27.4 too tight and 27.2 too slack

[d8mok]

Re:

Clinically clean? No idea. Can’t imagine it would stop the post inserting even if it wasn’t. It’s clean and I’m 85kg and Ive pushed pretty hard so cant imagine dirt would stop it.

There’s no rust or obstruction at all.

I reckon it’s a slightly too big post. Going to try to measure it tomorrow at work

 

[jimo746]

Re:

Coke can shim.

Or something a little more upmarket if you prefer.

 

[d8mok]

Re:

A beer can shim isn’t happening as that means I’ve got to buy another Thomson 27.2 post and sell the 27.4 and it’s a bodge too.

 

[cce]

I once got a 27.2 seatpost (race face) stuck in a 27.2 frame. a Thomson fitted perfectly. Tolerances are funny old things.

 

[Gerard]

I once got a 27.2 seatpost (race face) stuck in a 27.2 frame. a Thomson fitted perfectly. Tolerances are funny old things.

^^^^^^So true. One mans 27.2 is anothers 27.0 etc. I have specific post for specific frames (factory) and they are as tight as a nun's nasty.... :facepalm:

Have you run some emery paper in the seat tue? By a roll of fine, roll it up so a length of 10" or so and then insert in the tube and spin and pull up and down. You then have to really clean the tube out of the fine grit, so ideally don't have the BB in when you flush it. The use air pressure to blast. Try the 27.4mm.
Thomson are well constructed and if you are talking about 0.05mm it could be rubbed with emery as well.
Not ideal, but might work.

 

[d8mok]

Just dug our the original 27.4post and it slides in nicely actually. So either the Thomson isn’t truly 27.4 or my OE one is actually smaller.

I’ll try to measure both tomorrow.

 

[d8mok]

Re:

So I’ve measured 3 posts today

Thomson 27.2 = 27.12
Thomson 27.4 = 27.4
Original 27.4 = 27.32

So it seems that the tiny amount between the two makes a difference. Issue is finding a nice post that fits or resort to coke can method.

 

[hamster]

You won't manage it with a coke can shim - too thick. You could buy shim steel. A quick lick over with the reamer should do it.
The issue may also be ovality.

 

[k-rod]

Here's another suggestion:

Aluminum (or 'tin') foil comes in all sorts of thicknesses; you can find some of that (the thinnest being that which pre-rolled/packaged cigarettes come packaged in) which will serve as a possible 'shim', by simply slipping a sliver or two into the seat-tube before pushing the post in. Single layer, one on each side (two pces total), or one in each quadrant (four slivers) and off you go ...

 

[TOMAS]

I had a similar issue with my Fuquay frame (Ritchey Logic tubeset) that previously had a stuck seatpost (removed)... a 26.8 was too small and slipped, a 27.0 seemed too tight... In the end I've run a USE post with a shim and has done the trick for me.... now I can't actually remember if it was a 27.0 shim or 26.8 lol but it works fine