What is the largest size tires I can put on my 2000 wrangler without the adapters

225/72R16 tires are for a 16" rim. They will not fit your 15" rims. Metric tire sizes are confusing, but the first number is width (225 mm, or 8.858 inches). The second number is aspect ratio, or height of the sidewall as a percent of the width (sidewall height is 225*0.75=168.75 mm, or 6.643 inches). The "R" stands for radial tire, which most tires are these days. Lastly, the 16 stands for 16" diameter rim. So, the overall diameter of the tire is (6.643*2)+16 = 29.3 inches. Some off-road tires and light truck tires use standard units for their dimensions, which are much easier to understand. An example would be 31x10.5R15, which is a 31" diameter radial tire that's 10.5" wide and fits on a 15" diameter rim. 31" diameter tires are the largest you can fit on a 2000 Wrangler without a lift, but you will need to recalibrate the speedometer because it will show a slower speed than your actual speed. It will also be slower with larger diameter tires, so you will need to use a lower gear than you usually do. A 31x10.5" tire will fit with minor rubbing when turning at full lock, but you don't want to go any wider than 10.5" without spacers. I hope this helps.