TireSizesFinder

245/40R21 vs 265/40R21

265/40R21 is 0.63 in (16.0 mm) taller than 245/40R21, a +2.19% diameter difference. With the speedometer set for 245/40R21, an indicated 60 mph is 61.3 mph on 265/40R21.

Is this a safe swap?

Diameter difference +2.19%: within the ±3% guideline

By overall diameter alone, 265/40R21 falls inside the ±3% range commonly used as a guideline when replacing 245/40R21. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 245/40R21 (28.72 in) vs 265/40R21 (29.35 in)245/40R2128.72 in × 9.65 in265/40R2129.35 in × 10.43 in
Side profile and tread width, drawn to the same scale.
245/40R21 vs 265/40R21 differences
Measurement245/40R21265/40R21Difference% diff
Overall diameter28.72 in (729.4 mm)29.35 in (745.4 mm)+0.63 in (+16.0 mm)+2.19%
Sidewall height3.86 in (98.0 mm)4.17 in (106.0 mm)+0.31 in (+8.0 mm)+8.16%
Section width9.65 in (245.0 mm)10.43 in (265.0 mm)+0.79 in (+20.0 mm)+8.16%
Circumference90.22 in (2,291.5 mm)92.19 in (2,341.7 mm)+1.98 in (+50.3 mm)+2.19%
Revolutions per mile702687−15−2.15%
True speed with the speedometer calibrated for 245/40R21
IndicatedActual on 245/40R21Actual on 265/40R21Difference
30 mph30.0 mph30.7 mph+0.7 mph
60 mph60.0 mph61.3 mph+1.3 mph
75 mph75.0 mph76.6 mph+1.6 mph

Ride-height change: 265/40R21 raises the vehicle by 0.31 in (8.0 mm) at the axle (half the +16.0 mm diameter difference).

265/40R21 is 0.63 in taller than 245/40R21 and 20 mm wider, a 2.19% difference in overall diameter.

With the speedometer calibrated for 245/40R21, an indicated 60 mph is actually 61.3 mph on 265/40R21, and revolutions per mile change from 702 to 687.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 245/40R21

Other comparisons with 265/40R21

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