[edxmon]

Originally Posted by NinjaBoyEddy

No. Like I'm lost. What the hell is the 60? And 70 exactly. I got the 140/70
If you go 150/60 what dose the 60 mean compared to the 70

Metric
Examples: 180/55ZR-17 · M130/80-18 · 130/80HB-18 · 130/80H-18
The Metric tire size system is the most common and also the most descriptive. Metric sized tires are used on just about every type of motorcycle, from the latest sport bikes, to cruisers, touring bikes and everything in between. An "M" sometimes precedes a metric size when there is no speed rating used. It simply means that it is a motorcycle tire. Another letter is sometimes used after the speed rating to indicate belted (B) or radial (R) tire construction.

In the first example above, 180 is the width in millimeters, 55 is the aspect ratio (cross-section height is 55% of the width), Z is the speed rating (149+ mph), R specifies it's a radial construction tire, and 17 is the wheel diameter in inches.

Alpha
Examples: MT90S-16 · MT90HB-16
The Alpha size designation is most often used for touring motorcycle tires. They can be belted even without the B designation, which can appear after the speed rating.

In the first example above, M states that it is a motorcycle tire. T is the width (see cross-reference chart here.) 90 is the aspect ratio (cross-section height is 90% of the width). S is the speed rating (112mph) and 16 is the wheel diameter in inches. Since there is no designation of construction after the speed rating, it is a bias-ply tire.

Standard Inch
Example: 3.25H-19
The Standard Inch systems are found on older motorcycles. Tires with these Inch markings do not include an aspect ratio designation, which is 100%. It means the cross-section tire height is 100% of the width. Inch size tires are all bias-ply construction and not belted. They are no longer being fitted on new motorcycles and are gradually being phased out of use.

In the above size, 3.25 is the width, H is the speed rating, and 19 is the rim diameter in inches. The aspect ratio is not listed, but is 100% of the tire width.

Low Profile Inch
Examples: 4.25/85H-18 · 4.60S-16
This is also called the 82% Series Size System because the aspect ratio, when unspecified, is 82%. The tire's cross-section height is 82% of its width, except in cases where it's listed as 85%, as in the first example above. This system is limited to very few sizes and the motorcycle manufacturers are no longer using tires with this size system.

https://www.denniskirk.com/help_center/tire-sizes.jsp