What Size Tire Is a 315/35R17? Tire Size Explained in Inches

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A 315/35R17 sits near the wide end of the street-tire spectrum, and that number set trips up more people than it should. The “35” is not a sidewall height in inches — it’s a percentage, and misreading it throws off every other figure you calculate.

Here’s what each piece of the code actually controls, how the metric math converts to inches, and which fitment details still need checking before you buy.

Breaking Down the 315/35R17 Code

The string 315/35R17 splits into four separate specifications, and each one answers a different question.

  • 315 — section width in millimeters, measured across the widest point of the inflated tire.
  • 35 — aspect ratio. Sidewall height is 35% of the section width, not 35 of anything else.
  • R — radial construction. Nearly every modern passenger tire carries this letter.
  • 17 — rim diameter in inches. The metric units stop before this number.

The mixed measurement system is the trap here. Width arrives in millimeters, diameter in inches, and the aspect ratio is a bare percentage with no unit at all. Reading it top to bottom, three different systems are in play before you finish five characters.

315/35R17 in Inches: Every Key Measurement

The aspect ratio does the heavy lifting.

Measurement Metric Inches
Section width 315 mm 12.4 in
Sidewall height 110 mm 4.3 in
Overall diameter 652 mm 25.7 in
Circumference 2,048 mm 80.7 in
Rim diameter 432 mm 17 in
Revolutions per mile 785–786 785–786
Approved wheel width 267–318 mm 10.5–12.5 in

Those revolutions-per-mile figures matter more than they look. Any time the number drifts, your speedometer reading drifts with it, since the gauge is calibrated to a specific revolutions-per-mile value from the factory.

Why Two 315/35R17 Tires Can Measure Differently

Two tires stamped with identical 315/35R17 markings can still differ by a quarter inch or more in diameter.

The gap comes from brand engineering choices, tread depth, inflation pressure, load, and the actual width of the rim the tire sits on. A tire measured on a 10.5-inch wheel will not match the same tire on a 12.5-inch wheel, because a wider rim stretches the sidewall and drops the overall height slightly.

For suspension clearance work, always measure the specific tire you plan to run rather than trusting the catalog number. If you’re comparing actual products before you commit, this roundup of tested 315/35R17 tires worth ordering lays out how real-world fitment and specs differ across the options.

Fitment Checks Before You Buy

Tire size alone never guarantees a fit.

  • Wheel width —
  • Offset and clearance — check strut, fender, and brake-caliper room at full steering lock and at full suspension travel.
  • Load and speed ratings — match them to your vehicle’s requirements, not just the size stamp.

This is where catalog dimension pages and manufacturer fitment guides part ways. A dimension lookup gives you the numbers; only the tire maker’s own fitment data confirms whether the tire actually clears your car.

TireSize.com’s 315/35R17 specification page is a solid place to cross-check the width, diameter, and wheel-range figures before ordering.

FAQs

Is 315/35R17 the same as 12.4 inches wide?

Yes, that’s the conversion. Section width is 315 mm, which divides out to roughly 12.4 inches. Keep in mind that measurement is taken at the tire’s widest inflated point, not at the tread, so the number you get with a tape measure on an installed tire can read slightly different.

What does the 35 in 315/35R17 mean?

It’s the aspect ratio, meaning the sidewall height equals 35% of the 315 mm section width. That works out to about 110 mm, or 4.3 inches. It is not 35 millimeters and not 35 inches — it’s a percentage, which is the most common misread of this size code.

Will a 315/35R17 fit my 17-inch wheel?

The 17-inch rim diameter matches, but fitment also depends on wheel width, which needs to fall between 10.5 and 12.5 inches. Vehicle clearance, offset, suspension, and brake room all factor in too.

References & Sources

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