Tire Buying Guide

Learn how to read tire sizes, understand sidewall markings, and choose the right path from fitment to quote and fulfillment with NADM.

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Reading Tire Sizes

265/70R17

  • 265 — Width

    Section width in millimeters from sidewall to sidewall.

  • 70 — Aspect Ratio

    Sidewall height as a percentage of the tire’s width.

  • R — Construction

    Radial construction, the modern passenger and light-truck standard.

  • 17 — Wheel Diameter

    Wheel diameter in inches the tire is designed to fit.

Most modern passenger and light-truck tires use a size code like 265/70R17. Each part of that code tells you something important about the tire’s dimensions and construction.

Example: 265 / 70 R 17

  • 265 — Width: Section width in millimeters from sidewall to sidewall.
  • 70 — Aspect Ratio: Sidewall height as a percentage of the tire’s width.
  • R — Construction: Radial construction, the modern passenger and light-truck standard.
  • 17 — Wheel Diameter: Wheel diameter in inches the tire is designed to fit.

Width

Tire width is the first number in the size code (for example, 265 in 265/70R17). It is the section width in millimeters measured from sidewall to sidewall.

  • A higher number means a wider tire.
  • Width affects contact patch, appearance, and in some cases handling and fitment clearance.
  • Wider tires may require confirmation of wheel well, suspension, and rim compatibility before ordering.

Aspect Ratio

Aspect ratio is the second number in the size code (for example, 70 in 265/70R17). It is the sidewall height expressed as a percentage of the tire’s width.

  • A lower aspect ratio generally means a shorter sidewall.
  • Shorter sidewalls can feel more responsive.
  • Taller sidewalls can help with ride comfort and load support depending on the vehicle.

Wheel Diameter

Wheel diameter is the final number in the size code (for example, 17 in 265/70R17). It is the wheel diameter in inches the tire is designed to fit.

  • This must match your wheel size.
  • A 17-inch tire belongs on a 17-inch wheel.
  • Construction: R means radial. You may also see other prefixes or service descriptions on specialty tires, but radial is the common passenger and light-truck standard.

Load Index

After the size code, many tires show a service description such as 115T. The Load Index is the number (for example, 115).

  • It corresponds to the tire’s maximum load-carrying capacity when properly inflated.
  • Always match or exceed the load index recommended for your vehicle.
  • If you are unsure, share your current tire size and vehicle details with NADM and we can help you confirm a suitable replacement path.

Speed Rating

The Speed Rating is the letter in the service description (for example, T in 115T). It indicates the tire’s tested speed capability under controlled conditions.

  • Common examples include S, T, H, V, and W.
  • Choose a speed rating that meets or exceeds your vehicle’s requirement.
  • Speed rating is not a substitute for correct size, load index, and application fitment.

DOT Code

The DOT Code appears on the sidewall and identifies that the tire meets Department of Transportation requirements.

  • The last digits of the DOT code typically indicate the week and year of manufacture.
  • This helps you understand tire age when inspecting inventory or replacements.
  • Use DOT age information together with tread condition and visible damage when deciding whether to replace a tire.

UTQG

UTQG (Uniform Tire Quality Grading) appears on many passenger tires and includes three consumer-facing grades:

  • Treadwear — a comparative wear grade. Higher numbers generally indicate longer comparative tread life under the test standard, not a guaranteed mileage warranty.
  • Traction — graded AA, A, B, or C for straight-line wet traction performance in the UTQG test.
  • Temperature — graded A, B, or C for the tire’s ability to dissipate heat under the UTQG test conditions.

UTQG grades are useful comparison tools, but they are not a substitute for choosing the correct size, load index, speed rating, and application for your vehicle.

Where to Find Your Tire Size

You can usually find your tire size in these places:

  • On the sidewall of your current tires
  • On the driver’s door jamb placard
  • In your vehicle owner’s manual
  • On some fuel-door or glove-box labels, depending on the vehicle

Use the vehicle placard as the authority for original equipment sizing and load requirements. If your vehicle has been modified, or if you are switching applications, confirm fitment before ordering.

Tire Replacement

Plan for replacement when you notice any of the following:

  • Tread depth worn to or near 2/32 inch
  • Visible cords, bulges, cuts, or sidewall damage
  • Uneven wear that cannot be safely corrected
  • Vibration, cracking, or age-related deterioration
  • Repeated loss of pressure without a clear repairable cause

Do not wait for a failure on the road. If you are unsure whether a tire should be replaced or repaired, ask a trusted installer—and reach out to NADM if you need help sourcing the correct replacement size.

Start With the Right Fit

Match size, application, and order volume before you request pricing.

  • Choose Your Size

    Start with the sidewall code and vehicle placard before you compare brands or tread designs.

  • Match the Application

    Passenger, light truck, commercial, touring, performance, and seasonal needs should guide the shortlist.

  • Share Quantity Needs

    Single sets, stock-up orders, and fleet fills can follow different pricing and fulfillment paths.

Recommended Buying Flow

Four steps from shortlist to reorder.

  1. Browse or Search

    Explore categories or search by size to shortlist options that match your vehicle.

  2. Request a Quote

    Send sizes, quantities, and timing so we can confirm pricing and availability.

  3. Choose Fulfillment

    Ship to your shop or coordinate pickup when inventory allows.

  4. Reorder With Confidence

    Dealer accounts unlock wholesale pricing and faster repeat ordering.

Frequently Asked Questions

Quick answers while you evaluate options.

Do I Need a Dealer Account to Buy?

You can request quotes and shop available retail inventory without a dealer account. Dealer accounts unlock wholesale pricing and dedicated support after approval.

What If I’m Unsure of the Right Tire?

Share the vehicle application, size, and use case. Our team can help narrow options using the information on your placard and current tires.

Can I Change Load Index or Speed Rating?

Replacements should meet or exceed the vehicle’s required load index and speed rating. If you are considering a change, confirm fitment and vehicle requirements first.

Related Resources

Explore policies, support pages, and next steps without scrolling to the footer.

Ready to Get Pricing?

Request a quote with sizes and quantities, or apply for a dealer account.

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