CarSpecsHQ

265/30R19 vs 315/30R18

315/30R18 is a safe swap for 265/30R19 by the usual ±3% rule: the diameter differs by +0.72%.

19" → 18"
265/30R19 25.26" · 315/30R18 25.44" · drawn to scale

Side by side

265/30R19315/30R18Difference
Overall diameter25.26"25.44"+0.18" (+0.72%)
Section width265 mm315 mm+50 mm
Sidewall3.13"3.72"+0.59"
Rim19"18"-1"
Circumference79.4"79.9"+0.6"
Revs per mile798793-6
Ride height——+0.09"
Speedometer reads 60 mph60.060.4+0.4 mph

Speedometer and odometer

020406080100120 reads 60 · actual 60.4 mph

With 315/30R18 on a car calibrated for 265/30R19, the speedometer reads 59.6 mph when you're really doing 60, and the odometer under-counts by 0.7%.

Speedo showsActual speed
30 mph30.2 mph
45 mph45.3 mph
60 mph60.4 mph
70 mph70.5 mph
80 mph80.6 mph

Other sizes close to 265/30R19

Questions

Can I replace 265/30R19 with 315/30R18?

315/30R18 is a safe swap for 265/30R19 by the usual ±3% rule: the diameter differs by +0.72%.

What's the difference between 265/30R19 and 315/30R18?

315/30R18 is 0.18" taller and 50 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 60.4 mph.

Will 315/30R18 fit on 265/30R19 wheels?

No — 265/30R19 needs a 19" wheel and 315/30R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.