You don't figure out how long the fork needs to be, we do it
for you.
First you need your frame, rear wheel & tire, front wheel &
tire and a flat surface.
Mount the frame on the rear wheel and prop the frame upright as
it would be on the bike. Then get a piece of paper, a tape
measure and something to write with.
alternatively
if you have problems with the form send an e-mail to jeri@jeris-springer.com
or print this page and fax to 1-727 447 8786