How to accurately find out the size of wheels on a car: from markings to online services

Are you choosing new wheels for your car, but don’t know which parameters are suitable? Or want to check whether the installed wheels comply with the manufacturer's recommendations? Determining the size of the rims is a key step when buying wheels, since an error in even one parameter can lead to control problems, premature tire wear, or even an accident. In this article we will analyze all available methodsHow to find out the size of disks on a car - from deciphering the markings to using online databases.

It doesn't matter whether you're a beginner or an experienced car owner: there's a method for every occasion. We will look at where to look for information on the disk itself, in the documents for the car, and also how to measure the parameters manually if the markings have been erased. Plus - we'll sort it out common mistakes, which are allowed when choosing disks, and we will give a checklist to check compatibility.

1. Marking on the disk: decoding parameters

The most reliable way to find out the size of disks is to look at their markings. It is applied by the manufacturer to the inside of the rim and contains all the key parameters. A typical marking format looks like this:

7.5Jx16 H2 5x112 ET45 D57.1

Let's decipher each element:

• 🔢 7.5J — rim width in inches (here 7.5 inches). Letter J denotes the shape of the rim flange (for passenger cars it is most often used J).
• 📏 16 — wheel diameter in inches (corresponds to the tire diameter).
• 🔄 H2 — the number of humps (ring-shaped protrusions for fixing a tubeless tire). H2 means two hampas, H - one, FH - flat hump.
• ⚙️ 5x112 - number of holes for bolts (5) and the diameter of their location in mm (112 mm, also called PCD).
• ↗️ ET45 - disc ejection (ET from German EinpressTiefe). Here the offset is 45 mm. A positive offset means that the disc is “recessed” inward, a negative offset means that it protrudes outward.
• 🕳️ D57.1 — diameter of the central hole (hub) in mm. It is important that it matches the diameter of the car hub or is larger (in this case, adapter rings are used).

If the markings are erased or painted over, try cleaning the surface of the disc with solvent or fine sandpaper. Sometimes the data is duplicated on the outside of the rim or on the spokes.

⚠️ Attention: Some discs may not have the letter designation of the humps (H2). This is not critical for selection, but it is important for tubeless tires - without humps, the tire can “slide” off the rim during a sharp maneuver.

2. Car documents: where to look for disk data

If markings are not available, refer to the machine documents. Disk sizes are indicated in several sources:

B PTS (vehicle passport) the size of the rims is rarely indicated - only if they are non-standard. If the documents do not contain accurate data, please contact electronic databases (we'll talk about them below).

⚠️ Attention: The instruction manual may indicate several options disks for different configurations. Check which size is installed on your machine!

📊 Where do you usually look for disk size information?

In the markings on the disc

In car documents

On the Internet

I ask the tire specialists

3. Online services for selecting wheels by car brand

If it is not possible to view the markings or documents, use online services. They allow you to find out the size of the disks by make, model and year of manufacture car. Popular resources:

• 🌍 Diski.ru — a database for Russian and foreign cars, with filters by parameters.
• 🔧 Kolesa-Darom — catalog with the ability to select by VIN code.
• 📊 Wheel-Size.com (English) - international database with detailed characteristics.
• 🚗 Tyresize.ru — a service for selecting tires and wheels, taking into account interchangeability.

How to use:

1. Select the make, model and year of your vehicle.
2. Please indicate the modification (engine size, body type).
3. The system will display all valid disk sizes for your machine.

The advantage of online services is that they take into account factory tolerances and show alternative options (for example, wheels with a different offset, but suitable for other parameters). However always double-check the data with the actual markings on the disk — sometimes there are errors in the databases.

💡

If you are selecting wheels for a used car, check with the previous owner to see if the wheels were replaced with non-standard ones. For example, on Toyota RAV4 Often they install discs with a larger diameter than those provided by the factory.

4. How to measure disk size manually

If the markings have worn off and there are no documents, you can measure the parameters yourself. You will need:

• 📏 Calipers or ruler (for accurate measurements).
• 📐 Roulette or measuring tape.
• 🔩 Key for removing the wheel (if you need to measure the central hole).

Step by step instructions:

☑️ Measuring disk parameters

Remove the wheel from the carClean the disk from dirtMeasure diameter and widthDetermine PCD and offsetCheck the center hole

Done: 0 / 5

1. Disc diameter (fitting size)

Measure the distance from one edge of the rim to the opposite through the center. This will be the diameter in inches (for example, 16"). For accuracy, use a tape measure or place the disk against the wall and measure the height.

2. Disc width

Measure the distance between the inner edges of the rim (where it meets the tire). Usually indicated in inches in increments of 0.5 (for example, 7.5J).

3. PCD (bolt pattern)

Difficult parameter to measure without tools. Methods:

• 🔍 If on disk even number of holes (4 or 6), measure the distance between the centers of opposite holes - this will be the PCD.
• 🔢 If there are holes odd number (5), measure the distance between the centers of two adjacent holes and multiply by the coefficient (for 5 holes - 1.051).

4. Disc ejection (ET)

Place the disc face down on a flat surface. Attach a ruler to the rim and measure the distance from the surface to the plane of contact of the disc to the hub. If the disk does not touch the surface, the projection is positive, if it “falls” outward, it is negative.

5. Center Hole Diameter (DIA)

The easiest way to measure is with a caliper. If you don't have one, use a ruler: place it on the edges of the hole and measure the diameter.

⚠️ Attention: When measuring PCD and offset, an error of even 1-2mm can result in wheel runout or impossibility of installation. If in doubt, contact a tire shop.

5. Alternative methods: VIN code and mobile applications

If standard methods do not help, try the following options:

1. By VIN code

The VIN (Vehicle Identification Number) contains vehicle equipment information, including wheel sizes. Where to find it:

• 📄 B STS or PTS.
• 🚗 On the sign under the windshield (driver's side).
• 🔧 On the sign in the doorway.

Enter VIN into services like Vinformer or Autocod — the report will have a section with the characteristics of the wheels.

2. Mobile applications

Applications for car owners often contain databases of disk sizes:

• 📱 WheelFit (Android/iOS) - selection of wheels and tires taking into account interchangeability.
• 📱 TireSize — size calculator with visualization.
• 📱 AutoDoctor — scans VIN and provides technical data.

3. Forums and communities

On thematic forums (for example, Drive2 or Kolesa.ru) often discuss non-standard wheel sizes for specific models. Look for a topic about your car - there may be advice from owners with similar cars.

How to find out the size of disks from a photo?

Some services (for example, Wheel-Size.com) allow you to upload a photo of the disc and automatically recognize the markings. However, the accuracy of this method is lower than with manual measurement.

6. Common mistakes when determining disk size

Even experienced car owners sometimes make mistakes when selecting wheels. Let's look at typical mistakes and their consequences:

Error	Consequences	How to avoid
Unfaithful PCD (bolt pattern)	The wheel does not fit on the hub or is mounted askew → steering wheel beating and vibration.	Use centering bolts or choose a disk with the correct PCD.
Inconsistency departure (ET)	The disc touches the suspension elements or protrudes beyond the arch → damage to wheels and body.	Check the offset according to the manufacturer's markings or catalogs.
Unsuitable center hole diameter	The disc does not fit on the hub or is attached with play → uneven tire wear.	Use adapter rings (hubs) if necessary.
Incompatible rim width	The tire “inflates” or contracts → deterioration in controllability and the risk of disassembly.	Follow the manufacturer's recommendations for rim width.

Another common mistake is ignoring permissible deviations. For example, the offset can be changed within ±5 mm, and the diameter of the central hole should be greater than or equal to hub diameter. But it is better to stick to the factory settings.

💡

If you install discs with a different offset than the factory ones, be sure to check that they do not hit the brake calipers or suspension components when turning the steering wheel.

7. Checking disk compatibility: checklist before purchasing

Before buying new wheels, make sure they fit your car. Use this checklist:

☑️ Checking disks before purchasing

Does the PCD (bolt pattern) match the factory one?Is the diameter of the central hole suitable (or are there adapter rings)Overhang (ET) within tolerance (±5 mm)The width of the rim corresponds to the width of the tireThe disc is certified for your car model

Done: 0 / 5

Additional nuances:

• 🔄 For winter tires It is recommended to use wheels 0.5–1 inch narrower than for summer ones (for example, 7J instead of 7.5J). This improves handling on snow.
• 🚗 On SUVs and crossovers, wheels with a negative offset are often installed to widen the track. Check this point in the documentation.
• 🔧 If you install wheels with a larger diameter (for example, instead of R16 - R17), check if you need spacer for calipers.

After purchase, be sure to “try” the disc on the hub without tire. It should fit tightly, without play, and the holes for the bolts should match the holes on the hub.

FAQ: Frequently asked questions about disk size

Is it possible to install discs with another PCD if the holes are almost the same?

No! Even if the bolts are screwed in, the disk will be installed skewed. This will lead to steering wheel beating at speed and uneven wear of the wheel bearing. Use only exact match PCD discs or special eccentric bolts (but this is a temporary solution).

What happens if you install wheels with a shorter offset (ET)?

The disc will move outward, which can lead to:

• The wheel hitting the fender liner or arch when turning.
• Increased load on the wheel bearing.
• Deterioration in handling (the car becomes more “rolly”).

It is allowed to reduce the offset by no more than 5–10 mm from the factory value.

How to find out the size of the disks if they are hidden under the caps?

Remove the cap (usually it is secured with latches or bolts). If the cap won't come off, try looking through the bolt holes or jacking up the car a little to see the inside of the disc. As a last resort, go to a tire shop - they will remove the wheel in 5-10 minutes.

Is it possible to install wheels from another car model?

Theoretically yes, if they match PCD, diameter, width and offset. But there are nuances:

• U VAG concerns (Volkswagen, Audi, Škoda) often the same PCD (5x112), but different offset.
• On Japanese cars (Toyota, Honda) The diameter of the center hole may vary.
• Discs from crossovers usually do not fit sedans of the same brand due to different offsets.

Before installing, check compatibility on forums or directories.

What are humps (H2) and why are they important?

Humps are ring-shaped protrusions on the rim of a disc that secure a tubeless tire and prevent it from jumping off during a sharp maneuver or descent. There are:

• H - one hump.
• H2 — two humpas (the most common option).
• FH — flat hump (for some sports discs).

If there are no humps on the rim, the tire may slip off the rim under low pressure or under emergency braking.