Seat clamp sizing

Johno68
Johno68 Posts: 110
edited August 2007 in Workshop
I want to change a quick release seat post clamp to a bolt up one. How do I find out which size I need? :?

Is the clamp called the same size as the diameter of seat post?

Thanks,

John

Comments

  • MarvintheAndroid
    MarvintheAndroid Posts: 409
    You need to measure the diameter of the seat post tube just where the clamp sits, this is the clamp size. Then replace the clamp with an allen key clamp of the same diameter. If you can't measure accurately, take the old clamp (or better still the whole bike) to your LBS.

    Common sizes are 28.6, 31.8, 34.9 but there are others.

    Marv.
    What tree ? ...........

    Trek 8000 ZR XC hardtail.
  • JustRidecp
    JustRidecp Posts: 302
    An easy enough way to measure the diameter of your seat post tube if you dont have vernier callipers or diameter isn't marked on your seat tube is to wrap a piece of string or tape around your tube to get the circumference. As the circumference of a circle is pi * 2r then the diameter (2r) is circumference/pi. I did this for my seat post and got 27.05mm for a 27.2mm seatpost. Should be close enough for you to get an idea of what size you need.
    Real Ultimate Power

    "If I weren't a professional cyclist, I'd be a porn star" - Super Mario
  • Monty Dog
    Monty Dog Posts: 20,614
    From my experience, there are 3 sizes that cover 90% plus of most frames - unless you've got something unique to your frame.
    Most likely sizes: steel frame with 27.2 seatpost - 28.6mm clamp.
    Most aluminium, carbon and ti frames with 27.2 post - 31.4mm
    Most oversize frames with larger posts - 34.8.
    Make mine an Italian, with Campagnolo on the side..
  • Johno68
    Johno68 Posts: 110
    I've got a Marin Point Reyes, 7 years old with 700c wheels. Seat post is an odd size, 25.9mm I think (but I'll need to check). I'll ride into my LBS and ask for one to fit.

    Thanks for the replies,

    John

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