Mercian Frame Seatpost size?

Hi Folks

I recently bought this frameset:

Mercian pro lugless, reynolds 853 tubing (not oversize).

Problem is I can't seem to find the right seatpost to fit.

• 27.2 mm is too big.

• 27.0 mm squeezes in but with some effort.

The previous owner used a 26 mm with shim... my biggest fear is that the shim set up was incorrect and may have warped the top of the seat tube near the collar making it difficult to fit the correct seatpost.

I rang Mercian who said all of their frames have used 27.2 mm posts since the 50's.

Any ideas? I will be trying a 26.8 but perhaps someone with experience with Mercian frames can shed some light.

Cheers

my Mercian had a 27.0
It seemed a bit tight but after you got it past a few cm in it was better

27 is a bit tight try taking it to a bike shop who can try reaming it to 27.0 mm to clean it up a bit.

I've got 4 Mercian frames which are 531; 631 and 731 OS and they all take a 27.2mm seat post. I would take the frame to a decent bike shop and get them to ream out the seat tube to 27.2mm.

Good luck

Had the same problem with mine - it should have been 27.2, but that was too tight and 27.0 was too loose.

Have you checked that the clamp hasn't been overtightened? Thats what happend to mine.

In the end I (retro de corsa) gently prized open the clamp a little to get it back to its original state.

Post a pic of the back of the seat clamp and an aerial shot.

That plonker with their shim have fucked your seattube. I hope you can rectify it.

That plonker with their shim have fucked your seattube. I hope you can rectify it.

Well I went to the shop I used to work in and used some decent callipers to measure the seat tube.

27.2 width
26ish length

Looks like you were right, seat tube has been squished.

Is anyone familiar with builders/workshops that could repair this?

Take it to your nearest framebuilder and ask nicely if they can help.

Mercian in Derbyshire
Argos in Bristol
Roberts in London
SuperTed in London
Dave Yates in Lincoln
... yadda yadda

Im not that up on tubing, but 853s pretty topend and so prolly quite thin right?

If this is the case get it done properly.

Otherwise I'd still have a look at the clamp area and if its that thats been skwished rather than the whole hole (if you see what I mean) you could try and prize it open a bit.