What would cause brake pedal vibration so bad it makes the entire car shake?
11-07-2011, 09:31 PM
#1
Safety Car
Thread Starter
What would cause brake pedal vibration so bad it makes the entire car shake?
This weekend at Summit Point I had a student in a Charger SRT-8. The car was an automatic and the only modifications were:
1. K&N intake
2. Tune
3. Carbotech XP12/XP10s
4. Home made cooling ducts up front (no spindle ducts)
The car comes with nice Brembo calipers front/rear and large vented discs. He was getting pad judder/shake so bad the whole car would shake like we were driving over rumble strips... it was very disconcerting to him, especially in a car that will do 140ish on the front straight at Summit. It was most pronoucned in the 80-50 mph rage. Going faster and braking hard it could be felt, but wasn't bad, but when going through the 80-50 range it got the worst.
After a few sessions I helped him inspect the brakes and found nothing amiss. All bolts were tight, no cracked rotors (not even heat checked, and perfectly even pad wear. No play in the hubs etc.
He told me he had the car out at VIR in October and had no issues. That was his first time running the Carbotechs. After that event he put his street pads back in and daily drove the car as normal. I had him clean the rotors with brake clean and steel wool and it didn't help at all.
Only thing I can think of is that any pad deposits from the street pads weren't playing well with the Carbotechs, but if that was the case cleaning the rotors with steel wool should have fixed it... at least for a bit.
Any ideas? He ended up having to quit after Saturday's sessions as the big Dodge's PS pump didn't like 40 minute lapping sessions with about 500 pounds of person in the car
1. K&N intake
2. Tune
3. Carbotech XP12/XP10s
4. Home made cooling ducts up front (no spindle ducts)
The car comes with nice Brembo calipers front/rear and large vented discs. He was getting pad judder/shake so bad the whole car would shake like we were driving over rumble strips... it was very disconcerting to him, especially in a car that will do 140ish on the front straight at Summit. It was most pronoucned in the 80-50 mph rage. Going faster and braking hard it could be felt, but wasn't bad, but when going through the 80-50 range it got the worst.
After a few sessions I helped him inspect the brakes and found nothing amiss. All bolts were tight, no cracked rotors (not even heat checked, and perfectly even pad wear. No play in the hubs etc.
He told me he had the car out at VIR in October and had no issues. That was his first time running the Carbotechs. After that event he put his street pads back in and daily drove the car as normal. I had him clean the rotors with brake clean and steel wool and it didn't help at all.
Only thing I can think of is that any pad deposits from the street pads weren't playing well with the Carbotechs, but if that was the case cleaning the rotors with steel wool should have fixed it... at least for a bit.
Any ideas? He ended up having to quit after Saturday's sessions as the big Dodge's PS pump didn't like 40 minute lapping sessions with about 500 pounds of person in the car
11-07-2011, 09:49 PM
#3
Le Mans Master
Warped rotor, pad deposit or hub bearing.
I had a similar problem during ST2 practice and qualifying in June after everything warmed up. Everything checked out fine, but I decided to swap the RF hub since it was the oldest on the car. Problem solved.
I had a similar problem during ST2 practice and qualifying in June after everything warmed up. Everything checked out fine, but I decided to swap the RF hub since it was the oldest on the car. Problem solved.
11-07-2011, 09:54 PM
#4
Safety Car
Thread Starter
It's my understanding that rotors don't "warp" but that pad deposits give the impression of warping?
100% no cracks... I had an inspection mirror and checked everything.
Guess it could be a hub on its way out, but it was odd because it did it from the very first session and he said it was fine at VIR in October.
100% no cracks... I had an inspection mirror and checked everything.
Guess it could be a hub on its way out, but it was odd because it did it from the very first session and he said it was fine at VIR in October.
11-07-2011, 10:03 PM
#5
Le Mans Master
11-07-2011, 10:19 PM
#6
Burning Brakes
It's my understanding that rotors don't "warp" but that pad deposits give the impression of warping?
100% no cracks... I had an inspection mirror and checked everything.
Guess it could be a hub on its way out, but it was odd because it did it from the very first session and he said it was fine at VIR in October.
100% no cracks... I had an inspection mirror and checked everything.
Guess it could be a hub on its way out, but it was odd because it did it from the very first session and he said it was fine at VIR in October.
rotors absolutly physically warp...alot
11-07-2011, 11:23 PM
#7
Safety Car
I had this a few times - I think it was pad transfer issues.
Now that I only use race pads (for road and track), no issues. I also use different pads now than when this occurred - so some compounds may not mix well.
Now that I only use race pads (for road and track), no issues. I also use different pads now than when this occurred - so some compounds may not mix well.
11-08-2011, 12:07 AM
#8
Race Director
This weekend at Summit Point I had a student in a Charger SRT-8. The car was an automatic and the only modifications were:
1. K&N intake
2. Tune
3. Carbotech XP12/XP10s
4. Home made cooling ducts up front (no spindle ducts)
The car comes with nice Brembo calipers front/rear and large vented discs. He was getting pad judder/shake so bad the whole car would shake like we were driving over rumble strips... it was very disconcerting to him, especially in a car that will do 140ish on the front straight at Summit. It was most pronoucned in the 80-50 mph rage. Going faster and braking hard it could be felt, but wasn't bad, but when going through the 80-50 range it got the worst.
After a few sessions I helped him inspect the brakes and found nothing amiss. All bolts were tight, no cracked rotors (not even heat checked, and perfectly even pad wear. No play in the hubs etc.
He told me he had the car out at VIR in October and had no issues. That was his first time running the Carbotechs. After that event he put his street pads back in and daily drove the car as normal. I had him clean the rotors with brake clean and steel wool and it didn't help at all.
Only thing I can think of is that any pad deposits from the street pads weren't playing well with the Carbotechs, but if that was the case cleaning the rotors with steel wool should have fixed it... at least for a bit.
Any ideas? He ended up having to quit after Saturday's sessions as the big Dodge's PS pump didn't like 40 minute lapping sessions with about 500 pounds of person in the car
1. K&N intake
2. Tune
3. Carbotech XP12/XP10s
4. Home made cooling ducts up front (no spindle ducts)
The car comes with nice Brembo calipers front/rear and large vented discs. He was getting pad judder/shake so bad the whole car would shake like we were driving over rumble strips... it was very disconcerting to him, especially in a car that will do 140ish on the front straight at Summit. It was most pronoucned in the 80-50 mph rage. Going faster and braking hard it could be felt, but wasn't bad, but when going through the 80-50 range it got the worst.
After a few sessions I helped him inspect the brakes and found nothing amiss. All bolts were tight, no cracked rotors (not even heat checked, and perfectly even pad wear. No play in the hubs etc.
He told me he had the car out at VIR in October and had no issues. That was his first time running the Carbotechs. After that event he put his street pads back in and daily drove the car as normal. I had him clean the rotors with brake clean and steel wool and it didn't help at all.
Only thing I can think of is that any pad deposits from the street pads weren't playing well with the Carbotechs, but if that was the case cleaning the rotors with steel wool should have fixed it... at least for a bit.
Any ideas? He ended up having to quit after Saturday's sessions as the big Dodge's PS pump didn't like 40 minute lapping sessions with about 500 pounds of person in the car
I use GARNET paper (no other type of "sand paper") and brake clean.
11-08-2011, 03:20 AM
#10
Pro
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Location: California
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I would go with warped rotors as well.
11-08-2011, 09:31 AM
#11
I have had this problem with very high quality Brembo racing rotors twice this year. I have had it happen when I am not diligent about cooling the brakes enough after a hard run. If I come in hot and do not continue to drive around the paddock for a while, I have had problems the next session a couple of times. Also, once parked in the paddock, I put the car in neutral and roll it a few times to move where the caliper/pad sits on the rotor to promote even cooling of the rotor.
I have had the steering wheel shake pretty violently and have brake peddle pulsation when I don't properly cool the rotors. I have a local NAPA machine shop take a clean up cut on the rotors and have watched them do it. The rotors had warpage in both cases. Once cut, the same rotors had zero vibration the next time I used them on track.
If you didn't see uneven brake pad deposits on the rotor surface, I think the problem your student had was warpage.
Steve
I have had the steering wheel shake pretty violently and have brake peddle pulsation when I don't properly cool the rotors. I have a local NAPA machine shop take a clean up cut on the rotors and have watched them do it. The rotors had warpage in both cases. Once cut, the same rotors had zero vibration the next time I used them on track.
If you didn't see uneven brake pad deposits on the rotor surface, I think the problem your student had was warpage.
Steve
11-08-2011, 09:54 AM
#14
Instructor
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I agree with the GARNET paper along with brake clean. Various brand pads are definitely made up of different materials. Years ago when we were running a Camaro we switched between Hawk and Performance Friction pads and we either had to change the brake rotors or clean them very thourghly when we switched pads. We now use only Carbotech pads, they are the best and are alwlays consistance and we have never, never delaminated a pad.
