seatpost - very tight fit

[Poacher]

I will be sending it back rather than binning it, it cost quite a lot of money!

Phew! A result! I was starting to think this was a (very successful) wind-up.

 

[screenman]

Could it be say a 27 tube and a 27.2 post? Or some other small difference.

 

[jay clock]

I bought a seat post that was nominally the right size. Too tight. Sent it back. Seems to be a common problem

 

[screenman]

I bought a seat post that was nominally the right size. Too tight. Sent it back. Seems to be a common problem

How common? I must admit I have been lucky on this one. Did catch a Halfrauds technician banging a wrong size post into a bike whilst the customer was watching, I tried to stop him and was told by the tech and the customer he knew what he was doing, and that I should mind my own business. Or words to that effect.

 

[Cyclopathic]

Generally, I think the post is slightly too large as a manufacturing fault.
However, I have been thinking (always bad). If I were to get the LBS to run a 31.6 seat tube reamer through the frame would this do any harm? Assuming that it's already perfect, the reamer should just slide straight through without removing any additional material. If it's slightly too narrow the reamer would increase the hole diameter slightly. I can't see that this would do any harm either way, or am I missing something? Last thing I want is to make the hole too big!

If the other post fits ok then doing this will make all subsequent posts a bit too loose.

I've had this problem and sorted it by putting the seat post in a vice (use something to protect the post and don't make it too tight.) And then I went about reducing the post slightly with a good quality length of emery cloth. Several lengths in fact. Working up and down the post and turning the post at regular intervals gives a fairly even effect and it shouldn't take too long to remove what is probably just a fraction of a millimetre.

Also grease the post before fitting.

 

[e-rider]

If the other post fits ok then doing this will make all subsequent posts a bit too loose.

I've had this problem and sorted it by putting the seat post in a vice (use something to protect the post and don't make it too tight.) And then I went about reducing the post slightly with a good quality length of emery cloth. Several lengths in fact. Working up and down the post and turning the post at regular intervals gives a fairly even effect and it shouldn't take too long to remove what is probably just a fraction of a millimetre.

Also grease the post before fitting.

I always grease before fitting. You are right that it's just a fraction of a mm though.
It's a 31.6 Thomson Elite post RRP £80

 

[screenman]

Are you sure the seat tube is not a 31.4?

 

[Cycling Dan]

Just read that woman marrying her bike and now just read the title of this thread. My mind ran away a bit there

 

[Cyclopathic]

I always grease before fitting. You are right that it's just a fraction of a mm though.
It's a 31.6 Thomson Elite post RRP £80

Have you checked the diameter with some callipers? Perhaps at £80 I'd be reluctant to start emery clothing it...or even using it. And for £80 you shouldn't have to do anything to it to make it fit.

 

[02GF74]

measure the diameter of the post with vernier callipers - you should be able to get to within 0.1 mm or less

this being thomson post - is it ribbed i.e. the surface is not smooth by has machined rings.

oh, btw, there seem to be quite a lot of thomson elite posts on ebay .... make me wonder if other owners have experienced problems -not fitting and then slippage (the 'rings' give less of an area to grip the post)

 

[ayceejay]

Thomson have a web site, there amongst other information I found this in answer to question a bot grease:
A – A very light coat of grease is okay. Do not use anti-seize as it can lead to slipping. To prevent sticking the post in the frame, remove clean and re-install every 90 days. Do not use grease in a carbon fiber frame.
There is also information about clamping that I suggested earlier.

 

[e-rider]

The strange thing is, the existing post was also a Thomson (inline), I wanted to change to a setback model. The inline post fits fine. Anyway, Thomson have agreed to replace it even though it has been scratched-up from my efforts to fit it.

 

[e-rider]

measure the diameter of the post with vernier callipers - you should be able to get to within 0.1 mm or less

this being thomson post - is it ribbed i.e. the surface is not smooth by has machined rings.

oh, btw, there seem to be quite a lot of thomson elite posts on ebay .... make me wonder if other owners have experienced problems -not fitting and then slippage (the 'rings' give less of an area to grip the post)

if only I had some reliable calipers - they cost about £30 for some that actually work.

 

[raleighnut]

Thomson have a web site, there amongst other information I found this in answer to question a bot grease:
A – A very light coat of grease is okay. Do not use anti-seize as it can lead to slipping. To prevent sticking the post in the frame, remove clean and re-install every 90 days. Do not use grease in a carbon fiber frame.
There is also information about clamping that I suggested earlier.

Petroleum jelly is far better than grease in this application. Grease can promote corrosion due to most having soap in their formulation.

 

[e-rider]

FYI, I returned this post to the supplier of Thomson components in the UK (i-ride) - they said there was nothing wrong with it and are returning it to me!!! So, I now have an expensive seatpost that doesn't fit in my frame - great! I could sell it on ebay and shift the problem to some other poor person, or take the financial hit myself. This is very poor indeed - Thomson should be appalled at the service they are offering.