305/40R22 vs 285/45R22

Q: Can I replace 305/40R22 with 285/45R22?

285/45R22 is a safe swap for 305/40R22 by the usual ±3% rule: the diameter differs by +1.56%.

285/45R22 is a safe swap for 305/40R22 by the usual ±3% rule: the diameter differs by +1.56%.

305/40R22 31.61" · 285/45R22 32.10" · drawn to scale

Side by side

	305/40R22	285/45R22	Difference
Overall diameter	31.61"	32.10"	+0.49" (+1.56%)
Section width	305 mm	285 mm	-20 mm
Sidewall	4.80"	5.05"	+0.25"
Rim	22"	22"	same
Circumference	99.3"	100.8"	+1.5"
Revs per mile	638	628	-10
Ride height	—	—	+0.25"
Speedometer reads 60 mph	60.0	60.9	+0.9 mph

Speedometer and odometer

With 285/45R22 on a car calibrated for 305/40R22, the speedometer reads 59.1 mph when you're really doing 60, and the odometer under-counts by 1.6%.

Speedo shows	Actual speed
30 mph	30.5 mph
45 mph	45.7 mph
60 mph	60.9 mph
70 mph	71.1 mph
80 mph	81.2 mph

Other sizes close to 305/40R22

Questions

Can I replace 305/40R22 with 285/45R22?

285/45R22 is a safe swap for 305/40R22 by the usual ±3% rule: the diameter differs by +1.56%.

What's the difference between 305/40R22 and 285/45R22?

285/45R22 is 0.49" taller and 20 mm narrower; the sidewall is +0.25". At an indicated 60 mph you'd actually be doing 60.9 mph.

Will 285/45R22 fit on 305/40R22 wheels?

Both use a 22" rim, so the wheel diameter matches; check the wheel's width range for a 285 mm tire and the fender clearance.