slight fork problem - ok or not?

Discussion in 'Cycling Equipment' started by Ant, Jan 22, 2003.

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  1. Ant

    Ant Guest

    got a new fork, some sort of Look carbon blades pretty thing. when i put a perfectly dished wheel in
    it the wheel is a bit off to one side, around 2mm to one side near the brake mounting hole.

    i perused the archives, but couldnt find something that mentioned what w3as acceptable
    misalignment/fork misconstruction measurements. example:

    paul southworth in '93- "One pretty good indicator of mismatched blade lengths is to align the fork,
    the stick a known-good front wheel in it (no tire) that is perfectly dished (ie, no dish at all) and
    see if the brake bolt-hole in the crown lines up with the center of the rim (ie, the valve hole).
    It'll be pretty far off if there is even a millimeter or two of blade-length discrepancy because the
    distance from the axle to the rim will effectively exaggerate the difference."

    is my fork fine?based on my unexpert look, id guess that the discrepancy comes from a slightly less
    well fit dropout on one side, which effectively makes one blade a fraction longer. the
    off-centeredness wont stop me from putting in the tires i want to use, and i imagine i can adjust
    the brakes to deal with the small offset, but is there something i dont know?

    and- if i should or can fix this, is a little bit of delicate filing in one drop out (kinesis Al
    drops) acceptable? i imagine this would make cnetering the brakes nicer, if the offset didnt matter
    for anythign else.

    thanks, anthony
     
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  2. Did you try switching the wheel around to see if the offset was still on the same side of the fork?

    "ant" <[email protected]> wrote in message
    news:p[email protected]...
    > got a new fork, some sort of Look carbon blades pretty thing. when i put
    a
    > perfectly dished wheel in it the wheel is a bit off to one side, around 2mm to one side near the
    > brake mounting hole.
    >
    > i perused the archives, but couldnt find something that mentioned what w3as acceptable
    > misalignment/fork misconstruction measurements. example:
    >
    > paul southworth in '93- "One pretty good indicator of mismatched blade lengths is to align the
    > fork, the stick a known-good front wheel in it (no tire) that is
    perfectly
    > dished (ie, no dish at all) and see if the brake bolt-hole in the crown lines up with the center
    > of the rim (ie, the valve hole). It'll be pretty far off if there is even a millimeter or two of
    > blade-length discrepancy because the distance from the axle to the rim will effectively exaggerate
    > the difference."
    >
    > is my fork fine?based on my unexpert look, id guess that the discrepancy comes from a slightly
    > less well fit dropout on one side, which
    effectively
    > makes one blade a fraction longer. the off-centeredness wont stop me from putting in the tires i
    > want to use, and i imagine i can adjust the brakes to deal with the small offset, but is there
    > something i dont know?
    >
    > and- if i should or can fix this, is a little bit of delicate filing in one drop out (kinesis Al
    > drops) acceptable? i imagine this would make cnetering the brakes nicer, if the offset didnt
    > matter for anythign else.
    >
    > thanks, anthony
     
  3. Ant

    Ant Guest

    "David L. Johnson" <David L. Johnson <[email protected]>> wrote in message
    news:<[email protected]>...

    > Is the discrepency only in length, or is it out of alignment? My first bike had an
    > out-of-alignment fork, and I could not ride it no-hands. That would be a good test, if the fork is
    > on the bike. Line up the wheel properly (centered at the crown), and try to ride no hands. If it
    > doesn't pull, it should be OK to proceed.

    Thanks for the reply- just so im clear, are you suggesting i build the bike up (next week, when i
    have everything) and mount the front wheel in the fork in question by putting it fully into the
    drops (and letting the small offset be there) or are you suggesting i dont quite let the axle slot
    in all the way and tighten the QR so that the wheel is centered at the crown

    i suppose this would be kind of like having the flexibility of horizontal dropouts in the rear, but
    with the forces workingin the wrong direction. i imagine a good bump will knock the wheel all the
    way into the drops and offset the wheel again, but a flat road would work if all i had to do was
    check if the bike would track straight.

    so- am i checking to see if the bike will ride straight using the dropouts as-is, or am i fudging
    the alignment, essentially to see if filing the drops will correct the problem?

    thanks,

    anthony
     
  4. Ant

    Ant Guest

    "one of the six billion" <[email protected]> wrote in message
    news:<[email protected]>...
    > Did you try switching the wheel around to see if the offset was still on the same side of
    > the fork?

    heh. yep, did that. good thought, though.

    actually- on reinspection, the offset at the crown is probably more like 1mm, but still enough to
    visually pick out quite easily, especially since there is little clearance between the rim and
    blades. ive stuck a lot of wheels in a lot of forks, and never seen an offset before, which is why i
    thought to ask
     
  5. On Sat, 11 Jan 2003 23:34:19 -0500, ant wrote:

    > "David L. Johnson" <David L. Johnson <[email protected]>> wrote in message
    > news:<[email protected]>...
    >
    >> Is the discrepency only in length, or is it out of alignment? My first bike had an
    >> out-of-alignment fork, and I could not ride it no-hands. That would be a good test, if the fork
    >> is on the bike. Line up the wheel properly (centered at the crown), and try to ride no hands. If
    >> it doesn't pull, it should be OK to proceed.
    >
    > Thanks for the reply- just so im clear, are you suggesting i build the bike up (next week, when i
    > have everything) and mount the front wheel in the fork in question by putting it fully into the
    > drops (and letting the small offset be there) or are you suggesting i dont quite let the axle slot
    > in all the way and tighten the QR so that the wheel is centered at the crown

    The latter. One side, the longer one, will be all the way, and the other will be a slight bit off.
    >
    > i suppose this would be kind of like having the flexibility of horizontal dropouts in the rear,
    > but with the forces workingin the wrong direction. i imagine a good bump will knock the wheel all
    > the way into the drops and offset the wheel again,

    It would take quite a bump, if the QR is tight. Think about how much force those old horizontal
    dropouts could handle.

    > but a flat road would work if all i had to do was check if the bike would track straight.

    That's my suggestion.
    >
    > so- am i checking to see if the bike will ride straight using the dropouts as-is, or am i fudging
    > the alignment, essentially to see if filing the drops will correct the problem?

    You're fudging the length. If one fork is forward of the other, then you will still have problems
    riding no-hands.

    But, if you haven't installed the fork, why not send it back and ask for a new one? After all, it
    isn't right, and you paid for it, right? But I would do that before you built it up.

    --

    David L. Johnson

    __o | If all economists were laid end to end, they would not reach a _`\(,_ | conclusion. --
    George Bernard Shaw (_)/ (_) |
     
  6. A Muzi

    A Muzi Guest

    > On 11 Jan 2003, Qui si parla Campagnolo wrote:
    > > Either misaligned, dropouts aren't parallel or the legs aren't the same
    length
    > > but you should return it. These forks should be more straight than yours
    seems
    > > to be.

    "ant" <[email protected]> wrote in message
    news:p[email protected]...
    > What would be considered acceptable offset? As in, measuring from rim to fork blade near the brake
    > mounting hole how much off can an alignment be before it is not considered normal error? none?

    When you drop a wheel into a fork the rim should be visibly centered between the blades. If it is
    off, say 0.25mm, you would not be able to see that variance so I would say that's "close enough".

    Besides having one blade longer than the other, forks can be awry in lots of other ways. Check the
    tips with your H tools. If the ends are not parallel your quick release won't work right and that
    alone could account for some misalignmnet of the wheel.

    While the tools are in, lay a straightedge across the blades just below the crown. Is it parallel to
    the H tools? That is to say, is the fork twisted?

    Then sight the length of the fork. Are the blades straight in line with the column all the way to
    where the curve starts? Even a minor crash can move the blades back out of line. That would
    reduce the rake, but sometimes so slightly the rider doesn't notice until shown the fork on an
    alignment plate.

    Of course one blade could be bent back more than the other, but you'd notice that riding probably.

    Columns can also be bent. A straightedge on the column in a couple of places is a quick way to
    know that.

    --
    Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971
     
  7. Ant

    Ant Guest

    "David L. Johnson" <David L. Johnson <[email protected]>> wrote in message
    news:<[email protected]>...
    > But, if you haven't installed the fork, why not send it back and ask for a new one? After all, it
    > isn't right, and you paid for it, right? But I would do that before you built it up.

    yes- the trick is that it came from a r.b.market purchase, with a headset and a frame, 'almost
    new'. i feel like i got the deal i was looking for for the frameset/hs purchase, but now all i want
    to do is return the fork, and i dont know what proportion of the total price that would be.
    anyways, its complicated, and between time spent thinking about it, shipping it, cash for shipping,
    and finding a new one, i was hoping i could make this one work with a little filing and save myself
    some trouble. its not a top of the line fork, nor a top of the line build up, but i dont want it to
    be a piece of s*.

    thanks for all the help, i will email the seller and ask their advice as well.

    cheers anthony
     
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