big chainwheel or shorter cranks?

Discussion in 'Recumbent bicycles' started by geepeetee, May 7, 2006.

  1. geepeetee

    geepeetee Guest

    Hi

    I want to gear my 20" wheel recumbent up a bit. At the moment i have a 54t
    chainwheel but to gain a bit more speed i would like a 60t but these dont
    seem to be widely available. Reading various places an option seems to be
    shortening the cranks, is this a real alternative or does it come a price?

    cheers

    Gary

    --
    Visit my websites at
    www.justjents.co.uk
    www.recumbent.50megs.com
     
    Tags:


  2. In alt.rec.bicycles.recumbent on Sun, 7 May 2006 21:01:40 +0100
    geepeetee <[email protected]> wrote:
    > Hi
    >
    > I want to gear my 20" wheel recumbent up a bit. At the moment i have a 54t
    > chainwheel but to gain a bit more speed i would like a 60t but these dont
    > seem to be widely available. Reading various places an option seems to be
    > shortening the cranks, is this a real alternative or does it come a price?


    How does that gear the bike up?

    I shortened the cranks on mine because I have short legs. I think I
    spin more than I would with longer ones, but I can't see how that
    would be a result useful to you.

    Zebee
     
  3. JW

    JW Guest

    On Sun, 07 May 2006 20:40:23 +0000, Zebee Johnstone wrote:

    > ... How does that gear the bike up?


    See: http://www.sheldonbrown.com/gain.html

    I'm afraid that short cranks are just the latest magic pixie dust. They
    fit in nicely with Rotor cranks, weird chainring shapes, etc. They ease
    knee pain, increase top speed and cure cancer.

    To get the kind of "development" the OP wants, I'm afraid (s)he will end
    up resembling Laugh-In's Arte Johnson, perhaps minus the pratfall.

    IMO, a geared hub is the only practical way to achieve reasonable gearing
    with a 20" wheel.

    Jim Wilson
    Gainesville, FL
     
  4. DougC

    DougC Guest

    geepeetee wrote:
    > Hi
    >
    > I want to gear my 20" wheel recumbent up a bit. At the moment i have a 54t
    > chainwheel but to gain a bit more speed i would like a 60t but these dont
    > seem to be widely available. Reading various places an option seems to be
    > shortening the cranks, is this a real alternative or does it come a price?
    >
    > cheers
    >
    > Gary
    >

    54T is about the largest you will find on bicycles that use "normal"
    26-27 inch rear wheels. Hostelshop sells Vuelta Alloy chainrings, up to
    72T or so. You might need to switch your whole crankset/BB to put on one
    that can take them, but there you go. ....Shorter cranks wouldn't do
    what you wanted, I'd bet.
    ----
    Also the problem with putting on a monster chainring is that then your
    front derailleur may not be able to reach across all three chainrings
    (or may not be able to reach across two, if you only had two to begin
    with,,,,). If that's the case you might have to live with just two: a
    52T or so and the big 60T.
    -----
    Also you might check your rear cluster and see if you can't get
    something with a higher top end that way.
    ~~~~~
     
  5. Peter Clinch

    Peter Clinch Guest

    JW wrote:

    > IMO, a geared hub is the only practical way to achieve reasonable gearing
    > with a 20" wheel.


    Schlumpf Super Speed Drive will gear up the top end 2.5 times from your
    cranks, no geared hub required. Though a geared hub's a good way to do
    it too: my Other Half has a DualDrive setup on her 20" 'bent, likes it a
    lot.

    Pete.
    --
    Peter Clinch Medical Physics IT Officer
    Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
    Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
    net [email protected] http://www.dundee.ac.uk/~pjclinch/
     
  6. Mike Causer

    Mike Causer Guest

    On Sun, 07 May 2006 21:01:40 +0100, geepeetee wrote:

    > I want to gear my 20" wheel recumbent up a bit. At the moment i have a
    > 54t chainwheel but to gain a bit more speed i would like a 60t but these
    > dont seem to be widely available. Reading various places an option seems
    > to be shortening the cranks, is this a real alternative or does it come a
    > price?


    It depends what is actually limiting your speed. If you're spinning out
    at 120+ then you need a bigger chainwheel or smaller cogs at the back. If
    you reach top speed at a cadence of less than 80, then use a *smaller*
    chainwheel and train your legs to go faster -- shorter cranks might help
    with this, but practice is really what you need.

    You don't say if the cogs are still the ones from the 8-year-old child's
    bike you based your 'bent on, but if they are you might find that an
    adult's gear cluster with 11 or 12 tooth top is going to be better.


    Mike
     
  7. geepeetee

    geepeetee Guest

    Hi

    No none of teh gears or brakes were retained. I have a54/13 combination at
    the highest gear. You may be right, i may just need to train myself to use
    a higher cadence, will stick at it

    cheers

    Gary

    --
    Visit my websites at
    www.justjents.co.uk
    www.recumbent.50megs.com
    "Mike Causer" <[email protected]> wrote in message
    news:p[email protected]
    > On Sun, 07 May 2006 21:01:40 +0100, geepeetee wrote:
    >
    >> I want to gear my 20" wheel recumbent up a bit. At the moment i have a
    >> 54t chainwheel but to gain a bit more speed i would like a 60t but these
    >> dont seem to be widely available. Reading various places an option
    >> seems
    >> to be shortening the cranks, is this a real alternative or does it come a
    >> price?

    >
    > It depends what is actually limiting your speed. If you're spinning out
    > at 120+ then you need a bigger chainwheel or smaller cogs at the back. If
    > you reach top speed at a cadence of less than 80, then use a *smaller*
    > chainwheel and train your legs to go faster -- shorter cranks might help
    > with this, but practice is really what you need.
    >
    > You don't say if the cogs are still the ones from the 8-year-old child's
    > bike you based your 'bent on, but if they are you might find that an
    > adult's gear cluster with 11 or 12 tooth top is going to be better.
    >
    >
    > Mike
     
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