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Ideal wheel size(3 posts)

Ideal wheel sizeLuckyStrike
Dec 6, 2001 12:22 PM
I recently read an article discussing how the modern wheel size of 700mm was more or less just a size picked arbitrarilly rather than a size picked by design. This raises the question: If the bicycle were re-designed from scratch today, what size wheel would be used?

Here are some points quoted from the book 'High-Tech Cycling' by Edmund Burke(c 1996):
1. "Aerodynamically, there doesn't seem to be too much difference between the best wheels in 24-in., 26-in., and 27-in., diameter."
2. "They (smaller wheels) are lighter and stronger, and the bicycle frame can also be made lighter and stiffer with consequent advantage in acceleration, cornering, and hill climbing."
3. "Small front disk wheels have more stability in unsteady crosswinds..."
4. "In a pace line, small-wheeled bikes can draft closer, and therefore the bikes in the pace line have a lower average wind resistance."
5. "And in a road race where there is constant acceleration and deceleration, the small-wheeled 24 X 24 should be best."
6. "...the only obvious disadvantage to small wheels is their higher rolling resistance."

According to Edmund Burke, it sounds like our wheels are too big!

24 inch = 600 mm
26 inch = 650 mm
27 inch = 700 mm
re: Ideal wheel sizebrider
Dec 6, 2001 1:11 PM
If I remember right, in the days of wooden rims, there were three standard sizes -- 700 A, B, and C. The idea was that the outside circumference of the tire/rim combination was the same for all three sizes (each rim had a corresponding tire). The industry just settle on one rim size -- 700C -- and the tire manufacturers made the changes. True, the smaller wheels are stronger (due to the smaller distance that the spokes travel from hub to rim, making the spoke angle better). So itwould appear that the best wheel would be the 24" (imagine everyone riding Bike Fridays).
There are other issues...TJeanloz
Dec 7, 2001 8:41 AM
In addition to the rolling resistance issue, there are some others.

24" wheels were all the rage for TT bikes after Jan Ulrich won the Tour de France with a TT bike with 24" wheels. It seemed like the old argument about 700c vs. 650c was being thrown out in favor of 24". But there are some real drawbacks to little wheels. One is that as wheels get smaller, gearing needs to get bigger. If you ran a 55/11 as your top gear with 700c wheels (which is not uncommon for TT bikes), you would need to run a 64/11 to achieve a similar gear with a 24" wheel. So, assuming you could find a 64t chainring, no front derailluer would be able to handle it.

Another issue is bottom bracket height. A 24" wheel would bring the bike ~1.5" closer to the ground, reducing cornering clearance. This could be accomadated with a change in geometry, but that would almost certainly compromise handling.

People like to think that a lot of things in bikes are arbitrary decisions, but they're not. 700c didn't become the standard just because Mavic said it was (though Mavic likes to think this was the case). 700c won out over other sizes because it was the best. It was an evolutionary process that settled on 700c, not a decision by some French guys over some bread and wine.