TireSizesFinder

265/45R20 vs 235/45R21

235/45R21 is 0.06 in (1.6 mm) shorter than 265/45R20, a −0.21% diameter difference. With the speedometer set for 265/45R20, an indicated 60 mph is 59.9 mph on 235/45R21.

Is this a safe swap?

Diameter difference −0.21%: under 1%

By overall diameter alone, 235/45R21 is a near match for 265/45R20; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 265/45R20 (29.39 in) vs 235/45R21 (29.33 in)265/45R2029.39 in × 10.43 in235/45R2129.33 in × 9.25 in
Side profile and tread width, drawn to the same scale.
265/45R20 vs 235/45R21 differences
Measurement265/45R20235/45R21Difference% diff
Overall diameter29.39 in (746.5 mm)29.33 in (744.9 mm)−0.06 in (−1.6 mm)−0.21%
Sidewall height4.69 in (119.3 mm)4.16 in (105.8 mm)−0.53 in (−13.5 mm)−11.32%
Section width10.43 in (265.0 mm)9.25 in (235.0 mm)−1.18 in (−30.0 mm)−11.32%
Circumference92.33 in (2,345.2 mm)92.13 in (2,340.2 mm)−0.20 in (−5.0 mm)−0.21%
Revolutions per mile686688+1+0.21%
True speed with the speedometer calibrated for 265/45R20
IndicatedActual on 265/45R20Actual on 235/45R21Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.8 mph−0.2 mph

Ride-height change: 235/45R21 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.6 mm diameter difference).

235/45R21 is 0.06 in shorter than 265/45R20 and 30 mm narrower, a 0.21% difference in overall diameter.

With the speedometer calibrated for 265/45R20, an indicated 60 mph is actually 59.9 mph on 235/45R21, and revolutions per mile change from 686 to 688.

235/45R21 mounts on a 21-inch wheel, a plus-1 fitment from the 20-inch wheel of 265/45R20.

Size pages

Other comparisons with 265/45R20

Other comparisons with 235/45R21

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