Seatpost slipping / any Chas Roberts Transcontinental owners here?

Hello!

Just got a lovely second hand Roberts - what I believe to be a Transcontinental, build in 1990.

Bicycle rides like a charm, but the 27.0mm seatpost is slipping a cm over ~10km. Already tried another one, than the one that came with it (looked original in terms of the group), but still no luck.

A 27.2 feels really wrong when trying to insert, it would need more force even for the first millimeters.

As the nice guys from Roberts are taking a sabbatical and records are not available currently: are there any Transcontinental owners, from roughly that period, who can tell me which diameter is right?

Reaming to 27.2 would feel a little bit strange with such a high quality frame, if it would have been made for 27.0...

Thanks in advance,

Micha

Btw: framesize is 58cm, if this has an impact on the used tubes...

Have you tried installing with carbon assembly paste rather than greese?

Not yet, also feel a little bit strange about this as this is my tourer - which will get ridden in corners of the world where the assembly paste may be not available...ok, of course i could take some with me...

What's the frame made of? If it's British then it's probably 27.2

Nothing wrong with reaming an old frame if needed.

I suspect that over time the slot on the seat lug has closed up slightly. Take a large flat blade screwdriver, insert it into the slot and gently open up the slot. Then try your 27.2 seatpost again, well greased.

There are no stickers on the frame, probably it is a special selected mixture of Columbus and Reynolds. I assume also that there is some 531st in there, first thoughts would be seattube, that's why 27.0 is also an option.

But I also thought the lug would have been squeezed, so tried the trick with the screwdriver and i can fit the seatpost in, allthough with a little work...

Just btw and probably a little bit of stupid question, how can you tell if you inserted a to big seatpost?

Go to a reputable bicycle shop and ask them to check seatpost properly.

Did you measure the seat tube?

how can you tell if you inserted a to big seatpost?

Simple; it does not go in.

Carbon fibre grip is something I have to use on alot of aluminium parts like my seat post in my MTB's, my extension bars on my TT bike. I have taken to applying to everything that can slip because you never know.

A vernier caliper will tell you the seat tube ID if you don't own one buy one it is so useful.

i can fit the seatpost in, allthough with a little work.

If that refers to a 27.2 seatpost then your seat tube is 27.2. I suggest that you take it to a shop and get it reamed to 27.2.

A vernier will only really tell you what the top of the seat tube has been squeezed to.

I've had a few frames that have had this issue. My advice would be to clean the seatube out as much as possible. Use something like gt85 and rags rammed down inside the seatube to dissolve and remove any crud, old grease, corrosion etc and then try the 27.2 again.

Also, I'd advise trying a few different posts, the higher quality the better as I've found large descrepancies in cheap posts.

Thanks ed.

The lug was definitely sqeezed, in the end i could put the 27.2 seatpost in while widening the lug with the help of a screwdriver.

So if my guess with the 531st seattube is right, Tony Oliver is also right - guess the Roberts is silver brazed, so another 531st with 27.2 diameter here.

The Roberts rides really really nice btw.. Will post some pictures if it has been converted from its ugly trekking-ness to drop bars...

Thanks everyone...cheers.

i have 2 Roberts - both are 27.2