315/40R21 tire size
A 315/40R21 tire stands 30.9 inches tall and 12.4 inches wide, with a 5.0-inch sidewall on a 21-inch rim.
- Overall height
- 30.9 in785 mm
- Section width
- 12.4 in315 mm
- Sidewall height
- 5.0 in126 mm
- Rim diameter
- 21 in533 mm
- Circumference
- 97.1 in2467 mm
- Revolutions per mile
- 652405 per km
- Inch size
- 30.9x12.4R21
Compare it with any other size in the tire size calculator.
Sizes you can swap to
These 21-inch sizes are within two width steps and 3% of a 315/40R21's overall height, the usual limit before the speedometer, ABS and transmission notice. The closest is 325/40R21, 1.0% taller (0.31 in). Wider sizes also need room in the wheel well and a rim width that suits them.
Plus and minus sizes
Changing rim size means changing the sidewall to keep the same overall height. On 19-inch or 20-inch or 22-inch rims, these are the closest matches to a 315/40R21.
Other 21-inch sizes near 315/40R21
40 series, other widths
See the other sizes for this rim on 21-inch tire sizes, or other tires about this tall on 31-inch tires.
Shop 315/40R21 tires
These open each store's own list of 315/40R21 tires, where you can filter by type, load and speed rating.
315/40R21 questions
How tall is a 315/40R21 tire?
About 30.9 inches (785 mm) from the ground to the top of the tread, unloaded. On the vehicle, carrying weight, it sits a little lower.
What does 315/40R21 mean?
315 is the section width in millimetres (12.4 in). 40 means the sidewall is 40% of that width: 126 mm, or 5.0 in. R means radial construction, and 21 is the rim diameter in inches.
Can I use 295/40R21 instead of 315/40R21?
295/40R21 is 2.0% shorter (0.63 in) and 20 mm narrower, which is inside the usual 3% rule. With it fitted, the speedometer shows 60 mph when you are doing 58.8 mph.
What is 315/40R21 in inches?
In inch terms it is 30.9x12.4R21: 30.9 inches tall, 12.4 inches wide, for a 21-inch rim.
How many revolutions per mile does a 315/40R21 make?
About 652 turns per mile, worked out from its unloaded circumference of 97.1 inches. Makers list slightly higher numbers for their own tires, because a loaded tire rolls on a smaller radius.