TireSizesFinder

35x12.50R18 vs 275/65R20

275/65R20 is 0.93 in (23.5 mm) shorter than 35x12.50R18, a −2.64% diameter difference. With the speedometer set for 35x12.50R18, an indicated 60 mph is 58.4 mph on 275/65R20.

Is this a safe swap?

Diameter difference −2.64%: within the ±3% guideline

By overall diameter alone, 275/65R20 falls inside the ±3% range commonly used as a guideline when replacing 35x12.50R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 35x12.50R18 (35.00 in) vs 275/65R20 (34.07 in)35x12.50R1835.00 in × 12.50 in275/65R2034.07 in × 10.83 in
Side profile and tread width, drawn to the same scale.
35x12.50R18 vs 275/65R20 differences
Measurement35x12.50R18275/65R20Difference% diff
Overall diameter35.00 in (889.0 mm)34.07 in (865.5 mm)−0.93 in (−23.5 mm)−2.64%
Sidewall height8.50 in (215.9 mm)7.04 in (178.8 mm)−1.46 in (−37.2 mm)−17.21%
Section width12.50 in (317.5 mm)10.83 in (275.0 mm)−1.67 in (−42.5 mm)−13.39%
Circumference109.96 in (2,792.9 mm)107.05 in (2,719.0 mm)−2.91 in (−73.8 mm)−2.64%
Revolutions per mile576592+16+2.72%
True speed with the speedometer calibrated for 35x12.50R18
IndicatedActual on 35x12.50R18Actual on 275/65R20Difference
30 mph30.0 mph29.2 mph−0.8 mph
60 mph60.0 mph58.4 mph−1.6 mph
75 mph75.0 mph73.0 mph−2.0 mph

Ride-height change: 275/65R20 lowers the vehicle by 0.46 in (11.8 mm) at the axle (half the −23.5 mm diameter difference).

275/65R20 is 0.93 in shorter than 35x12.50R18 and 43 mm narrower, a 2.64% difference in overall diameter.

With the speedometer calibrated for 35x12.50R18, an indicated 60 mph is actually 58.4 mph on 275/65R20, and revolutions per mile change from 576 to 592.

275/65R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 35x12.50R18.

Size pages

Other comparisons with 35x12.50R18

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