275/40R19 vs 225/55R18

Q: Can I replace 275/40R19 with 225/55R18?

225/55R18 is a safe swap for 275/40R19 by the usual ±3% rule: the diameter differs by +0.30%.

225/55R18 is a safe swap for 275/40R19 by the usual ±3% rule: the diameter differs by +0.30%.

275/40R19 27.66" · 225/55R18 27.74" · drawn to scale

Side by side

	275/40R19	225/55R18	Difference
Overall diameter	27.66"	27.74"	+0.08" (+0.30%)
Section width	275 mm	225 mm	-50 mm
Sidewall	4.33"	4.87"	+0.54"
Rim	19"	18"	-1"
Circumference	86.9"	87.2"	+0.3"
Revs per mile	729	727	-2
Ride height	—	—	+0.04"
Speedometer reads 60 mph	60.0	60.2	+0.2 mph

Speedometer and odometer

With 225/55R18 on a car calibrated for 275/40R19, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.3%.

Speedo shows	Actual speed
30 mph	30.1 mph
45 mph	45.1 mph
60 mph	60.2 mph
70 mph	70.2 mph
80 mph	80.2 mph

Other sizes close to 275/40R19

Questions

Can I replace 275/40R19 with 225/55R18?

225/55R18 is a safe swap for 275/40R19 by the usual ±3% rule: the diameter differs by +0.30%.

What's the difference between 275/40R19 and 225/55R18?

225/55R18 is 0.08" taller and 50 mm narrower; the sidewall is +0.54". At an indicated 60 mph you'd actually be doing 60.2 mph.

Will 225/55R18 fit on 275/40R19 wheels?

No — 275/40R19 needs a 19" wheel and 225/55R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.