How do I know the size of my seat post tube/clamp?

mrfmilo

Hi,
How do i find out what size diameter seat post tube i have?
The bike is a GT Avalanche
Thanks

nicklouse

look on the old one. it will be stamped on it need the min.insertion mark.

the clamp could have it on the underside as well.

and is likely to be the same size os your front mech.

scale20

nicklouse wrote:

and is likely to be the same size os your front mech.

You learn something new every day!

nicklouse

scale20 wrote:

nicklouse wrote:

and is likely to be the same size os your front mech.

You learn something new every day!

most bikes have a seat tube that is the same size from top to bottom so the mech and the seat clamp have to be the same size and that means the clamp will be one of the three standard mech band sizes.

but with more hydro-formed and carbonish frames the seat clamp area can very variable in size.

I even have a bike that does not have a seat post clamp.

JayKingFunk

If its a GT Avalanche it will most likely be 28.6mm for the seat tube clamp and 27.2mm for the seat tube!

I found this out whilst upgrading a while back by using a tape measure to get the right size!

nicklouse

the new Avalanches come with 31.6mm seatposts

mrfmilo

Hi,
I looked on my seat post and it says ' 27.2 x 0.22' and the clamp says 32

Are they correct?

Thanks

nicklouse

so the post is 27.2mm and the clamp will be 31.8mm (32mm).

mrfmilo

Thanks for the fast reply and thanks for the answers.

elcani

Any idea what the 2008 GT Avalanche clamp diameter is?

Thanks.

mrfmilo

Will look soon

mrfmilo

31.8mm

elcani

Great, many thanks.