Subject: Ideal Tire Sizes
From: Jobst Brandt
I'm getting a custom frame built and wondered what people thought of using 26 inch road wheels. Smaller wheels ought to be lighter and stronger.
...and goes on to list advantages and disadvantages that aren't as clear as the writer assumes. The main reasons for using 700c or 27" wheels, the common sizes for most adult bicycles is better understood by smaller riders who have a hard time fitting these wheels into their smaller bicycle frames. On the other hand, the larger the wheel the better the ride by averaging road roughness. Riders who encounter cattle guards can best explain this. Don't try that with roller blades.
Cross-sectional area of the rim limits total tension of its spoke complement, whose individual spoke tension limits how much weight the wheel can support. Two to four spokes near the ground contact point of the average wheel support the load at any moment. For this reason, larger wheels would require more spokes that would require a heavier rim to withstand total tension of a greater number of spokes.
It seems to me that the most obvious reason for using 27" wheels is tradition, but I'm not sure the advantages make it worth trying to swim upstream. What do you think?
Fortunately "standard" wheel size was arrived upon in days when economics played a role and produced a design that optimized many aspects of performance, weight and economy. Hub width was one of these criteria because as the wheel gets larger the hub must become wider to offer reasonable lateral stability. Today much money is spent by people who want the best, or at least better than their peers without consideration of durability and safety. Riders often buy exotic wheels, spending more than double than what would serve them best. Most of these wheels offer no advantage other than that a famous racer won a major race on them.
If enough riders ask for 24", 25" and 26" wheels, manufacturers will increase prices as their product lines expand, total sales remaining constant. Tires and spokes would follow as a whole range of sizes that were not previously stocked become part of inventory. Meanwhile, bike frames will come in different configurations to take advantage of the special wheel sizes. Sizes whose advantages are imperceptibly small are touted by riders who talk of seconds saved in their last race or while riding to work.
Fat-tired wheels generally use 559 mm (26") rims that give roughly the same outside diameter of the 622 mm (700c) road wheel. The wheel size we ride today was not an idly chosen compromise.
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