(Paul C. Cox) wrote:

My kids have been riding since age 3,

Cool.

and two of them are now in the
awkward point of not fitting any of the "standard" sizes. Does anyone
know of a good quality multi-speed 18" (tire, not frame) boy's bike?
Though not quite as critical, I also am looking for a girl's 22" in at
least a six-speed.

There is so much variation in the sizes of bikes equipped with 16",
20", and 24" wheels, that they overlap with regard to rider fit.

Any single-speed bike can be fitted with some sort of gearhub, which
you could successively relace into bigger wheels as Junior needs a
bigger ride. This seems preferable to derailleur shifting for kid
use. Tykes and derailleurs are a bad mix, at least from the
derailleur's standpoint. I wonder what use a child too small for a
20-incher has for multiple speeds? Certainly derailleurs, fussy and
vulnerable to damage even for adults, are not something that would
tend to foster a funloving interest in cycling on the part of a small
child.

My corner bike shop hsa a Haro 16" freestyle bike, complete with gyro,
U-brakes, and axle pegs, that is generously-sized enough to entertain
the owner's teenaged sons. It's proportioned larger than many 20" kid
bikes, though not so large as a normal 20" freestyle bike.

Likewise, BMX bikes all feature 20" wheels, but are sized with top
tube lengths from about 16" to about 22" depending on the application
and anticipated rider size. A 20" BMX frame sized XL or XXL would
almost certainly provide more cockpit room than most 24" wheel kid
bikes.

18" and 22" wheels are rare and growing scarcer, and have poor tire
and tube support. They serve no need that can't be addressed by a
judiciously chosen 16", 20", or 24" wheeled bike.

Chalo Colina