disk rotor choice

('04 Cavalier) I need to replace the disk rotors. Everyone hereabouts seems to have two varieties: one at $22-ish, the other at $38. The $38
ones have a longer warranty, but only for "defects".
My guess is, the $38 ones are 'better' (more metal?); but, it could be just charging more for a pretty meaningless warranty. Does anyone know?
Thanks, George
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I've seen the same, and I dont know the real answer, BUT if you compare this with brake pads price and quality, you will definitely see a quality difference with the more expensive pads.
And I would not put cheap rotors on my car, regardless.
Out of some sense of statistics, why did you find it necessary to replace the rotors?
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Well, they're warped ... thump, thump, thump when I brake. As to why, and not to be blaming any one particular person, but it seems to have started after someone I'm married to went down a long hill. Which has happened in the past, depending on who's doing the remembering.
We bought the car used. Considering who we got it from, my guess is, if there is such a thing as cheap aftermarket rotors, that's probably what they had on there.
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wrote:

Take an old rotor to the store if possible. Sometimes they put unexpected rotors on cars at the factory. Had heavy duty rotors on my '88 Celebrity sedan. The auto store book said they should only be on wagons. Had to make a second trip. Think the only ones they had were 18 bucks each. Made in China, but they looked the same as the originals. Didn't have them cut true, as some people recommend. No problems with them. Unless you're a metallurgist and can test them, just compare them as best you can and pick what you think is best. The counterman can put both in front of you. Making sure the tires aren't over-torqued is one way to prevent warping. But I think some rotors will warp from overheating. My Celebrity rotors were thumping, but they were also deeply grooved. If they were warped that's probably what caused it. Had about 150k miles on them.
--Vic
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some rotors will warp from overheating.

I think overheating will warp them too, especially if the torqueing is not properly done.
On things I consider critical, including brakes and tires, I dont bet my life on a couple of bucks. There are areas where one can go with the cheapo parts maybe.
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Thanks, George. Warped rotors is a major cause of complaints nowadays. There is some disagreement about exactly why this happens, but I think that we would all agree that just using the brakes going down a long hill should not cause this.
If this link still works, there is a good bit of useful information on it: http://www.brakeandfrontend.com/Article/46342/rotor_runout_check_list.aspx
In addition, never let any jerkwagon tire changer use an impact wrench to put your wheels on your car. Torque wrench all the way.
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George wrote:

You should be able to tell by looking at them. Have them get both kinds for you then check them when they come in. Some really cheap ones are thinner, don't have as many cooling fins, etc. Everything is made in China, but some are better than others.
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I hear what you are saying, but when metallurgy is involved, I dont believe you can tell by looking. Certain good machine work looks better, usually, than crappy machine work. Metallurgy??? A different thing.
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hls wrote:

Good point. Hopefully good machining and more metal is indicative of better metal. It would be a shame to use poor metal with good machining. There was an article on the subject in Pop. Mech. about a year ago. I will see if I can locate it.
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On 3/18/2011 1:03 AM, George wrote:

Go the the store and ask to see both rotors. Buy the one with more metal. In my case, I'd probably get the cheap rotors. My old Cavalier was a great car and served me well. For me, only the cheapest parts would go into that baby. :-)
I read a startling article that said that the pulsating rotors are actually caused by transference of pad material onto the surface of the rotor at a molecular level which causes uneven braking. Beats the heck out of me if this is true but if it is, then breaking-in the pads could be critical. My understanding of the article is that applying the brakes after heating them up will cause a visible imprint of the pad onto the rotor. Weird stuff!
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I dont believe that. When I have chocked up the rotors in the brake lathe, there is definitely a significant warp. I have never seen much pad material transfer to the rotor surface, but then again I buy good pads.
There are several factors at work here.
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On 3/18/2011 2:36 PM, hls wrote:

My guess is that most car guys won't believe it.
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Im sure you are right.
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Do you wash your new rotors in soap and water as the makers of the rotors say is mandatory?
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I do wash them to get the rust preventative grease off of them. I have also used brake cleaner (largely methanol) in the past.
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The experts say brake cleaner is not good enough. It won't remove the metal particles left by the machining process, only soap and water will. Supposedly it's important to remove the metal particles.
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Could be.. I have never noticed any difference, really, but then this might be something I wouldn't notice. Certainly cheaper to use soap and water.
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On 03/22/2011 10:42 PM, Ashton Crusher wrote:

disk pads contain abrasives that make "metal particles" completely irrelevant. the reason to clean is so you get braking, not lubrication when the brakes are applied the first time.
--
nomina rutrum rutrum

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On 3/18/2011 2:36 PM, hls wrote:

Here's the little article:
http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml
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On 03/23/2011 03:52 AM, dsi1 wrote:

"in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history - I have never seen a warped brake disc"
indeed.
this is preceded by: "presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification"
you will find that in most cases, simply scraping surface rust off the hub/wheel interface, applying a little antiseize, and correctly torquing fasteners will cure most "warped" disks.
the fact that disk machining also "cures" is usually due to the coincidence that cleaning is done at the same time.
--
nomina rutrum rutrum

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