TireSizesFinder

235/45R21 vs 245/45R21

245/45R21 is 0.35 in (9.0 mm) taller than 235/45R21, a +1.21% diameter difference. With the speedometer set for 235/45R21, an indicated 60 mph is 60.7 mph on 245/45R21.

Is this a safe swap?

Diameter difference +1.21%: within the ±3% guideline

By overall diameter alone, 245/45R21 falls inside the ±3% range commonly used as a guideline when replacing 235/45R21. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 235/45R21 (29.33 in) vs 245/45R21 (29.68 in)235/45R2129.33 in × 9.25 in245/45R2129.68 in × 9.65 in
Side profile and tread width, drawn to the same scale.
235/45R21 vs 245/45R21 differences
Measurement235/45R21245/45R21Difference% diff
Overall diameter29.33 in (744.9 mm)29.68 in (753.9 mm)+0.35 in (+9.0 mm)+1.21%
Sidewall height4.16 in (105.8 mm)4.34 in (110.3 mm)+0.18 in (+4.5 mm)+4.26%
Section width9.25 in (235.0 mm)9.65 in (245.0 mm)+0.39 in (+10.0 mm)+4.26%
Circumference92.13 in (2,340.2 mm)93.25 in (2,368.4 mm)+1.11 in (+28.3 mm)+1.21%
Revolutions per mile688679−8−1.19%
True speed with the speedometer calibrated for 235/45R21
IndicatedActual on 235/45R21Actual on 245/45R21Difference
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: 245/45R21 raises the vehicle by 0.18 in (4.5 mm) at the axle (half the +9.0 mm diameter difference).

245/45R21 is 0.35 in taller than 235/45R21 and 10 mm wider, a 1.21% difference in overall diameter.

With the speedometer calibrated for 235/45R21, an indicated 60 mph is actually 60.7 mph on 245/45R21, and revolutions per mile change from 688 to 679.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 235/45R21

Other comparisons with 245/45R21

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