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Old 11-13-2017, 07:34 PM   #1
metal
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Default Bad vibration and shaking under braking

06 WRX Had new rotors, pads, SS lines and fluid all done a few months ago and everything seemed great for the first bit. I'm just approximating but it must have been at least a couple thousand KMs before I started having this issue.


I'm getting a fairly pronounced shudder and vibration felt through the wheel and pedal that is more pronounced with light to medium braking rather than heavy braking. It's felt up at highway speeds but the intensity is very bad and prominent between 45-75 kph and as I slow to a stop, it feels like the pads are biting harder on some areas of the rotor as it's almost a pulsating grab and release under light braking. I opened the windows and listened to it echo as I did this coasting down through my underground parkade using super super light braking and I could hear a squeek from the right front caliper everytime the wheel would rotate through this problem area.


I recently had my right front CV axle replaced as well as the ball joint. I knew it was going already, but it was making a really bad knocking sound due to this braking vibration. I did some reading about uneven brake pad deposits so I went out and rebedded the pads which didn't help at all. Checked the rotors and they seem fine; one area on the outer rotor seemed like it had a very very fine pattern on it when I ran my fingers across it so I sanded it a bit. Pulled the pads out, everything looked fine there, sanded those as well, reversed the inner and outer pads and put em back in. Everything is still the same.


Anyone have any suggestions or ideas?
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Old 11-13-2017, 11:11 PM   #2
Charlie-III
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Try rebedding your pads, StopTech has a tech write up on how to do it and why.
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Old 11-14-2017, 02:59 AM   #3
metal
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That was one of the first things I tried, and it didn't change a thing unfortunately.
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Old 11-14-2017, 10:58 AM   #4
Samurai Jack
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Do you only get the vibration while braking?
If so, most likely a brake issue, as opposed to tires or suspension.

Are you sure you followed the StopTech break in procedure properly?
Your pads/rotors should be smoking ( any brand cigarette/cigar they like ) when you complete this. They have to get hot to burn off the pad deposits.

What brand rotors?
What brand pads?
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Old 11-14-2017, 01:14 PM   #5
metal
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Stoptech Centric blanks, Stoptech sport performance pads. Yep, I had no issues like I said for the first couple thousand kms at least until this started happening, and I rebedded the pads properly which didn't change a thing.
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Old 11-14-2017, 03:12 PM   #6
DNeid
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Default Ball Joints?

Sounds a bit odd, but I just had the same problem myself recently, shudder wasnt always there for me sometimes worse sometimes in corners harder sometimes not but slowly got worse over time and I jacked that sucker up and the ball joints were shot, visible slop in the wheel and the rubber seal was torn to shreds.

word of advice, have lots and lots and lots of PB-Blaster/WD-40/liquid wrench or whatever you prefer. those ball joints can be a pain in the ass.
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Old 11-14-2017, 08:03 PM   #7
metal
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Yeah my CV and ball joint are all new anyways. Bought a new rotor today and threw it on, solved the issue. I guess we'll see what happens.
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Old 11-15-2017, 09:46 AM   #8
klinebau
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The problem is likely due to Disc Thickness Variation (DTV) and is caused when there is excessive runout in the hub/rotor stack. Runout should be checked after putting on new or resurfaced rotors to make sure it is less than .003 (check the service manual for exact tolerance). With new rotors, you will probably be fine for a few thousand miles, but the problem will likely come back.

Excessive runout needs to be corrected either with shims or by having the rotors turned with an on-car lathe. Do a google search on disc thickness variation for more information.
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Old 11-15-2017, 02:13 PM   #9
metal
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Would this still be the case considering that I had no issues with the previous rotor that was on, and the symptoms only came after it was changed?
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Old 11-15-2017, 04:24 PM   #10
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Quote:
Originally Posted by metal View Post
Stoptech Centric blanks, Stoptech sport performance pads. Yep, I had no issues like I said for the first couple thousand kms at least until this started happening, and I rebedded the pads properly which didn't change a thing.
those pads looooooove leaving deposits on the rotors if they are driven gently for to long, which cause the exact issue you are having.

Go seriously beat on your brakes and the issue should go away, but be aware it will recurr regularly if the brakes aren't regularly abused.

something like 8x 70mph-20mph HARD stops as fast as you can should do the trick ( don't forget not to come to a full stop untill you've given they system 10-15 minutes or so of driving to cool off or you'll make new pad imprints on your rotors
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Old 11-15-2017, 05:23 PM   #11
klinebau
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Quote:
Originally Posted by metal View Post
Would this still be the case considering that I had no issues with the previous rotor that was on, and the symptoms only came after it was changed?
Measure the rotor that you just replaced with a micrometer to check the thickness in various locations.
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Old 11-15-2017, 05:30 PM   #12
HeubergerMotors
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Hot spots on the Rotors? look for color variations and see if it you see a color change on the surface of your rotors. should be a shiny silver and the hot spots will be darker.
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