Brakes Wheels 1st Gen Tires Rotor thickness question.

Discussion in '1st Generation: 2002–06 R50, R53 & 2004–08 R52' started by goaljnky, Aug 8, 2010.

  1. goaljnky

    goaljnky New Member

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    Anyone know what the minimal rotor thickness is before they should be replaced? This is for Gen 1 JCW (R56 regular) brakes. Someone suggested to replace them every time the pads are changed, but I am not convinced.
     
  2. lotsie

    lotsie Club Coordinator

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    I've heard the same thing, change pads and rotors. Seems strange to me also.

    Mark
     
  3. Nitrominis

    Nitrominis Banned

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    The most accurate way is not by the oem specification but by the actual information on the rotor itself.
    The minimum thickness should be stamped on the rotor which the usual location is inside center. This number location can vary depending on supplier.Using this specification you measure by way of vernier caliper or similar measuring device the smallest thickness and compare to the rotors specifications to determine if it is machinable?


    Generally if the rotor is serviceable you only need machine the rotor and change out the pads.

    Do not cut corners and change only the pads.You will not get full braking efficiency out of the new pads and may cause damage or uneven wear patterns in the new pads.
     
  4. goaljnky

    goaljnky New Member

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    Lynn,

    Inside center? So I would need to remove the rotor to find it? And are you saying a rotor should be turned (machined) if not replaced when pads are replaced?
     
  5. lotsie

    lotsie Club Coordinator

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    I have always heard, except on MINIs, to get the rotors turned/machined, when changing pads.
    Again, this is strange to me. Are the rotors milled OEM to only last as long as normal pad life:eek:ut::confused5:

    Mark
     
  6. Nitrominis

    Nitrominis Banned

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    You might need to remove the wheel to see it.
    You would have to see the cost between a new rotor and machining yours. In either case I recommend checking even a new rotor for being true.

    When ever you do a friction pad/shoe re fresh part of the job is not only the replacement of new pads/shoes but the turning/machining of the disc's/rotors.
     
  7. Nitrominis

    Nitrominis Banned

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    There are way to many variables that effect the condition and longevity of the pads and rotors. The pads will wear a pattern into the rotor over time and how you use your brakes. So when you change pads you want the best surface for your new pads. This is why you place a nice flat surface on the rotors by machining them.
     
  8. goaljnky

    goaljnky New Member

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    So how much is a good lathe these days? LOL..
     
  9. lotsie

    lotsie Club Coordinator

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    I understand that:), but why does MINI say you CAN"T machine the OEM rotor, you must replace it?

    Mark
     
  10. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    I have no idea what their "reason" is.

    But my cynical reason, which I believe to be somewhat rooted in fact, is:

    Because the stealer sells *expensive* rotors.

    And my local shop only charges me 12 bucks to turn a rotor.
     
  11. mini_racer

    mini_racer Well-Known Member

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    Min thickness on this rotor (i.e. 1st Gen JCW and/or 2nd Gen S) is 20.4 mm, and yes it is indicated on the rotor hat. It is on that little painted ring area around the contact of the wheel to the hat.
    It is not possible to see it with an OEM wheel, but I am sure there are a few after market wheels with a small enough hub/center section to see it. It is easy to see with the wheel removed.

    Not everything MINI says are words to live by, they say you should NOT rotate tires, go figure.
     
  12. goaljnky

    goaljnky New Member

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    Mini_racer,

    Do you know if it's the same for fronts and rears?
     
  13. mini_racer

    mini_racer Well-Known Member

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    No, not the same. The rear discs much smaller and are not vented. For the 1st and 2nd gen they have a min thickness of 8.4mm, with a nominal thickness of 9.9 mm.

    I think about the only difference between the 1st and 2nd Gen is the hole size for the lug bolts or studs.
     
  14. goaljnky

    goaljnky New Member

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    Thanks for the info. Now I need to pick up a micrometer and find a local shop to machine my rotors.
     
  15. mini_racer

    mini_racer Well-Known Member

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    Sure, happy to help.

    Blanchard spiral grinding is best to resurface a rotor, but not many shops have that equipment. Much more common is lathe turning of the rotor to resurface and it is cheap as well, I can get a rotor turned for $10 each, and Paul reports he can get Blimey's rotors turned for $12 each at his local shop.
     
  16. goaljnky

    goaljnky New Member

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    Yeah, I remember way back in the day paying about 10 a rotor. That was a while ago. Like 20+ years a while. I think I will pick up some new rotors and then just machine the ones that are on now for use next time.
     
  17. Nitrominis

    Nitrominis Banned

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    You should always have even the new rotors checked and a surface turn before installing them. Never assume because they are new that they are true.


    A great desk tool to have and cheap is a MOUNTAIN MTN5900 Digital Caliper. Makes your forum posting I.Q increase by 300 :lol:

    [ame="http://www.amazon.com/Mountain-6-Inch-Digital-Stainless-Caliper/dp/B000LQEUHC"]Amazon.com: Mountain 5900 6-Inch Digital Stainless Steel Caliper with Case: Home [email protected]@[email protected]@http://ecx.images-amazon.com/images/I/[email protected]@[email protected]@41mEG3nx5aL[/ame]
     
  18. goaljnky

    goaljnky New Member

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  19. mini_racer

    mini_racer Well-Known Member

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    If you didn't waste so much of the budget on fancy tools, you would have more to spend on fancy brake components. :D
    This is all you need....... 6" Utility Caliper

    Ok, maybe the $20 model just might be a little better, but just a little.
     
  20. k-huevo

    k-huevo Club Coordinator

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    #20 k-huevo, Aug 9, 2010
    Last edited: Aug 9, 2010
    None of the calipers shown so far are appropriate. It will require an outside micrometer or a rotor measuring caliper. If you attempt a measurement with one of the calipers shown to this point, the outer lip will be the only width measured and not any of the swept area. By far a micrometer is most accurate and will measure differences in width across the surface and around the entire rotor. I use a rotor measuring caliper and it can become skewed with varying amounts of pressure, but with a light touch and starting calibration it works reasonably well. http://djvmerchandise.com/pro1305979.html

    A finger nail test is a good indicator, if you can feel a lip on the edge, and the nail undulates across the rotor surface, toss the rotor.
     

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