Why wouldn't this work?

Discussion in 'Cycling Equipment' started by Jasper Janssen, May 27, 2003.

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  1. Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
    frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
    rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.

    Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of
    the reasons..

    Jasper
     
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  2. Ajames54

    Ajames54 Guest

    On Tue, 27 May 2003 12:58:39 GMT, Jasper Janssen <[email protected]> wrote:

    >Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
    >frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
    >rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
    >
    >Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of the
    >reasons..
    >
    >Jasper
    First off it would but the wheel out of line in the frame making it difficult to adjust the brakes
    ... and having the tire rub against the stays... even if you were to realign the frame to make use
    of this if the tire is not centered then the bike gets really tough to ride.... lots of wasted
    energy kind tough to balance..
     
  3. Mark Hickey

    Mark Hickey Guest

    Jasper Janssen <[email protected]> wrote:

    >Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
    >frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
    >rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
    >
    >Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of the
    >reasons..

    It would work, as long as you also moved the brake mounting points accordingly. I suppose there
    might be some assymetrical movement in the rear triangle if you were really torquing the frame in a
    sprint - but would guess that wouldn't be a real issue.

    The bottom line is that wheel dish isn't a huge issue at all if your rear wheel is simply built
    correctly. It's certainly not a big enough "problem" to make it worth the hassles of riding a bike
    that has a wider than necessary Q factor (due to the chainline), and that can't use any
    off-the-shelf wheels, ever.

    There are easier ways to reduce dish, such as using an off-center rim or building the wheel on a MTB
    hub (or by adding a longer axle and 5mm spacer on the left). Of course, going with a 135mm hub is
    going to make it hard to buy off-the-shelf wheels as well, and will kick out the chainline 2.5mm -
    but at least everything else is "standard".

    Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
     
  4. Jeff Wills

    Jeff Wills Guest

    Jasper Janssen <[email protected]> wrote in message
    news:<[email protected]>...
    > Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
    > frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
    > rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
    >
    > Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of
    > the reasons..
    >
    > Jasper

    Some bicycles have been built this way- earlier Vision recumbent bicycles had offset frames and
    undished wheels.

    One this that you'd have to deal with is frame alignment- it's quite easy for your average bike
    mechanic to measure and align a frame to a centerline. I've done it with a string and a ruler. To
    align everything to a given offset is a somewhat tougher job and would require a frame plate and
    good measuring devices.

    Another thing is that you'd mess up the chainline- the chain has to curve further to the right with
    an offset frame. That's less of an issue with a recumbent, where the chain's 3 times as long as an
    upright, but it would get real messy on a short-chainstay racing bike.

    FWIW: Vision's current recumbents are symetrical.

    Jeff
     
  5. DiabloScott

    DiabloScott New Member

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    I don't think it would work at all because the rear wheel wouldn't be tracking directly behind the front wheel. I can't believe a bike like that would be rideable.
     
  6. Going off topic, on 28 May 2003, DiabloScott wrote:

    > wrote:
    > > Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think
    > > of the reasons..
    >
    > I don't think it would work at all because the rear wheel wouldn't be tracking directly behind the
    > front wheel. I can't believe a bike like that would be rideable.

    Try before you comment -- it's easy to ride a bike with offset rear wheel, but may be difficult to
    ride no hands. If the offset is huge, then the steering is noticably asymmetric (I'm thinking of a
    criuser bike I rode years ago that had been bent ~4 inches sideways when run over by a car). Even
    severe offset like that is easy to ride--the kid who owned that bike rode it all summer after the
    damage, we all had fun riding a bike that "dog-tracked".

    -- Doug Milliken www.millikenresearch.com
     
  7. DiabloScott

    DiabloScott New Member

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    Off topic? How is that off topic? I gave the OP something he hadn't thought of, a direct answer to his question.

    OK, change my comment from "I can't believe a bike like that would be rideable." to
    "A bike like that would ride like it had been run over by a car."
     
  8. On Tue, 27 May 2003 15:50:46 -0400, Doug Milliken <[email protected]> wrote:

    >Try before you comment -- it's easy to ride a bike with offset rear wheel, but may be difficult to
    >ride no hands. If the offset is huge, then the steering is noticably asymmetric (I'm thinking of a
    >criuser bike I rode years ago that had been bent ~4 inches sideways when run over by a car). Even
    >severe offset like that is easy to ride--the kid who owned that bike rode it all summer after the
    >damage, we all had fun riding a bike that "dog-tracked".

    Wow, that's a lot of offset. Mine always leaned a little bit, and when I measured it I found that
    the strings passed 3.5 and 4 cm from the seat tube, so that works out to.. only 2.5 mm offset. Of
    course, this was not a bike with relaxed steering. It's downright jittery, almost. But that degree
    of offset is already enough in that bike to be significantly uncomfortable for longer rides, because
    you're *always* pushing the bars to keep the damn thing straight.

    Jasper
     
  9. On 28 May 2003 03:32:57 +0950, DiabloScott <[email protected]> wrote:

    >I don't think it would work at all because the rear wheel wouldn't be tracking directly behind the
    >front wheel. I can't believe a bike like that would be rideable.

    But, actually, no. What I'm proposing is a dishless rear wheel, where you put that tracking behind
    the front wheel, and base the rest off of that --so you bend the rear of the frame (particularly the
    right side) in such a way that your cogset fits in.

    Jasper
     
  10. Bob Taylor

    Bob Taylor Guest

    I believe I remember that an Orbit bicycle (built in Britain) is built with an offset rear triangle
    to reduce the dish in the rear wheel. I read about it in the CTC magazine in a test article by
    Chris Juden.

    Bob Taylor

    Jasper Janssen <[email protected]> wrote in message
    news:<[email protected]>...
    > Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
    > frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just the
    > rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.
    >
    > Why won't it work? I'm sure it wouldn't, or people'd be doing it all over, but I can't think of
    > the reasons..
    >
    > Jasper
     
  11. jasper-<< Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear
    of the frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than
    just the rim? It'd bring chainline farther right, so you'd also need a longer bottom bracket.

    Aslo buy lots of padded clothing so when the thing starts to shuck and jive down that hill, you
    don't get hurt to much...

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
    (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"
     
  12. Bluto

    Bluto Guest

    Jasper Janssen <[email protected]> wrote:

    > Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
    > frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just
    > the rim?

    Some frame makers have done just that. An example is Orbit Cycles:

    http://www.orbit-cycles.co.uk/techspecsolo.shtml (The heading "offset rear triangle" is partway down
    the page.)

    Chalo Colina
     
  13. On 28 May 2003 13:07:32 -0700, [email protected] (Bluto) wrote:
    >Jasper Janssen <[email protected]> wrote:
    >
    >> Okay, so dish is a rear wheel's worst enemy. Why can't you deliberately misalign the rear of the
    >> frame somewhat to the right, so the axle and thus the entire wheel is offset, rather than just
    >> the rim?
    >
    >Some frame makers have done just that. An example is Orbit Cycles:
    >
    >http://www.orbit-cycles.co.uk/techspecsolo.shtml (The heading "offset rear triangle" is partway
    >down the page.)

    So, to sum up, the main thing keeping this back from being standard is non-standardness?

    If enough bike makers start doing it, it will of course eventually become standard..

    Jasper
     
  14. Bluto

    Bluto Guest

    Jasper Janssen <[email protected]> wrote:

    > So, to sum up, the main thing keeping this [rear frame offset] back from being standard is
    > non-standardness?
    >
    > If enough bike makers start doing it, it will of course eventually become standard..

    Actually, I think the main thing keeping it out of the mass market is that it negates the subtle but
    significant advantages of symmetrical construction. Comparative measurements between one side and
    the other save both bike makers and bike mechanics from having to make a lot of painstaking absolute
    measurements and keep a lot of references on hand.

    Bicycle framebuilding is a lot more rudimentary a craft than many people think, with stretched
    strings and meter sticks frequently used to check alignment. A maker who doesn't use industrial
    inspection techniques or at least pretty elaborate purpose-built measuring tools would not be able
    to yield as straight an offset frame for a similar amount of time and effort.

    Likewise bike shop mechanics are able to do a lot of frame diagnostic work on a bike that's presumed
    to be symmetrical. Not as much with an offset frame. In the worst case, an offset frame would get a
    costly "straightening" by a thorough but ill-informed mechanic!

    Similarly, offset built wheels pose a tiresome measurement chore to verify proper dish, a task
    that's thus not likely to be repeated between successive wheel builds.

    Something else to consider is that an offset frame (say a dishless 9sp
    130mm) poses all the same clearance, chainline, Q-factor and related issues as does a 160mm dishless
    rear, just all on one side. Meaning that the wider hub size possesses all the advantages of
    both a dishless rear wheel and symmetrical frame construction, with no more complicating
    issues than the offset rear already has.

    Chalo Colina
     
  15. On 29 May 2003 12:54:12 -0700, [email protected] (Bluto) wrote:

    >Something else to consider is that an offset frame (say a dishless 9sp
    >130mm) poses all the same clearance, chainline, Q-factor and related issues as does a 160mm
    > dishless rear, just all on one side. Meaning that the wider hub size possesses all the
    > advantages of both a dishless rear wheel and symmetrical frame construction, with no more
    > complicating issues than the offset rear already has.

    Except for the position of the bearing on the left side, putting more stress on the axle. Well,
    unless you use a hub that takes that into account, I guess.

    Jasper
     
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