Originally Posted by
corvuscorvax
Sure. A rigid sidewall could carry part of the load on the tire, which would make the contact patch smaller than it would otherwise be given the pressure. Likewise, elasticity in the tread might make the contact patch a little larger than it might otherwise be. So two different tires on the same rim at the same pressure will have slightly different contact patch sizes, depending on the details of the tire construction. None of these things changes the underlying physics a bit, and none of these things have anything at all to do with the "29ers have a bigger contact patch" myth. Equilibrium demands that the total force pushing up on the wheel be equal to the total force pushing down on the wheel. Period.
If you really want to believe that tires are magic objects capable of defying basic physical constraints, I really don't know what to say. This is the same kind of logic that leads people to buy $100 digital cables for their home audio system.
Originally Posted by
corvuscorvax
The pressure on the contact patch multiplied by the area of the contact patch is equal to the weight on the wheel. This is Newton's Third Law. It is a basic law of the universe. It is true for bike tires, for car tires, for train wheels, for wagon wheels, for the tires on a 747, and for the wheels on a rickshaw. It is true whether the tire is made from rubber, or steel, or marshmallows, or granite, or unobtanium. It is true on Earth, it is true on the moon, it is true in orbit, it is true on Jupiter, and it is true in the Andromeda galaxy.
Anybody who claims to have measured differently either measured wrong, or doesn't understand his measurements. I suggest a
$1000 HDMI cable to go with those magic tires.
Nawwww .... Newton's third law is : The mutual forces of action and reaction between two bodies are equal, opposite and collinear.
You're just assuming that the forces at work are entirely limited to what you've listed. Typical difference between theory and reality.
Even based on your own oversimplified analysis you've overlooked a little detail. A larger wheel has more metal in it and a larger tire and tube have more rubber in them so a 29er wheelset using the same build components and tires would weigh more than a 26er. That alone would change the load on the tire with the same rider and result in a larger contact patch. Even using your own slightly linked view on things.
PS: Why do I suspect you yourself got sucked into buying those digital cables you're whining about?
'Nuff said - think I've already wasted too much time on this thread.