Got a pulsation when braking at highway speeds....

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That is an indication of rotor thickness variation. This is often improperly called "warped rotors".

Machining them is often the answer, but that depends on the amount of material left on the rotor, the nature of the material that the rotor is made from, and car makers recommendations. European car makes usually call for rotor replacement and don't recommend machining them.

Replacing the rotors is never a bad answer, but it may not be the most cost effective.
 
Which pads did you install? I would buy middle range rotors to solve this problem while your pads are still new. Try Centric Premium rotors 120.XXX from Rock Auto.
 
I installed Akebono's. Actually they are not so new, I have put on around 30,000 kilometers on them since install. I just don't get on the highway much and never really noticed it till now. Is that a problem that they are not so new if I do replace the rotor?
 
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It's possible that the old rotor had some degree of disc thickness variation and runout prior to installing the new pads. So, I guess when you add normal wear to that, it eventually reached a point where you noticed problems.

This is why I always recommend either resurfacing or replacing the rotors with every brake job. The rotor may be near the specified limit for runout or disc thickness variation (but is still okay at the time of the brake job), but shortly afterwards, problems will arise.

Replacing or resurfacing the rotors will resolve the problem. If you do the work yourself and can have the rotors resurfaced for under $15/rotor, I would give that a try first.
 
I would buy new rotors and bed in according to: http://www.zeckhausen.com/bedding_in_brakes.htm

Check my previous post above as well. You may end up paying more for new rotors versus re-surfacing your old but on the same token, new rotors will give you more rotor life and will be less prone to warping due to being thicker.
 
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Hasn't anyone considered that this isn't the rotor or the brakes at all? I've never had high speed run out that wasn't apparent at lower speeds. If anything, it was more pronounced since the frequency was lower. Even CV joints will act this way. Now I've seen a vibration that didn't show itself until high(er) speeds (like 75+) that wasn't apparent below that threshold ..but..

Just seeing if you've thought along this line
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Hmm...other way around for me. Every time I've had warped rotors it's more noticeable when braking from highway speeds.

Having experienced how long a machined rotor takes to warp again, I always replace my rotors now.
 
Originally Posted By: Gary Allan
Hasn't anyone considered that this isn't the rotor or the brakes at all? I've never had high speed run out that wasn't apparent at lower speeds. If anything, it was more pronounced since the frequency was lower. Even CV joints will act this way. Now I've seen a vibration that didn't show itself until high(er) speeds (like 75+) that wasn't apparent below that threshold ..but..

Just seeing if you've thought along this line
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I've got the same thing- it's only noticeable at high speeds. (Or when pulling to a stop. I can feel the "tight" spot grab.)

I suspect that it is because at lower speeds, we're not pushing as hard on the pedal. And possibly at higher speeds the pulsation starts to be some kind of resonant frequency of the wheels and gets amplified.

(Although in my case, I think it's fouled rotors/pads. Or the runout is causing some kind of pad deposits. If I do a couple of high speed stops and burn off the rotors a little, the brakes feel better for a while.)
 
Brake pulsation is quite often brake pad material deposited onto the surface of the rotor in an irregular pattern, and not rotor warpage at all. The last time I replaced rotor/pads on the front of my car, I put the old "warped" rotors on a lathe spindle and checked the run out with a dial indicator. Results : the rotors were not warped at all. But they were severely 'glazed' in a couple of spots and that caused the the brake pads to 'skip' or skid over those areas during braking. And that causes pulsation.

On most vehicles (all of them ?), the drive axles (with CV joints) play no part in holding the wheel hub assembly "true" at all. Therefore a worn CV joint would have no effect on braking pulsation.
 
I have heard that a few massive high speed hard stops can 'cure' deposits on the rotors.
Perform at your own discretion. I have never found this to work, but some have.
New plain cheap Chinese rotors are often very reasonable. Check into it. Often they are just a little more $ than machining the old ones. Clean the hub mounting area perfectly, and use a little anti-seize.
 
Next time you reline your brakes..resurface the rotors and try bedding in the pads by doing 25 to 30 30-5mph slow downs with a few miles of cool down driving in between. Do this right after you put the new pads on. I have eliminated judder in all my cars by doing this.
 
I have cured shudder by warming up the brakes with a normal deceleration, then accelerating to 60-70 mph, slow to 15, and do that cycle four to five times, then allow them to cool off and they are much better.
 
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the drive axles (with CV joints) play no part in holding the wheel hub assembly "true" at all. Therefore a worn CV joint would have no effect on braking pulsation.


But they sure will make your steering wheel wobble and give you the impression of brake pulsation. They will produce tire runout and when brakes are applied Chubby Checker doing the twist is going to can surely be transmitted to the pedal. You can feel improper toe with the brakes applied.
 
Thanks for all the advice.

Turned the oem rotors and reused the akebonos. Had a chance to test it out at highways speeds and the pulsation has completely disappeared.

I would hope that I will at least get twice the brake pad life out of these oem rotors. The next time around that the pads are changed will be when I will replace the rotors with some shiny new ones.
 
Originally Posted By: rcy
Hmm...other way around for me. Every time I've had warped rotors it's more noticeable when braking from highway speeds.

Having experienced how long a machined rotor takes to warp again, I always replace my rotors now.


I completely agree with you on both points. Same here!
 
Originally Posted By: byez
Thanks for all the advice.



I would hope that I will at least get twice the brake pad life out of these oem rotors. The next time around that the pads are changed will be when I will replace the rotors with some shiny new ones.


Just out of curiosity, is it your policy to wait until you need new pads to get them? Although I will surely replace/machine rotors as needed ..AND ..they've gotten more "fragile" in recent evolutions in automotive "advancement", I found it far more economical in time and $$ to preemptively change pads (do whatever other nth degree maintenance to the calipers while there). Now some rotors are cheap enough to just throw on new ones, but I NEVER have to "cope" with a pulsating pedal until I muster the time to deal with it in whatever way is required that always includes additional expense. Many seem to have this method of brake maintenance ..so please understand that I'm the lone coyote here.
 
Well if the rotors fail before needing new pads I will replace them. I just couldn't justify buying new rotors on with only 60 miles of use when I knew it was the leftover transfer material from the old pads combined with the new pads causing the problem.

I have not visited a mechanic in years. The only time I ever really require service is when I need tires mounted & balanced, otherwise most everything else is done in my garage.

So it may take more time to replace things as I go along but not $$ although some would argue that time is money. I'm willing to put in some effort, save money, & learn along the way.
 
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Originally Posted By: va3ux
Brake pulsation is quite often brake pad material deposited onto the surface of the rotor in an irregular pattern, and not rotor warpage at all.


I take a disc sander to my front rotors when the pulsation starts, and it's worked every time so far. They're approaching 80,000 miles of use now.
 
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