is engaging, short of wheel vibrations.
I've actually had this issue with CCB brake booster profile (which is part of this brake by wire system; brake booster seems to have a different tune/map per C8 model), and high bite pads. I had to switch to milder 'enduro' type pads with less initial bite to fix this issue.
The pedal vibrates, the sterring wheel, the entire car vibrates violently. You can barely read the HUD display the car is vibrating so much...
I'm running out of ideas : ) I'd try to repro the vibrations with a different set of wheels/tires if you have another set, to eliminate any issue with the front tires and wheels (it must he coming from the front if it shakes everything up front).
I'm running out of ideas : ) I'd try to repro the vibrations with a different set of wheels/tires if you have another set, to eliminate any issue with the front tires and wheels (it must he coming from the front if it shakes everything up front).
Yes, I'm running out of ideas as well... Had a different set of tires, Goodyear at VIR, Road America and got the vibration, tried Toyo at Road America and now Watkins Glen, still vibration. New wheels as well, same brand / size: Apex, but new.
It's just strange how the vibration comes and goes. If it was all the time, I could understand it better.
So it's looking like ABS is kicking in quite often, but it must be more aggressive than the C7 as my braking style hasn't changed. Also it appears as though the ABS kicks in more as the brake pad thickness decreases...On new pads my braking style is the same as later in life pads after a day or so of track life.
My first day at Watkins Glen, really no vibration. Second day, some vibration, 3rd day even worse vibration. Same set of pads, they were done by the 3rd day. if it wasn't for the fact this was the first time at this track, the pads would have been done by the second day.
Maybe my braking style is incorrect for this C8 car and needs to be adjusted vs. what I was accustom to on my C7 Z06...
All the blue marks around the track outline denote ABS kicking in...
Just so you know, I was using highest bite pads with my C7, too, and never had these issues.
I'm not sure about Z51 part numbers. I think EBC SR11 could be a good start. KNSBrakes.com has them, and there are cheaper places online, too.
I'm using Pagid RS1, but I buy it directly from UK (half the price), and they're for my AP calipers..
OK, thank you...
Going to Mid-Ohio next week, have to change pads, and have some Carbotech XP24's with me, just because I had them before I saw that they aren't that great. Will try them, then try some EBC's, heard good things about them.
During the Winter / off season, I'm going to get some AP calipers. Mostly because changing front pads on these C8's is such a pain vs. C7.
If you run the z51 brakes hard you almost always end up with judder, then the rotors are junk. Even if you resurface them the metallurgy of the rotor has been changed and it comes back. The "semi brake by wire system" gives very poor feedback to the driver and you end up over braking a lot. The AP brakes are great, but they are 10K. I bought Z06 brakes from GM when they were on sale and got both front and rear for under 4K. The kicker is to avoid having to spend 1K on parking brakes you have to move them to the trunk. It is fairly easy. I'm on G LOCK R8 pads which is their enduro pad. Long lasting and easy on the rotors. The EBC SR11 pads are a sintered metal pad which is great, but they do not have a pad for the rear in that compound. If you are interested I have a complete parts list for the Z06 brakes. Not as light or elegant as the AP setup, but similar performance at half the price. Paragon makes replacement rings for the GM Z06 top hats which come with all new hardware for around $700. Z06 rear w/o parking brake Front Z06 Parking brakes in the trunk
Thank you for the information, I don't run the stock pads / rotors, have tried Girodisc as I did on my C7 and tried EBC rotors as well. I'm not that interested in losing the parking brake, so may just have to bite the expense for the AP brakes, plus I like their option to have 1" thick pads...
Just a thought, is it possible that when the ABS kicks in it "unevenly" scrubs some of the deposited pad material from the rotors thereby causing the judder? Is the ABS kicking in on the first few laps when things are not as bad or does it start to kick in when you are having the issue. Frustrating for sure.
Just a thought, is it possible that when the ABS kicks in it "unevenly" scrubs some of the deposited pad material from the rotors thereby causing the judder? Is the ABS kicking in on the first few laps when things are not as bad or does it start to kick in when you are having the issue. Frustrating for sure.
It seems like when the pads are newer, ABS / vibration kicks in less. And also if I go out for a session, let's say it's 30 minutes. The first few laps, things are fine, the middle few laps, it's very violent vibration, the last few laps vibration is reduced and sometimes goes away altogether. Like the car is learning how I am driving during a session, just weird. But then it starts all over the next session.
I've even tried to "reset" ABS per procedures I've seen on here, but don't think that works, I never hear the "clicking" that's mentioned.
Not sure what mode you run in but curious if changing from Sport to Race1 or 2 would result in a difference in the issue. May be worth a try and see if it provides any clues.
The uneven pad deposition is caused by heat. Once the metallurgy of the rotors is changed they are junk. I initially had trouble with the stock brembo pads and rotors. Spent 1K with KNS on his "super rotors" and Carbotech pads. This set up lasted exactly 30 minutes and the judder was back. That was a fast 1K spend. The Z51 package is severely under braked if you are going to push the car hard. The front calipers are off a Camaro, the rears off an Escalade. Nothing special. GM basically admits the car is under braked because they put a much larger braking system on the Z06. Think about it, both cars are the same weight one just has more HP. You are going to have to slow down the same amount of speed entering a given corner most of the time, so why does the Z06 need much bigger brakes? The Z51 is under braked for heavy track use. As to the drive by wire issues, use Z mode or my mode and set the brakes to minimum sensitivity, everything else to max ptm off. Get enduro pads.
The AP kit is the way to go if you don't mind spending the 10K. The Z06 stuff with the enduro pads eliminated the judder issues. Moving the parking brakes to the trunk, reduces unsprung weight, gives you a little more "tail weight", being so far back on the car the weight has a little more leverage. Also it removes a heat sink spot from the rear rotors. I'm having trouble adjusting to driving a car on a track with power brakes. I circle tracked for 20 years and always had manual brakes. They are the best for feel. Cup cars weigh a ton but they all have manual brakes. Porsche has made their power brake system to have a feel similar to manual brakes.
Manual brakes are often preferred in racing due to their superior consistency and feel, allowing for more precise control and predictable braking performance. While they require more physical effort, the increased feedback and ability to modulate braking at the edge of lock-up can lead to faster lap times and improved driver confidence
Not sure what mode you run in but curious if changing from Sport to Race1 or 2 would result in a difference in the issue. May be worth a try and see if it provides any clues.
The uneven pad deposition is caused by heat. Once the metallurgy of the rotors is changed they are junk. I initially had trouble with the stock brembo pads and rotors. Spent 1K with KNS on his "super rotors" and Carbotech pads. This set up lasted exactly 30 minutes and the judder was back. That was a fast 1K spend. The Z51 package is severely under braked if you are going to push the car hard. The front calipers are off a Camaro, the rears off an Escalade. Nothing special. GM basically admits the car is under braked because they put a much larger braking system on the Z06. Think about it, both cars are the same weight one just has more HP. You are going to have to slow down the same amount of speed entering a given corner most of the time, so why does the Z06 need much bigger brakes? The Z51 is under braked for heavy track use. As to the drive by wire issues, use Z mode or my mode and set the brakes to minimum sensitivity, everything else to max ptm off. Get enduro pads.
The AP kit is the way to go if you don't mind spending the 10K. The Z06 stuff with the enduro pads eliminated the judder issues. Moving the parking brakes to the trunk, reduces unsprung weight, gives you a little more "tail weight", being so far back on the car the weight has a little more leverage. Also it removes a heat sink spot from the rear rotors. I'm having trouble adjusting to driving a car on a track with power brakes. I circle tracked for 20 years and always had manual brakes. They are the best for feel. Cup cars weigh a ton but they all have manual brakes. Porsche has made their power brake system to have a feel similar to manual brakes.
Manual brakes are often preferred in racing due to their superior consistency and feel, allowing for more precise control and predictable braking performance. While they require more physical effort, the increased feedback and ability to modulate braking at the edge of lock-up can lead to faster lap times and improved driver confidence
Yes, kinda wished I never got rid of my 2017 Z06, this C8 will take some time to get used to. I always run in Z Mode, with PTM at Sport or higher. I may consider the Z06 calipers, but do not want holes in my trunk to store the parking brakes. Thank you for all the information though. I'll see how I do at Mid-Ohio Monday/Tuesday with adjusting my braking technique...
Hear me out here... vibration issues...
