TireSizesFinder

35x12.50R17 vs 305/70R18

305/70R18 is 0.19 in (4.8 mm) shorter than 35x12.50R17, a −0.54% diameter difference. With the speedometer set for 35x12.50R17, an indicated 60 mph is 59.7 mph on 305/70R18.

Is this a safe swap?

Diameter difference −0.54%: under 1%

By overall diameter alone, 305/70R18 is a near match for 35x12.50R17; 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: 35x12.50R17 (35.00 in) vs 305/70R18 (34.81 in)35x12.50R1735.00 in × 12.50 in305/70R1834.81 in × 12.01 in
Side profile and tread width, drawn to the same scale.
35x12.50R17 vs 305/70R18 differences
Measurement35x12.50R17305/70R18Difference% diff
Overall diameter35.00 in (889.0 mm)34.81 in (884.2 mm)−0.19 in (−4.8 mm)−0.54%
Sidewall height9.00 in (228.6 mm)8.41 in (213.5 mm)−0.59 in (−15.1 mm)−6.61%
Section width12.50 in (317.5 mm)12.01 in (305.0 mm)−0.49 in (−12.5 mm)−3.94%
Circumference109.96 in (2,792.9 mm)109.36 in (2,777.8 mm)−0.59 in (−15.1 mm)−0.54%
Revolutions per mile576579+3+0.54%
True speed with the speedometer calibrated for 35x12.50R17
IndicatedActual on 35x12.50R17Actual on 305/70R18Difference
30 mph30.0 mph29.8 mph−0.2 mph
60 mph60.0 mph59.7 mph−0.3 mph
75 mph75.0 mph74.6 mph−0.4 mph

Ride-height change: 305/70R18 lowers the vehicle by 0.09 in (2.4 mm) at the axle (half the −4.8 mm diameter difference).

305/70R18 is 0.19 in shorter than 35x12.50R17 and 13 mm narrower, a 0.54% difference in overall diameter.

With the speedometer calibrated for 35x12.50R17, an indicated 60 mph is actually 59.7 mph on 305/70R18, and revolutions per mile change from 576 to 579.

305/70R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 35x12.50R17.

Size pages

Other comparisons with 35x12.50R17

Other comparisons with 305/70R18

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