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315/70R17 vs 35x12.50R17

35x12.50R17 is +0.64″ in overall diameter and +3 mm in section width against 315/70R17 — a diameter change of +1.86%, which stays inside the ±3% substitution rule. An indicated 60 mph would really be 61.1 mph.

Within 3%

Every dimension

Difference between 315/70R17 and 35x12.50R17
Dimension315/70R1735x12.50R17Change
Overall diameter34.36″ → 35.00″+0.64″ (+1.86%)
Section width315 mm → 318 mm+3 mm (+0.79%)
Sidewall height220.5 mm → 228.6 mm+8.1 mm
Rolling circumference107.95″ → 109.96″+2.00″
Revolutions per mile586.9 → 576.2−10.7
Axle height / clearance17.18″ → 17.50″+0.32″
315/70R17315 mm
35x12.50R17318 mm
Scale drawing comparing 315/70R17 and 35x12.50R17, both standing on the same ground line
315/70R17 34.36″35x12.50R17 35.00″

Which is taller, 315/70R17 or 35x12.50R17?

35x12.50R17 is the taller of the two, at 35.00″ against 34.36″. The gap is 0.64 inches, or 16.2 mm.

One of these is a flotation size, which states its overall diameter on the sidewall, while the metric size only implies one — so the comparison is between a stated height and a derived one. 315/70R17 is 315 mm wide with a 220.5 mm sidewall on a 17 wheel; 35x12.50R17 is 317.5 mm wide with a 228.6 mm sidewall on a 17 wheel.

What the speedometer will read

Indicated versus actual speed after the size change
Speedometer readsActual speedError
25 mph25.5 mph+0.5 mph
40 mph40.7 mph+0.7 mph
55 mph56.0 mph+1.0 mph
60 mph61.1 mph+1.1 mph
70 mph71.3 mph+1.3 mph
80 mph81.5 mph+1.5 mph

Fitting 35x12.50R17 in place of 315/70R17 multiplies every speed and distance reading by 1.01856. Over 10,000 indicated miles the odometer is out by +186 miles.

Effective gearing moves by the same proportion. A vehicle with 3.73 axles running 315/70R17 would need 3.80 to keep the same engine speed on 35x12.50R17. Work it out for your own axle ratio.

Full specification of each size

315/70R17

Derived dimensions for 315/70R17
DimensionMetricImperial
Section width315.0 mm12.40″
Sidewall height220.5 mm8.68″
Wheel diameter431.8 mm17.0″
Overall diameter872.8 mm34.36″
Rolling circumference2,742.0 mm107.95″
Revolutions per mile364.7 / km586.9 / mile
Measuring rim (estimate)241 mm9.5″

35x12.50R17

Derived dimensions for 35x12.50R17
DimensionMetricImperial
Section width317.5 mm12.50″
Sidewall height228.6 mm9.00″
Wheel diameter431.8 mm17.0″
Overall diameter889.0 mm35.00″
Rolling circumference2,792.9 mm109.96″
Revolutions per mile358.1 / km576.2 / mile
Measuring rim (estimate)254 mm10″

Rim widths differ too: 315/70R17 is designed for 9″10.5″ and 35x12.50R17 for 9″11″. Their measuring rims differ, so the same wheel will not be ideal for both.

Can you swap one for the other?

Inside the ±3% rule

The diameter difference of +1.86% is within the ±3% that fitters use as the boundary for a substitution, so the speedometer, odometer and wheel-speed-derived systems stay close enough to calibration. The section width difference of +3 mm is a separate question and is the one that decides whether it rubs.

Neither figure says anything about physical fitment. Whether 35x12.50R17 clears the strut, the fender liner and the steering stops depends on wheel offset and suspension geometry that a size code does not encode. For maintenance rather than sizing, Car Basics covers tire care.

315/70R17 vs 35x12.50R17: common questions

Is 35x12.50R17 bigger than 315/70R17?
35x12.50R17 is 0.64 inches taller and 3 mm wider. In overall diameter that is +1.86%, which stays inside the ±3% rule of thumb for a substitution.
How much will 35x12.50R17 throw off my speedometer?
Every reading scales by 1.01856. An indicated 60 mph becomes 61.1 mph, and every 100 miles on the odometer is really 101.9 miles.
How much does 35x12.50R17 change ground clearance over 315/70R17?
The axle centerline moves by 0.32 inches — half the diameter change, because half the extra height sits below the hub and half above it.
Will 35x12.50R17 fit where 315/70R17 fits?
Nothing derived from the size code can answer that. Clearance depends on wheel offset, suspension travel and body dimensions that no tire size contains. This page tells you exactly what changes dimensionally, which is the part that can be calculated.

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