old steel frame sizes Vs modern geometry

chill123

i'm thinking about trying to find an old 80's steel frame (531 etc) and build a fixed/ss to ride over the winter.

my current frame size is 53/54cm. when looking at these old frames am i rihght in thinking they come up bigger than the modern frame geometry?

i.e. what frame size (seems most are quoted in inches) shoul I go for? i'm 5'8" if that helps.

gaspode

steel framed bikes tend to have horizontal top tubes as opposed to the sloping tubes favoured by more modern designs. If you're happy with the fit of your current bike, easiest method would be to hold a piece of wood horizontally from the top tube where it joins the headset and stick a bit of tape where it crosses the seat post. Measure from the centre of the cranks to the tape and you've got a rough size for the old shaped frame.
Conventional wisdom was to measure your inside leg and subtract 10 inches to find the correct size - I have a 32" inside leg and ride a 22.5" Mercian, so it pretty much works for me, but there are numerous variables (e.g. long legs/short body or vice-versa) that can invalidate that method.....

shaw8670

head tube length is the best guide for doing a comparison with the frame you have.

rolf_f

shaw8670 wrote:

head tube length is the best guide for doing a comparison with the frame you have.

I'd disagree there. I've recently renovated an old Carlton Corsair which has a shorter frame than my Dawes Tourer but a higher top tube.

Period top tube length to virtual top tube length on a modern bike has to be the single most useful comparison; head tube is useful but quill stems give easy fine adjustment anyway.