Tire Rack Wheels by Size: How to Read Your Size and Shop the Right Fit
Shopping for wheels by size? Learn how the tire sidewall code reveals your wheel diameter, and which other measurements, such as bolt pattern, offset and width, decide whether a wheel fits.
Contents
The short answer
To shop wheels by size, start with the tire size printed on your sidewall. The number after the letter R is the wheel diameter in inches. For example, a tire marked 225/45R17 mounts on a 17-inch wheel. Diameter alone does not guarantee fit, though. A wheel must also match your vehicle's bolt pattern, center bore, offset and a width suited to the tire. Searching by size on Tire Rack or any other wheel retailer only works when all of these line up.
In this guide, wheel size means the wheel's own dimensions. Tire size is the code molded into the tire's sidewall. The two are linked through diameter and width, but they are separate specifications.
Reading the tire size on your sidewall
Most passenger tires sold in the US use a metric size code. Each part of the code means something different:
P 225 / 45 R 17 91V
| | | | | |
| | | | | +-- load index and speed rating
| | | | +------ wheel (rim) diameter, inches
| | | +--------- construction: R = radial
| | +------------ aspect ratio: sidewall height as % of width
| +------------------ section width, millimeters
+--------------------- service type: P = passenger (may be absent)- Section width: the tire's width in millimeters, measured from sidewall to sidewall.
- Aspect ratio: the sidewall height expressed as a percentage of the section width. A lower number means a shorter sidewall.
- Construction: R stands for radial, which is the construction used on nearly all modern passenger tires.
- Rim diameter: the wheel diameter, in inches, that the tire is built to mount on. This is the number to carry over when shopping for wheels by size.
- Load index and speed rating: the tire's load-carrying and speed capability. These numbers describe the tire, not the wheel.
If the tire currently on your car is not the original size, check the tire information placard. It is usually on the driver's door jamb. Your owner's manual also lists the size the manufacturer specified for your model year and trim.
Wheel measurements that decide fit
| Measurement | What it means | Where to find it |
| Diameter | Wheel size in inches; must match the tire's rim diameter | Tire sidewall code, door-jamb placard, owner's manual |
| Width | Distance between the wheel's bead seats, in inches; must fall within the range approved for the tire | Wheel specification; tire manufacturer's approved rim widths |
| Bolt pattern | Number of lug holes and the diameter of the circle they sit on | Vehicle specifications for your make, model and year |
| Center bore | Diameter of the wheel's center hole that fits over the hub | Vehicle and wheel specifications |
| Offset | Distance from the wheel's mounting face to its centerline; affects how far the wheel sits in or out | Wheel specification; compare with your original wheels |
Wheel sizes are often written as diameter by width, such as 17x7.5, alongside the bolt pattern and offset. The bolt pattern, center bore and offset come from the vehicle, not the tire. Two cars that use the same tire size can still need different wheels.
Changing wheel diameter
Going up or down in wheel diameter is common, but the tire must change along with it. To keep the overall tire diameter close to the original, a larger wheel usually takes a tire with a lower aspect ratio, and a smaller wheel takes a taller sidewall. Changing the overall diameter can affect speedometer reading, clearance and other vehicle systems. Confirm any alternative size with the wheel and tire manufacturers or a qualified installer for your specific vehicle.
A practical next step
- Write down the full tire size from your sidewall or door-jamb placard.
- Note your vehicle's year, make, model and trim. Fitment can differ between trims and model years.
- Use a vehicle-based fitment search where available, or confirm bolt pattern, center bore and offset before buying a wheel listed only by diameter and width.
- Check that the wheel width falls within the range approved for your chosen tire.
Limits of this guide
This guide explains how wheel and tire sizes relate in general. It does not confirm how any particular retailer's size search currently works, what it stocks, or what fitment guarantees it offers. It also gives no vehicle-specific dimensions. Check bolt pattern, offset, approved rim widths and load requirements against your vehicle's documentation and the manufacturers' specifications.
Related articles
Identify headings and units in tire load-inflation tables
How to read the headings in a tire load-inflation table: tire category, size, service description, PR/Load Range/XL, single or twin fitment, load basis and pressure units.
Identify Pirelli Seal Inside and distinguish self-sealing from run-flat terminology
How to recognize Pirelli Seal Inside in a tire designation, how the sealing layer works, and why self-sealing, run-flat and added sealant belong in separate records.
Read three-number radial ATV and UTV tire sizes and separate wheel specifications
How to decode radial ATV and UTV tire sizes like 27 x 11 R14: diameter, width, the R symbol and rim diameter, plus how nominal sizes differ from catalog dimensions and rim-size entries.
How to interpret forklift press-on and pneumatic tire size markings
Decode forklift tire sizes like 16×6×10½, 200/75-100, 7.00 R12, 180/70 R8 and 18×7-8. Learn which number is outer diameter, width or rim diameter.
Interpret legacy numeric and alphanumeric tire sizes and comparison charts
What a 7.35-14 tire size means, how to read old numeric and letter-series codes, and how to compare conversion-chart rows with real tire specifications.
Read agricultural tire size markings
What the numbers on tractor tires mean: decode modern metric and legacy inch sizes, R and dash construction symbols, and the two different slash conventions.
Reading Motorcycle Tire Size and Sidewall Markings
Decode motorcycle tire sizes such as 120/70 ZR17 M/C (58W): nominal width, aspect ratio, construction, rim diameter, load index and speed symbol, plus a printable decoding worksheet.
Tire Number Guide: Understanding Manufacturer OE Markings Like Star, MO and AO
What OE tire markings such as the BMW star, Mercedes MO, Audi AO and Porsche N0 mean, where to find them, and how to use them when choosing replacements.
Motorcycle Tires: Front and Rear Sizes, Terminology and Mixing Rules Explained
Can a motorcycle run different tire sizes front and rear? Learn how to read motorcycle tire sizes, why front and rear tires differ, and what to check before mixing sizes or types.
Do LT tires ride rough?
LT (light truck) tires generally ride firmer than P-metric tires because they are built more heavily to carry loads. Here is why, and what changes the answer.