Firestone Duraforce RT 340/80R18 143B - 375975

The Firestone Duraforce RT in 340/80R18 ships free from ThreePiece.us, with Affirm financing available at checkout and fast delivery from a nationwide warehouse network.

What 340/80R18 means

In the size 340/80R18, 340 is the section width in millimeters (13.39 in), 80 is the aspect ratio — the sidewall stands 80% as tall as the tire is wide, or 272.0 mm (10.71 in) — R denotes radial construction, and 18 is the wheel diameter in inches. That works out to an overall diameter of about 39.42 inches, turning roughly 512 revolutions per mile. Overall diameter is what matters for speedometer accuracy and clearance when you change sizes, so compare it — not just the width — against your current tire.

The service description on this tire decodes to a load index of 143 — a maximum load of 6,008 lbs per tire.

Specifications

Frequently asked questions

What does 143B mean on the Firestone Duraforce RT?

143B breaks down as load index 143 — rated for 6,008 lbs per tire.

Will 340/80R18 tires fit my vehicle?

Check the size molded into your current tire's sidewall or the tire placard inside the driver's door jamb — if it reads 340/80R18, this tire matches your vehicle's fitment. If you're changing sizes, compare overall diameter to keep your speedometer and clearances right.

How fast does this tire ship?

Every order at ThreePiece.us ships free, with fast delivery from a nationwide warehouse network. Affirm financing is available at checkout.

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