CXP21 Effective Rim Diameter

Discussion in 'Cycling Equipment' started by Andrew Martin, Feb 17, 2003.

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  1. Hey all - just wanted to see if any of you had access to the Wheelsmith builders guide that might
    have the ERD for the CXP21 rim. I'm trying to replace a velocity Aerohead that's a 601mm. They look
    rather close in design.

    From http://www.branfordbike.com/wheels/wheel1.html:

    For spoke calculation purposes, the effective rim diameter (ERD) is 601 mm.

    The CXP33 is 596mm, so I'm hoping it's close (by my math (596 + ((33x2) - (31x2) ) = 600?). I
    assume that a diameter difference of 1 mil is good enough? I've always been told that +/- 1mm
    isn't an issue.

    Any input is appreciated.

    Thanks - a (note - being a cheap bastard here and don't want to fork out $60 for a Velocity when I
    can get a CXP31 for $20).
     
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  2. Andrew Martin wrote:
    >
    > Hey all - just wanted to see if any of you had access to the Wheelsmith builders guide that might
    > have the ERD for the CXP21 rim. I'm trying to replace a velocity Aerohead that's a 601mm. They
    > look rather close in design.
    >
    > From http://www.branfordbike.com/wheels/wheel1.html:
    >
    > For spoke calculation purposes, the effective rim diameter (ERD) is 601 mm.
    >
    > The CXP33 is 596mm, so I'm hoping it's close (by my math (596 + ((33x2) - (31x2) ) = 600?). I
    > assume that a diameter difference of 1 mil is good enough? I've always been told that +/- 1mm
    > isn't an issue.
    >
    > Any input is appreciated.
    >
    > Thanks - a (note - being a cheap bastard here and don't want to fork out $60 for a Velocity when I
    > can get a CXP31 for $20).

    http://www.tech-mavic.com/uk/sources/Produits/ROUTE/Jantes/99RoadRimRange/ClincherRoadRim99.pdf

    There it is listed as 598.5 mm.
     
  3. Paul Kopit

    Paul Kopit Guest

    I believe that both the CXP21 and newer Aerohead rims have ERD of 602. You should be fine.

    On 17 Feb 2003 17:36:03 -0800, [email protected] (Andrew Martin) wrote:

    >Hey all - just wanted to see if any of you had access to the Wheelsmith builders guide that might
    >have the ERD for the CXP21 rim. I'm trying to replace a velocity Aerohead that's a 601mm. They look
    >rather close in design.
     
  4. Peter Cole

    Peter Cole Guest

    "Andrew Martin" <[email protected]> wrote in message
    news:[email protected]...
    > Hey all - just wanted to see if any of you had access to the Wheelsmith builders guide that might
    > have the ERD for the CXP21 rim. I'm trying to replace a velocity Aerohead that's a 601mm. They
    > look rather close in design.
    >
    > From http://www.branfordbike.com/wheels/wheel1.html:
    >
    > For spoke calculation purposes, the effective rim diameter (ERD) is 601 mm.
    >
    > The CXP33 is 596mm, so I'm hoping it's close (by my math (596 + ((33x2) - (31x2) ) = 600?). I
    > assume that a diameter difference of 1 mil is good enough? I've always been told that +/- 1mm
    > isn't an issue.
    >
    > Any input is appreciated.
    >
    > Thanks - a (note - being a cheap bastard here and don't want to fork out $60 for a Velocity when I
    > can get a CXP31 for $20).

    This site: http://www.fa-technik.adfc.de/Komponenten/Felge/Felge622.html (an excellent one to
    bookmark) gives it as 601.5.
     
  5. Paul Kopit <[email protected]> wrote in message
    news:<[email protected]>...
    > I believe that both the CXP21 and newer Aerohead rims have ERD of 602. You should be fine.
    >
    > On 17 Feb 2003 17:36:03 -0800, [email protected] (Andrew Martin) wrote:
    >
    > >Hey all - just wanted to see if any of you had access to the Wheelsmith builders guide that might
    > >have the ERD for the CXP21 rim. I'm trying to replace a velocity Aerohead that's a 601mm. They
    > >look rather close in design.

    After some more searching on sheldon's page (should have started there, not google) I found
    references with all the ERD's. Looks like I'm in the right ballpark - thanks for your help.

    Spoke Calculators with Common Hub and Rim data (Effective Rim Diameter)
    http://www.sheldonbrown.com/wheelbuild.html#length
     
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