285/40R17 vs 275/40R17

285/40R17 is 0.3" taller than 275/40R17 (1.2%)

Diameter difference−1.21%diameter 25.98" → 25.66"
285/40R17275/40R17
285/40R17275/40R17Difference
Overall diameter25.98"25.66"−0.31"
Section width11.22"10.83"−0.39"
Sidewall height4.49"4.33"−0.16"
Circumference81.6"80.6"−1.0"
Revolutions per mile776786+10
Wheel diameter17"17"±0"

Speedometer

ShowsActualDiff
30 mph29.6 mph−0.4
45 mph44.5 mph−0.5
60 mph59.3 mph−0.7
70 mph69.2 mph−0.8
80 mph79.0 mph−1.0

Gear ratio to match

CurrentEquivalent
3.423.38
3.553.51
3.733.68
4.104.05

275/40R17 is 0.31" shorter than 285/40R17, a −1.21% 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" less room above it.

285/40R17 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" shorter on 275/40R17.

Details: 285/40R17 in inches · 275/40R17 in inches · change sizes in the calculator

FAQ

What is the difference between 285/40R17 and 275/40R17?

275/40R17 is 0.31" shorter (−1.21%) and 0.39" narrower than 285/40R17.

Will 275/40R17 change my speedometer?

Yes, by −1.21%. When the speedometer shows 60 mph you would be going 59.3 mph.

Can I replace 285/40R17 with 275/40R17?

Often yes: the diameter change of −1.2% is within the common 3% guideline. Check the load index, speed rating and clearance.