Road Cycling - Bikes with two different wheel sizes?

Hello all... I received a catalog the other day (from Terry Cycles) showing regular road bikes with a smaller front wheel than the rear. Does anyone know the theory/ reasoning behind that? It certainly looks strange.

It's only on the smaller frames. With the shorter top tubes, if they used a 700c wheel, you'd be running your toes into the front wheel when you tried to take a sharp turn - very dangerous.

With their larger sized frames ( I think 19" and larger, but I could be off a size), both wheels are 700c.

ah, that makes sense. I've never seen it except in the photos, I thought maybe it was a new style! thanks.

Terry has been doing that for years. It makes some sense for small frames, and has its drawbacks. You need to carry two spare tubes.

I happen to know Georgina Terry (she's a member of our local bike club), and, yes, toe overlap was her main reason for advocating the 24" front wheel. Since women tend to have shorter upper bodies, they can better use a shorter top tube. Unfortunately, using 700c wheels will result in either toe overlap, or some very strange geometry. Her larger MTB's have 2 similar sized wheels, but I'm fairly sure that all her road bikes have 24" front wheels.
When she rides, she only carries a single spare tube. I asked her about that, and she says that all you need to do is overlap the tube when you mount the tyre. It may be a bit lumpy, but it works. This is coming from the woman that designed the bike......

The important thing to remember about these kinds of bikes is you have to carry two sizes of spare tubes in your seat pack. :crash:
You never know if the front or rear wheel will have a flat. :eek:

Weren't there some TT and Tri bikes made with 700 rear/650 front to achieve a more aerodynamic position? Or am I just thinking of the 650c bikes?

You see that configuration on bikes made for small women. Women tend to have longer legs and shorter torsos then men of the same height. That means to get a decent geometry on a bike for a small woman, it is an advantage to have a smaller front wheel. I believe women of nearly average height can get along well with 2 700c wheels.

Yes, in the 1980s, TT bikes were built with smaller front wheels. These were known as "funny bikes". I have a Nishiki TT bike with a 700C rear, and a 20" front. The idea is to allow you to get lower on the bars (this design predates aerobars) for improved aerodynamics.

Mine is very fast, but uncomfortable. Faster than my other bikes over short distances, but on longer rides, the pain slows me down. I should add that this bike is a little too small for me, and that is the source of alot of the discomfort. For a smaller rider, this bike would be awesome!

Those low-profile time-trial bikes used 650c front wheels to lower the front end for a more aerodynamic position. With modern designes, you dont need as much head-tube length, so average male riders can get very aerodynamic with standard wheel sizes.
For small riders, smaller wheels make a whole lot of sence, but apart from Terry, most experienced custom builders would use identical wheels sizes, either 650c for racing bikes or 26"MTB size for touring/general purpose bikes (using thin slick tyres). The advantages of large rear wheels in small bikes are marginal.