Warped Brake Rotors

Discussion in 'OT Driven' started by benny196, Oct 13, 2008.

  1. benny196

    benny196 New Member

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    My steering wheel has begun to shake on my mazda 3 when I am brake while going over 50 mph. This leads me to believe that I have warped brake rotors at only 18000 miles... :( However one of the common symptoms of the brake pedal pulsating isn't happening, only the steering wheel is affected. Does anyone have any other ideas what this might be? If it is the brake rotors, how much does it usually cost to have them trued?
     
  2. PanzerAce

    PanzerAce Active Member

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    possibly a wheel out of balance, or the alignment is fubar.

    And AFAIK, there is no way to have them trued. They can be machined to a flat surface, but unless you are dealing with normal wear, that is going to cause thick and thin spots, which are a great way to snap a rotor in half.
     
  3. vgeek

    vgeek New Member

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    Can't you just buy a new pair?
     
  4. benny196

    benny196 New Member

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    Ya. Could it be balance or alignment issues though? Cause this only happens when I brake. Vgeek- Ya, thats what I'll probaly end up doing.
     
  5. PanzerAce

    PanzerAce Active Member

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    It could be, depending on the actual issue. I would suggest take it to a shop that knows brakes/alignment, etc.
     
  6. benny196

    benny196 New Member

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    Thanks a lot. I'll take it in tommorow.
     
  7. deusexaethera

    deusexaethera OT Supporter

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    Warped rotors wouldn't pulse the pedal, not if the width of the rotor hasn't been affected. Excessive runout (side-to-side warping) would make the car shake without affecting the brake pedal.

    It might be a slight wheel-balance problem, though, and it only shows up when you step on the brakes and give the wheels another contact point to transmit vibration to the chassis.
     
  8. GammaRadiation

    GammaRadiation Active Member

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  9. PanzerAce

    PanzerAce Active Member

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  10. alltracman78

    alltracman78 New Member

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    Most likely your rotors are somewhat warped. Either have them resurfaced or replace them [can be cheaper, it depends how much the new rotors are and how much it will cost to resurface].
    Cost depends where you live and who does it.
    If you pull the rotors yourself and bring them to a shop that can do it, maybe $20 per rotor?
    If you have a shop do it, I would guess at least an hours labor, and they'll probably want to replace the pads while they're at it.

    IMO your best option is to replace the rotors, and possibly the pads [depending on condition].
    Then don't brake as hard and they'll last longer. :)

    Not so.
    It's VERY unlikely that a wheel out of balance will cause shimmy only during braking.
    It's also very unlikely that an alignment will cause any kind of shimmy, especially only during braking.

    Also, you can safely resurface brake rotors to get rid of warpage. If a rotor is solid it will be the same thickness [yes I know solids are normally on the rear].
    And while vented rotors will have slightly different thicknesses [on either side of the vent] from this, it's not enough to cause a safety issue under normal braking [assuming the rotor isn't too warped to begin with, there are limits to what can be remachined].

    You're an idiot.
    That's exactly what excessive runout does, make things shake when you press the pedal.
    What it doesn't do is make it shake when you're driving along. The rotor is too small [and the runout not enough in the grand scheme of things] to cause any noticeable shaking.


    This is why one needs to think a little deeper about things before they are produced as "facts".
    Not your fault, you simply went to a respected manufacturer [StopTech] and read what they had to say. :)
    StopTech should be more careful what they produce as information pertinent to modern cars.

    There's a couple of problems with that article.

    1-The writer is constantly referring to race experience. Race brakes are a different animal than normal everyday brakes. The pads and rotors tend to be somewhat different material and the brakes are put under much more stress than normal, which gives different results.

    2-He seems to have gained most of his knowledge in the 60s and 70s [look at what cars he references; and if you care, his life]. Nothing wrong with this, but brake technology and materials now is a far cry from what it was back then. Even 1990 technology is 18 years old at this point....

    3-What he refers to as
    is basically what is referred to as a warped rotor. Take that "cone" and make it distort in a wavy pattern [~]instead of all one direction.
    The friction surface of the rotor warped from it's original state.
    Warped means: "the state of being twisted or bent out of shape; a distortion or twist"

    Most modern brake pads don't need to be broken in, they're ready to use from the box. I'm talking about the ones for your everyday Fords and Mazdas and Toyotas and Chevys, not Ferrari or Porsche or even maybe Corvetts and GT500s. I don't know much about those, don't deal with them, never worked on them.

    I've seen plenty of warped brake rotors. Not deposits on the rotor, but lateral runout [as deusche so nicely mentioned]. It happens and it's very common when you a lot of hard braking. Some can be machined [resurfaced] back to true, others are too far warped, or too thin, or both.

    Bottom line, not good info if you're trying to learn about the brakes on your 200x whatever.
     
  11. deusexaethera

    deusexaethera OT Supporter

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    And you didn't read what I said. I said runout (and only runout, without other factors involved) will make the steering shake, but it won't make the pedal pulsate, because the distance between the pads won't change. You have to have uneven wear on the rotor, uneven deposition of brake dust, or warping that somehow causes the two sides of the disc to spread apart from each other (which indicates a structural flaw in the vanes that holds the two sides together) before the pedal will pulsate.

    True. Usually the only break-in needed is to mate the pad surfaces to the grooves in the rotors; the pad material is pre-cured nowadays.
     
  12. alltracman78

    alltracman78 New Member

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    And this is why I [and probably many others] dislike you.
    You read something somewhere [or you sit down and think about it], have no real world experience, and somehow you know what you're talking about.

    Let me give you a little tip; "experts" that write books, and talk about whatever field, don't necessarily really know what they're talking about.
    So, do yourself a favor, and the next time you have the urge to spout some knowledge, unless you have real personal experience in it [for instance doing your brakes on your car once or twice doesn't give you that much expertise on brakes] don't phrase it as set in stone, phrase it as a possibility.
    When you don't know, "I think this is how it works" is a lot more palatable than "I know", and makes you look smarter, not dumber.


    Now, on to why you are wrong [again]. If your rotor has runout it's going to move back and forth as it spins. This back and forth is going to move the pads back and forth as well, assuming there is pressure holding them against the rotor.
    What do you think is contacting the back of each pad?
    The caliper on one side, and the caliper piston on the other.
    So, as the rotor "wobbles", it's going to cause the pads to wobble in and out.
    This will push on the caliper AND the caliper piston, causing them to wobble in and out as well.
    If you start pushing the caliper piston in and out, it's going to cause a pressure fluctuation in the system, which will make your pedal pulsate.

    This comes from book knowledge AND real world experience [the best combination IMO].

    I'm smarter than you, and I really know what I'm talking about,so next time I tell you your wrong, I suggest you ask why instead of telling me I'm wrong. You wont look as stupid.

    And, who knows, people might not dislike you so much either. ;)
     
  13. deusexaethera

    deusexaethera OT Supporter

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    I agree with your description of how a rotor with runout affects the caliper. I continue to disagree with the effect that has on the brake pedal, and here's why:

    1. If you have single-piston floating calipers, which a lot of cars have, then the caliper will simply slide back and forth on its sliders.

    2. If you have opposing-piston fixed calipers, then as the rotor wobbles it will push fluid out of one piston or the other, yes, but that fluid will just go into the opposing piston, not into the brake line.

    The only thing that will cause movement of brake fluid outside of the caliper itself (and that's the only way you could feel it in the brake pedal) is if BOTH pads are pushed away from each other, or BOTH pads are allowed to move towards each other. For that to happen, the thickness of the rotor has to change from one point to the next; it's not enough for it to simply wobble side to side, though wobbling can induce vibration in the steering and suspension.

    As for asking politely the next time you tell me I'm wrong, you can kiss my ass. You may be right, but you're going to have to prove it by explaining yourself.
     
  14. PanzerAce

    PanzerAce Active Member

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    I was going to say this as well :o
     
  15. meervincent

    meervincent New Member

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    i dont understand why on a single piston design there would not be pulsing. it would make sence to me if there where less but not none. could someone explain?
     
  16. alltracman78

    alltracman78 New Member

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    I don't care what you agree or disagree with, you don't matter.
    Bottom line, you read something in a book, I do it in real life.
    Experience>book knowledge.

    No, you can kiss my ass, I don't have to prove anything to you.
    See my above reply if you have any questions about that.

    There will be pulsing.
    I sent you a PM explaining why, I'm going to let dueche wallow in his ignorance.
     
  17. meervincent

    meervincent New Member

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    i got no pm do you need to have a sub or something now??
     

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