245/60R20 vs 275/55R20

Q: Can I replace 245/60R20 with 275/55R20?

275/55R20 is a safe swap for 245/60R20 by the usual ±3% rule: the diameter differs by +1.06%.

275/55R20 is a safe swap for 245/60R20 by the usual ±3% rule: the diameter differs by +1.06%.

245/60R20 31.57" · 275/55R20 31.91" · drawn to scale

Side by side

	245/60R20	275/55R20	Difference
Overall diameter	31.57"	31.91"	+0.33" (+1.06%)
Section width	245 mm	275 mm	+30 mm
Sidewall	5.79"	5.95"	+0.17"
Rim	20"	20"	same
Circumference	99.2"	100.2"	+1.1"
Revs per mile	639	632	-7
Ride height	—	—	+0.17"
Speedometer reads 60 mph	60.0	60.6	+0.6 mph

Speedometer and odometer

With 275/55R20 on a car calibrated for 245/60R20, the speedometer reads 59.4 mph when you're really doing 60, and the odometer under-counts by 1.1%.

Speedo shows	Actual speed
30 mph	30.3 mph
45 mph	45.5 mph
60 mph	60.6 mph
70 mph	70.7 mph
80 mph	80.8 mph

Other sizes close to 245/60R20

Questions

Can I replace 245/60R20 with 275/55R20?

275/55R20 is a safe swap for 245/60R20 by the usual ±3% rule: the diameter differs by +1.06%.

What's the difference between 245/60R20 and 275/55R20?

275/55R20 is 0.33" taller and 30 mm wider; the sidewall is +0.17". At an indicated 60 mph you'd actually be doing 60.6 mph.

Will 275/55R20 fit on 245/60R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 275 mm tire and the fender clearance.