215/70R15 vs 255/50R17

255/50R17 is 0.19 in (4.8 mm) taller than 215/70R15, a +0.70% diameter difference. With the speedometer set for 215/70R15, an indicated 60 mph is 60.4 mph on 255/50R17.

Is this a safe swap?

Diameter difference +0.70%: under 1%

By overall diameter alone, 255/50R17 is a near match for 215/70R15; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

215/70R15 vs 255/50R17 differences
Measurement	215/70R15	255/50R17	Difference	% diff
Overall diameter	26.85 in (682.0 mm)	27.04 in (686.8 mm)	+0.19 in (+4.8 mm)	+0.70%
Sidewall height	5.93 in (150.5 mm)	5.02 in (127.5 mm)	−0.91 in (−23.0 mm)	−15.28%
Section width	8.46 in (215.0 mm)	10.04 in (255.0 mm)	+1.57 in (+40.0 mm)	+18.60%
Circumference	84.35 in (2,142.6 mm)	84.95 in (2,157.6 mm)	+0.59 in (+15.1 mm)	+0.70%
Revolutions per mile	751	746	−5	−0.70%

True speed with the speedometer calibrated for 215/70R15
Indicated	Actual on 215/70R15	Actual on 255/50R17	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.4 mph	+0.4 mph
75 mph	75.0 mph	75.5 mph	+0.5 mph

Ride-height change: 255/50R17 raises the vehicle by 0.09 in (2.4 mm) at the axle (half the +4.8 mm diameter difference).

255/50R17 is 0.19 in taller than 215/70R15 and 40 mm wider, a 0.70% difference in overall diameter.

With the speedometer calibrated for 215/70R15, an indicated 60 mph is actually 60.4 mph on 255/50R17, and revolutions per mile change from 751 to 746.

255/50R17 mounts on a 17-inch wheel, a plus-2 fitment from the 15-inch wheel of 215/70R15.

Size pages

Other comparisons with 215/70R15

Other comparisons with 255/50R17

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.