285/40R21 Tire Size Specifications & Compatible Vehicles
Overall Diameter
761.4 mm
Section Width
285 mm
Sidewall Height
114.0 mm
Circumference
2392.0 mm
Revs/Mile
673
Rim Diameter
21"
Inch Equivalent
30x11.2R21
Rim Width (ETRTO)
8.5" – 11.0"
Compatible Vehicles
The following vehicles use 285/40R21 tires from the factory:
Alternative Tire Sizes
These tire sizes are within 3% overall diameter of 285/40R21 and may be used as replacements:
Understanding 285/40R21
The tire size 285/40R21 means the tire has a section width of 285mm, an aspect ratio of 40% (the sidewall height is 40% of the width), and fits a 21-inch rim.
Sidewall Height = 285 x 0.4 = 114.0 mm
Overall Diameter = (114.0 x 2) + (21 x 25.4) = 761.4 mm
Circumference = 761.4 x π = 2392.0 mm
Overall Diameter = (114.0 x 2) + (21 x 25.4) = 761.4 mm
Circumference = 761.4 x π = 2392.0 mm
Frequently Asked Questions
The 285/40R21 tire size is used on 4 vehicle trims including the 2025 Audi Q7, 2024 Audi Q7, 2023 Audi Q7 and 1 more.
A 285/40R21 tire has an overall diameter of 761.4mm (30.0 inches). The sidewall height is 114.0mm, and the total circumference is 2392mm.
For 285/40R21 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 285/40R21 761.4mm diameter. Compatible alternatives include 195/65R20, 225/45R22, 175/65R21. Use our Tire Size Calculator to compare any two sizes.