What does 345/30R21 mean?

In 345/30R21, 345 is the tread width in millimeters (about 13.6 inches). 30 is the aspect ratio: the sidewall height is 30% of the width, or about 104 mm (4.1 inches). "R" means radial construction, which nearly all passenger and light truck tires use today. 21 is the wheel diameter in inches. Put together, the tire stands about 29.1 inches tall when new.

What do the load index and speed rating after the size mean?

The code after the size, such as 102H, tells you how much weight each tire can carry and how fast it is rated to go. The number is the load index (102 means 1,874 lbs per tire) and the letter is the speed rating (H means up to 130 mph). Your replacement tires should meet or exceed the load index and speed rating on the placard in your driver’s door jamb.

What is the difference between SL (Standard Load) and XL (Extra Load) tires?

An XL tire is built to carry more weight than an SL tire of the same size, and it reaches that higher capacity at a higher inflation pressure. Heavier crossovers, trucks, and many electric vehicles come with XL tires from the factory because of their weight. If your vehicle’s placard or original tires call for XL in 345/30R21, replace them with XL. Putting XL tires on a vehicle that only needs SL is fine, though the ride can be slightly firmer.

Can I use a different size instead of 345/30R21?

Often, yes, within limits. A common guideline is to keep the new tire’s overall diameter within about 3% of the original. For 345/30R21, which is about 29.1 inches tall, that means roughly 28.3 to 30.0 inches. A taller tire makes your speedometer read low: with a tire 3% larger, it shows about 58 mph when you’re actually going 60. Also check that the new size fits your wheel width, clears the suspension and fenders at full steering lock, and meets your vehicle’s load rating. When in doubt, ask a tire installer before switching.

Why do prices for the same 345/30R21 tire vary across retailers?

Each retailer sets its own prices and runs its own promotions. The total you pay also depends on shipping costs, installation and disposal fees, road hazard coverage, and manufacturer mail-in rebates, which can be worth $50 to $100 or more on a set of four. Stock and pricing can also vary by region. Compare the full cost at checkout, not only the tire price.

Do the prices shown include installation or shipping?

The prices we show are the per-tire prices listed by each retailer. Shipping, installation, taxes, and fees depend on the retailer and your location, and are shown at the retailer’s checkout.

Should I replace all four tires at once?

Replacing all four keeps handling and braking even. If you replace only two, most tire makers recommend putting the new pair on the rear axle to help prevent oversteer on wet roads. All-wheel-drive vehicles often need all four tires to have closely matched tread depth to protect the drivetrain, so check your owner’s manual before replacing only some.

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Gladiator X COMP H/P

345/30R21 111Y

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The Gladiator X-Comp H/P is a 200-treadwear summer ultra-high-performance tire for performance cars in warm weather, with a race-inspired compound and an asymme…Full details

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Gladiator X COMP H/P

Bridgestone Potenza Sport RFT

Bridgestone Blizzak LM 005

Michelin Pilot Sport Cup 2 (240)

Michelin Pilot Sport Cup 2

Michelin Pilot Sport Cup 2 R

Bridgestone POTENZA SPORT

Pirelli P ZERO

Pirelli P ZERO CORSA (PZC4)

345/30R21 Tires — Compare Prices

Find the right tires. Clearly.

All Tires(9)

Gladiator X COMP H/P

Bridgestone Potenza Sport RFT

Bridgestone Blizzak LM 005

Michelin Pilot Sport Cup 2 (240)

Michelin Pilot Sport Cup 2

Michelin Pilot Sport Cup 2 R

Bridgestone POTENZA SPORT

Pirelli P ZERO

Pirelli P ZERO CORSA (PZC4)

345/30R21 tire FAQ

What does 345/30R21 mean?

What do the load index and speed rating after the size mean?

What is the difference between SL (Standard Load) and XL (Extra Load) tires?

Can I use a different size instead of 345/30R21?

Why do prices for the same 345/30R21 tire vary across retailers?

Do the prices shown include installation or shipping?

Should I replace all four tires at once?