I have tracked my 2006 Z51 with stock rotors and calipers as well as my 2015 Z51 with stock rotors and calipers and never experienced brake shudder. From my very first track day at VIR with my 2021 Z51 I have experienced severe brake shudder. Using Motul 600 fluid, stock calipers, new stock rotors and stock tires. First track day used CT XP12 and the shudder was so severe it felt like I was riding on Fred Flintstone's square tires. Turned the front rotors. The next track day used XP12's again and it was ok for a couple of sessions before the shudder returned. For the next track day. I used the stock rotors that came with the car and had been used for street duty only and installed new GM pads. At the end of the track day the shudder was much improved but not eliminated. The stock GM pads were done after five 30 minute sessions. Discussed the issue with 2 brake pad vendors. One vendor said installing new rotors at $500 apiece would solve the problem. After considerable discussion with the second vendor the conclusion was that the shudder was caused by uneven pad material buildup on the rotor. The vendor was of the opinion that the cause of the uneven pad material being deposited on the rotor was excessive heat. The XP12 pad I used has a heat range of 250°F-1850°F. I don't know what the heat range of the stock GM pad is. He recommended using a front pad with a heat range of 255°F-2000°F. Additionally he did not feel it was necessary to change to the $500 apiece rotor. The next track day I used R16 pads (temp range 255°F-2000°F) and new front rotors. The shudder was much better but again not eliminated. At the end of the first day the front rotors still showed uneven pad material with some bluing in spots. The pad wear was excellent with 75% of the thickness left. I checked the rotor temperature after each session after driving around the paddock several times. I recognize that this would cool the rotors. I initially used a probe to measure rotor temp then used an infra-red probe as well. The front rotor temps were a max of 317°F using the infra-red probe.

Again, this is not my first rodeo. I did not experience this issue with the C7 or C6 so what is different in the make up of the C8 that is causing it? The C8 front brake duct design is the same as the C7 Z06. I did change my C7 Z51 to the Z06 front fascia and thus larger front brake duct but again did not experience any brake cooling issues. The C8 front wheel well has the output of the front radiators exiting into it as well as the brake ducts. Is the radiator air disrupting the flow of the air from the brake duct so that it is not working properly on the track? The design of the hub, knuckle, dust shield as well as shields for the tie rod boot and ball joint boot all work to limit access to get air directly to the rotor. I posed a question in the C8 Z06 section about changes in brake cooling if any on the C8 Z06. There does not appear to be any changes. But one member posted an excellent paper from Essex that described brake issues and brake ducts. Severe shudder (uneven pad material buildup) was not one of the issues listed as a result of the rotors running too hot. I have also discussed front brake issues with several C8 Z51 owners at the track and they all said they also experienced brake shudder although not as severe as mine. One did change the the front rotors to the $500 version and another also change front calipers to AP and 2 piece rotors and still occasionally experienced shudder.

Where do I go from here? It may seem obvious but I fail to see how changing to $5,000 calipers and $500 rotors will solve the issue of too much heat between the pad and the friction surface of the rotor. I have looked at trying to get more air to the rotor with brake ducts but there does not appear to be a viable way to do it.

After all of the above, what can you tell me? Have you experienced the same shudder issues? How did you solve them?

thanks

bill

 

We had the same nasty shudder on our second weekend testing at COTA a year or so ago. We didn't look into it much, I just ordered giro disc from the guys at KNS and haven't had an issue since. Pad wise we used Raybestos ST43, Carbotech XP12 (didn't care for them and switched with 3/4 pad left) and now we're using Cobalt XR2.

 

Dane. Thanks. glad to know I am not the only one that had the problem. So the $500 apiece rotors solved the problem. And you still have all the shielding...dust and boot shielding in place?

thanks

 

No shudder on track with OEM rotors and pads. Wore pads out in 4000 miles (2000 track miles). Next track event Encountered severe brake shudder when heated after installing Hawk HP+ pads on OEM original rotors. No subsequent shudder in street use
Hawk recommended replacing rotors. I’m not convinced.
Next step is to turn rotors and go back to oem pads

 

I also had bad shudder after a few track days on the original equipment. I replaced the rotors and pads (with OEM parts) hoping this would fix the problem, but after a couple days the shudder was back. Once cooled off, driving the car on the street after the track does not cause the shudder. It seems the hotter the rotors get the more it causes the shudder, but once they cool, the shudder goes away.
I also previously tracked a C7-Z51 and C7-Z06 and never had this problem.

 

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Yes we do.

 

I use xp12 and 2 sets of stock rotors and same issue. I got tired of it and ordered the AP competition kit 9668 today and will get it Friday. I am tired of dealing with warp rotors

 

I don't think the shudder is caused from the rotor being warped. I think it is pad material being deposited unevenly on the rotor because the rotor and pad are not cooling properly. I have been wrong before and this could be another instance of being wrong but to illustrate, I am attaching pictures of my front rotors and you can see what I am describing. When the C7 Z06 came out, they started experiencing front brake cooling issues and the fix was a Brake Shield that could be ordered and installed. It was supposed to keep air circulating thru the rotor.

 

I agree. Pad material. Not sure about the cooling issue. I did not encounter the shudder using stock pads turning faster laps with similar weather. Started to show up with new Hawk HP+ pads. Plan to turn discs and instal oem pads next spring, scrap the Hawks. Expensive lesson. In future will use oem pads and consider them a consumable.

 

What tracks were you running that allowed you to get 2000 miles out of the stock pads? I was not able to get but 5-30min sessions at VIR and they still shuddered although not as severe as CT and GLoc.

thanks

 

Canadian Tire Motorsport Park - formerly known as Mosport

 

Problem to be solved soon

 

I am experiencing the same issues as car54 and happyC8. I track mainly at CTMP Mosport and Grand Bend in a fully stock 2020 Z51 Michelin 4S tires and SRF fliud. . I am not a racer but do 15 track lapping days at an intermediate level and drive to and from the track with these pads etc. I get judder using stock rotors and have tried many pads. Ranked worst first - Gloc 10/10 FR/RR, Carbobotech 10/8, hawk HP+ GM stock . The Gm stock pads are done after 1 track day and the others go 7-8 days. I have 2 sets of factory rotors which work after they are turned (for clean up) and Judder starts again after 2 or 3 sessions. I would upgrade the brake rotors to Girodisc if that solved the problem but varied results from others make me hesitant. I also had C6 Z06, C7 Z51 and no issues with Stoptech sport pads and Carbotech 10. I hoped to get a Z06 but that looks like it will never happen so I want to fix my problem as my track days the past 2 1/2 years were sub par. would also consider a full brake bigger brake conversion here if it didn't require new wheels as I have 2 sets of stock rims now. Curious to know if there is a GM response as they chimed in here.

 

Are you using factory wheels?

 

Yes factory wheels, same spec as your car

 

I have been reluctant to provide any updates until there was something positive to report. It finally looks like there will be nothing positive so let here goes. I will try to keep it as brief as possible. The short answer is that GM will do nothing. They will not touch the car or look at the car because I said the shudder had occurred with aftermarket pads along with stock pads. So here is the rest of the story.

First lets review the timeline. My initial post on the forum was 12-14-22. I was trying to find out if others had experienced brake shudder like I had and what they had done about it. Turns out that 5 out of 6 have experienced the same thing. On 12-16-22 Chevy Customer Svc replied to my post and encouraged me to take it to the dealer. On 12-27-22 I took it into the dealer and left a copy of my forum post along with a copy of the rotor temperature log. The dealer did not look at the car or drive the car. Had they done that they would have experienced the same brake shudder with the stock GM pads and rotors that were still on the car. The dealer told me he had no idea what to do but was going to reach out to his Southeast Division Rep who was gone for the week. On 1-10-23 I called the dealer who said that the Rep would come by the dealership later in the week and look at the forum post and temp log. I told the dealer that I would sent him digital copies so he would then forward them to the Rep. On 1-18-23 I contacted the dealer again and was told that the rep had come by and reviewed the forum post and temp log and would send that to "some folks" at GM and see what kind of feedback was given. Later in the day on 1-18-23 the dealer sent me an email with a reply from the "GM Brand Quality Manager for Corvette". The Quality person says "since our customer has informed us that they have used aftermarket brake pads we should not support any brake repairs. I would inform customer the brake system on the C8 is very different from the C6 and C7 generation vehicles. This is why the following information is in the owner's manual. The only approved brake pads are the OEM ones.". He goes on to quote issues about brake fade caused by boiling the brake fluid and if anything besides stock pads are used the brake fade warning system will not work. On 1-19-23 I sent a note to Chevy Customer Service pointing out that I had not mentioned any issues with brake fade or fluid boiling and I pointed out one more time that I had experienced the issue with stock pads and rotors. Chevy Customer Service says they will go back to the dealer again but that they are only a liaison between the customer and the dealer. On 1-24-23 Chevy Customer Service sends me a note that says they can go no further because the car has aftermarket parts. On 1-24-23 I replied to Chevy Customer Service that it is not true that the car has aftermarket parts. I mentioned one more time that the car currently has stock parts and had it been looked at and driven on 12-27-23 the dealer would have noticed that and experienced the brake shudder with the stock parts in place.

So there is the rest of the story. Regardless of the fact that the issue occurs with Stock Parts nothing will be done by GM because it also occurs with non-stock parts.

It is worth noting that the C8 Z06 stock base brake rotors (not carbon ceramic) are 2 piece rotors. Is that a recognition that there are heat issues with the solid rotors on the Z51 or are they on the Z06 just for looks? Will changing the rotors on the Z51 to 2 piece rotors move enough air to solve the problem? As has been pointed out that does not always seem to fix it completely so I am willing to bet that Z06 base brake owners will experience the same brake shudder as Z51 owners.

thanks

bill

 

First, I would check the rotors for runout with a dial gauge... this is cheap way to confirm or eliminate warpage... I suspect it is not warpage...

Assuming the rotors are true, this would indicate that new rotors are not a solution, 1 piece vs 2 piece is primarily a maintenance issue... this should not necessarily impact cooling... again, I'd assume the Z51 rotors are up to the task...

This points directly to material build-up.... IMHO this is the problem in 90% of these situations... this implies improper pad material, inadequate cooling or a combination... given that the C8 is still relatively new, I'd keep this as an issue and continue to collect info...

Check rotor temps with the IR as you come immediately off the track after hard laps... ... this will give objective data on cooling... if the rotors are over-heated, then you will know for sure, and begin to explore options to improve cooling...

If they are not over-heated, this points squarely at the pad material... these cars are heavy, and very fast, and put alot of heat-load into the brakes... if the pads are not up to to the task, you will need to upgrade...

In my C7Z51 the factory material was not up to the task... I swapped pads each time I went to the track... a pretty simple task... at this point, work with a good aftermarket brake specialist to explore options... I use KNS, but use someone you trust... depending on your use, you may have to go to a pretty serious racing compound... once an appropriate pad has been Identified, you will still have to dress your rotors, either by turning them, hand sanding (yuk), or just buying new ones... and carefully bed the pads...

BTW, forget going through GM... they are not legally in position to deal with this... they are not jerking you around, but they have to protect their ***... their hands are tied....

Also, while it is OK to solicit opinions on this site, everybody drives differently... at best you will get anecdotal speculation that does not address your specific situation...

There is a solution...

 

FWIW.. The OEM Z51 brake pads and rotors w/ Castrol SRF have worked exceptionally well for me on track. The only downside so far is they only last 2 days or 10-12 session at Carolina Motorsports Park, which is notoriously hard on brakes (MUCH harder on brakes than VIR). I have a hard time wrapping my head around burning through a set in 5 sessions at VIR unless you're on a slick. What is the wheel/tire setup?

 

I am running stock wheels and stock Michelins with Motul 600.

You are right about CMP being hard on brakes.. VIR has 18 turns in 3.3 miles vs CMP that has 14 turns in 2.3 miles. The back straight at VIR is 4000' and you are going to be trying to haul the car down from 150-160mph so much harder for longer and thus more heat. The front straight is 3000' and you will be 140-150mph and again braking much harder and longer and more heat. At CMP T7 to T8 is about 1400' and you probably will nail the brake between 120-130mph so a much shorter braking zone. T8 to the kink is about 1300' but you may not be braking at all. The front straight T14 to T1 is longer at 1650' but you are entering at a much slower speed so when you hit the braking zone you may not be going but 110-120.