245/40R19 vs 345/30R19

Q: Can I replace 245/40R19 with 345/30R19?

345/30R19 is a safe swap for 245/40R19 by the usual ±3% rule: the diameter differs by +1.62%.

345/30R19 is a safe swap for 245/40R19 by the usual ±3% rule: the diameter differs by +1.62%.

245/40R19 26.72" · 345/30R19 27.15" · drawn to scale

Side by side

	245/40R19	345/30R19	Difference
Overall diameter	26.72"	27.15"	+0.43" (+1.62%)
Section width	245 mm	345 mm	+100 mm
Sidewall	3.86"	4.07"	+0.22"
Rim	19"	19"	same
Circumference	83.9"	85.3"	+1.4"
Revs per mile	755	743	-12
Ride height	—	—	+0.22"
Speedometer reads 60 mph	60.0	61.0	+1.0 mph

Speedometer and odometer

With 345/30R19 on a car calibrated for 245/40R19, the speedometer reads 59.0 mph when you're really doing 60, and the odometer under-counts by 1.6%.

Speedo shows	Actual speed
30 mph	30.5 mph
45 mph	45.7 mph
60 mph	61.0 mph
70 mph	71.1 mph
80 mph	81.3 mph

Other sizes close to 245/40R19

Questions

Can I replace 245/40R19 with 345/30R19?

345/30R19 is a safe swap for 245/40R19 by the usual ±3% rule: the diameter differs by +1.62%.

What's the difference between 245/40R19 and 345/30R19?

345/30R19 is 0.43" taller and 100 mm wider; the sidewall is +0.22". At an indicated 60 mph you'd actually be doing 61.0 mph.

Will 345/30R19 fit on 245/40R19 wheels?

Both use a 19" rim, so the wheel diameter matches; check the wheel's width range for a 345 mm tire and the fender clearance.