Quote:
Originally Posted by tasdrouille
I don't get why if I switch to a tire that is larger, the contact patch would be larger. The load on the tire being the same and the pressure too, the contact patch should keep approximately the same area. no?
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First, let me state that the information available about contact patch is really sparse. So I am going on a lot of ..... ah ...... let's call it innuendo in the literature.
The best I can figure out is that you can envision the contact patch as a line bisecting a circle, with the length of the line being the length of the footprint. So you can go from being tangent to the circle, through barely bisecting the circle, and into the circle so you get a sizeable cresent. As you do that, the effect of the circumference diminishes. Put another way, moving further into the circle the same amount as previous, results in less than twice the length.
Part of the problem here is that when you go larger in diameter, you also have to change something else - the width, the load carrying capacity, etc. You just can not do anything without having a confounding issue.
So if you put those 2 pieces together and try to keep the same load carrying capacity as well as the diameter, the result is a narrower tire.
When you go to consider the same load (on the same load carrying capacity, but larger diameter) the % deflection remains the same and that means an ever so slightly longer footprint.
But this is really "picking nits". There is such a small difference it is not worth discussing.