305/70R17 vs 315/70R17

315/70R17 is 0.6" taller than 305/70R17 (1.6%)

Diameter difference+1.63%diameter 33.81" → 34.36"
305/70R17315/70R17
305/70R17315/70R17Difference
Overall diameter33.81"34.36"+0.55"
Section width12.01"12.40"+0.39"
Sidewall height8.41"8.68"+0.28"
Circumference106.2"108.0"+1.7"
Revolutions per mile596587−10
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph30.5 mph+0.5
45 mph45.7 mph+0.7
60 mph61.0 mph+1.0
70 mph71.1 mph+1.1
80 mph81.3 mph+1.3

Gear ratio to match

CurrentEquivalent
3.423.48
3.553.61
3.733.79
4.104.17

315/70R17 is 0.55" taller than 305/70R17, a +1.63% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.28" (half the diameter change), and the tire needs 0.28" more room above it.

315/70R17 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 0.28" taller on 315/70R17.

Details: 305/70R17 in inches · 315/70R17 in inches · change sizes in the calculator

FAQ

What is the difference between 305/70R17 and 315/70R17?

315/70R17 is 0.55" taller (+1.63%) and 0.39" wider than 305/70R17.

Will 315/70R17 change my speedometer?

Yes, by +1.63%. When the speedometer shows 60 mph you would be going 61.0 mph.

Can I replace 305/70R17 with 315/70R17?

Often yes: the diameter change of +1.6% is within the common 3% guideline. Check the load index, speed rating and clearance.