265/45R20 vs 255/50R20

Q: Can I replace 265/45R20 with 255/50R20?

255/50R20 is a safe swap for 265/45R20 by the usual ±3% rule: the diameter differs by +2.21%.

255/50R20 is a safe swap for 265/45R20 by the usual ±3% rule: the diameter differs by +2.21%.

265/45R20 29.39" · 255/50R20 30.04" · drawn to scale

Side by side

	265/45R20	255/50R20	Difference
Overall diameter	29.39"	30.04"	+0.65" (+2.21%)
Section width	265 mm	255 mm	-10 mm
Sidewall	4.69"	5.02"	+0.32"
Rim	20"	20"	same
Circumference	92.3"	94.4"	+2.0"
Revs per mile	686	671	-15
Ride height	—	—	+0.32"
Speedometer reads 60 mph	60.0	61.3	+1.3 mph

Speedometer and odometer

With 255/50R20 on a car calibrated for 265/45R20, the speedometer reads 58.7 mph when you're really doing 60, and the odometer under-counts by 2.2%.

Speedo shows	Actual speed
30 mph	30.7 mph
45 mph	46.0 mph
60 mph	61.3 mph
70 mph	71.5 mph
80 mph	81.8 mph

Other sizes close to 265/45R20

Questions

Can I replace 265/45R20 with 255/50R20?

255/50R20 is a safe swap for 265/45R20 by the usual ±3% rule: the diameter differs by +2.21%.

What's the difference between 265/45R20 and 255/50R20?

255/50R20 is 0.65" taller and 10 mm narrower; the sidewall is +0.32". At an indicated 60 mph you'd actually be doing 61.3 mph.

Will 255/50R20 fit on 265/45R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.