Tire size designations include:
- Section width in millimeters
- Aspect ratio (section height divided by section width) as a percentage
- Rim diameter in inches.
The stock front tire on the 2000 to 2002 ZX-6R has a size of 120/65 17, which indicates that it has a section width of 120 mm, a section height at 65% of the section width or 78 mm, and a rim diameter of 17 inches. A 120/70 17 tire shares the section width and rim diameter of the stock tire, but has a section height at 70% of the section width or 84 mm.
The section height of a 120/70 tire is 6 mm greater than the section height of a 120/65 tire. As a result, a 120/70 tire stands 12 mm taller than a 120/65 tire.
The taller 120/70 tire effectively increases the rake, which slows steering and increases straight-line stability. You may like this just fine.
To maintain the stock ride height, raise the forks 6 mm or 1/4 inch through the triple clamps.