265/40R21 vs 315/30R22

Q: Can I replace 265/40R21 with 315/30R22?

315/30R22 is a safe swap for 265/40R21 by the usual ±3% rule: the diameter differs by +0.32%.

315/30R22 is a safe swap for 265/40R21 by the usual ±3% rule: the diameter differs by +0.32%.

265/40R21 29.35" · 315/30R22 29.44" · drawn to scale

Side by side

	265/40R21	315/30R22	Difference
Overall diameter	29.35"	29.44"	+0.09" (+0.32%)
Section width	265 mm	315 mm	+50 mm
Sidewall	4.17"	3.72"	-0.45"
Rim	21"	22"	+1"
Circumference	92.2"	92.5"	+0.3"
Revs per mile	687	685	-2
Ride height	—	—	+0.05"
Speedometer reads 60 mph	60.0	60.2	+0.2 mph

Speedometer and odometer

With 315/30R22 on a car calibrated for 265/40R21, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.3%.

Speedo shows	Actual speed
30 mph	30.1 mph
45 mph	45.1 mph
60 mph	60.2 mph
70 mph	70.2 mph
80 mph	80.3 mph

Other sizes close to 265/40R21

Questions

Can I replace 265/40R21 with 315/30R22?

315/30R22 is a safe swap for 265/40R21 by the usual ±3% rule: the diameter differs by +0.32%.

What's the difference between 265/40R21 and 315/30R22?

315/30R22 is 0.09" taller and 50 mm wider; the sidewall is -0.45". At an indicated 60 mph you'd actually be doing 60.2 mph.

Will 315/30R22 fit on 265/40R21 wheels?

No — 265/40R21 needs a 21" wheel and 315/30R22 a 22" wheel. This is a plus/minus-size swap that changes wheels too.