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255/70R18 vs 275/65R18 tire size

275/65R18 vs 255/70R18, diameter

Same diameter

Speedometer
60.0 mph
At a true 60 mph
Diameter
32.07 in
Was 32.06 in
Revs per mile
629
Was 629
3% guideline
Within

Car built for 255/70R18, now on 275/65R18.

255/70R18 and 275/65R18

255/70R18 vs 275/65R18 tire size
Measure255/70R18275/65R18Difference
Width, mm255275+20
Sidewall, % of width7065-5
Rim, in18180
Section height, in7.037.04+0.01
Diameter, in32.0632.07+0.02 (+0.1%)
Circumference, in100.7100.8+0.1
Revs per mile629629-0 (-0.1%)

Fitting 275/65R18 instead of 255/70R18

Within the usual 3% diameter guideline.

  • 20 mm wider. Check rubbing at full lock.

Cars with 255/70R18

Cars with 275/65R18

What this cannot tell you

Diameter within 3% is a common shop guideline, not a maker spec.

Load index, offset and clearance are not in this data.

How values are checked