Here is a quote from Article 12 section 4.1 (12.4.1) from the FIA Tecnical regulations on tyres. "Complete wheel width must lie between 305mm and 355mm when fitted to the front of the car and between 365mm and 380mm when fitted to the rear."
Depending on circuits
The recommended tire size for a 27x1 1/4 bike tire is 27 inches in diameter and 1 1/4 inches in width.
It usually can
The width of the contact patch of the tire on the road.
For a 12.50 inch wide tire, the Tire & Rim Association approves a rim width range of 8 1/2 inches to 11 inches.
Typically there is a margin of error with tires and tire manufacturers of just 1mm in width or 1 pound per square inch. This margin of error is dependant on whether it is the width of the tire or the air within the tire.
The width of the road.
The recommended tire size for a bike that requires a 27 x 1 1/4 tire is 27 inches in diameter and 1 1/4 inches in width.
To determine the width of a tire, you can look at the sidewall of the tire where the size information is usually printed. The width is typically indicated in millimeters and is the first number listed in the tire size. You can also measure the width of the tire using a ruler or tape measure if the size information is not visible.
The recommended tire size for a bike with a 27-inch wheel diameter and 1 1/4-inch width is 27 x 1 1/4 inches.
That is the tire profile or section width. The number is a metric figure standing for the width of the tire in millimeters.
265 on a tire is the width of the tire in mm