305/60R18 vs 265/70R18

Q: Can I replace 305/60R18 with 265/70R18?

265/70R18 is a safe swap for 305/60R18 by the usual ±3% rule: the diameter differs by +0.61%.

265/70R18 is a safe swap for 305/60R18 by the usual ±3% rule: the diameter differs by +0.61%.

305/60R18 32.41" · 265/70R18 32.61" · drawn to scale

Side by side

	305/60R18	265/70R18	Difference
Overall diameter	32.41"	32.61"	+0.20" (+0.61%)
Section width	305 mm	265 mm	-40 mm
Sidewall	7.20"	7.30"	+0.10"
Rim	18"	18"	same
Circumference	101.8"	102.4"	+0.6"
Revs per mile	622	619	-4
Ride height	—	—	+0.10"
Speedometer reads 60 mph	60.0	60.4	+0.4 mph

Speedometer and odometer

With 265/70R18 on a car calibrated for 305/60R18, the speedometer reads 59.6 mph when you're really doing 60, and the odometer under-counts by 0.6%.

Speedo shows	Actual speed
30 mph	30.2 mph
45 mph	45.3 mph
60 mph	60.4 mph
70 mph	70.4 mph
80 mph	80.5 mph

Other sizes close to 305/60R18

Questions

Can I replace 305/60R18 with 265/70R18?

265/70R18 is a safe swap for 305/60R18 by the usual ±3% rule: the diameter differs by +0.61%.

What's the difference between 305/60R18 and 265/70R18?

265/70R18 is 0.20" taller and 40 mm narrower; the sidewall is +0.10". At an indicated 60 mph you'd actually be doing 60.4 mph.

Will 265/70R18 fit on 305/60R18 wheels?

Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 265 mm tire and the fender clearance.