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Discussion Starter #1
Hello All-

I got my trans shifting problem fixed and I am onto fixing the rear brakes and rotors.

When my mechanic (al's autohaus in denver) and I went for a drive to adjust the vacuum modulator he thought the rear rotors were warped. The car has a slight front to back rocking that slows down in tempo as the car slows down. While his diagnosis seems to make sense. The steering wheel has no shimmy or shake so front rotors seem alright.

The car had rear rotors, and rear pads 35k miles ago, and new front rotors bearings, and pads 30K miles ago. The front pads are ok for now and the rear pads are almost shot. The rotors were bought at auto zone for $40 a piece and the receipt says VDO rotor. Is that a reputable brand? I only saw duralast and beck arnley for sale on their website.

Is is possible for rotors to warp after such a short time? Are there other potential brake problems that would produce a front to back rocking as you slow down?

I am leaning towards ADE rotors from Autohaus AZ, OE pads, and will repack the rear bearings while I am in there. I am going to use this pictorial as a guide.

How To Replace Front Rotor W123 - ShopForum

If anyone has any tips or thoughts I would appreciate them. I am hoping it warms up so I can get this done. I have a new set of bilstein hds to put in next. Can't wait.

Thanks again for all your help,

Bill
 

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they can warp if you over tighten the lug bolts. Never use a impact wrench on them or your sure to have warped rotors. 82 ft pounds is all you need.
 

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Discussion Starter #3
If the guy who had the car before me overtightened the rotors, would that ruin the hubs too?
 

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no just the rotors
 

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hubs should be fine, you will however have to, at minimum, repack the bearings, when moving the hubs to the new rotors. 79Mercy has a write up of the process.
When I changed mine out, also due to PO gorilla tightening the lug bolts, I got new bearings. Getting the old races out is a bit of a challenge and I don't recommend it unless the bearings look dark and shot.

good time to change your pads if they're close...
 

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As a guy who's in the parts business, generally speaking AutoZone sells the lowest quality parts - down there with Wal-Mart and Advance. Warped 35k-mile rotors from AutoZone wouldn't surprise me at all; warping can also be caused from your driving style (too much "on" or last minute "on"), not to mention from water puddle on a hot rotor, or any kind of misalignment (wrong torque on the bolts).

You can probably get those rotors turned for $10 a piece and you'll be as good as new, but the AutoZone crap won't last 60k-70k miles like a good rotor or pads will.
 

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W123 rotors are meant to be replaced with every set of pads. Rotors are much more likely to warp from heat than over tightening.

You should get W126 brake setup so you don't have to worry about these silly things.
 

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Rotors can warp in a drastic change in temperatures too.

If you've been using your brakes a lot (heavy traffic) and splash into a puddle, it can warp the rotors...OEM or not.
 

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They also warp as they get thinner from wearing. Turning the w123 rotors just makes them even thinner. For the cost of turning, you would be better off just applying that money to good, new rotors, or do like Winmutt and do the w126 upgrade. All you need are w126 calipers, rotors, and backing plate.
 

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Rotors are meant to be replaced when they are warped, have cracks or when they are below minimum specs.

Len
 

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Keep in mind that as liquids don't compress, any shimmy from the rear rotors is taxing the entire hydraulic system on the car every time the brakes are depressed, from couplings to master cylinder seals to brake line brackets etc.
 

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In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.
Funny, uneven and thickness variation sure sounds like warpage to me.
 

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Discussion Starter #19
Thanks again for all the good info. I really do appreciate all the good info I have gotten from this site. I could never have done so much without all your help.

I ordered ate rotors, oe pads, pad wear sensors, brake paste, and new inside and outside oil seals. Also this job is going to be a good excuse to buy a hex socket set and a torque wrench.

I will let you guys know how it goes when I get home and can work on it. We are in Northern MI at my inlaws place and it is snowing like crazy.
 
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