Seat post diameter.
- Thread starter BretonM
- Start date
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Grant Fondo
Guru
- Location
- Cheshire
Unfortunately not, just measure internal diameter of your seat tube in mm hey presto!
ChrisEyles
Guru
- Location
- Devon
You have to be quite accurate when you're sizing a seat post, usually to within 0.2mm, so eyeballing it with a tape measure is tricky, it's better to use calipers if you can get hold of a set.
How old is your bike? Lots of decent old frames use 27.2mm posts. My old '97 Marin took a 27.0mm post and someone had rammed in a 27.2mm... it was functional but tricky to adjust and had visibly bent the top of the seat tube a little.
How old is your bike? Lots of decent old frames use 27.2mm posts. My old '97 Marin took a 27.0mm post and someone had rammed in a 27.2mm... it was functional but tricky to adjust and had visibly bent the top of the seat tube a little.
OP
OP
BretonM
Well-Known Member
I'll measure it thanks.
HLaB
Marie Attoinette Fan
Google it the specs might be listed somewhere. My bikes are 33.4mm for what its worth, that quite a common size too IME.
e-rider
crappy member
- Location
- South West
it needs to be measured to the nearest 0.2mm to be correct which is actaully not that easy to do - the most common size is 27.2 but there are loads of sizes out there
Nigeyy
Legendary Member
- Location
- Massachusetts, USA
or try looking up your bike on bikepedia.com, though of course proper measurement is a better guarantee of correct information. If your bike is an old steel bike then chances are it's 27.2mm (it was a very common size), if it's a more modern alu frame, then it's very likely it will be a larger diameter (e.g. 30.9mm but not necessarily). Generally speaking steel frames have smaller diameter tubes than alu and hence seatpost diameters are usually smaller on steel framed bikes than alu ones. Alas, standardization of seatpost diameters isn't... standard.
I'm going to respectfully disagree with the poster and say that it's probably not a good idea to go to the nearest 0.2mm (though I'll freely admit I haven't tried it), particularly if you are oversizing the seatpost. Certainly with steel frames you can have an issue of alloy seatposts bonding to steel frames and being 0.2mm oversize won't help this. And I'm not sure I'd want to force in a seatpost in an alu frame either. I would think it's best to get the seatpost size intended for the frame.
I'm going to respectfully disagree with the poster and say that it's probably not a good idea to go to the nearest 0.2mm (though I'll freely admit I haven't tried it), particularly if you are oversizing the seatpost. Certainly with steel frames you can have an issue of alloy seatposts bonding to steel frames and being 0.2mm oversize won't help this. And I'm not sure I'd want to force in a seatpost in an alu frame either. I would think it's best to get the seatpost size intended for the frame.
RegG
Über Member
- Location
- Nottingham
If this is of any use, I found a new seat post, for the Diamondback I recently rebuilt, from Wheelies......
http://www.wheelies.co.uk/p19056/System-EX-Seat-Post.aspx
They list a dozen different sizes for this particular seat post which I have been very pleased with. But as others have said, you do need to make sure you get the right size so get the old one measured before ordering! Good luck.
http://www.wheelies.co.uk/p19056/System-EX-Seat-Post.aspx
They list a dozen different sizes for this particular seat post which I have been very pleased with. But as others have said, you do need to make sure you get the right size so get the old one measured before ordering! Good luck.