235/80R17 vs 245/70R17

235/80R17 is 1.3" taller than 245/70R17 (4.1%)

Diameter difference−4.09%diameter 31.80" → 30.50"
235/80R17245/70R17
235/80R17245/70R17Difference
Overall diameter31.80"30.50"−1.30"
Section width9.25"9.65"+0.39"
Sidewall height7.40"6.75"−0.65"
Circumference99.9"95.8"−4.1"
Revolutions per mile634661+27
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph28.8 mph−1.2
45 mph43.2 mph−1.8
60 mph57.5 mph−2.5
70 mph67.1 mph−2.9
80 mph76.7 mph−3.3

Gear ratio to match

CurrentEquivalent
3.423.28
3.553.40
3.733.58
4.103.93

245/70R17 is 1.30" shorter than 235/80R17, a −4.09% change in diameter. That is more than the 3% many tire shops use as a limit, so plan on recalibrating the speedometer and checking ABS and stability control.

Ground clearance changes by 0.65" (half the diameter change), and the tire needs 0.65" less room above it.

245/70R17 is 0.39" wider. On the same wheel offset about half of that, 0.20", moves toward the suspension and half toward the fender.

Both fit a 17" wheel; the sidewall is 0.65" shorter on 245/70R17.

Details: 235/80R17 in inches · 245/70R17 in inches · change sizes in the calculator

FAQ

What is the difference between 235/80R17 and 245/70R17?

245/70R17 is 1.30" shorter (−4.09%) and 0.39" wider than 235/80R17.

Will 245/70R17 change my speedometer?

Yes, by −4.09%. When the speedometer shows 60 mph you would be going 57.5 mph.

Can I replace 235/80R17 with 245/70R17?

It is a −4.1% diameter change, larger than the common 3% guideline, so check clearance and plan to recalibrate.