CarSpecsHQ

205/40R17 vs 205/45R17

205/45R17 is outside the ±3% rule as a replacement for 205/40R17: the diameter differs by +3.44%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

17" rim
205/40R17 23.46" · 205/45R17 24.26" · drawn to scale

Side by side

205/40R17205/45R17Difference
Overall diameter23.46"24.26"+0.81" (+3.44%)
Section width205 mm205 mm0 mm
Sidewall3.23"3.63"+0.40"
Rim17"17"same
Circumference73.7"76.2"+2.5"
Revs per mile860831-29
Ride height——+0.40"
Speedometer reads 60 mph60.062.1+2.1 mph

Speedometer and odometer

020406080100120 reads 60 · actual 62.1 mph

With 205/45R17 on a car calibrated for 205/40R17, the speedometer reads 58.0 mph when you're really doing 60, and the odometer under-counts by 3.4%.

Speedo showsActual speed
30 mph31.0 mph
45 mph46.5 mph
60 mph62.1 mph
70 mph72.4 mph
80 mph82.8 mph

Other sizes close to 205/40R17

Questions

Can I replace 205/40R17 with 205/45R17?

205/45R17 is outside the ±3% rule as a replacement for 205/40R17: the diameter differs by +3.44%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.

What's the difference between 205/40R17 and 205/45R17?

205/45R17 is 0.81" taller and 0 mm wider; the sidewall is +0.40". At an indicated 60 mph you'd actually be doing 62.1 mph.

Will 205/45R17 fit on 205/40R17 wheels?

Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 205 mm tire and the fender clearance.