wheel size rant

It's been a while since my last post. Here's a recap of 2009 - I rode the Orange bike as often as I could, it has become my favorite bicycle. I'm not getting many emails, so I don't think this blog is generating much interest. For now, I have no plans to build more prototypes, and this venture has resulted in two nice bicycles (mixte and 650B sportif) for me to ride. I thought of building a 559 road bike more or less like the Orange bike but have shelved that idea for now.

I have come to the conclusion that 700C wheels are not ideal for people who are shorter than average. I think a road bike with a shorter front center has a better front/rear weight distribution and handles better. To enable a large wheel (diameter) bike to fit shorter individuals, compromises are made to push out (forward) the front wheel (hence longer front-center distance) while keeping a shorter reach to the handlebars. My somewhat smaller wheeled Orange bike is a delight partly because it fits me better than my other bikes - I feel better balanced on it despite nearly identical contact points (seat, handlebar, and cranks) as my 700C bikes.

Some have argued for the benefits of wider road tires, in the range from 1 1/2" to about 1 3/4" width. Personally, I think that is too wide for a smaller/lighter rider who is riding mostly on paved roads, and would like to see more road tires in the width range from about 1" to 1 1/4". In the world of 700C road bikes, the common size for high performance tires is a nominal 23mm width - less than an inch. At least in 700C many lightweight performance road tires are available in 25 mm, and there are a few speciality tires (Grand Bois, Challenge) in about a 27-29 mm width that offer more comfort for bumpy roads and little if any performance penalty.

There is a family of "26 inch" wheel sizes (iso rim diameters 559, 650A, 650B, 650C) that I think make great road bikes, but there are few tires available in the 1 1/8" +/- range that I am advocating. The most common smaller wheel size is 559 (mountain bike), and roady tires for it tend to be wider and heavier and for commuters seeking flat-resistance. The common smaller wheel size for road bikes is 650C, and tires for it are almost exclusively 23mm width., and no mass market road bikes built for the alternative smaller wheel sizes, excepting various lower end comfort bikes, urban bikes, and some road bikes for women intended for 23 mm width 650C tires.

So - it's not going to happen anytime soon, but I feel confident stating that if lightweight, supple, 1 1/8" +/-width tires were made for the family of 26" wheels (pick one, I don't think the small difference in diameter among these sizes matters that much) and roadish bicycles designed for those wheels were easily available, most shorter than average road bikers would get a better fit, better handling, and be happier riding such a bike.

Somewhat related to the above, I have thought about ideas for mixing wheel sizes, and I worked out some equations for forks which I'll write up sometime. The idea is that using different front/rear wheel diameters and changing the front fork is a fairly easy way to modify one's bicycle.

Basically, I recognized that there are 3 separate/orthogonal transformations that can be combined to get any desired result. The 3 transformations are: i) changing the fork (length, rake) and diameter of the front wheel so as to maintain constant front center and trail, b) changing fork length and rake without changing front wheel diameter so as to increase/decrease trail (what someone else referred to as "frame neutral geometry"), and c) changing fork length and rake so as to cause a rotation of the bicycle about the rear axle.

That's all for now. If you're reading this, leave a comment!

Happy 2010,

Michael