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Old 03-18-2015, 07:06 PM   #1
robbiegordon
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Braking Vibration/problems under heavy braking.. Please help!

ok so i have a 2011 camaro ss, with a detailed story leading up to my current troubleshooting/problem ... please bare with me...

my car has 28k miles on the original pads/rotors...which all appear to be in good condition with decent pad left well beyond the brake pad feeler and same with the inner pads..

The problem:
when braking moderately-heavy from speeds over 60mph there is a strong vibration/pulsating felt through the pedal and an intermittent audible thud, that can be felt and heard, during the initial press of the pedal. then as the car decelerates the brakes grab normally and feel smooth all the way to stopped.

when braking quickly at slower speeds 20-25mph similar symptoms happen, but for a shorter time. and occasionally the thud is heard when the car comes to a complete stop.. when i drive (normally) light braking.. or what i would consider comfortable deceleration from any speed.. the car brakes normally all the way to stop

The Trouble shooting:
i have a dial indicator that i used to measure rotor runout and the measurement is a variation of .0015-.0020 on the two rotors that i checked.. (havent had time to check all 4 also not sure what the tolerance should be) but since i was getting the same results i figured either both are bad or both are good.... haha which is one of my questions..

Possible contributing factors:

i was hit by car changing lanes at my front right fender a few months prior. but had no damage to wheels/tire or any structure of the front end.. just damaged the plastic bumper and a little paint on the fender. but i didnt want to rule that out as a possible factor.

i installed bmr toe rods and adjustable trailing arms months after the accident but a few weeks before these symptoms started ...

a few weeks later i had the rear tires replaced ( due to my old ones getting destroyed by poor alignment/thinking i could get away without alignment) and literally on the way home from the tire shop is when i first noticed the braking problems...

the day after they symptoms started i got a 4 wheel alignment from a separate shop that showed minimal adjustment to the front and major adjustment to the rear, as i never had it aligned after the bmr installs mentioned above...

i could not replicate the symptoms by only using the Emergency brake. so i feel that its probably a front end issue. but not 100%

i did a thorough visual inspection of pads, rotor and suspension components and couldnt find anything that seemed to be out of place or loose. no shiny spots on the rotor or anything that would give away a problem...

any thoughts, things to try or possible solutions i am happy to hear. thank you all in advance for taking the time to read this !
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Old 03-18-2015, 08:10 PM   #2
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do you feel the issue through the steering wheel or does the steering wheel feel largely uneffected vs the feel you get through the pedal

do you feel it more in the seat of your pants?

did you disconnect the rear calipers at all when you installed the rear arms?

when you hear the thud, is it repetitive as if something rotational, or is it more of an initial thud and then you don't really hear it again until you are stopping or disengaging the brakes.

the emergency brake is inside the rotor, so if there is an issue with the pads/rotor you will not hear it by using the e brake.

on an empty road, or with a helper, turn your head sideways any listen for the thud to pin point if it's coming from the front or back.

does the suspension/steering shift at all when you hear the thud? even slightly?

how many miles do you have on the car?
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Old 03-19-2015, 05:29 AM   #3
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Quote:
Originally Posted by Rob@WretchedMS View Post
do you feel the issue through the steering wheel or does the steering wheel feel largely uneffected vs the feel you get through the pedal

do you feel it more in the seat of your pants?

did you disconnect the rear calipers at all when you installed the rear arms?

when you hear the thud, is it repetitive as if something rotational, or is it more of an initial thud and then you don't really hear it again until you are stopping or disengaging the brakes.

the emergency brake is inside the rotor, so if there is an issue with the pads/rotor you will not hear it by using the e brake.

on an empty road, or with a helper, turn your head sideways any listen for the thud to pin point if it's coming from the front or back.

does the suspension/steering shift at all when you hear the thud? even slightly?

how many miles do you have on the car?
the steering wheel seems mostly unaffected compared to what is felt through the pedal, but you can feel it throughout the whole car or seat of your pants when the thud /pulsating vibration is happening. it does feel repetitive at first, which leads me to believe its rotational but goes away after the initial press and comes back slightly towards the stop completion when slowing the car to a complete stop. (it is not felt through the entire stop, ie from 60-0, i feel it from 60-55 and then again from 2-3mph-0). almost feels like grabbing and letting go or brake pads slipping during the noise.. almost like abs but a lot more aggressive.

i didnt disconnect the brakes during any of the suspension installs.

it does seem like the steering wheel shifted to the right during a couple of the times i was braking hard from around 25mph-0mph but i wasnt sure if that happened because i locked up the front tires for a second at the very end. *small tire chirp* although with hands off the steering wheel it drives and brakes pretty straight all the way to a stop. ill do a couple more test runs today and pay more attention to the wheel..

with a friend in the car we both determined the noise seemed to be coming from the front end.. and the car has 28k miles on it

Update** no noticeable pulling or vibration in the steering wheel

thank you for your help!
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Last edited by robbiegordon; 03-19-2015 at 06:00 AM. Reason: update
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Old 03-19-2015, 06:19 AM   #4
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Same thing here...I had to slam on my brakes to avoid hitting a biker that blew his light. Felt a lot of vibration in the pedal. Kind of like when you brake in snow...
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Old 03-19-2015, 08:14 AM   #5
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your ABS or Traction Light is not coming on at all correct?
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Old 03-19-2015, 08:34 AM   #6
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No lights.. tried it in all three traction control settings too with the same results
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Old 03-19-2015, 11:04 AM   #7
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The reason i asked about the Traction lights is if the alignment was off enough and the computer was thinking the car was in a skid due to the steering angle sensor not giving the computer the expected information, then the ABS could be kicking in and doing all kinds of wacky things.

go from forward to reverse a few times with normal braking, and then a few times with hard/sudden braking when stopping each time. The transition from forward to reverse is not important, the braking each way is, we are looking to see if we can reproduce the thud at very slow speed by stressing the suspension in each direction. Not more than 5 or 10mph in either direction. If you can make the thud happen, have someone stand outside the car going from wheel to wheel listening and looking for noise/movement that shouldn't be there.

If you can't pin point anything from that, and If you are positive that it's coming from the front...

Check the lug nut torque on all 4 wheels, (doesn't have to be perfect, just verifying that there is not a loose wheel)

Get the front of the car in the air and secure with both wheels hanging.
Look for play in things with the tires on, everything should feel secure and no looseness should be felt. I don't expect you to find a problem but i want to make sure the basics are checked.
-Grab each tire at 3 and 9 and shake
-Grab each tire at 6 and 12 and shake
-Grab each tire at 4:30 with one hand on the inside and the other on the outside, wiggle in and out
-Grab each tire at 7:30 same way and do the same.
-Grab each wheel at the front lower half and try to push it front to back while looking at the radius arm ball joint

If that is all good pull the front wheels off,
-Check the strut bolts that bolt to the knuckle, make sure both of those are tight
-Check the ball joint nuts (all 4) and verify that they are tight
-Check the Radius Arm to Frame and Control Arm to Frame Bolts and make sure they are tight.

Check that they are tight means that you are putting a socket or wrench on it and making 100% sure.

Do you have a printout from the alignment?
Is your Steering Wheel straight?


let me know what you find, and if you have questions on anything.
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Old 03-19-2015, 05:07 PM   #8
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Quote:
Originally Posted by Rob@WretchedMS View Post
The reason i asked about the Traction lights is if the alignment was off enough and the computer was thinking the car was in a skid due to the steering angle sensor not giving the computer the expected information, then the ABS could be kicking in and doing all kinds of wacky things.

go from forward to reverse a few times with normal braking, and then a few times with hard/sudden braking when stopping each time. The transition from forward to reverse is not important, the braking each way is, we are looking to see if we can reproduce the thud at very slow speed by stressing the suspension in each direction. Not more than 5 or 10mph in either direction. If you can make the thud happen, have someone stand outside the car going from wheel to wheel listening and looking for noise/movement that shouldn't be there.

If you can't pin point anything from that, and If you are positive that it's coming from the front...

Check the lug nut torque on all 4 wheels, (doesn't have to be perfect, just verifying that there is not a loose wheel)

Get the front of the car in the air and secure with both wheels hanging.
Look for play in things with the tires on, everything should feel secure and no looseness should be felt. I don't expect you to find a problem but i want to make sure the basics are checked.
-Grab each tire at 3 and 9 and shake
-Grab each tire at 6 and 12 and shake
-Grab each tire at 4:30 with one hand on the inside and the other on the outside, wiggle in and out
-Grab each tire at 7:30 same way and do the same.
-Grab each wheel at the front lower half and try to push it front to back while looking at the radius arm ball joint

If that is all good pull the front wheels off,
-Check the strut bolts that bolt to the knuckle, make sure both of those are tight
-Check the ball joint nuts (all 4) and verify that they are tight
-Check the Radius Arm to Frame and Control Arm to Frame Bolts and make sure they are tight.

Check that they are tight means that you are putting a socket or wrench on it and making 100% sure.

Do you have a printout from the alignment?
Is your Steering Wheel straight?


let me know what you find, and if you have questions on anything.
First off , thank you so much for taking the time to help me figure this out..
so i went through everything you mentioned. no wheel play aside from the back and forth i can get from the steering and can see the steering wheel move. (hitting the steering lock in either direction) im assuming that is normal. but no other play trying to move the tire at the different grab points you explained.

next i took the wheels off and didnt find anything loose bolts and put some decent torque into trying and tighten them.
my steering wheel is straight while driving and i tried going from forward to reversing and braking up to 10mph and if i brake hard enough i can replicate it moving forward occasionally however everything works/sounds normal in reverse .

after i put the wheels back on i drove it again and the first time getting on the brakes moderately it grabbed and jerked the wheel pretty hard to the right , but after that initial time i couldnt replicate that again.. and it is possible that it was the abs kicking in since i was on a road that had a little sand on it from the snow we got a few weeks back. now that ive been more care fully paying attention to the noise i could describe it almost like a rubbing/groaning noise .. almost like what you would hear from a semi truck feathering the brakes forward from a stop.. but it starts and stops abruptly which makes it seem like more of a thud at first.

i tried setting my gopro up but between wind noise and my exhaust you cant hear much and you can barely see the brakes (as i dont have a long enough go pro extension) as soon as i can ill get a spotter to stand outside of the car to get some more feed back im definitely going to .

im pretty positive that its coming from the front.. base on the feel and sounds.

i sent a copy of my first post to a friend of mine who works at a chevy dealer across the country from me and he said i should check my rotors with a digital micrometer to see if there are any places where there is greater or less distance from either side . if i can get my hands on one from work i might give it a shot but otherwise i dont have access to one at the moment.

i wouldnt mind just replacing the rotors, but didnt want to blindly throw money at a problem before i knew what the real issue was. although i guess sometimes that works.. haha
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Old 03-19-2015, 07:53 PM   #9
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I have something called chassis ears, it has 4 'sensors' that you can clip on to different areas of the car and a receiver that you hold, and clamp the sensor to which item you think might be making noises. it's not a perfect tool, but it's something that someone in your area might have that they could use to help track it down.

i agree, don't spend money until you have a good idea what the issue is.

I don't think it's a rotor issue because that will be consistent and not only sometimes.

do you ever hear it when you are not hitting the brakes? over certain types of bump or anything?
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Old 03-19-2015, 08:46 PM   #10
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Ill have to ask around about that , those would definitely help I would imagine..
the only time it shows any symptoms is when im braking so far. I've been paying pretty close attention over speed bumps and up drive ways and haven't noticed anything. Hopefully tomorrow I can get someone to stand outside my car while I brake. Ill keep you posted
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Old 03-23-2015, 03:46 PM   #11
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so these videos didnt do much for me but i thought i might as well post them to see if anyone else sees anything that i dont... pretty much braking from 25-0 every time. yah i know the tire stretch looks pretty bad here but its not as bad in person .. haha. (im working on getting new ones, drives me crazy.... anyhow) still getting the same symptoms. pretty much through every hard braking stop.

http://youtu.be/fyeeSY1zmfQ

http://youtu.be/mblXenGfztY

also noise is definitly coming from the front end and the sounds heard match the pulsation/vibration through the pedal

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Old 03-24-2015, 01:22 AM   #12
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Did you take the rotors off? If so did you clean the rust off the hub and rotors?

When you have the wheels off the ground, how do they spin? Any binding?
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Old 03-24-2015, 10:24 AM   #13
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Never/ havent takin the rotors off yet.. rotates freely with wheels on or off. I did clean up the rotors with done brake cleaner with the wheels off but caliper s on
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Old 03-24-2015, 06:30 PM   #14
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Do you think this is something to be concerned about it's never caused a low reservoir our anything... what do you guys think? Sorry the photo is upside down I'm working from the phone.
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