Find out seatpost size?

[samid]

As Gerry said. While it seems that 0.2mm is nothing, in practice a wrong-sized seatpost may be very hard to clamp tight enough for it to stay put. You could use beer can shims of course, or even maybe a little bit of Loctite but just don't assume that 0.2mm wont matter either way, it might.

 

[bigfella]

Tricky one! I might buy a few and resell them if they aren't right.

I wonder if (don't have the frame atm) the pinch bolt was in it might be 25mm? I have been looking at this:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=400048508971&_trkparms=tab=Watching

 

[mickle]

It's a inch.

 

[bigfella]

Yeah you said an inch (25.4mm) in a previous post. Just wasn't sure if 25mm I could try?

 

[mickle]

Trouble is, seatposts are absolutely not interchangeable. 0.2 doesn't sound like much but it means the difference between 'not going in without a pile driver', 'fitting perfectly' and 'tighten it all you can but it will still slip down and probably knacker the seat lug in the process'.

0.2mm diameter multiplied by the circumference of the seat post is quite a chunk of material to expect the seat lug to make up.

As a matter of interest. The outside diameter of a lugged steel seat tube is always 28.6mm. Differences in internal diameters are determined by the quality of the tubing. The higher the quality - the thinner the tube - the larger the internal diameter - the larger the seatpost.
Hence; 531 = 27.2, 501 = 27.0mm, Generic Chromoly = 26.8mm etc etc.

It's an inch

 

[bigfella]

Argh! Ok, say I get some posts, should they slide down easily, what is a good fitting post?

 

[MacB]

little threadjack here, I need to get a 1" seatpost for the Dawes frame and I was looking for an inline microadjustable one. The only one I can find is the Thomson Elite but I consider nearly £70 for a seatpost very high, especially as it is only my backup bike.

Anyone know where I can get a more reasonably priced version of the Thomson?

 

[PpPete]

Argh! Ok, say I get some posts, should they slide down easily, what is a good fitting post?

If post goes in easily - it's too small - and if you crank up the bolt in an effort to hold it you may damage the frame. It needs to be a good snug fit before you start doing up the bolt.

However, if it's a steel frame you could find inside of seat tube has some surface rust that makes it's diameter smaller - especially lower down (the crap on the upper part having been removed by previous installation & removal of seat posts.)

I had one that I measured with vernier as 27.0 mm Seat post inside diameter.
Could only ever get a 26.8 post in it - and that after a thorough clean of the inside of the seat tube - and a bit of emery paper / buffing with scotchbrite on the post itself.

Trouble is if you get a 25.4 mm post and it won't go in, you will have scratched the surface of it and made it much less saleable before you decide it's too big!

 

[mearle]

little threadjack here, I need to get a 1" seatpost for the Dawes frame and I was looking for an inline microadjustable one. The only one I can find is the Thomson Elite but I consider nearly £70 for a seatpost very high, especially as it is only my backup bike.

Anyone know where I can get a more reasonably priced version of the Thomson?

Dare I suggest Halfords:
http://www.halfords.com/webapp/wcs/...151_storeId_10001_partNumber_259952_langId_-1

Price seems very reasonable !!!

 

[MacB]

Dare I suggest Halfords:
http://www.halfords.com/webapp/wcs/...151_storeId_10001_partNumber_259952_langId_-1

Price seems very reasonable !!!

thanks Mearle, I actually found one at Parkers last night and ordered, it was about £15

 

[Aperitif]

little threadjack here, I need to get a 1" seatpost for the Dawes frame and I was looking for an inline microadjustable one. The only one I can find is the Thomson Elite but I consider nearly £70 for a seatpost very high, especially as it is only my backup bike.

Anyone know where I can get a more reasonably priced version of the Thomson?

http://cgi.ebay.co.uk/Kalloy-350mm-...-RRP-%a31_W0QQitemZ190306844776QQcmdZViewItem Here?

Hope your new arrival is cool MacB!

 

[MacB]

http://cgi.ebay.co.uk/Kalloy-350mm-...-RRP-%a31_W0QQitemZ190306844776QQcmdZViewItem Here?

Hope your new arrival is cool MacB!

cheers A, sorted now and the e-bay one is set back, no shortage of those, it's the inline that are tougher to find in 25.4mm.

I'd actually like 3 of the Thonson ones, but just can't justify spending £220 on seatposts at present.

 

[Aperitif]

silly me - too rushed.