305/65R17 vs 285/70R17

285/70R17 is 0.1" taller than 305/65R17 (0.3%)

Diameter difference+0.30%diameter 32.61" → 32.71"
305/65R17285/70R17
305/65R17285/70R17Difference
Overall diameter32.61"32.71"+0.10"
Section width12.01"11.22"−0.79"
Sidewall height7.81"7.85"+0.05"
Circumference102.4"102.8"+0.3"
Revolutions per mile618617−2
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph30.1 mph+0.1
45 mph45.1 mph+0.1
60 mph60.2 mph+0.2
70 mph70.2 mph+0.2
80 mph80.2 mph+0.2

Gear ratio to match

CurrentEquivalent
3.423.43
3.553.56
3.733.74
4.104.11

285/70R17 is 0.10" taller than 305/65R17, a +0.30% change in diameter, inside the 3% range most shops treat as a safe swap.

Ground clearance changes by 0.05" (half the diameter change), and the tire needs 0.05" more room above it.

305/65R17 is 0.79" wider. On the same wheel offset about half of that, 0.39", moves toward the suspension and half toward the fender.

Both fit a 17" wheel; the sidewall is 0.05" taller on 285/70R17.

Details: 305/65R17 in inches · 285/70R17 in inches · change sizes in the calculator

FAQ

What is the difference between 305/65R17 and 285/70R17?

285/70R17 is 0.10" taller (+0.30%) and 0.79" narrower than 305/65R17.

Will 285/70R17 change my speedometer?

Yes, by +0.30%. When the speedometer shows 60 mph you would be going 60.2 mph.

Can I replace 305/65R17 with 285/70R17?

Often yes: the diameter change of +0.3% is within the common 3% guideline. Check the load index, speed rating and clearance.