265/65R17 vs 265/70R17

Nominal diameter increases from 30.6 in (776 mm) to 31.6 in (803 mm). Section width remains 10.4 in (265 mm), while sidewall height rises from 6.8 in to 7.3 in, an increase of 13 mm.

By the formula, revolutions per mile fall from 660 to 638. Ground clearance at the axle increases by 0.52 in (13 mm). These are unloaded nominal dimensions; actual tires measure differently.

After changing to 265/70R17, an unchanged speedometer indicating 60 mph corresponds to 62.0 mph by the formula. At 100 km/h indicated, calculated true speed is 103.4 km/h. Actual distance traveled is also 3.4% greater than the odometer records.

At 65 mph with a 3.73 axle ratio and a 1.00 transmission gear, calculated engine speed drops from 2,666 rpm to 2,578 rpm, down 3.3%. The nominal ratio that restores the original engine speed is 3.86: 3.73 × 31.61 / 30.56. The gear ratio calculator shows this relationship; it is formula math, not a modification recommendation.

Across Mickey Thompson, Nitto, Firestone, Toyo and Kumho size tables, 265/65R17 has 15 listed tires: 5 LT and 10 P-metric or passenger versions. Their published diameters range from 30.5 in to 30.8 in. The same makers list 33 tires in 265/70R17: 21 LT and 12 P-metric or passenger versions, measuring 31.6 in to 32 in. Both sizes have SL, XL and E load ranges listed.

For the Open Country A/T III, Toyo lists 30.6 in and 680 revs per mile for LT265/65R17. Toyo lists 31.7 in and 656 revs per mile for LT265/70R17. These published measurements differ from the nominal formula results.

For added nominal axle clearance and sidewall height, 265/70R17 changes both without increasing nominal width. The shorter 265/65R17 produces more revolutions per mile and higher engine rpm at the same road speed.

Neither size is nominally wider, though model-specific widths vary. Compare the maker-listed dimensions, load ranges and approved rim widths for the actual tires. Fit depends on the vehicle, wheels and suspension.