TireSizesFinder

315/35R21 vs 255/40R22

255/40R22 is 0.35 in (8.9 mm) taller than 315/35R21, a +1.18% diameter difference. With the speedometer set for 315/35R21, an indicated 60 mph is 60.7 mph on 255/40R22.

Is this a safe swap?

Diameter difference +1.18%: within the ±3% guideline

By overall diameter alone, 255/40R22 falls inside the ±3% range commonly used as a guideline when replacing 315/35R21. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 315/35R21 (29.68 in) vs 255/40R22 (30.03 in)315/35R2129.68 in × 12.40 in255/40R2230.03 in × 10.04 in
Side profile and tread width, drawn to the same scale.
315/35R21 vs 255/40R22 differences
Measurement315/35R21255/40R22Difference% diff
Overall diameter29.68 in (753.9 mm)30.03 in (762.8 mm)+0.35 in (+8.9 mm)+1.18%
Sidewall height4.34 in (110.3 mm)4.02 in (102.0 mm)−0.32 in (−8.2 mm)−7.48%
Section width12.40 in (315.0 mm)10.04 in (255.0 mm)−2.36 in (−60.0 mm)−19.05%
Circumference93.25 in (2,368.4 mm)94.35 in (2,396.4 mm)+1.10 in (+28.0 mm)+1.18%
Revolutions per mile679672−8−1.17%
True speed with the speedometer calibrated for 315/35R21
IndicatedActual on 315/35R21Actual on 255/40R22Difference
30 mph30.0 mph30.4 mph+0.4 mph
60 mph60.0 mph60.7 mph+0.7 mph
75 mph75.0 mph75.9 mph+0.9 mph

Ride-height change: 255/40R22 raises the vehicle by 0.18 in (4.4 mm) at the axle (half the +8.9 mm diameter difference).

255/40R22 is 0.35 in taller than 315/35R21 and 60 mm narrower, a 1.18% difference in overall diameter.

With the speedometer calibrated for 315/35R21, an indicated 60 mph is actually 60.7 mph on 255/40R22, and revolutions per mile change from 679 to 672.

255/40R22 mounts on a 22-inch wheel, a plus-1 fitment from the 21-inch wheel of 315/35R21.

Size pages

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