TireSizesFinder

265/40R21 vs 315/35R21

315/35R21 is 0.33 in (8.5 mm) taller than 265/40R21, a +1.14% diameter difference. With the speedometer set for 265/40R21, an indicated 60 mph is 60.7 mph on 315/35R21.

Is this a safe swap?

Diameter difference +1.14%: within the ±3% guideline

By overall diameter alone, 315/35R21 falls inside the ±3% range commonly used as a guideline when replacing 265/40R21. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 265/40R21 (29.35 in) vs 315/35R21 (29.68 in)265/40R2129.35 in × 10.43 in315/35R2129.68 in × 12.40 in
Side profile and tread width, drawn to the same scale.
265/40R21 vs 315/35R21 differences
Measurement265/40R21315/35R21Difference% diff
Overall diameter29.35 in (745.4 mm)29.68 in (753.9 mm)+0.33 in (+8.5 mm)+1.14%
Sidewall height4.17 in (106.0 mm)4.34 in (110.3 mm)+0.17 in (+4.3 mm)+4.01%
Section width10.43 in (265.0 mm)12.40 in (315.0 mm)+1.97 in (+50.0 mm)+18.87%
Circumference92.19 in (2,341.7 mm)93.25 in (2,368.4 mm)+1.05 in (+26.7 mm)+1.14%
Revolutions per mile687679−8−1.13%
True speed with the speedometer calibrated for 265/40R21
IndicatedActual on 265/40R21Actual on 315/35R21Difference
30 mph30.0 mph30.3 mph+0.3 mph
60 mph60.0 mph60.7 mph+0.7 mph
75 mph75.0 mph75.9 mph+0.9 mph

Ride-height change: 315/35R21 raises the vehicle by 0.17 in (4.3 mm) at the axle (half the +8.5 mm diameter difference).

315/35R21 is 0.33 in taller than 265/40R21 and 50 mm wider, a 1.14% difference in overall diameter.

With the speedometer calibrated for 265/40R21, an indicated 60 mph is actually 60.7 mph on 315/35R21, and revolutions per mile change from 687 to 679.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 265/40R21

Other comparisons with 315/35R21

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