TireSizesFinder

205/70R15 vs 255/45R17

255/45R17 is 0.26 in (6.7 mm) shorter than 205/70R15, a −1.00% diameter difference. With the speedometer set for 205/70R15, an indicated 60 mph is 59.4 mph on 255/45R17.

Is this a safe swap?

Diameter difference −1.00%: within the ±3% guideline

By overall diameter alone, 255/45R17 falls inside the ±3% range commonly used as a guideline when replacing 205/70R15. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 205/70R15 (26.30 in) vs 255/45R17 (26.04 in)205/70R1526.30 in × 8.07 in255/45R1726.04 in × 10.04 in
Side profile and tread width, drawn to the same scale.
205/70R15 vs 255/45R17 differences
Measurement205/70R15255/45R17Difference% diff
Overall diameter26.30 in (668.0 mm)26.04 in (661.3 mm)−0.26 in (−6.7 mm)−1.00%
Sidewall height5.65 in (143.5 mm)4.52 in (114.8 mm)−1.13 in (−28.7 mm)−20.03%
Section width8.07 in (205.0 mm)10.04 in (255.0 mm)+1.97 in (+50.0 mm)+24.39%
Circumference82.62 in (2,098.6 mm)81.79 in (2,077.5 mm)−0.83 in (−21.0 mm)−1.00%
Revolutions per mile767775+8+1.01%
True speed with the speedometer calibrated for 205/70R15
IndicatedActual on 205/70R15Actual on 255/45R17Difference
30 mph30.0 mph29.7 mph−0.3 mph
60 mph60.0 mph59.4 mph−0.6 mph
75 mph75.0 mph74.2 mph−0.8 mph

Ride-height change: 255/45R17 lowers the vehicle by 0.13 in (3.4 mm) at the axle (half the −6.7 mm diameter difference).

255/45R17 is 0.26 in shorter than 205/70R15 and 50 mm wider, a 1.00% difference in overall diameter.

With the speedometer calibrated for 205/70R15, an indicated 60 mph is actually 59.4 mph on 255/45R17, and revolutions per mile change from 767 to 775.

255/45R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 205/70R15.

Size pages

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