245/60R20 vs 285/55R20

Q: Can I replace 245/60R20 with 285/55R20?

285/55R20 is a safe swap for 245/60R20 by the usual ±3% rule: the diameter differs by +2.43%.

285/55R20 is a safe swap for 245/60R20 by the usual ±3% rule: the diameter differs by +2.43%.

245/60R20 31.57" · 285/55R20 32.34" · drawn to scale

Side by side

	245/60R20	285/55R20	Difference
Overall diameter	31.57"	32.34"	+0.77" (+2.43%)
Section width	245 mm	285 mm	+40 mm
Sidewall	5.79"	6.17"	+0.38"
Rim	20"	20"	same
Circumference	99.2"	101.6"	+2.4"
Revs per mile	639	624	-15
Ride height	—	—	+0.38"
Speedometer reads 60 mph	60.0	61.5	+1.5 mph

Speedometer and odometer

With 285/55R20 on a car calibrated for 245/60R20, the speedometer reads 58.6 mph when you're really doing 60, and the odometer under-counts by 2.4%.

Speedo shows	Actual speed
30 mph	30.7 mph
45 mph	46.1 mph
60 mph	61.5 mph
70 mph	71.7 mph
80 mph	81.9 mph

Other sizes close to 245/60R20

Questions

Can I replace 245/60R20 with 285/55R20?

285/55R20 is a safe swap for 245/60R20 by the usual ±3% rule: the diameter differs by +2.43%.

What's the difference between 245/60R20 and 285/55R20?

285/55R20 is 0.77" taller and 40 mm wider; the sidewall is +0.38". At an indicated 60 mph you'd actually be doing 61.5 mph.

Will 285/55R20 fit on 245/60R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 285 mm tire and the fender clearance.