Ride height and different tire sizes
How do different sizes feel/work?
You can generally change tire sizes within the recommended tires in the FAQ without noticing any great difference in handling. It is important to remind yourself for the first several rides that you have a new tire that is rounder (less squared-off) than your old one. Take it easy and get used to the different handling.
Caution: One change that is not recommended is putting a taller tire on the front without putting an equivalent on the rear. In other words, if you're putting a 100/90-16 on the front, use a 130/90-16 on the back. The handling of the bike will be compromised with a taller front tire.
Comments from people who have changed tire sizes:
Tire sizes and ride height
Figuring out the difference in ride height between different tire sizes is relatively simple. We'll use a common replacement size for the rear, 130/90-16. The first number (130) is the width of the tire in millimeters. The second (90) is the aspect ratio (profile), or how tall the tire sidewall is as a percentage of its width. To get the sidewall height and figure out the difference in ride height, you just multiply the width by the aspect ratio (expressed as a decimal). So, for our example the math works out this way:
130/90-16 Sidewall height = 130 x .9 = 117
And a shorter tire would look like this:
120/80-16 Sidewall height = 120 X .8 = 96
So, the ride height difference is 117-96 = 21mm
If you need inches to visualize the difference, divide 21/25.4 = .83 inches
But wait, you say; there are sidewalls on the top and bottom of the tire. This is immaterial for calculating ride height, as the extra diameter above the axle does not affect the height of the bike. Only the distance from the axle to the ground affects the change in ride height.
Remember also that tire sizing is not an exact science, even between different tires from the same manufacturer. So, a 120-width tire may be 118mm or 123mm. The few millimeters won't make any noticeable difference.
For more information on calculating tire dimensions, see Tire Rack's Tire Tech.
Ride height for tires that fit the Ninja
So, a 130/90-16 tire has a ride height of 13mm taller than stock, and a 120/80-16 gives a ride 8mm shorter than OEM.
A 100/90-16 is therefore 10mm taller than OEM.