Advertise on Bikeforums.net



User Tag List

Results 1 to 6 of 6
  1. #1
    Senior Member
    Join Date
    Mar 2010
    Posts
    117
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    What size seat clamp/collar do I need?

    Hi,
    I am trying to find a seat clamp/collar for my old Gary Fisher Montare bike. The seatpost is 27.2mm x 350 mm. What size seat clamp do I need? I would like a quick release one.

    Thanks.
    David

  2. #2
    Senior Member
    Join Date
    Mar 2010
    Location
    City of Brotherly Love
    My Bikes
    Raleigh Companion, Nashbar Touring, Novara DiVano, Trek FX 7.1, Giant Upland
    Posts
    1,063
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    The clamp is sized according to the outside diameter of the seat tube. There are 3 standard sizes 28.6mm, 31.8mm, and 34.9mm. Aluminum frames that accept a 27.2mm seatpost will generally use a 31.8mm clamp.

  3. #3
    Senior Member
    Join Date
    Aug 2005
    Location
    Pittsburgh, PA
    My Bikes
    '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
    Posts
    25,287
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Bezalel View Post
    The clamp is sized according to the outside diameter of the seat tube. There are 3 standard sizes 28.6mm, 31.8mm, and 34.9mm. Aluminum frames that accept a 27.2mm seatpost will generally use a 31.8mm clamp.
    There is also a 30.0 mm clamp and it's used on several bikes, particularly on Surly frames.

  4. #4
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    39,147
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    With the seat post out, you can measure the OD of the seat tube ..

    FWIW, tubes used in most bikes are fractional 1-1/8, 1-1/4, 1-3/8"..
    the numbers, 28.6mm, 31.8mm, and 34.9mm are the metric equivalents.

    then a manufacturer maybe, shims inside the seat tube ID
    to use the common seat post sizes.

  5. #5
    Senior Member Jed19's Avatar
    Join Date
    Oct 2004
    Posts
    3,742
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DGonzalez View Post
    Hi,
    I am trying to find a seat clamp/collar for my old Gary Fisher Montare bike. The seatpost is 27.2mm x 350 mm. What size seat clamp do I need? I would like a quick release one.

    Thanks.
    David
    Take a piece of string or strip of paper, wrap it around your seat-tube precisely, take that string and measure its length in mm, then divide by the number pi. That is the seatpost clamp size you need.
    Regards,

    Jed

  6. #6
    Senior Member
    Join Date
    Mar 2010
    Posts
    117
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    That is what I thought. So I bought a 31.8mm clamp and it was too small.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •