I have a 1990 GT Team Avalanche that I've just built up. Everything is working great, except I'm struggling with the seat post, and I was wondering if I could get some tips.
(measured with callipers)
The seat post tube is: 26.9mm internal, 30mm external
I have 2x seat posts:
1. 26.6mm seat post diameter, using 30mm clamp - after 5-10 miles has completely fallen down
2. 27mm seat post diameter, no clamp needed - this will go in about 80mm but no further
Is the answer to just get a 26.8mm seat post? Is that the difference here? Or is there something I can use with the 26.6 or 27? Both seat posts are old GT posts, so I assume that maybe the seat tube of the GT has expanded over the last 20-30 years and therefore doesnt fit properly anymore?
(measured with callipers)
The seat post tube is: 26.9mm internal, 30mm external
I have 2x seat posts:
1. 26.6mm seat post diameter, using 30mm clamp - after 5-10 miles has completely fallen down
2. 27mm seat post diameter, no clamp needed - this will go in about 80mm but no further
Is the answer to just get a 26.8mm seat post? Is that the difference here? Or is there something I can use with the 26.6 or 27? Both seat posts are old GT posts, so I assume that maybe the seat tube of the GT has expanded over the last 20-30 years and therefore doesnt fit properly anymore?