Sure, lets break it down!
- 26" is the approximate outer diameter of the tire (26" sized tires come in slightly different sizes and so the inch size is just a rough guide).
- 1.95" is the width of the tire.
Hope this makes sense!
- 50 is the width of the tire in millimeters so 50mm.
- 559 is the tire inner diameter so 559mm. This is an exact measurement and therefore you can calculate the exact rim size.