Accelera Iota ST68 285/40R21

Shop the Accelera Iota ST68 285/40R21 at ThreePiece.us — free shipping on every order, Affirm financing available, and fast delivery nationwide.

What 285/40R21 means

In the size 285/40R21, 285 is the section width in millimeters (11.22 in), 40 is the aspect ratio — the sidewall stands 40% as tall as the tire is wide, or 114.0 mm (4.49 in) — R denotes radial construction, and 21 is the wheel diameter in inches. That works out to an overall diameter of about 29.98 inches, turning roughly 673 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 109 — a maximum load of 2,271 lbs per tire. The speed symbol S corresponds to a maximum sustained speed of 112 mph.

Specifications

Frequently asked questions

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.

What does 109S mean on the Accelera Iota ST68?

109S breaks down as load index 109 — rated for 2,271 lbs per tire — with an S speed rating, good for a maximum sustained 112 mph.

Will 285/40R21 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 285/40R21, this tire matches your vehicle's fitment. If you're changing sizes, compare overall diameter to keep your speedometer and clearances right.

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