Originally Posted by
smashndash
Boy I hate to pile in on this zombie thread...
but why should a 23mm bike tire and a 50mm bike tire have the same contact patch size? Shouldn’t your contact patch size be proportional to the size of the tire?
You are certainly wrong that a 100psi tire feels just as hard regardless of tire size.
I was baffled by that claim too. I think that claim is based on using the same pressure in each tire. 30 psi in the 23 mm tire might yield a tire drop of 65% with a 175 lb person on the bike giving a very long, But narrow tire patch. The same pressure in a 50 mm tire of the same design with the same load (bike and rider) might have a drop of 20%, For a short but wide tire patch. End results might be very close.
However, Many real world tire pressure calculators are based on the 15% drop method. So the tire patch would not only longer (15% of a tire height of 23mm vs 50 mm) but wider too, Yielding a much larger contact patch. One reason we use wide tires for beach cruisers and narrow tires (to about 32mm) for road bikes.