I have a 20" frame and with fixed posts would require 7-8 inches extension from seat clamp for the flats and uphills.
Taking into account my frame requires roughly 7 inches + to be below where the top tube and down tube meets area.
I reckon a 125mm drop which is 420mm in full overall length.
I'm also guessing that with a 32inch inside leg and taking into account the 5cm or so collar above the seat clamp that 22" height when the post is dropped all the way would be good for DH sections...?
Can anyone confirm whether or not that 22" will allow good space to move around on on the DH sections.
any advice welcome as I seem to jump on the technology wagon a bit late when it
comes to advances like droppers.
:_)
Shit. When I bought mine I just looked at the diameter. My bad?
Rule of thumb for me would be a small frame could get away with 100mm drop, medium and large on 125mm drop and x-large and above is 150mm drop
Putting a 125mm drop onto (what is basically) a large frame should be ok. If you were longer in the leg I'd go for a 150mm drop but as with all rules of thumb, it's there to be broken (for reasons of money, fashion or whatever other thinking takes over)
[img] 
[/img]
Cheers for that jam bo, was wondering about dimensions as being a short arse wanted to know rail to bottom of bearing housing on posts for getting one.
I've a med frame and got a 100mm.
Reason was, the post nearly fully inserted gave me the perfect extended hieght. A 125mm would have been pretty much 25mm to high.
If you've got 7" (aprox 175mm) take away the collar hieght and get a post to suit what's left.
thanks to most especially Jambo for the visual take on measurements.
No problem. That diagram saved me buying a 150 dropper that wouldn't have fitted my frame/legs...