When you plan on putting larger wheels on a 4WD -

Why would you need more stopping force?

Picture an imaginary lever arm between the center of your wheel / brake caliper and the ground. To make the concept easier to understand I have moved the caliper (the thing that grabs the rotor to stop the wheel) ontop of the rotor.
The engineers of your car have carefully calculated the size of your brake booster, your master cylinder, the length and diameter of the lines, the number size of the brake pistons, the brake pad surface area and the size of your rotor in relation to vehicle weight and tire size (they care only about the radius - the "lever arm" shown below). All this of course to give you short and safe stopping distances.

If you would later put large tires on your vehicle and the imaginary radius/lever arm increases (in the image below twice as long as in image above) your stopping force decreases proportional to the increase of the radius/lever arm (in this example creating only half the stopping power).

In order to regain decent stopping power you will need to upgrade your brake system. I'll offer examples as soon as I have them in.