I always figured that the size of the tire has nothing to do with tire patch size. It in my mind is a function of tire pressure. You have 500 pounds on a tire and there is 50 psi in the tire. you will have 10 sq inches of contact patch. a wide tire will have a wider patch and a narrow tire will have a longer patch but both have 10 sq inches.
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Originally Posted by 3-Wheeler
Actually, saying a wider tire alone decreases rolling resistance is half the story.
Any tire shape that increases the contact patch with the road decreases rolling resistance.
The main reason why?
The larger contact patch allows the tire carcass to flex less, which in turn takes less energy to roll.
Pumping a tire to a higher pressure accomplishes the same thing, but not as greatly as going to a larger contact area.
Why?
Because as you pump up the tire, what happens to the contact patch?
Right, it gets even smaller, which then in turn causes the carcass to be stressed over a smaller area.
Instead, think ATV tires or similar and you get the idea on a better approach.
However there are side effects:
1) A big balloon tire can easily upset the handling of the vehicle
2) Offers more frontal area to the wind, with an increase in drag
3) In extreme cases can raise the vehicle CG and affect handling
4) More unsprung mass, which lowers ability to respond to bumps
5) More gas to accelerate the mass of the larger tires
6) Harder on brakes when slowing down
7) Less mechanical advantage of disks/drums, making pedal pressure go up
Jim
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