235/40R17 vs 245/40R17

245/40R17 is 0.3" taller than 235/40R17 (1.3%)

Diameter difference+1.29%diameter 24.40" → 24.72"
235/40R17245/40R17
235/40R17245/40R17Difference
Overall diameter24.40"24.72"+0.31"
Section width9.25"9.65"+0.39"
Sidewall height3.70"3.86"+0.16"
Circumference76.7"77.6"+1.0"
Revolutions per mile827816−11
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph30.4 mph+0.4
45 mph45.6 mph+0.6
60 mph60.8 mph+0.8
70 mph70.9 mph+0.9
80 mph81.0 mph+1.0

Gear ratio to match

CurrentEquivalent
3.423.46
3.553.60
3.733.78
4.104.15

245/40R17 is 0.31" taller than 235/40R17, a +1.29% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.16" (half the diameter change), and the tire needs 0.16" more room above it.

245/40R17 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 0.16" taller on 245/40R17.

Details: 235/40R17 in inches · 245/40R17 in inches · change sizes in the calculator

FAQ

What is the difference between 235/40R17 and 245/40R17?

245/40R17 is 0.31" taller (+1.29%) and 0.39" wider than 235/40R17.

Will 245/40R17 change my speedometer?

Yes, by +1.29%. When the speedometer shows 60 mph you would be going 60.8 mph.

Can I replace 235/40R17 with 245/40R17?

Often yes: the diameter change of +1.3% is within the common 3% guideline. Check the load index, speed rating and clearance.