TireSizesFinder

235/85R16 vs 255/70R17

255/70R17 is 0.67 in (17.1 mm) shorter than 235/85R16, a −2.12% diameter difference. With the speedometer set for 235/85R16, an indicated 60 mph is 58.7 mph on 255/70R17.

Is this a safe swap?

Diameter difference −2.12%: within the ±3% guideline

By overall diameter alone, 255/70R17 falls inside the ±3% range commonly used as a guideline when replacing 235/85R16. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 235/85R16 (31.73 in) vs 255/70R17 (31.06 in)235/85R1631.73 in × 9.25 in255/70R1731.06 in × 10.04 in
Side profile and tread width, drawn to the same scale.
235/85R16 vs 255/70R17 differences
Measurement235/85R16255/70R17Difference% diff
Overall diameter31.73 in (805.9 mm)31.06 in (788.8 mm)−0.67 in (−17.1 mm)−2.12%
Sidewall height7.86 in (199.8 mm)7.03 in (178.5 mm)−0.84 in (−21.2 mm)−10.64%
Section width9.25 in (235.0 mm)10.04 in (255.0 mm)+0.79 in (+20.0 mm)+8.51%
Circumference99.68 in (2,531.8 mm)97.56 in (2,478.1 mm)−2.12 in (−53.7 mm)−2.12%
Revolutions per mile636649+14+2.17%
True speed with the speedometer calibrated for 235/85R16
IndicatedActual on 235/85R16Actual on 255/70R17Difference
30 mph30.0 mph29.4 mph−0.6 mph
60 mph60.0 mph58.7 mph−1.3 mph
75 mph75.0 mph73.4 mph−1.6 mph

Ride-height change: 255/70R17 lowers the vehicle by 0.34 in (8.6 mm) at the axle (half the −17.1 mm diameter difference).

255/70R17 is 0.67 in shorter than 235/85R16 and 20 mm wider, a 2.12% difference in overall diameter.

With the speedometer calibrated for 235/85R16, an indicated 60 mph is actually 58.7 mph on 255/70R17, and revolutions per mile change from 636 to 649.

255/70R17 mounts on a 17-inch wheel, a plus-1 fitment from the 16-inch wheel of 235/85R16.

Size pages

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Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.