It’s hard to know where to start with the perfect bicycle The frame is the basis for many of the ride characteristics of a complete bicycle, but as I have a few frames in mind with different wheel sizes I starting this rambling discussion with wheels and tyres.
29 inch or 700c (622mm)
These wheels have the same rim diameter, however with the addition of their usually very different tyre, the effective diameter changes significantly.
Built as 29 inch mountain bike wheels, these large wheels usually have a relatively heavy duty rim and tire, and because they are heavier, they take more effort to start and stop. These wheels also take more effort to turn due to having a larger footprint and higher rotating mass. What this tyre and rim combination does well is roll over obstacles.
Built as 700c road wheels with a light rim and smaller tyre, they maintain their ability to roll over obstacles, and shed much of their weight. The compromise is a better handling wheel, that isn’t built to take the punishment you might dish out to a mountain bike wheel on a fast decent. This is a very popular size and the availability of tyres, mud guards, spokes etc is all essentially universal.
The issue that is generally cited about this wheel size is toe overlap. It is something that I’ve noticed in the past and given that I am considering a bike that will be touring, city commuting and shopping, I’m definitely interested in making sure that toe overlap isn’t an issue with the bike I decide upon.
650b (584 mm)
This is a size that is regaining some popularity in the touring and randonneuring community. Availability of parts isn’t as good as with 700c and 26 inch, but it is getting better. This wheel is less likely to have toe overlap issues and is lighter, stronger, and a more responsive than the 700c wheel. When this wheel is coupled with a 700c purposed frame, the wheel size will slightly lower the bottom bracket, reduce toe overlap and slightly reduce the ‘trail’ of the front wheel – quickening the handling. The main draw back is availability of tyres and mudguards, but what I have found so far isn’t too expensive, and suits my purposes. If you use this size wheel on a 700c frame – you may want to get a slightly shorter crank.
26 Inch (559mm)
This is a size most commonly applied to mountain bikes. It further reduces the possibility of toe overlap, is very responsive, is strong, and allows plenty of room for mud guards. My guess is that this wheel will eventually loose out to the 29er on mountain bikes as it doesn’t roll or look as good as the 29 inch. However in other respects it is a good package for the maneuverability required in mountain biking. Availability of all related consumables is good.
The flanges on a hub, I believe, don’t radically change the stiffness of a wheel and mostly the flanging relates more to the arrangement, number and lace pattern of the spokes. Aesthetics and fashion also play a role here. The width of the hub however does have a significant effect, and a centred rim, rather than a dished rim is much stronger. So a wheel that has been dished to include sprockets, will be weaker than a fixed, single or internally geared hub.
There are heaps of tyres out there in many different styles so I am going to keep this general. Probably the best tyres I’ve owned would be Continental, Town and Country. A tyre for all seasons but only available in 26 inch. I’ve done alot of touring on these tyres and they were extremely puncture resistant, durable, comfortable and efficient. I’d like to replicate this feel on the new bike if possible.
Jan Heine, Editor of Bicycle Quarterly has written a great deal about his experiences and has also done some testing relating to tyres, wheel size and pressure on his website “Off the Beaten Path” – If you want to find out about wheels and tyres (and randoneuring) the Bicycle Quarterly and Off the Beaten Path is going to toast your bread! In summary, it’s complicated. According to Jan and his testing, increases in tyre pressure don’t necessarily lead to increases in efficiency and decreases in rolling resistance and so a medium sized, supple, softer walled tyre may be more efficient than hyper hard, 23mm racing tyre – This is good news and somewhat vindicates my oft misty eyed remembrance of the performance of my town and country tyres. There are optimum pressures depending on your weight and tyre choice so there’s plenty to consider in selecting a tyre if you want to get fanatical about it. If you’d like to know more – try – Science and Bicycles 1: Tires and Pressure by Jan Heine.
I’d be happy with any of the wheel sizes and so I suppose they aren’t a determining factor. The 650b does seem to be a rather happy medium between the various sizes – but I wouldn’t choose a bike on it’s ability to accept a 650b wheel.
Tyre choice and pressure, on the other hand, is something I’ll look at more closely when I have decided on a frame and wheel – it’s crucial.