What size seat clamp/collar do I need?
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.
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.
Originally Posted by Bezalel
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.
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.
Originally Posted by DGonzalez
That is what I thought. So I bought a 31.8mm clamp and it was too small.