bottom bracket sizing question

Discussion in 'Cycling Equipment' started by Peter Z, Sep 21, 2003.

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  1. Peter Z

    Peter Z Guest

    Hello,

    I seem to be in need of a new bottom bracket. I can't adjust the bearings so that I get no side to
    side play and at the same time a smooth feel to the rotation. I definitely can't get it any where
    near as smooth as my wheel bearings are for example.

    My problem is that I don't know what size to get.

    Bike is a 1992 Trek 2100 road frame (on which I had the components from a same year 2300 switched
    over at purchase time when new, so it's mostly Shimano 600 7 speed from that era). I don't know if
    the BB was also switched but in any event mine is a Tange with Shimano spindle. I looked in the
    Nashbar catalog but their sizes for road BBs are not any where the same as what I found on mine.
    Hopefully someone can set me straight :).

    My spindle is labeled 68 = T = 117.5 and is the type which takes 14mm hex head bolts on the ends.
    The left cup is labeled 1.37 x 24T but none of these numbers appear in the Nashbar catalog.

    My bike has a double crank (also Shimano 600) but the catalog suggests that this size spindle (118.5
    actually) is for triple cranks. The double crank BBs (Dura Ace for example) seem to have 109.5mm
    spindles. I'm confused, do I have a triple crank BB on my bike even though it only has a double
    crank? Or have BB sizes changed so much in 12 years?

    I bought this bike new and have never swapped BBs.

    Any help greatly appreciated. I have some images of my set up at http://members.shaw.ca/plz/bb/.

    -Peter
     
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  2. Peter Z

    Peter Z Guest

    I forgot to also inquire as to suggestions for replacement BBs. Are Phil Wood BBs still the top of
    the line? Or are there other comparable BBs?

    In either case, I will need something which sill still work with my cranks, I don't want to change
    them at this time.

    Thanks again for any help.

    -Peter

    "peter z" <[email protected]> wrote in message news:[email protected]...
    > Hello,
    >
    > I seem to be in need of a new bottom bracket. I can't adjust the bearings
    so
    > that I get no side to side play and at the same time a smooth feel to the rotation. I definitely
    > can't get it any where near as smooth as my wheel bearings are for example.
    >
    > My problem is that I don't know what size to get.
    >
    > Bike is a 1992 Trek 2100 road frame (on which I had the components from a same year 2300 switched
    > over at purchase time when new, so it's mostly Shimano 600 7 speed from that era). I don't know if
    > the BB was also
    switched
    > but in any event mine is a Tange with Shimano spindle. I looked in the Nashbar catalog but their
    > sizes for road BBs are not any where the same as what I found on mine. Hopefully someone can set
    > me straight :).
    >
    > My spindle is labeled 68 = T = 117.5 and is the type which takes 14mm hex head bolts on the ends.
    > The left cup is labeled 1.37 x 24T but none of
    these
    > numbers appear in the Nashbar catalog.
    >
    > My bike has a double crank (also Shimano 600) but the catalog suggests
    that
    > this size spindle (118.5 actually) is for triple cranks. The double crank BBs (Dura Ace for
    > example) seem to have 109.5mm spindles. I'm confused, do
    I
    > have a triple crank BB on my bike even though it only has a double crank?
    Or
    > have BB sizes changed so much in 12 years?
    >
    > I bought this bike new and have never swapped BBs.
    >
    > Any help greatly appreciated. I have some images of my set up at http://members.shaw.ca/plz/bb/.
    >
    > -Peter
     
  3. peter z wrote:
    > Hello,
    >
    > I seem to be in need of a new bottom bracket. I can't adjust the bearings so that I get no side to
    > side play and at the same time a smooth feel to the rotation. I definitely can't get it any where
    > near as smooth as my wheel bearings are for example.
    >
    > My problem is that I don't know what size to get.
    >
    > Bike is a 1992 Trek 2100 road frame (on which I had the components from a same year 2300 switched
    > over at purchase time when new, so it's mostly Shimano 600 7 speed from that era). I don't know if
    > the BB was also switched but in any event mine is a Tange with Shimano spindle. I looked in the
    > Nashbar catalog but their sizes for road BBs are not any where the same as what I found on mine.
    > Hopefully someone can set me straight :).
    >
    > My spindle is labeled 68 = T = 117.5 and is the type which takes 14mm hex head bolts on the ends.
    > The left cup is labeled 1.37 x 24T but none of these numbers appear in the Nashbar catalog.
    >
    > My bike has a double crank (also Shimano 600) but the catalog suggests that this size spindle
    > (118.5 actually) is for triple cranks. The double crank BBs (Dura Ace for example) seem to have
    > 109.5mm spindles. I'm confused, do I have a triple crank BB on my bike even though it only has a
    > double crank? Or have BB sizes changed so much in 12 years?
    >
    > I bought this bike new and have never swapped BBs.
    >
    > Any help greatly appreciated. I have some images of my set up at http://members.shaw.ca/plz/bb/.
    >
    > -Peter

    I'm not an expert but I'm pretty sure that it's usually impossible to get BB bearings working as
    smoothly as wheel bearings. Usually you have to allow a small amount of play into the adjustment.

    Adam
     
  4. Matt O'Toole

    Matt O'Toole Guest

    "Jacobe Hazzard" <[email protected]> wrote in message
    news:[email protected]...

    > I'm not an expert but I'm pretty sure that it's usually impossible to get BB bearings working as
    > smoothly as wheel bearings.

    Yes.

    > Usually you have to allow a small amount of play into the adjustment.

    Do not leave any play at all! These bearings carry a pretty big load, and the BB axle is subject to
    flex, so the bearings should have some preload. How much? They should definately have no play, or
    even spin freely, but should still turn easily with the fingers.

    If there's no preload, the spindle will wear prematurely. A worn spindle turns roughly, because it
    wears out-of-round due to axle flex. Preload mitigates this somewhat.

    Of course, this applies only to older, cup-and-cone BBs -- not newer, cartridge BBs, or ones with
    cartridge bearings.

    BTW, cup-and-cone pedal bearings should have some preload too.

    Matt O.
     
  5. satanas

    satanas New Member

    Joined:
    Sep 28, 2003
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    For Shimano Ultegra 7 speed, the correct length BB is 113mm; I have used 107mm successfully as well. I'd recommend a Shimano cartridge unit if you (probably) can't find a new axle, ie UN-72 or UN-52, etc.

    117.5 seems excessively long, and I'd suspect this was swapped for some unknown reason in the past.
     
  6. Jeff Wills

    Jeff Wills Guest

    "peter z" <[email protected]> wrote in message news:<[email protected]>...
    > Hello,
    >
    > I seem to be in need of a new bottom bracket. I can't adjust the bearings so that I get no side to
    > side play and at the same time a smooth feel to the rotation. I definitely can't get it any where
    > near as smooth as my wheel bearings are for example.
    >
    > My problem is that I don't know what size to get.
    >
    > Bike is a 1992 Trek 2100 road frame (on which I had the components from a same year 2300 switched
    > over at purchase time when new, so it's mostly Shimano 600 7 speed from that era). I don't know if
    > the BB was also switched but in any event mine is a Tange with Shimano spindle. I looked in the
    > Nashbar catalog but their sizes for road BBs are not any where the same as what I found on mine.
    > Hopefully someone can set me straight :).
    >
    > My spindle is labeled 68 = T = 117.5 and is the type which takes 14mm hex head bolts on the ends.
    > The left cup is labeled 1.37 x 24T but none of these numbers appear in the Nashbar catalog.
    >
    > My bike has a double crank (also Shimano 600) but the catalog suggests that this size spindle
    > (118.5 actually) is for triple cranks. The double crank BBs (Dura Ace for example) seem to have
    > 109.5mm spindles. I'm confused, do I have a triple crank BB on my bike even though it only has a
    > double crank? Or have BB sizes changed so much in 12 years?
    >
    > I bought this bike new and have never swapped BBs.
    >
    > Any help greatly appreciated. I have some images of my set up at http://members.shaw.ca/plz/bb/.
    >
    > -Peter

    Peter-

    Your bike dates from a time before "low-profile" cranks became popular. A 118mm spindle length for a
    double crank is appropriate. Installing a cartridge BB with a 118mm spindle is a no-brainer.

    Yes, spindle "standards" have changed radically in the past 12 years. They weren't all that
    standardized to begin with.

    Jeff
     
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