265/30R22 vs 315/30R21

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

315/30R21 is a safe swap for 265/30R22 by the usual ±3% rule: the diameter differs by +0.64%.

315/30R21 is a safe swap for 265/30R22 by the usual ±3% rule: the diameter differs by +0.64%.

265/30R22 28.26" · 315/30R21 28.44" · drawn to scale

Side by side

	265/30R22	315/30R21	Difference
Overall diameter	28.26"	28.44"	+0.18" (+0.64%)
Section width	265 mm	315 mm	+50 mm
Sidewall	3.13"	3.72"	+0.59"
Rim	22"	21"	-1"
Circumference	88.8"	89.3"	+0.6"
Revs per mile	714	709	-5
Ride height	—	—	+0.09"
Speedometer reads 60 mph	60.0	60.4	+0.4 mph

Speedometer and odometer

With 315/30R21 on a car calibrated for 265/30R22, the speedometer reads 59.6 mph when you're really doing 60, and the odometer under-counts by 0.6%.

Speedo shows	Actual speed
30 mph	30.2 mph
45 mph	45.3 mph
60 mph	60.4 mph
70 mph	70.4 mph
80 mph	80.5 mph

Other sizes close to 265/30R22

Questions

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

315/30R21 is a safe swap for 265/30R22 by the usual ±3% rule: the diameter differs by +0.64%.

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

315/30R21 is 0.18" taller and 50 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 60.4 mph.

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

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