What size bike to buy?

[ana]

My 8 year old daughter has outgrown her 20" bike but I need help deciding which size to buy next. She is 54" tall,with a 24" inseam. She fits the 24" bike when the seat is raised almost to its full extension.In one year,(or less)she'll need a new bike.I've had feedback from two different bike shop employees, one saying it's better to go with the 24",the other saying the 24" is already too small if you have to raise the seat before you start riding it.He recommended the 12"adult bike which is the same size frame,but a 26" wheel. I'd really appreciate some advice from all of you!
Thanks
Ana

[st0ut]

How about a litle bit of both?

http://www.terrybicycles.com/cycling_savvy/fit.html

Terry bike are for women only so this is prolly a good starting place for you

[deraltekluge]

Something doesn't compute there. I'm an adult male, 5' 7" tall (about a foot taller than your daughter) with a 29" inseam, and a toy store 24" kid's mountain bike fits me. It certainly seems strange that someone a foot shorter would max out the adjustment range on a bike that size. I bought it when I started riding again at age 65 because it was extremely cheap and I wanted to see if I could ride at my age before spending a lot of money. After about a month, I switched to a real bike...a 16" frame mountain bike.

[MichaelW]

Bikes are designed to fit with some seat extension, traditionally a handfull of exposed post. Some styles of bikes (compact frame) are designed to be used with about 6-8" of post showing.
With the 24" bike, how long is the seatpost.
How much extension does your daughter need right now? Is the saddle correctly positioned (ie not too low)
That will give you an idea of the growth potential.
The other important dimension is reach from saddle to bars. Is the 26" bike too long?
Generally, if your bike has no exposed seatpost it is too big. This means the reach is also too long.
Is there any difference in weight or rideability (which does she prefer?)

The advice for adults who are inbetween sizes is to opt for the smaller bike.
12" is very small for a 26", I have never seen below 13". The Kona (http://www.konaworld.com/08_hula_w.htm)kids bike uses 12" frame with 24"wheels and looks nicely proportioned.