Bicycle Tyre Size
Generally, bike tire sizes are indicated with two numbers that correspond roughly to the tire’s outside diameter and width. These would usually show in inches (26″, 27″, etc.) or millimetres (650, 700, etc.).
While neither are exact measurements, every tire has its size printed or embossed on the outside near the brand name, just like your car’s tires.
On a standard bicycle
A standard road tire is 700c x 23mm, indicating a tire diameter of approximately 700mm and a width of 23mm. When shopping for road tires, you’ll look for 700c x your preferred width, 23mm being the slimmest option and going up to 36mm. 650c: size used on high-performance road and triathlon bikes, especially those designed for smaller riders.
27″ Twenty-Seven inch was a size used on many older road bikes. Modern manufacturers do not use it, but because so many bikes were made for wheels and tires this size, these tires are still readily available.
MOUNTAIN TIRE SIZES
Twenty-Six inch 26″ is the most commonly used size for modern mountain bikes and is also used on many hybrid or utility bikes.
The 29″ is another popular size for mountain bike wheels and tires. It’s the same bead-seat diameter as 700c tires, but most 29″ tires are too wide and tall to fit 700c wheels.
27.5″/650B Making a comeback in mountain biking is the 650b. Modern mountain bike tires using this size may be labelled 650B or 27.5″. It was also used for some older mountain bikes and French utility and touring bikes and never fell entirely out of use.