[dogbluedrummer]

It is a fact that going from stock tires to larger tires results in a loss of power (without regearing). My questions is, what is the reason for this? This is an issue of physics. Below are some suggested reasons:

Weight of the tire
Diameter of the tire
Rolling resistance (contact surface area)
Tire mass (weight is not the same thing as mass)

[Chris_]

Are you just making idle chit-chat?

[dogbluedrummer]

Not idle chit-chat. I want to understand the physics behind the fact.

[Jerry Bransford]

A larger diameter tire also has a longer radius, which equates to the tire having more leverage (moment/arm) against the drivetrain which means the engine must develop more power to overcome that increased leverage.

Plus a larger tire can be thought of as a larger gear against a smaller gear (the ground) that requires more force to turn (a higher ratio).

Then there's the larger tire's increased rolling resistance, its increased weight, increased enertia, and its increased mass that the engine must work harder in order to overcome. Also a factor is that taller tires cause a Jeep to sit higher up in the windstream for higher wind resistance that must also be overcome.

Those will do for starters, right?

[hoseclamp]

Originally Posted by Jerry Bransford

A larger diameter tire also has a longer radius, which equates to the tire having more leverage (moment/arm) against the drivetrain which means the engine must develop more power to overcome that increased leverage.

Plus a larger tire can be thought of as a larger gear against a smaller gear (the ground) that requires more force to turn (a higher ratio).

Then there's the larger tire's increased rolling resistance, its increased weight, increased enertia, and its increased mass that the engine must work harder in order to overcome. Also a factor is that taller tires cause a Jeep to sit higher up in the windstream for higher wind resistance that must also be overcome.

Those will do for starters, right?

This is all wrong, power loss occurs because of increased weight of the heavier muffler bearings which are required when installing bigger rubber.