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Thread: Do you have your brake rotors turned?

  1. #1
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    Do you have your brake rotors turned?

    A friend of mine insists that it is pointless to have brake rotors turned since minor imperfections will be worn even. He says If the whole rotor is warped then it should be replaced. I've never had brake rotors turned, myself, but I'm not that hard on my brakes. Whats the story on "to turn" or "not to turn"?

  2. #2
    The shop I take my car to does not recommend turning the discs. About the only issue I can see is that when you put new pads on, they are not fully bedded and it may take more brake pressure until they bed, which happens fairly quickly.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  3. #3
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    I am from the opposite camp. I live in a mountainous area. I want full brakes now. Not a few weeks or days from now. I lose 800' in elevation just from where I live to the downtown historic area of town.

    I turn the rotors when I replace the pads. I want a flat surface to a flat surface.

    I have heard but not verified there are some rotors they don't recommend turning however.
    Ken

  4. #4
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    Turning brake rotors used to be common when there were such things as "Service Stations". Every service station had the machine and it was easy to drop them off, stop back by in a few hours and pick them up. So it was easy and it was cheap and it worked well. Fast forward to today and just trying to find a place that can turn them that you can trust is a challenge. It's something the people in the business don't even do much, so it's normally a hassle to have them do it. Last set I tried to have turned, I was told "Come get them tomorrow afternoon". I explained that I had the car apart and needed them back today. Didn't matter. Seemed they had one guy that did it and he was busy working on other jobs. I went and bought new rotors for about $25 each at the time, and never tried to have another one turned.

    I sure miss Service Stations where they did work like that, patched tires, did the pain in the tail things that you can't find people to do these days.
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  5. #5
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    Given the relative low price of rotors today, replace them. Properly installed pads and new rotors will virtually eliminate any brake squeal. One of the big three, I think it was GM, once tried cutting a V groove in the rotor and produce a brake pad with a corresponding profile to fit the groove. The idea was this would reduce squeal. Don't see any of those on the market these days. The only way to prevent squeal is to use quality components and install them correctly.

    Hang and bang shops usually just install new rotors because its quicker. Plus, they don't have to maintain one or more brake lathes. Look at a shop with several bays or more and imagine the down time with mechanics standing in line waiting to turn a set of rotors. Some applications required the rotor to be on the vehicle in order to turn them accurately, which is yet another machine.

    The cost of rotors has dropped so much in recent years that it makes sense for the professional installer to have new rotors in stock or out for delivery by the time the car is going up on the rack.

    BTW, I don't think of brakes as a stopping device or system, although this is the end result. I think of brakes as an energy converter. They convert the inertia or momentum of the vehicle into heat. It takes a lot of energy to move a one to two ton vehicle forward. That energy doesn't disappear when we apply the brakes, it has to go somewhere. It gets converted to heat.

    Hybrid vehicles convert as much off this invested energy as possible into a flywheel rather than just convert it to heat.
    Last edited by Greg Peterson; 08-07-2011 at 1:36 PM.
    Measure twice, cut three times, start over. Repeat as necessary.

  6. #6
    No one has yet addressed the question of whether it's necessary to have the rotors turned. The only reasons I can see are if the rotor is not running true, and to get better initial bedding when replacing the pads. I questioned my shop, which is not a "hang and bang" shop, and their answer was that if the rotor is within spec for running true, they do not recommend turning the rotors.

    By turning the rotors when they don't need to be turned, all you're doing is taking metal off that doesn't need to be taken off and shortening the life of the rotor. There's a spec for the thickness of the rotor and when they are thinner than that, you need to replace them. So if a shop wished to "pad the bill" they'd turn the rotors ever time they changed the pads. They'd get the cost of the turning and you'd have to replace the rotors faster than if they didn't turn them.

    So if you have your rotors turned every time you have the pads changed, for what reason do you do that?

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  7. #7
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    Turning the rotors when installing new pads, along with making sure the calipers are working properly and greasing the parts that require lubrication, is the surest way to prevent squealing brakes.

    I don't know if you can turn the warp out of a set of rotors. The warping occurred as a result of improper lug torque and heat. I would not be surprised if the combination permanently altered the properties of the metal so that it is prone to warping again.

    The brake pad warranties we deal with are almost always the result of improper installation.

    A rotor can be turned if it is within spec, so long as it does not end up to close to minimal tolerances after turning. You certainly would not want to put a rotor back on that was at or near minimum tolerances.
    Last edited by Greg Peterson; 08-07-2011 at 2:02 PM.
    Measure twice, cut three times, start over. Repeat as necessary.

  8. #8
    My understanding is that if the rotor is thick enough that they should be turned so you have good braking surface. If you look closely at a used rotor there will be a series of humps and dips that also match the contours worn into the pads. Changing just the pads results in less than 40-50% contact between each pad and the rotor. This can dramatically affect your stopping distance. Pads don't wear down to match very quickly.

    For safety reasons either get new rotors or have the old ones turned whenever you install new pads. The cost of either process will be less than the deductable on your insurance if you hit someone because of reduced braking capacity.
    Lee Schierer - McKean, PA

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  9. #9
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    I live in a mountainous area. One of the warrantee issues I had on a new 83 K-5 Blazer was brakes not working properly. We fought brake issues for the entire warrantee period. One time the dealer would replace the pads...the next time he'd turn the rotors and reinstall the same pads. Once the warrantee period was over, I assumed the maintenance on the vehicle. I would remove the rotors and have them turned whenever I replaced the pads. We never had brake problems after I took over the maintenance.

    It's a matter of safety. Flat surfaces against flat surfaces..immediately. If you put flat pads against a grooved surface EVENTUALLY the pad may wear to the contour of the rotor but until does you don't have 100% of the available pad surface providing braking force. In mountainous areas it's best to be a little conservative.
    Ken

  10. #10
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    The answer to the OP's question is "it depends".

    IF, your rotors run true (checked with a dial indicator), IF they do not have grooves cut into them from pad wear, IF the vehicle did not have a problem with surging when braking, and IF the rotors are thicker than the minimum spec, you do not need to turn them.

    If your vehicle exhibits brake surge and a dial indicator shows that the rotors are true, then they should be turned or replaced. The reason why is because some rotors can develop hardened spots on them which can cause the same sympton as a warped rotor. This typically happens on heavier vehicles that are subjected to higher brake loading and temperatures.

    They should be turned or replaced also if they have a few thousands of runout or are grooved, presuming that they will still meet minimum thickness specs after turning.

    Warped rotors can result from improper torque (or inproper torque sequence) when attaching wheels too.
    Last edited by Scott T Smith; 08-07-2011 at 3:31 PM.

  11. #11
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    My local NAPA dealer turns them in an hour for like $10 each, so why not? I like to get the ridges off and especially the rusty ridge at the outside that is always bigger than the worn section of the rotor. Plus, how thin will you let your rotors get if you don't get them measured once in a while? I suppose that if I didn't have a shop close and the rotors still looked in good shape, I would consider leaving them on for one more set of pads.

    Ok, those that don't turn, just reuse, how many sets of pads have you gotten out of one rotor?

  12. #12
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    Ken,
    Have you ever tried cross drilled rotors on your rigs?
    Measure twice, cut three times, start over. Repeat as necessary.

  13. #13
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    Greg.....I considered it on a used F-350 4-WD I bought. I had to do some serious front end work (shim the straight axle FE), realign FE and replace both rotors, calipers and steering wheel pump. But I have considered it.
    Ken

  14. #14
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    You may want to consider them in the future. They are an effective solutions to poor brake performance and/or life on the bigger rigs like yours.
    Measure twice, cut three times, start over. Repeat as necessary.

  15. #15
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    Whenever I do my brakes, I have the rotors (or drums) turned, or, if they are too thin, replaced.

    I'd still love to know what the combination of parts was on our (now gone) '96 Dodge Grand Caravan. My parents were the first owners, never did the brakes, and I first did the front brakes on it at 105,000 miles. After that, I would get about 25-30,000 miles between rehabs.
    Jason

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore


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