Designing a bike around a 24″ wheel
Recently I was contacted by a customer who was concerned that my bikes using a 24” front wheel/700c rear wheel design were flawed. Wouldn’t the design put pressure on the neck and shoulders because the 24” bicycle wheel made the front of the bike lower than the rear?
Ah, if were only so simple as throwing a 24” bicycle wheel on a bike designed for a 700c wheel. If one picture is worth a thousand words, then four pictures must be even better.
1). Here’s a bike with 700c front and rear wheels.
2). If the 700c front wheel is replaced with a 24” wheel and no other changes made to the bike, the picture below shows how it would look. Not only is the bike very low in the front, but the brake pads are far above the wheel. The rider would definitely feel not only pressure on her hands and shoulders, but she would feel the thrill of no front brake!
3). If the 700c wheel and fork is replaced with a 24” front wheel and fork, braking is restored, but the bike still “points down.”
4). Here’s the right way to do it. The head tube on this bike is much longer than on the bike using twin 700c wheels. This keeps the front of the bike in the proper position so the top tube is horizontal again and the rider is in a normal position. Compare this to the first picture.
Bottom line: When a bike with a 24” front wheel is build this way, there is no design flaw. If the rider feels as though she is bearing too much force in her arms, the solution lies in tweaking the stem and handlebars.
Comments
Cool stuff, but I wish you made 650B wheel-size bikes.
I can make 650B bikes in a custom design.
Over time I’ve come around to understand these not as “a (normal) bike with a small front wheel” but as “a small bike with a big rear wheel”. An alternate presentation of the design philosophy might start from a fully proportional design for a smaller rider with same-size wheels and then explore why you would choose, and how you would use, a larger wheel in the rear.
Excellent! A creative way to frame the situation. I’ll take you up on your suggestion in a forthcoming blog.
Great bike! Perfect for my short stature! Love it!
[…] there is a series of youtube videos about designing frames and small ones in particular by framebuilderess Georgena Terry. Here is the first part: Bicycle Frame Design, Part I – YouTube She also builds small bikes with normal 700c wheel at back and small wheel in front: Designing a bike around a 24" bicycle wheelGeorgena Terry […]
do you find people shy away from the idea of a smaller front wheel for reasons of having to carry 2 different tube sizes, less of a supply of 24″ tyres etc at all ?
also if you were to build the rear wheel smaller to avoid the tube size issue, do you consider that might be a bigger disadvantage than using the bigger wheel for gearing reasons among others ?
thanks
NBC
Yes — people are reluctant to carry two tubes, even though they take up very little room. Even though the bike I ride has the same wheel sizes front and rear, I carry two tubes — insurance!
The need for higher gearing is the only downside I see to using small wheels front and rear. Yes, smaller wheels have slightly more rolling resistance than larger wheels, but this is negligible for most riders.