i chose 'other.'
mtb 26" wheels, 24*30 = 20.8 gi
used often for 2-3 hours at a time, on those loooooong climbs in arizona
and nevada.
my road bike has a 19.4gi, 700c, 24*34
very handy on that 5-hour climb from estes park to the visitor center
at rocky mountain national park.