My kids went through what seems like a gap in bike sizes, where they were too big for kids' bikes, but not big enough for adult sized bikes. A lot of parents I've talked to report the same problem. Some solutions carried a price premium, such as sizes tailored for women from specialty brands. It hardly made sense to pay a lot for bikes that would be outgrown in a few years. Or out of style as tastes change. We came up with a couple of solutions worth looking into:
1. Both of them had 24" wheel mountain bikes, but had run out of seat post. Amazingly, these bikes had both come with very short posts. We got roughly an extra year of use out of each bike by finding longer posts on eBay. And the bikes had come to us second-hand in the first place.
2. Keep a constant eye out for the small number of mainstream brands that make smaller frames. My spouse had a Fuji hybrid that she didn't really like but had a tiny frame, so it became a kids bike for a few years as each kid used it in succession. Also, there are some bikes in the "mountain bike" category that look surprisingly like hybrids if you put smooth tires on them, but have shorter frames.
3. The penalty of not getting to ride their first choice of bike was compensated by an assurance that they could get nice bikes when they got close enough to their adult stature.
4. I got them involved in the mechanical work required to provision their bikes. Getting familiar with a wrench will pay them back forever. And as an odd benefit, as they got older, they both realized that they would be heading to college eventually, and fancy bikes would be a liability. Plus they developed "hipster" sensibilities, and decided that they wanted cool bikes thrown together from old parts. Cross my fingers, but maybe our days of buying fancy new bikes are over.
