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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.
 

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Assuming identical compound and construction, a 120/65 tire has a stiffer sidewall than a 120/70 tire because of its shorter section height. A stiff sidewall deflects less, aiding steering but offering a smaller contact patch at lean and inferior bump absorption.

Even with identical ride heights, the 120/65 tire provides quicker steering and better feel. The 120/70 tire provides better bump absorption, a larger contact patch, and ultimately more grip. The choice is personal.
 

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quote:
So what sort of characteristics, apart from quick steering, will the 120/60 fronts deliver, good and bad. Would fork adjustments also need to be made?
A 120/60 tire gives quicker steering and better feel than a 120/65 tire at the cost of inferior bump absorption, straight-line stability, and grip at lean.

If the top end of the inner tube is flush with the upper surface of the handlebar holder, you cannot increase the ride height at the forks.
 
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