315/30R21 Tire Size Specifications & Compatible Vehicles
Overall Diameter
722.4 mm
Section Width
315 mm
Sidewall Height
94.5 mm
Circumference
2269.5 mm
Revs/Mile
709
Rim Diameter
21"
Inch Equivalent
28.4x12.4R21
Rim Width (ETRTO)
10.0" – 12.5"
Alternative Tire Sizes
These tire sizes are within 3% overall diameter of 315/30R21 and may be used as replacements:
Understanding 315/30R21
The tire size 315/30R21 means the tire has a section width of 315mm, an aspect ratio of 30% (the sidewall height is 30% of the width), and fits a 21-inch rim.
Sidewall Height = 315 x 0.3 = 94.5 mm
Overall Diameter = (94.5 x 2) + (21 x 25.4) = 722.4 mm
Circumference = 722.4 x π = 2269.5 mm
Overall Diameter = (94.5 x 2) + (21 x 25.4) = 722.4 mm
Circumference = 722.4 x π = 2269.5 mm
Frequently Asked Questions
The 315/30R21 is a standard tire size. Check your vehicle door jamb sticker or owner manual to confirm compatibility.
A 315/30R21 tire has an overall diameter of 722.4mm (28.4 inches). The sidewall height is 94.5mm, and the total circumference is 2270mm.
For 315/30R21 tires, the ETRTO recommended rim width is 11.0". The acceptable range is 10.0" minimum to 12.5" 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 315/30R21 722.4mm diameter. Compatible alternatives include 165/65R20, 195/55R20, 205/40R22. Use our Tire Size Calculator to compare any two sizes.