245/35R21 vs 255/30R22

Q: Can I replace 245/35R21 with 255/30R22?

255/30R22 is a safe swap for 245/35R21 by the usual ±3% rule: the diameter differs by +0.98%.

255/30R22 is a safe swap for 245/35R21 by the usual ±3% rule: the diameter differs by +0.98%.

245/35R21 27.75" · 255/30R22 28.02" · drawn to scale

Side by side

	245/35R21	255/30R22	Difference
Overall diameter	27.75"	28.02"	+0.27" (+0.98%)
Section width	245 mm	255 mm	+10 mm
Sidewall	3.38"	3.01"	-0.36"
Rim	21"	22"	+1"
Circumference	87.2"	88.0"	+0.9"
Revs per mile	727	720	-7
Ride height	—	—	+0.14"
Speedometer reads 60 mph	60.0	60.6	+0.6 mph

Speedometer and odometer

With 255/30R22 on a car calibrated for 245/35R21, the speedometer reads 59.4 mph when you're really doing 60, and the odometer under-counts by 1.0%.

Speedo shows	Actual speed
30 mph	30.3 mph
45 mph	45.4 mph
60 mph	60.6 mph
70 mph	70.7 mph
80 mph	80.8 mph

Other sizes close to 245/35R21

Questions

Can I replace 245/35R21 with 255/30R22?

255/30R22 is a safe swap for 245/35R21 by the usual ±3% rule: the diameter differs by +0.98%.

What's the difference between 245/35R21 and 255/30R22?

255/30R22 is 0.27" taller and 10 mm wider; the sidewall is -0.36". At an indicated 60 mph you'd actually be doing 60.6 mph.

Will 255/30R22 fit on 245/35R21 wheels?

No — 245/35R21 needs a 21" wheel and 255/30R22 a 22" wheel. This is a plus/minus-size swap that changes wheels too.