235/50R20 vs 265/45R20

Q: Can I replace 235/50R20 with 265/45R20?

265/45R20 is a safe swap for 235/50R20 by the usual ±3% rule: the diameter differs by +0.47%.

265/45R20 is a safe swap for 235/50R20 by the usual ±3% rule: the diameter differs by +0.47%.

235/50R20 29.25" · 265/45R20 29.39" · drawn to scale

Side by side

	235/50R20	265/45R20	Difference
Overall diameter	29.25"	29.39"	+0.14" (+0.47%)
Section width	235 mm	265 mm	+30 mm
Sidewall	4.63"	4.69"	+0.07"
Rim	20"	20"	same
Circumference	91.9"	92.3"	+0.4"
Revs per mile	689	686	-3
Ride height	—	—	+0.07"
Speedometer reads 60 mph	60.0	60.3	+0.3 mph

Speedometer and odometer

With 265/45R20 on a car calibrated for 235/50R20, the speedometer reads 59.7 mph when you're really doing 60, and the odometer under-counts by 0.5%.

Speedo shows	Actual speed
30 mph	30.1 mph
45 mph	45.2 mph
60 mph	60.3 mph
70 mph	70.3 mph
80 mph	80.4 mph

Other sizes close to 235/50R20

Questions

Can I replace 235/50R20 with 265/45R20?

265/45R20 is a safe swap for 235/50R20 by the usual ±3% rule: the diameter differs by +0.47%.

What's the difference between 235/50R20 and 265/45R20?

265/45R20 is 0.14" taller and 30 mm wider; the sidewall is +0.07". At an indicated 60 mph you'd actually be doing 60.3 mph.

Will 265/45R20 fit on 235/50R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 265 mm tire and the fender clearance.