Seatpost worries - Help required

I'd be grateful if you could give me a little advice; I'm having difficulty finding a suitable seatpost for Raleigh which has a 753 frame and was built by the Special Products Division .

When I bought the frame, I was told that it took a 27.2 seatpost.

I've tried a 27.2 seatpost, but I feel that I'd really have to force it in for it to fit. I'm reluctant to do so for fear of damaging the frame. The top of the seat tube is slightly 'ovalised' - no doubt due to previous tightening of the seatpost bolt over the years. (I haven't tried to force the bolt flanges apart for fear of damaging the frame).

I've taken the frame to a bike shop and they've found that a 27.0 goes in okay, but it might not be correct, due to the 'ovalised' effect at the top of the seatpost. ie. A 27.0 post might be okay at the top of the seat tube, but could be too slack further down.

Should I fit a 27.0 seatpost or try a little more force with the 27.2 seatpost ?

I'm told that 753 tubing is quite fragile stuff and I'm worried about damaging it.

Can anyone give me any advice please ?

Thank you !!!

sounds like it might've been used with a too small seatpost before that squeezed the tube?

Any of these fit the bill?
http://www.sheldonbrown.com/seatpost-sizes-m-z.html#r

Why not fit the smaller size post, but shim the sides which are the wider part of the oval?

There was a 27.2mm seatpost in my 753 frame when I got it.
I carried on using a 27.2 - but longer.. this is what happened:

http://www.lfgss.com/post242277-1.html

Further investigation by using different sized posts (thanks retro di corsa) suggested the seattube was meant for a 27.0.

My only advice is to be careful.

Ride with NoSeat™

There was a 27.2mm seatpost in my 753 frame when I got it.
I carried on using a 27.2 - but longer.. this is what happened:

http://www.lfgss.com/post242277-1.html

Further investigation by using different sized posts (thanks retro di corsa) suggested the seattube was meant for a 27.0.

Bloody hell - that's scarey !!!

Ta for the warning - I'm going to have to be very careful !!!

Any of these fit the bill?
http://www.sheldonbrown.com/seatpost-sizes-m-z.html#r

That's a great link !

I think that it should be 27.2 - but boy is it tight - as the actress said to the bishop.

There was a 27.2mm seatpost in my 753 frame when I got it.
I carried on using a 27.2 - but longer.. this is what happened:

http://www.lfgss.com/post242277-1.html

Further investigation by using different sized posts (thanks retro di corsa) suggested the seattube was meant for a 27.0.

Presumably, that was the end of the frame ?

753 could be had in 27.0 and 27.2 seat tubes. And other sizes too.

If a 27.0 fits and is snug, use a 27.0. 753 can be paper thin in the middle, and doesn't take well to being forced.

If you posted a photo of the seat binder part perhaps it would help us work out whether it is deformed from being tightened around a too-small post or whether it could be prised open.

There was a 27.2mm seatpost in my 753 frame when I got it.

Is that the post I bought? ~The shiny hardware now adorns the Christmas Quinn.

753 could be had in 27.0 and 27.2 seat tubes. And other sizes too.

If a 27.0 fits and is snug, use a 27.0. 753 can be paper thin in the middle, and doesn't take well to being forced.

If you posted a photo of the seat binder part perhaps it would help us work out whether it is deformed from being tightened around a too-small post or whether it could be prised open.

Cheers BlueQuinn, I'll post a pic tomorrow.

Thank you all for taking the trouble to reply.

Having seen the link kindly provided by provenrad, I'm now even more anxious to avoid any sort of 'foul-ups'.

There was a 27.2mm seatpost in my 753 frame when I got it.
I carried on using a 27.2 - but longer.. this is what happened:

http://www.lfgss.com/post242277-1.html

Further investigation by using different sized posts (thanks retro di corsa) suggested the seattube was meant for a 27.0.

What was your bike like to ride ? I've never riden my 753; is there much difference compared to 531 ?

My road bike is 753. It's light, stiff, harsh-riding and transmits every bump. but I don't have another bike with the same geometry to compare it to.

My track bike is probably 531c. It weighs virtually nothing and is even stiffer and harsher. The angles and clearances are very severe.

both are fucking brilliant when you ride them hard and fast, however.

I carried on using a 27.2 - but longer.. this is what happened:

http://www.lfgss.com/post242277-1.html

Further investigation by using different sized posts (thanks retro di corsa) suggested the seattube was meant for a 27.0.

Holy crap. And I just came on looking for a longer seatpost for my ridiculously long legs..

Is it possible that you destroyed the tube by using a too wide seatpost, not a too long one?

Ride with NoSeat™

'ride it like you stole it' look

Holy crap. And I just came on looking for a longer seatpost for my ridiculously long legs..

Is it possible that you destroyed the tube by using a too wide seatpost, not a too long one?

yes - the previous owner had shoved the 27.2 in, but it wouldn't go far enough to support the forces of a longer post which I needed. I should have used a 27.0 + shim, but had no idea it was a problem, and just rode it.

The seatpost should at least reach to below the bottom of the top tube junction, or 85mm, or to the minimum insert mark - whichever is more.

Good criteria. The original seatpost I'm riding is at the stop mark, which leaves about 65mm of post in the tube. I shall hunt for something longer of the correct diameter.