265/35R20 vs 245/40R20

Q: Can I replace 265/35R20 with 245/40R20?

245/40R20 is a safe swap for 265/35R20 by the usual ±3% rule: the diameter differs by +1.51%.

245/40R20 is a safe swap for 265/35R20 by the usual ±3% rule: the diameter differs by +1.51%.

265/35R20 27.30" · 245/40R20 27.72" · drawn to scale

Side by side

	265/35R20	245/40R20	Difference
Overall diameter	27.30"	27.72"	+0.41" (+1.51%)
Section width	265 mm	245 mm	-20 mm
Sidewall	3.65"	3.86"	+0.21"
Rim	20"	20"	same
Circumference	85.8"	87.1"	+1.3"
Revs per mile	739	728	-11
Ride height	—	—	+0.21"
Speedometer reads 60 mph	60.0	60.9	+0.9 mph

Speedometer and odometer

With 245/40R20 on a car calibrated for 265/35R20, the speedometer reads 59.1 mph when you're really doing 60, and the odometer under-counts by 1.5%.

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 265/35R20

Questions

Can I replace 265/35R20 with 245/40R20?

245/40R20 is a safe swap for 265/35R20 by the usual ±3% rule: the diameter differs by +1.51%.

What's the difference between 265/35R20 and 245/40R20?

245/40R20 is 0.41" taller and 20 mm narrower; the sidewall is +0.21". At an indicated 60 mph you'd actually be doing 60.9 mph.

Will 245/40R20 fit on 265/35R20 wheels?

Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 245 mm tire and the fender clearance.