275/45R21 Tire Size Specifications & Compatible Vehicles
Overall Diameter
780.9 mm
Section Width
275 mm
Sidewall Height
123.8 mm
Circumference
2453.3 mm
Revs/Mile
656
Rim Diameter
21"
Inch Equivalent
30.7x10.8R21
Rim Width (ETRTO)
8.5" – 11.0"
Compatible Vehicles
The following vehicles use 275/45R21 tires from the factory:
Alternative Tire Sizes
These tire sizes are within 3% overall diameter of 275/45R21 and may be used as replacements:
Understanding 275/45R21
The tire size 275/45R21 means the tire has a section width of 275mm, an aspect ratio of 45% (the sidewall height is 45% of the width), and fits a 21-inch rim.
Sidewall Height = 275 x 0.45 = 123.8 mm
Overall Diameter = (123.8 x 2) + (21 x 25.4) = 780.9 mm
Circumference = 780.9 x π = 2453.3 mm
Overall Diameter = (123.8 x 2) + (21 x 25.4) = 780.9 mm
Circumference = 780.9 x π = 2453.3 mm
Frequently Asked Questions
The 275/45R21 tire size is used on 9 vehicle trims including the 2025 Acura MDX, 2024 Acura MDX, 2023 Acura MDX and 6 more.
A 275/45R21 tire has an overall diameter of 780.9mm (30.7 inches). The sidewall height is 123.8mm, and the total circumference is 2453mm.
For 275/45R21 tires, the ETRTO recommended rim width is 9.5". The acceptable range is 8.5" minimum to 11.0" maximum. Using a rim outside this range can cause improper bead seating and unsafe handling.
Yes, as long as the replacement tire overall diameter is within 3% of the 275/45R21 780.9mm diameter. Compatible alternatives include 165/75R21, 225/55R21, 195/70R20. Use our Tire Size Calculator to compare any two sizes.