Why do tuk-tuks have such small wheels? Wouldn’t they be more comfortable and more versatile if they were, say, twice the diameter?
Yes. They would also be potentially quicker. And be better able to handle rougher roads. But they would also be heavier, more expensive, and need different – and more costly – gearboxes.
What the traditional tuk-tuk design offers is somewhere near the lowest common denominator for the motorised transport of goods and people.
Cheap to buy, cheap to run, has zero frills, and yet has useful cargo capacity. Predominantly in urban environments.
The designers must have understood what the target market wants and judged the balance between compromises that would be acceptable and upgrades that would be unaffordable.
Bigger wheels would certainly be more comfortable over bumps and holes and would make tuk-tuks less incompetent in deep sand. It would also offer them a higher cruising speed, but more sophisticated gearing would be needed to enable that while preserving enough power - from very small engines - for hills and heavy loads. Or they could use bigger engines, and upgrade other things to cope with more weight and pace, and thus the cost snowball effect rolls on.
It is significant the more recent boda-boda motorcycles converted to three-wheelers with a trailer completely outsell scooter-based tuk-tuks up-country, while tuk-tuks still thrive at the coast and on the shores of Lake Victoria. Climate and power-sapping altitude are probably important factors in explaining that polarisation. Wheel size upcountry could be another.
