Gitane Seat post.........

solosuperia

I have a Gitane with GTI Vitus tubes with a seat tube internal Diameter of 25.7mm this is measured using old style manual callipers. My seat post has an external dia. of 25.5mm infinite difference using eye with the manual callipers.
Even when I bolt the seat post in as tight as anything after twenty odd miles the the saddle has dropped!!!!
Any bright ideas for getting the saddle to remain at the same height once it is bolted up tight?
Cheers

team47b

Measure the seat tube accurately and buy the right size seat post

Stand up more

Only go out for 19 mile rides

Loose 20kgs

Send the bike to me, metal expands in the heat (currently 36c)

Get a 25.8 seat post and some grease

Take it to a bike shop and get them to measure it accurately, I would expect your frame to be 26.4 ish at a guess, but best to get it measured.

term1te

I can't remember the exact diameters, but we had a similar issue with my son's bike, 653 frame and a slowly slipping seat post, no matter how tight we did up the bolt. I made a shim by cutting up an old drinks can. With lots of grease, to minimise corrosion, its worked fine ever since.

solosuperia

"I made a shim by cutting up an old drinks can. With lots of grease, to minimise corrosion, its worked fine ever since".
Sounds like my sort of solution.
Will give it a try
Cheers.

team47b

...if you fold the top of the 'shim' over to sit on the top edge of the seat tube it will prevent it slipping down the tube and causing future problems

solosuperia

All tested and ok...........
Thanks for your advice.
I have unearthed a bit of a conundrum.
I thought I didn't have any grease, but deep in the dark regions of the shed.
I found a tub of "Graphite Grease"!!!!
For the life of me cannot ever remember buying it ............ Any ideas why I might have bought it for?
some of it had been used.

team47b

Graphite grease is a dry lubricant.

Used in air compressors, food industry, railway track joints, open gear, ball bearings, machine-shop works, etc. It is also very common for lubricating locks, since a liquid lubricant allows particles to get stuck in the lock worsening the problem.

You bought it to use on that garage door lock that keeps sticking and is subject to a lot of rain, but misplaced it and can't get in the garage anyway 'cos it's full of vintage bikes...or should be :roll:

I bought a tub of general purpose grease for a steering box I was rebuilding in 1978, still using it now, seems appropriate to use it on vintage bikes!