Cavalier brake problem

My 98 car with 70,000 miles has a strange problem. When slowing to a normal stop the brakes will throb "similar" to the ABS activation and I fear the car
will not stop. The ABS light does not turn on. This occurs intermittently on both dry and wet pavement. With hard braking this does not happen and the stop is normal. I took the car to my regular service mechanic and he said there were no error codes and he found no electronic or mechanical problems. New front rotors were installed and the rear drums cut along with new pads and shoes, which now have about 10,000 miles on them. My brother said that a rotor is "probably" warped. Is he correct or has anyone experienced this problem and know what is wrong? Thank you.
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Karen, That throbbing is a common symptom of warped or unevenly worn rotors (thickness variation) .
If the rotors are not cut properly, or are installed without attention to trueness, this can become noticeable, and can get worse.
It can also develop if someone has improperly tightened your lugnuts, or if you have overheated the rotors excessively.
If the work is not done correctly (to rectify the problem), the symptoms can return after a short period.
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Thank you HLS, I feel more confident now that you confirmed my (non-mechanic) brother's guess. I was concerned that I would be paying for something that would not fix the problem. Karen

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Another tip..dont ever let anyone near your rotors with an impact wrench (air wrench) This is common when some companies rotate your tires.
Not even if they tell you they use Torque Stix which will assure proper lugnut tightening. In the hands of an idiot, they can cause variations in tightening that will come back to cause you a repeat of the throbbing. Insist on hand tightening using a torque wrench.
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HLS wrote, "Another tip..dont ever let anyone near your rotors with an impact wrench (air wrench) This is common when some companies rotate your tires. Not even if they tell you they use Torque Stix which will assure proper lugnut tightening. In the hands of an idiot, they can cause variations in tightening that will come back to cause you a repeat of the throbbing. Insist on hand tightening using a torque wrench. " ********************************************** One thing I would add to that is that even with a torque wrench, I think it can still be done improperly. I have seen people tighten lugnuts and jerk the wrench to make it click, versus applying an even, steady pull to the wrench until it clicks, as the wrench was designed to be used It's like rather than trying to achieve uniform torque, they're merely trying to make the wrench click. :-)
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This would have been my response too. Except, my 2002 Cavalier started the pulsing brake thing. It was after a tire change and I thought the same about warped rotors. Then I changed the front brake pads. No more pulsing. No idea why.
Al
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Big Al, I find your reply most interesting as I believe my problem showed up shortly after having a front tire flat repaired and they did a courtesy tire rotation. Approximately how many miles on your brake pads at that time? I have about 10,000 on mine at the moment.
Karen
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Good thing to keep in mind, Karen.. When I have had warpage problems in the past, they have also come after the tire rotations..Because the idiots with the impact wrenches distorted my rotors.
A good mechanic can sort it out for you, whatever the cause. A bad one can charge you a lot, and your problem can recur.
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Big Al wrote:

I have noticed one issue with some after market brake pads on other vehicles. It seems the friction surface is slightly too large or off center. Then when the pads wear down, it leaves a edge over the top of the rotor that can cause some strange effects. I just took a set of my Taurus that had this very issue.
Bob
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It sounds like wharped rotors some new rotors sold by advance auto etc. require turning before use and if your regular mechanic missed it I would look for another mechanic!

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Some rotors need surfacing before being installed. It helps bring the braking system to optimum quicker.
The runout (warp) and thickness variations should be measured to be sure that they are within reason. In some cases, the warp can be decreased by proper indexing of the disc upon the hub. In all cases, the seating areas of the disc (when applicable) should be cleaned, and variances checked after installation.
These problems seem to have become more prominent over the years.
One way to minimize the problems is to have the disc machined on the car. This brings a variations into specification if properly done.
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