255/30R22 vs 255/35R21

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

255/35R21 is a safe swap for 255/30R22 by the usual ±3% rule: the diameter differs by +0.01%.

255/35R21 is a safe swap for 255/30R22 by the usual ±3% rule: the diameter differs by +0.01%.

255/30R22 28.02" · 255/35R21 28.03" · drawn to scale

Side by side

	255/30R22	255/35R21	Difference
Overall diameter	28.02"	28.03"	+0.00" (+0.01%)
Section width	255 mm	255 mm	0 mm
Sidewall	3.01"	3.51"	+0.50"
Rim	22"	21"	-1"
Circumference	88.0"	88.1"	+0.0"
Revs per mile	720	720	-0
Ride height	—	—	+0.00"
Speedometer reads 60 mph	60.0	60.0	+0.0 mph

Speedometer and odometer

With 255/35R21 on a car calibrated for 255/30R22, the speedometer reads 60.0 mph when you're really doing 60, and the odometer under-counts by 0.0%.

Speedo shows	Actual speed
30 mph	30.0 mph
45 mph	45.0 mph
60 mph	60.0 mph
70 mph	70.0 mph
80 mph	80.0 mph

Other sizes close to 255/30R22

Questions

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

255/35R21 is a safe swap for 255/30R22 by the usual ±3% rule: the diameter differs by +0.01%.

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

255/35R21 is 0.00" taller and 0 mm wider; the sidewall is +0.50". At an indicated 60 mph you'd actually be doing 60.0 mph.

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

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