275/70R18 vs 275/65R18

275/70R18 is 1.1" taller than 275/65R18 (3.3%)

Diameter difference−3.27%diameter 33.16" → 32.07"
275/70R18275/65R18
275/70R18275/65R18Difference
Overall diameter33.16"32.07"−1.08"
Section width10.83"10.83"±0.00"
Sidewall height7.58"7.04"−0.54"
Circumference104.2"100.8"−3.4"
Revolutions per mile608629+21
Wheel diameter18"18"±0"

Speedometer

ShowsActualDiff
30 mph29.0 mph−1.0
45 mph43.5 mph−1.5
60 mph58.0 mph−2.0
70 mph67.7 mph−2.3
80 mph77.4 mph−2.6

Gear ratio to match

CurrentEquivalent
3.423.31
3.553.43
3.733.61
4.103.97

275/65R18 is 1.08" shorter than 275/70R18, a −3.27% 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 0.54" (half the diameter change), and the tire needs 0.54" less room above it.

Both tires are the same width, 10.83".

Both fit a 18" wheel; the sidewall is 0.54" shorter on 275/65R18.

Details: 275/70R18 in inches · 275/65R18 in inches · change sizes in the calculator

FAQ

What is the difference between 275/70R18 and 275/65R18?

275/65R18 is 1.08" shorter (−3.27%) and 0.00" wider than 275/70R18.

Will 275/65R18 change my speedometer?

Yes, by −3.27%. When the speedometer shows 60 mph you would be going 58.0 mph.

Can I replace 275/70R18 with 275/65R18?

It is a −3.3% diameter change, larger than the common 3% guideline, so check clearance and plan to recalibrate.