CarSpecsHQ

245/40R18 vs 245/35R19

245/35R19 is a safe swap for 245/40R18 by the usual ±3% rule: the diameter differs by +0.14%.

18" → 19"
245/40R18 25.72" · 245/35R19 25.75" · drawn to scale

Side by side

245/40R18245/35R19Difference
Overall diameter25.72"25.75"+0.04" (+0.14%)
Section width245 mm245 mm0 mm
Sidewall3.86"3.38"-0.48"
Rim18"19"+1"
Circumference80.8"80.9"+0.1"
Revs per mile784783-1
Ride height——+0.02"
Speedometer reads 60 mph60.060.1+0.1 mph

Speedometer and odometer

020406080100120 reads 60 · actual 60.1 mph

With 245/35R19 on a car calibrated for 245/40R18, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.1%.

Speedo showsActual speed
30 mph30.0 mph
45 mph45.1 mph
60 mph60.1 mph
70 mph70.1 mph
80 mph80.1 mph

Other sizes close to 245/40R18

Questions

Can I replace 245/40R18 with 245/35R19?

245/35R19 is a safe swap for 245/40R18 by the usual ±3% rule: the diameter differs by +0.14%.

What's the difference between 245/40R18 and 245/35R19?

245/35R19 is 0.04" taller and 0 mm wider; the sidewall is -0.48". At an indicated 60 mph you'd actually be doing 60.1 mph.

Will 245/35R19 fit on 245/40R18 wheels?

No — 245/40R18 needs a 18" wheel and 245/35R19 a 19" wheel. This is a plus/minus-size swap that changes wheels too.