531 seat tube diameter

Afternoon all from a very chilly Norn Iron,

I have come into the heat from the garage as i have a problem with a seat post. I was testing various seat posts in my 1974 (ish) Gazelle - it is a 531 frame and i presumed it would be 27.2mm diameter but the seat posts i have tried do not seem to fit. Is it possible that the frame could have a diameter of 27mm?

It may be the case that i need more force to insert the seat post, so far i have only put the post into the frame when i know i can remove it.

Here is the frame -



The pic was not taken today!! Brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

Richard

Hi,

Nice thread about exactly your dilemma on bikeforums:

http://www.bikeforums.net/archive/index ... 34968.html

Interesting opinions on here, such as:

"my Gazelle Champion Mondial with 531 Speedstream tubing came with a 26,6 mm Campy Victory seatpost. Since I wanted to build the whole bike in C-Record (it had a Victory/Triomphe mix), and I had a C-Record 27,0 mm seatpost, I had the seattube reamed. It's a very good fit now. Leaves with the still unanswered question why 531 Speedstream should take a 26,6 mm seatpost; why not just 27,2?"

and

"I have two Gazelle bikes with 531 tubes. first one was build in autumn 1980 and the second one was build in autumn 1981. to confuse you more the first one was delivered with a Campagnolo record seatpost of 27.2; the second one with a pantographed Campagnolo record seatpost of 27.0. both bikes were bough new from a bike shop specialized in building bikes for race purpose."

Interesting link but no definitive answer that i can see. They seem sure that 531c is 27.2mm but that does not help me at the moment.

Thanks,

Richard

I thought Reynolds also made a metric tube set (such as seen on Peugeots) - unfortunately I don't have the dimensions as Tony Oliver's book only covers their imperial tube sets.

UPDATE

After some pulling and tugging and a large amount of grease, I worked the 27.2 post in and out of the frame a few mm's at a time and it appears that it is a 27.2 tube. I am now absolutely freezing but, at least, I am happy.

Richard

TGR":584yk0h4 said:

After some pulling and tugging and a large amount of grease

Click to expand...

Shouldn't you be writing this on a fetish forum?

I did actually notice that when i typed it - i have also copied it to my retro fetish forum too.

Richard

My 90's Raleigh in 531 has a 27.0 seatpost and my Bob Jackson has a 27.2 which won't go in but it would if I forced it. The only real way to check is to stick a vernier caliper in the tube and measure it across the diameter. It's a fair clearance fit for both but add a bit of corrosion, muck and dried out old grease and it becomes tight. I think if it's that tight that you had to twist it in and out with grease to make it go in, you've probably worn the seatpost down a bit in the process and made it fit. Not a problem, just watch it doesn't bind in the tube or you won't get it back out!

Am I right in thinking that the outside diameter of tubes is standard so the inside diameter tells you the wall thickness?

Buy a vernier it is the best thing you can do.