215/45R17 vs 245/40R17

Q: Can I replace 215/45R17 with 245/40R17?

245/40R17 is a safe swap for 215/45R17 by the usual ±3% rule: the diameter differs by +0.40%.

245/40R17 is a safe swap for 215/45R17 by the usual ±3% rule: the diameter differs by +0.40%.

215/45R17 24.62" · 245/40R17 24.72" · drawn to scale

Side by side

	215/45R17	245/40R17	Difference
Overall diameter	24.62"	24.72"	+0.10" (+0.40%)
Section width	215 mm	245 mm	+30 mm
Sidewall	3.81"	3.86"	+0.05"
Rim	17"	17"	same
Circumference	77.3"	77.6"	+0.3"
Revs per mile	819	816	-3
Ride height	—	—	+0.05"
Speedometer reads 60 mph	60.0	60.2	+0.2 mph

Speedometer and odometer

With 245/40R17 on a car calibrated for 215/45R17, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.4%.

Speedo shows	Actual speed
30 mph	30.1 mph
45 mph	45.2 mph
60 mph	60.2 mph
70 mph	70.3 mph
80 mph	80.3 mph

Other sizes close to 215/45R17

Questions

Can I replace 215/45R17 with 245/40R17?

245/40R17 is a safe swap for 215/45R17 by the usual ±3% rule: the diameter differs by +0.40%.

What's the difference between 215/45R17 and 245/40R17?

245/40R17 is 0.10" taller and 30 mm wider; the sidewall is +0.05". At an indicated 60 mph you'd actually be doing 60.2 mph.

Will 245/40R17 fit on 215/45R17 wheels?

Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 245 mm tire and the fender clearance.