305/70R16 vs 255/85R16

Q: Can I replace 305/70R16 with 255/85R16?

255/85R16 is a safe swap for 305/70R16 by the usual ±3% rule: the diameter differs by +0.78%.

255/85R16 is a safe swap for 305/70R16 by the usual ±3% rule: the diameter differs by +0.78%.

305/70R16 32.81" · 255/85R16 33.07" · drawn to scale

Side by side

	305/70R16	255/85R16	Difference
Overall diameter	32.81"	33.07"	+0.26" (+0.78%)
Section width	305 mm	255 mm	-50 mm
Sidewall	8.41"	8.53"	+0.13"
Rim	16"	16"	same
Circumference	103.1"	103.9"	+0.8"
Revs per mile	615	610	-5
Ride height	—	—	+0.13"
Speedometer reads 60 mph	60.0	60.5	+0.5 mph

Speedometer and odometer

With 255/85R16 on a car calibrated for 305/70R16, the speedometer reads 59.5 mph when you're really doing 60, and the odometer under-counts by 0.8%.

Speedo shows	Actual speed
30 mph	30.2 mph
45 mph	45.4 mph
60 mph	60.5 mph
70 mph	70.5 mph
80 mph	80.6 mph

Other sizes close to 305/70R16

Questions

Can I replace 305/70R16 with 255/85R16?

255/85R16 is a safe swap for 305/70R16 by the usual ±3% rule: the diameter differs by +0.78%.

What's the difference between 305/70R16 and 255/85R16?

255/85R16 is 0.26" taller and 50 mm narrower; the sidewall is +0.13". At an indicated 60 mph you'd actually be doing 60.5 mph.

Will 255/85R16 fit on 305/70R16 wheels?

Both use a 16" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.