TireSizesFinder

295/35R21 vs 295/40R21

295/40R21 is 1.16 in (29.5 mm) taller than 295/35R21, a +3.99% diameter difference. With the speedometer set for 295/35R21, an indicated 60 mph is 62.4 mph on 295/40R21.

Is this a safe swap?

Diameter difference +3.99%: outside the ±3% guideline

By overall diameter alone, 295/40R21 falls outside the ±3% range commonly used as a guideline when replacing 295/35R21; speedometer and ride-height changes are larger. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 295/35R21 (29.13 in) vs 295/40R21 (30.29 in)295/35R2129.13 in × 11.61 in295/40R2130.29 in × 11.61 in
Side profile and tread width, drawn to the same scale.
295/35R21 vs 295/40R21 differences
Measurement295/35R21295/40R21Difference% diff
Overall diameter29.13 in (739.9 mm)30.29 in (769.4 mm)+1.16 in (+29.5 mm)+3.99%
Sidewall height4.06 in (103.3 mm)4.65 in (118.0 mm)+0.58 in (+14.8 mm)+14.29%
Section width11.61 in (295.0 mm)11.61 in (295.0 mm)0.00 in (0.0 mm)0.00%
Circumference91.51 in (2,324.5 mm)95.16 in (2,417.1 mm)+3.65 in (+92.7 mm)+3.99%
Revolutions per mile692666−27−3.83%
True speed with the speedometer calibrated for 295/35R21
IndicatedActual on 295/35R21Actual on 295/40R21Difference
30 mph30.0 mph31.2 mph+1.2 mph
60 mph60.0 mph62.4 mph+2.4 mph
75 mph75.0 mph78.0 mph+3.0 mph

Ride-height change: 295/40R21 raises the vehicle by 0.58 in (14.8 mm) at the axle (half the +29.5 mm diameter difference).

295/40R21 is 1.16 in taller than 295/35R21 and the same width, a 3.99% difference in overall diameter.

With the speedometer calibrated for 295/35R21, an indicated 60 mph is actually 62.4 mph on 295/40R21, and revolutions per mile change from 692 to 666.

Both sizes mount on 21-inch wheels.

Size pages

Other comparisons with 295/35R21

Other comparisons with 295/40R21

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