Cycling UK Forum

Thanks for that, Greg. Interesting stuff.

I always understood the difference between 531C ("competition") and 531ST ("special tourist") was wall thickness, with C being lighter for performance and ST being heavier for knockability.

I hadn't encountered the silver/brass brazing distinction. I suppose there might also be an age problem, with corrosion reducing the internal diameter of the downtube.

Very interesting, thank you.

I've just dug out the original catalogue I received from Mercian back in 1986 when I ordered my Vincitore.

Description of all but a couple of their frames says:
Seat Pillar Size - 27.2mm (not included)

The 753 Special has a choice of 27.0mm and 27.2mm

Frames listed:
Tourist Tandem - 531db
Super Tourist Tandem - 531db
Vincitore - 531c
Professional - 531c
Strada Speciale - 531c
Miss Mercian - 531c
753 Special - 753
King of Mercia Touring - 531c
King of Mercia Racing - 531c
Olympic - 531db

There is a Superlight frame that can be "Reynolds Professional" or "Reynolds Special Lightweight" but it doesn't say anything about the seat post.

Thanks for all the helpful replies. Some interesting facts and I feel more confident about my seatpost size now.

I have a 92/3 orange clockwork mtb frame and I had the same thing - the seat tube diameter is said to be 26.8 but a 26.8 post rattled about in it and required far too much torquing down to get it secure. I found that a 27.0 post still fitted without having to twist it from side to side, and the split section at the top of the seatube looked much more healthy when tightened.

Currently operating with a beer can shim and all seems ok.

Hi,
Does anyone know what the standard length of the seatpost is for a Dawes Galaxy. I've had my original seatpost removed after it seized in the frame so I didn't get a chance to measure its length. I've bought a couple of replacement posts (27.0mm and 27.2mm 400mm length) that I intend to shorten.
The frame accepts 18cm of the tube before it gets stuck and there is a 10cm minimum length marked on the new seatposts so I should be ok. The original seatpost suited me fine, it's just that it got stuck. If I knew the original length it would save me some time. Thanks.

there is no 'right length'; it depends whether you want to be able to move the saddle up or down in the future or not. So for example if you have 14cm in the frame when the saddle is the right height for you, that leaves +/- 4cm leeway. Cut it 4cm different and you could have 0-8cm of adjustment, all in one direction.

cheers

The question you should be addressing is why is it getting stuck? If you shine a torch down the seat tube can you see any obstruction? If its corrosion or rust you may be able to clean it up yourself using a broom handle, slotted with a saw and some emery paper wound around it. Bike shops have a reamer for this purpose.
Merry Xmas

I don't know why some people are dismissing the very idea of seatpost diameters other than 27.2: my 1983 Holdsworth Mistral tourer has 531ST tubing throughout and came factory-fitted with a 27.0mm seatpost. However, I have never heard of any size other than 27.0 and 27.2 being used with that tubeset.

Oliver notes in the text of Touring Bikes that there are rare variables in tube wall thicknesses where a size smaller seat pillar is required. And also that seat pillars can vary in as much as 0.2mm.

edit

FWIW plenty of 531ST framesets accept a 26.4mm seat pin.

cheers

Would they be European metric?

nsew wrote:Would they be European metric?

no, they offered different seat tube specifications, intended for larger/stiffer framesets. They may have started to do this after Tony Oliver's book was published.

cheers