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Brakes "pulsing" after front pad replace and rotor turning

 
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Old 12 Dec 2011, 09:36 am
Samson's Avatar
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Question Brakes "pulsing" after front pad replace and rotor turning

Hi all,
yesterday I replaced the front pads and had my slotted/drilled rotors turned on my 2006 non-turbo.
Prior to the pad replacement and rotor turning, there were no major issues other than the pads were getting very thin. After putting everything back together and taking the car out to bed the pads, I noticed the brakes were pulsing/surging as I gradually applied pressure. It was almost if the pads were hitting slick spots on the rotors. The rotors didnt appear to be warped before the turning. I have full brake pressure (brakes depress to a normal level).
My guess is the pads and newly turned rotor surface, but I have never experienced this before. Any help would be greatly appreciated.

Thank you
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Old 12 Dec 2011, 10:45 am
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

You say the rotors didn't appear to be warped so I guess you didn't do any kind of measuring. Just a guess but I would say they are warped but didn't show too much and once you changed the dynamics by turning them and putting new pads, the warp showed up more so.

My own experience and from what I've seen on the forum, if this is the first time the pads have been changed, most owners find that the original rotors were worn to far to be turned down and had to be replaced. Were your measured before they were turned?
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Old 12 Dec 2011, 11:18 am
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

Crewzin I think you nailed it. Car has 145k miles on it, 4th brake change, 3 rotor changes. In the past I have just replaced the rotors, but this time I had them turned as they "appeared" to be in pretty good shape. The pads before the change were very thin, but hadnt really scored or grooved the rotor face.
As far as measuring to see if they were warped, no I didnt do that. I was just confused as I thought turning the rotors would alleviate any minor warpage, as there was a slight indication upon heavy braking of minor warping before the current pad change/rotor turning. The "surging" was immediately noticed after putting the turned rotors back on, even at slow speeds during pad bedding.
I am ordering new rotors today.

Thank you Crewzin
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Old 12 Dec 2011, 01:19 pm
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

I never agree with turning rotors. Rotors warp because of heat, and the less metal (thickness) the less able they are to get rid of the heat and more prone to warping.
Replacing the disks with good new ones will fix your problem.
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Old 12 Dec 2011, 09:56 pm
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

I had my brakes done at Big O and they screwed up one rotor by turning it improperly. They paid for a new rotor. Apparently, there is a right way and a wrong way to turn rotors. As long as you have the required amount of rotor left, a professional turning works well.

Tim
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Old 14 Dec 2011, 08:12 am
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

The only way to tell for sure if the rotors are warped is to measure with a dial indicator...if the TIR run out is any more than 5 thousandths (sometimes less), you will feel the pulsing in the pedal.

Having rotors turned will result in a job only as good as the brake lathe they are done on and the skill of the guy doing the job.

One other thing to consider is when tightening the lug nuts... tighten them evenly to specs with a torque wrench in steps in a star pattern so as not to possibly create a condition that cause the rotors to warp.

Let us know how the new rotors work for you.
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Old 15 Dec 2011, 12:58 pm
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

Quote:
Originally Posted by Carl48 View Post
One other thing to consider is when tightening the lug nuts... tighten them evenly to specs with a torque wrench in steps in a star pattern so as not to possibly create a condition that cause the rotors to warp.
QFT!

Especially with alloy wheels; steelies will 'bend' a bit and are forgiving to exuberant tightening, alloy doesn't bend
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Old 27 Dec 2011, 05:32 pm
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

New rotors, problem solved, thank you crewzin and all who replied
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Old 28 Dec 2011, 05:11 pm
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Default Re: Brakes "pulsing" after front pad replace and rotor turning

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Originally Posted by Samson View Post
New rotors, problem solved, thank you crewzin and all who replied
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