Help Diagnosing Braking (?) Issue - C5 Z06
08-03-2015, 11:18 AM
#1
Le Mans Master
Thread Starter
Help Diagnosing Braking (?) Issue - C5 Z06
Symptom: Under braking there is WICKED, might even describe it as violent, hammering and shaking. The brakes are still very effective, pedal is firm. You can feel a slight vibration at first but once you build up heat it's like flipping a switch, by the end of 2nd lap or start of 3rd at NJMP Thunderbolt.
What I've done so far: I installed a "Sprint" kit from Essex so the car has brand new calipers, rotors (hats & rings), pads, brake lines and fresh fluid. Swapped tires & wheels.
If pictures are worth 1000 words maybe a video is worth 10,000?
Figured I'd give the precis and then if folks want the whole story they could keep reading! This hammering issue first developed at the NCM VIR event. At that point I had the original Hardbar/Essex kit on the car so I used it as an excuse to switch to the updated kit from Essex. This is my wife's car, I put their newer kit on my car last year and so much prefer the design of their brackets & hats that all I needed was a good excuse to make the switch.
So the issue pre-existed and a complete change out of the front brakes didn't do anything. The rear brakes are KNS rotors with Hawk DTC pads(can't remember if 60 or 70). They appear in excellent condition and the feel & strength of what's going on doesn't make me think rear brakes in any way.
The issue has the vague feel of ABS but 'ABS ACTIVE' does not appear in the DIC and really it's a much more violent feel. I got into ABS deep into a brake zone the same day in my car and while similar, it's not the same feeling.
I didn't have my code reader with me but the CEL isn't on. Will pull codes soon. I just don't believe there is something wrong with the brakes themselves so I wonder if there's a suspension issue? Maybe it could be ABS even though the notice doesn't appear? Could a failing master cylinder create something like that? HELP!!!
What I've done so far: I installed a "Sprint" kit from Essex so the car has brand new calipers, rotors (hats & rings), pads, brake lines and fresh fluid. Swapped tires & wheels.
If pictures are worth 1000 words maybe a video is worth 10,000?
Figured I'd give the precis and then if folks want the whole story they could keep reading! This hammering issue first developed at the NCM VIR event. At that point I had the original Hardbar/Essex kit on the car so I used it as an excuse to switch to the updated kit from Essex. This is my wife's car, I put their newer kit on my car last year and so much prefer the design of their brackets & hats that all I needed was a good excuse to make the switch.
So the issue pre-existed and a complete change out of the front brakes didn't do anything. The rear brakes are KNS rotors with Hawk DTC pads(can't remember if 60 or 70). They appear in excellent condition and the feel & strength of what's going on doesn't make me think rear brakes in any way.
The issue has the vague feel of ABS but 'ABS ACTIVE' does not appear in the DIC and really it's a much more violent feel. I got into ABS deep into a brake zone the same day in my car and while similar, it's not the same feeling.
I didn't have my code reader with me but the CEL isn't on. Will pull codes soon. I just don't believe there is something wrong with the brakes themselves so I wonder if there's a suspension issue? Maybe it could be ABS even though the notice doesn't appear? Could a failing master cylinder create something like that? HELP!!!
08-03-2015, 12:21 PM
#4
Racer
I hate to state the obvious but did you check to be sure the rotor ring isn't cracked or that the retaining bolts are properly tightened? Did you check to be sure the wheel bearings are tight?
08-03-2015, 12:27 PM
#5
Le Mans Master
Thread Starter
Did not. Did some Googling on my phone but didn't see a definitive enough "pull THIS fuse" post to be comfortable knowing I was doing the right thing.
The feeling is much more chassis than wheel. The whole car vibrates, the motion feels kinda up & down.
No reason to hate it, I try to never avoid the obvious issues, that's an easy way to miss something and waste a lot of time!! But... rotor rings are brand new, solid, no cracks or even heat checks and they're solidly attached to the hats. Lug nuts torqued to spec, two different sets of wheels & tires, caliper mounting bolts and bracket bolts all tight and to spec. I have not yet checked the wheel bearings, it's on my list.
The feeling is much more chassis than wheel. The whole car vibrates, the motion feels kinda up & down.
No reason to hate it, I try to never avoid the obvious issues, that's an easy way to miss something and waste a lot of time!! But... rotor rings are brand new, solid, no cracks or even heat checks and they're solidly attached to the hats. Lug nuts torqued to spec, two different sets of wheels & tires, caliper mounting bolts and bracket bolts all tight and to spec. I have not yet checked the wheel bearings, it's on my list.
08-03-2015, 12:49 PM
#6
08-03-2015, 12:53 PM
#7
Le Mans Master
Thread Starter
08-03-2015, 01:08 PM
#8
Le Mans Master
Thread Starter
I hear something rattle in the video, other than that it looked normal. What was the rattle from?
More information about the problem would be helpful. Compare the violent shaking and hammering to braking while the ABS is active, what brake pads do you have on front and rear and what tires did you run and how much life was left.
Shooting from the hip in the dark, I think the ABS gets activated. This would make sense because if you have race pads, they don't work well until heated up and the problem doesn't happen until heat is built up. Figure out if you need more traction to prevent the ABS from activating or determine if the ABS is getting activated when it should not be.
More information about the problem would be helpful. Compare the violent shaking and hammering to braking while the ABS is active, what brake pads do you have on front and rear and what tires did you run and how much life was left.
Shooting from the hip in the dark, I think the ABS gets activated. This would make sense because if you have race pads, they don't work well until heated up and the problem doesn't happen until heat is built up. Figure out if you need more traction to prevent the ABS from activating or determine if the ABS is getting activated when it should not be.
The fronts pads are Ferodo DS1.11's on AP calipers and we've been using the setup on that car for 2 seasons. The rears are stock calipers on Hawk DTC-60. I use the exact same setup on my car and it works flawlessly so I do not believe this is a brake balance or configuration issue.
My first thought was ABS as well, but the feeling is much stronger than ABS. As I said above I had gotten into ABS that same day on my car in a rippled brake zone and that you feel but it doesn't feel much different than rippled surface. This shakes the whole car. Also you do not get the activation notice for ABS in the DIC and I would think that even if it were a wheel speed sensor issue activating ABS you'd get that message.
08-03-2015, 01:36 PM
#9
The rattle goes with the shake and it's a symptom of the problem.
The fronts pads are Ferodo DS1.11's on AP calipers and we've been using the setup on that car for 2 seasons. The rears are stock calipers on Hawk DTC-60. I use the exact same setup on my car and it works flawlessly so I do not believe this is a brake balance or configuration issue.
My first thought was ABS as well, but the feeling is much stronger than ABS. As I said above I had gotten into ABS that same day on my car in a rippled brake zone and that you feel but it doesn't feel much different than rippled surface. This shakes the whole car. Also you do not get the activation notice for ABS in the DIC and I would think that even if it were a wheel speed sensor issue activating ABS you'd get that message.
The fronts pads are Ferodo DS1.11's on AP calipers and we've been using the setup on that car for 2 seasons. The rears are stock calipers on Hawk DTC-60. I use the exact same setup on my car and it works flawlessly so I do not believe this is a brake balance or configuration issue.
My first thought was ABS as well, but the feeling is much stronger than ABS. As I said above I had gotten into ABS that same day on my car in a rippled brake zone and that you feel but it doesn't feel much different than rippled surface. This shakes the whole car. Also you do not get the activation notice for ABS in the DIC and I would think that even if it were a wheel speed sensor issue activating ABS you'd get that message.
08-03-2015, 01:39 PM
#10
Le Mans Master
Thread Starter
Nothing. It was fine on day 1 at VIR, then on day 2 it started happening. We started out this past weekend on the same tires & wheels as VIR and then I switched once the problem happened to eliminate that. The wheels & tires were scrubs I had run on my car previously with no issues (I had a fresh set of A7's I wanted to run at VIR).
08-03-2015, 01:57 PM
#11
Safety Car
The rattle goes with the shake and it's a symptom of the problem.
The fronts pads are Ferodo DS1.11's on AP calipers and we've been using the setup on that car for 2 seasons. The rears are stock calipers on Hawk DTC-60. I use the exact same setup on my car and it works flawlessly so I do not believe this is a brake balance or configuration issue.
My first thought was ABS as well, but the feeling is much stronger than ABS. As I said above I had gotten into ABS that same day on my car in a rippled brake zone and that you feel but it doesn't feel much different than rippled surface. This shakes the whole car. Also you do not get the activation notice for ABS in the DIC and I would think that even if it were a wheel speed sensor issue activating ABS you'd get that message.
The fronts pads are Ferodo DS1.11's on AP calipers and we've been using the setup on that car for 2 seasons. The rears are stock calipers on Hawk DTC-60. I use the exact same setup on my car and it works flawlessly so I do not believe this is a brake balance or configuration issue.
My first thought was ABS as well, but the feeling is much stronger than ABS. As I said above I had gotten into ABS that same day on my car in a rippled brake zone and that you feel but it doesn't feel much different than rippled surface. This shakes the whole car. Also you do not get the activation notice for ABS in the DIC and I would think that even if it were a wheel speed sensor issue activating ABS you'd get that message.
turned out to be a pad deposit on a rear disc..new disk and all was good
08-03-2015, 02:07 PM
#12
have you checked your hubs?
when i see judder like this 9/10 it's lateral run out on the rotor.
this video is old as vhs tapes but explains it well.
when i see judder like this 9/10 it's lateral run out on the rotor.
this video is old as vhs tapes but explains it well.
Last edited by johnny c; 08-03-2015 at 02:11 PM.
08-03-2015, 02:12 PM
#13
Le Mans Master
Thread Starter
But hey, I do have the parts so there's no reason to not try it.Not yet, mostly because they're nearly-new SKF's with only about 15 track days on them. That doesn't mean they can't have failed of course and I will check them, but they were just down on my list of culprits.
08-03-2015, 02:14 PM
#14
Not sure how to feel about that. Would love it if it were that simple but would be quite mad at myself and embarrassed for dismissing the possibility. But hey, I do have the parts so there's no reason to not try it.
Not yet, mostly because they're nearly-new SKF's with only about 15 track days on them. That doesn't mean they can't have failed of course and I will check them, but they were just down on my list of culprits.
But hey, I do have the parts so there's no reason to not try it.Not yet, mostly because they're nearly-new SKF's with only about 15 track days on them. That doesn't mean they can't have failed of course and I will check them, but they were just down on my list of culprits.
08-03-2015, 02:45 PM
#15
Le Mans Master
Thread Starter
08-03-2015, 03:46 PM
#16
Pro
I woulda suggested hubs too, but hubs going bad has always been more obvious to me going around turns rather than in braking.
I ran an identical setup to yours the last 2 seasons and have never had a braking issue since I switched to the AP kit. Good luck figuring that one out!
PS. What lap times you running in that video?
I ran an identical setup to yours the last 2 seasons and have never had a braking issue since I switched to the AP kit. Good luck figuring that one out!
PS. What lap times you running in that video?
08-03-2015, 03:51 PM
#17
Le Mans Master
Thread Starter
I woulda suggested hubs too, but hubs going bad has always been more obvious to me going around turns rather than in braking.
I ran an identical setup to yours the last 2 seasons and have never had a braking issue since I switched to the AP kit. Good luck figuring that one out!
PS. What lap times you running in that video?
I ran an identical setup to yours the last 2 seasons and have never had a braking issue since I switched to the AP kit. Good luck figuring that one out!
PS. What lap times you running in that video?
08-03-2015, 07:05 PM
#18
There is a first time for everything. I hope the fix is that easy for ya
Post back what you find!
08-04-2015, 07:58 AM
#19
Le Mans Master
Thread Starter
No opportunity last night to even get the car out of the trailer let alone look at anything. Our son's Grand Cherokee needed new rear brakes so there went my evening. Will report in when I figure it out.
08-04-2015, 08:27 AM
#20
Burning Brakes
It's easy enough to rule out ABS - just pull fuse #52. Its a 40amp fuse in the main fuse box, right side. A flat spotted tire or out of balance wheel can do this - but doubt thats the issue since you've tried two sets. If the feeling is coming thru the chassis more than the wheel then it wouldn't be the front rotors warped or pad-deposits - could be the rears. If its not hubs then - ball joints? suspension bushings?