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Replaced 1 rotor...still vibrating


ApexAnalog

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I've had vibration/shaking when braking lately. I looked at the front rotors and they looked fine - not warped or anything.

 

The rears were bad, though. One was visibly warped and the other is not flat as it should be, but kind of grooved, like the pad is cutting into it.

 

I replaced the warped one, and it stops more smoothly, but still there is still some vibration. I will replace the other caliper tomorrow morning, and that may solve the problem, but I thought it was strange that the vibration was still there.

 

Any other ideas about what could be causing the vibration? It is slightly audible, so its clear that its coming from the rear brakes...I think.

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I own two early Luminas--so I bought a disc (and a drum) lathe.

 

ONE hard stop from highway speed and the front rotors warp. And I'm sick of buying rotors. I got the last pair from NAPA, the heavy-duty slotted versions. About $85 each. Those seem to hold up better than the previous units. I was buying the mid-grade Canadian or Mexican rotors. I refuse to use Chinese rotors, they're just a failure waiting to happen.

 

You can have the rotors warped enough to cause problems, and you'll NEVER see it with the naked eye. Shows up right away on the lathe, though. It's easy to see the problems as the rotor is getting machined!

 

Be sure that the inside mounting surface of the rotor, and the outside of the hub, are free of rust and debris. I use a wire brush on a drill, and then final polish that area with emery cloth.

 

Torque the lug nuts as specified in the owner's manual. I torque in 20 ft/lb increments.

 

Assure that the calipers aren't sticking--the pistons need to move, and the whole caliper must float on the mounts. If not, you'll wear pads unevenly or too fast, and both the rotor and the brake fluid run too hot.

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well... One thing many don't realize is that a warped rotor can't (or shouldn't) be turned. If it has started warping it will continue to warp. could that be your issue Schurkey?

 

I warped the new front rotors on my first lumina..... I have since discovered that they make both composite and solid rotors.

 

composite rotors have a thin sheetmetal hat, or hub area.

solid ones are fully cast and have a thick hub or hat.

 

so thats to say my first Lumina's new rotos were composites.

 

I've had NO trouble with any rotor on any of my fleet of cars, as long as that rotor is a solid design.... although I should say that my 92 luminas has gone 45,000 miles on the composite front rotors that were on the car when I bought it... :shrugs:

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Yeah, I had GM fix the brake pulsation under warranty--official factory "cure" is to cut the rotors. Didn't last. This is on my "prime" car, '92 Euro 3.4.

 

Then I threw the original GM rotors in the scrap bin, and installed full-cast rotors (not composite) Better than the GM, still not that great. Constant problems with steering shake only when braking.

 

This last round I went with the slotted rotors from NAPA. I think those are composites, again. So far, so good, but only about 4K miles on them, and very little of that is "spririted" driving. I can't afford to buy new rotors every time I nail the brakes hard. So it's only been three sets of front rotors in 112,000 miles + the original ones were cut once = 4 fresh braking surfaces. Problem is, I've had to continue to use them even though they are causing steering wheel shake, or else I'd be dicking with it every month or two.

 

Then I bought another Lumina last summer, one year newer. Has lightly warped rotors, not real terrible...yet. It gets pretty light-duty useage. We'll see what happens in another 2 weeks--I'm taking that car on a 4K mile trip starting Sunday or Monday.

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hmm... well... I have one rear hub on my 95 cs that has scaled with rust and this makes the rotor act like it is warped but is is really the rust unevenly offsetting the rotor... On a warm day I intend to grind the hub down to fix it. any thought?

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Right, but when I had a panic stop a few years back and had tons of fade; I got vibrations like it was warped rotors.

 

When my dad had his '01 alero that thing would have vibrations every 20k and would need to get the rotors turned.

 

I'm not saying your wrong just giveing some insight.

 

FWIW- The z34 had p-friction pads, and white-box specials.

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tie rods or suspension... my braking wobbles a little bit, but its not wobbling so much as pulsation anymore... which, with abs, is somewhat unavoidable isn't it, being that they tighten and release in an ummm.... pulsating fashion?

 

My car didn't stop very well before we fixed my "tie rod" issue.... but the front suspension helped enormously in the control of the car... I've replaced two rotors since I got the car, over a year and a half ago when I got the car... hah maybe I should check into new ones, but I check the ones on it periodically and they all look fine...

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I read through the thread posted by mfewtrail, and also the link that appeared in that thread. That link is to an article authored by Carroll Smith, whom I greatly respect. I have several of his books, Engineer to Win, Tune to Win, Drive to Win, and Nuts, Bolts, Fasteners, and Plumbing. All of those books are recommended, ESPECIALLY the Nuts, Bolts, Fasteners and Plumbing book. Wonderful stuff.

 

That said, I'm reluctant to contradict the man. But I'm going to anyway.

 

He talks about thickness variation, even discusses how to measure it with a micrometer, but that isn't what rotor warping is.

 

Anyone who has read service manuals for disc brakes knows there is a spec for thickness variation, and also a spec for lateral runout. And the lateral runout is what most folks would call "rotor warpage". It's not the ONLY kind of rotor warping, but it's a common one.

 

Thickness variation can cause brake puslation felt in the brake pedal--similar but not the same as the pulsation of anti-lock action. The car may shudder to a stop, as the linings will grip more then less in rapid succession. Of course, the thick sections of the rotor grip more, because they're applying more pressure to the pads--so more friction. In extreme cases, thickness variation will show up as steering wheel shake.

 

Lateral runout tends to show up as steering wheel shake that can cause unsteady application of the brakes if bad enough. Not exactly the opposite of thickness variation, but close.

 

If you don't believe that rotors can warp:

Measure the lateral runout of several well-used rotors using a dial indicator "sideways" against the outside of the braking surface; (you need to be cautious about wheel bearing play screwing up your measurement) or,

Watch a few rotors, correctly mounted in a brake lathe, while the operator takes a light cut. You'll see the most amazing patterns of cut vs. uncut material. (Assure that the rotor is true in the brake lathe.) Now, not every weird pattern is an indication of warped rotors, but when you are consistantly cutting more on one section of one side of the rotor, but the cut is 180 degrees off on the other side of the rotor, it's a pretty good indication of warpage.

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Had the same problem and did a couple of things. First I replace the rotors and pads on both sides and still had the vibration. After checing calipers, tires, alignment, etc.... ended up that the rear caliper on the drivers side was hanging up due to the caliper. Bought this kit http://store.yahoo.com/brandsplace/0246-otc7639.html

and put new all new mounting hardware in and it stopped.

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I have a similar situation with brakes pulsating. When I changed out the rear disks I noticed that I had some of the metal from the hub come off with the disk. It was in rust form but, now the surface that the disk sits against is "warped" or not true. I did the same as above where I replaced the rotors but had the same problem. I need to pull the hubs off, pop the lug bolts out and get the hub lathed back to smooth and true. if this cant be done then I will have to replace both rear hubs to get rid of the pulsating.

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  • 3 weeks later...

I have both rear rotors replaced now, and its apparent that warped rotors is not the cause. The vibration is always there, its just very subtle except when braking. The rear rotors WERE warped, but that was only part of the problem. What I thought was one problem was actually two or more problems...seems like thats an decent description of what its like to own a w-body... :lol:

 

Seriously, though, when this car is working well, I love it.[br]Posted on: March 30, 2006, 01:28:57 PM_________________________________________________I can hear a slight clunk from the rear passenger side hub, so that probably needs to be replaced - already had to replace the rear drivers side hub... I think I'll get an alightment/balance, too....that should solve some vibration problems, if not all...

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I have a similar situation with brakes pulsating. When I changed out the rear disks I noticed that I had some of the metal from the hub come off with the disk. It was in rust form but, now the surface that the disk sits against is "warped" or not true. I did the same as above where I replaced the rotors but had the same problem. I need to pull the hubs off, pop the lug bolts out and get the hub lathed back to smooth and true. if this cant be done then I will have to replace both rear hubs to get rid of the pulsating.

same problem I have experienced. this I have experienced ont the left rear hub on my 95 CS only.

anytime I mess with anything on the hub or brake rotor, i coat the contact surface with antisieze, to prevent future rust.

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