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Thread: Documentation Error /6 Engine Dims

  1. #1
    papafoxtrot
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    Documentation Error /6 Engine Dims

    I searched to see if I could find something on this but my search skills stink so pardon me if I'm being redundant. I am at the point with my 75 R90S rebuild where I need to do main & rod bearings. For guidance I go to the factory manual I have and it tells me the crank journals are a nominal 60 mm. But then they tell me that this is 2.34" nominal. I get really confused because my journals are miking at 2.36 something. Then I realize that somebody in Bavaria must had a couple too many dunklebeirs when they did the math 60mm IS 2.36 nominal. So I ask my dealer for the information to size the bearings and they send me the very same (WRONG) info.

    Now despite the obvious math problems above, I have a question for the technical cognoscenti;

    One document says crankshaft radial play should be 0.035 - 0.065mm (.0013 - .0025") the other says 0.020 - 0.065mm (.0008 -.0025")...... Who should I believe?

  2. #2
    Registered User toooldtocare's Avatar
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    From an early BMW Factory /7 manual, all I have, page 1 of 2

    But I think the dimensions may be the same. Hope it helps.
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  3. #3
    Registered User toooldtocare's Avatar
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    Second page of same manual

    Hope this helps you, maybe the errors were corrected in the latter manual? Wayne
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    English - Metric multiplier

    Having taught math for many years, and having to re-calculate back and forth many times, I have the multiplier memorized.

    .03937 = 1 mm

    So, if you wanted to calculate the English size of 40 mm. you would take .03937 x 40 = 1.5748"

    As a safety I would always do a mental calculation using .040 as the nominal and then multiply by mm dimension. For example, if I wanted to ROUGHLY know what 10mm would me in English, I would multiply .040 x 10 which equals .400 (slightly over 3/8" or .375). If I wanted to EXACTLY get the measurement, I would use .03937 using a calculator.

    Of course use division to go the other way.

  5. #5
    Day Dreaming ... happy wanderer's Avatar
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    Quote Originally Posted by jimmylee View Post
    Having taught math for many years, and having to re-calculate back and forth many times, I have the multiplier memorized.

    .03937 = 1 mm

    So, if you wanted to calculate the English size of 40 mm. you would take .03937 x 40 = 1.5748"

    As a safety I would always do a mental calculation using .040 as the nominal and then multiply by mm dimension. For example, if I wanted to ROUGHLY know what 10mm would me in English, I would multiply .040 x 10 which equals .400 (slightly over 3/8" or .375). If I wanted to EXACTLY get the measurement, I would use .03937 using a calculator.

    Of course use division to go the other way.
    I wonder when the US will go metric like the rest of the planet?

    I remember when they started teaching us the metric system in high school back in the 60's. At first a lot of folks thought the sky was falling and this was a radical idea. Before too long everyone got used to it and it was no big deal. Efficiencies gained in international trade alone more than paid for the switch. The math sure got easier and I for one was grateful for that!

    It's hard to believe the US, Liberia and Burma are now the only non metric nations on Earth.
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  6. #6
    Rally Rat
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    Quote Originally Posted by Happy Wanderer View Post
    I wonder when the US will go metric like the rest of the planet?

    I remember when they started teaching us the metric system in high school back in the 60's. At first a lot of folks thought the sky was falling and this was a radical idea. Before too long everyone got used to it and it was no big deal. Efficiencies gained in international trade alone more than paid for the switch. The math sure got easier and I for one was grateful for that!

    It's hard to believe the US, Liberia and Burma are now the only non metric nations on Earth.
    But even with that, after 20plus years in canada imperial circlips are standard in supply stores and metric are special order with min quantities

  7. #7
    papafoxtrot
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    Just what the doctor ordered

    Too Old,

    That's just what I was looking for. I'm surprised my dealer still had the bad info. Amazing how pervasive a mistake can be. I thought that 8 tenths was a bit on the tight side so I'm glad I got corroboration on the 13 tenths on the tight end. I'm ordering my bearings today!

    Cheers,
    Paul_F



    Quote Originally Posted by toooldtocare View Post
    But I think the dimensions may be the same. Hope it helps.

  8. #8
    Registered User kwb210's Avatar
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    Coming out

    Quote Originally Posted by Happy Wanderer View Post
    I wonder when the US will go metric like the rest of the planet?

    I remember when they started teaching us the metric system in high school back in the 60's. At first a lot of folks thought the sky was falling and this was a radical idea. Before too long everyone got used to it and it was no big deal. Efficiencies gained in international trade alone more than paid for the switch. The math sure got easier and I for one was grateful for that!

    It's hard to believe the US, Liberia and Burma are now the only non metric nations on Earth.
    Probably never. That would make us look weak and gay. lol
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