CarSpecsHQ

245/40R15 vs 225/50R15

225/50R15 is outside the ±3% rule as a replacement for 245/40R15: the diameter differs by +5.03%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

15" rim
245/40R15 22.72" · 225/50R15 23.86" · drawn to scale

Side by side

245/40R15225/50R15Difference
Overall diameter22.72"23.86"+1.14" (+5.03%)
Section width245 mm225 mm-20 mm
Sidewall3.86"4.43"+0.57"
Rim15"15"same
Circumference71.4"75.0"+3.6"
Revs per mile888845-42
Ride height——+0.57"
Speedometer reads 60 mph60.063.0+3.0 mph

Speedometer and odometer

020406080100120 reads 60 · actual 63.0 mph

With 225/50R15 on a car calibrated for 245/40R15, the speedometer reads 57.1 mph when you're really doing 60, and the odometer under-counts by 5.0%.

Speedo showsActual speed
30 mph31.5 mph
45 mph47.3 mph
60 mph63.0 mph
70 mph73.5 mph
80 mph84.0 mph

Other sizes close to 245/40R15

Questions

Can I replace 245/40R15 with 225/50R15?

225/50R15 is outside the ±3% rule as a replacement for 245/40R15: the diameter differs by +5.03%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

What's the difference between 245/40R15 and 225/50R15?

225/50R15 is 1.14" taller and 20 mm narrower; the sidewall is +0.57". At an indicated 60 mph you'd actually be doing 63.0 mph.

Will 225/50R15 fit on 245/40R15 wheels?

Both use a 15" rim, so the wheel diameter matches; check the wheel's width range for a 225 mm tire and the fender clearance.