TireSizesFinder

315/70R17 vs 295/70R18

295/70R18 is 0.10 in (2.6 mm) shorter than 315/70R17, a −0.30% diameter difference. With the speedometer set for 315/70R17, an indicated 60 mph is 59.8 mph on 295/70R18.

Is this a safe swap?

Diameter difference −0.30%: under 1%

By overall diameter alone, 295/70R18 is a near match for 315/70R17; 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: 315/70R17 (34.36 in) vs 295/70R18 (34.26 in)315/70R1734.36 in × 12.40 in295/70R1834.26 in × 11.61 in
Side profile and tread width, drawn to the same scale.
315/70R17 vs 295/70R18 differences
Measurement315/70R17295/70R18Difference% diff
Overall diameter34.36 in (872.8 mm)34.26 in (870.2 mm)−0.10 in (−2.6 mm)−0.30%
Sidewall height8.68 in (220.5 mm)8.13 in (206.5 mm)−0.55 in (−14.0 mm)−6.35%
Section width12.40 in (315.0 mm)11.61 in (295.0 mm)−0.79 in (−20.0 mm)−6.35%
Circumference107.95 in (2,742.0 mm)107.63 in (2,733.8 mm)−0.32 in (−8.2 mm)−0.30%
Revolutions per mile587589+2+0.30%
True speed with the speedometer calibrated for 315/70R17
IndicatedActual on 315/70R17Actual on 295/70R18Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.8 mph−0.2 mph
75 mph75.0 mph74.8 mph−0.2 mph

Ride-height change: 295/70R18 lowers the vehicle by 0.05 in (1.3 mm) at the axle (half the −2.6 mm diameter difference).

295/70R18 is 0.10 in shorter than 315/70R17 and 20 mm narrower, a 0.30% difference in overall diameter.

With the speedometer calibrated for 315/70R17, an indicated 60 mph is actually 59.8 mph on 295/70R18, and revolutions per mile change from 587 to 589.

295/70R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 315/70R17.

Size pages

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