If you notice a backlash, a steering wheel beat at speed or uneven tire wear when you install the wheel disk on the hub, there is a 90% probability that the discrepancy is a problem. central opening (CO). Even a minimum difference of 0.5 mm between the diameter of the disk and the landing diameter of the hub leads to an imbalance that at speeds above 80 km / h manifests itself as vibration. To measure the CO can be without removing the wheel - enough rod or digital nutromer, but there are nuances: for example, the discs with a humpe (step) measure only the flat part, not the edge of the hole.
In this instruction - 5 proven methods of measuring the CO (including the method of VIN-code of the car), the actual dimensions for the Toyota, Volkswagen, Hyundai/Kia and other brands, as well as a compatibility table taking into account humps. Separately, the errors that are allowed even in tire mounts are analyzed: for example, ignoring the cone of the hole or confusing the CO with the diameter of the fastening holes (PCD).
What is a disk’s CO and why its accuracy is critical
Central opening (CO) It is the landing diameter in the center of the disk, which provides its centering on the hub of the car. Unlike PCD (swabbing), which fixes the disk with bolts, the CO is responsible for hub-wheel. If the diameter of the hole is larger than the required, the disc will “walk” on the hub, even if the bolts are tightened. If less, the disc will not be worn.
Car manufacturers indicate the permissible diameter of the CO with an error of not more than ± 0.1 mm. For example, for Volkswagen Golf 7 The standard CO is 57.1 mm, and for Toyota Camry V50 - 60.1 mm. Many universal disks (for example, from the BBS or OZ Racinghave more than the standard COs - they are used for centripe Adapters that make up for the difference.
- 🔧 Consequences of incorrect CO:
- ⚠️ Steering vibration at a speed of 60-120 km / h (often confused with imbalance).
- ⚠️ Accelerated wear of hub bearings (due to uneven load).
- ⚠️ Uneven wear of the tire tread (especially the inner edge).
- ⚠️ Risk of wheel detachment during emergency braking (if the CO is much larger than the hub).
Important: CO does not affect ET (disc departure) or PCD (dublishing), but its inconsistency negates the correctness of these parameters. For example, a disk with a perfect 5×112 PCD and an ET45 departure, but with a 66.6 mm CO instead of the required 57.1 mm, will beat when moving.
Method 1: Measurement with a rod (more precisely 0.05 mm)
This is the most reliable method used in tire fittings. You'll need to measure it. depth-meter (e.g., Mitutoyo 500-196-30) or a digital nutrient meter. Algorithm:
- Remove the disc from the car or turn it face down.
- Clean the edge of the central hole from dirt and corrosion (use a wire brush).
- Dilute the rods of the barn by the estimated diameter (for example, 57 mm for VW).
- Put the sponges in the hole and fix them at the maximum distance at which they still touch the edges.
- Check the measurement from 3-4 sides of the hole - the values should coincide with an error of no more than 0.05 mm.
If the disk has hum (Step inside the CO), measure only flat-piece Do not take the protrusion with the rod sponges. Humps serve for additional centering, but their size is not taken into account in the parameter of the CO.
Clean the edge of the hole from dirt | Check calibration of the bar (reset) | Measure the diameter in 3-4 points | Account for the humpe (do not capture the ledge) | Check the result with the manufacturer's table-->
⚠️ Attention: Don’t confuse the CA with the diameter.DIA(Rim landing diameter). For example, there may be a marking on the disk.17×7.5 JJ 5×112 DIA 66.6 ET45whereDIA 66.6- it's CO, not rim size.
Method 2: Measure with a ruler or roulette (for “field” conditions)
If there is no bar at hand, you can do with a conventional metal ruler or a millimeter scale roulette. The accuracy of the method is ±0.5 mm, which is enough for a preliminary check. Procedure:
- Place the disc on a flat surface with the front side down.
- Apply the ruler to the edge of the central hole so that it passes through its center (visually or by tags).
- Measure the distance from one edge of the hole to the opposite, multiply by 2 (if the ruler does not pass through the center).
- Repeat the measurement at a 90° angle to check the hole roundness.
Use it to improve accuracy coal-stone: Apply it to the ruler to ensure perpendicularity of the measurement. If the hole has a cone (expands to one of the sides), take as a basis smaller-diameter - it corresponds to the landing part of the hub.
| Make of car | Model | CO, mm | Note |
|---|---|---|---|
| Volkswagen | Golf 7, Passat B8 | 57.1 | Hump is a must. |
| Toyota | Camry V50, RAV4 XA50 | 60.1 | Tolerance ± 0.1 mm |
| Hyundai/Kia | Solaris, Rio 4 | 67.1 | Often confused with the 54.1 (older models) |
| BMW | 3 Series (G20), 5 Series (G30) | 72.56 | Requires center rings for universal disks |
| Lada | Vesta, XRAY | 60.1 | Compatible with discs from Renault |
⚠️ Attention: The discs for BMW, Mercedes and Audi Frequently found CO with non-standard values (for example, 72.56 mm instead of 72.6). Rounding to whole millimeters is unacceptable!
Method 3: Determination of CO by VIN code of the car
If the disk is not yet purchased and you want to know the regular CO for your car, use it. VIN decoder. This method eliminates errors associated with modifications of one model. For example, Skoda Octavia A7 depending on the year of release, it can have a CO 57.1 mm or 65 mm.
Instructions:
- Find your car’s VIN (on the windshield, in the PTS, or on the plaque under the hood).
- Enter it on one of the services:
- 🔗 VIN Decoder (Free, basic information)
- 🔗 VinFreeCheck (Detailed data on suspension).
- 🔗 ETIMIS (Official catalogue for Russian cars)
Central Bore (CO).Example of decryption for Kia Sportage 4 (VIN: U5Y):
Model: Kia Sportage (QL)
Year 2020
COR (Central Bore): 67.1 mm
PCD: 5×114.3
Departure (ET): 35-45mm
If the decoder does not have data on the CO, check the documentation on the disk by its article. For example, for discs. Replica R90 The CO is indicated in the marking on the back: CB 67.1
Method 4: Use of center rings (for universal disks)
If you buy a disk with a CCO more than the regular (for example, universal). BBS CH-R with CO 72.6 mm for VW Polo with the required 57.1 mm), required centripe. Their internal diameter should coincide with the hub, and the external - with the CO of the disk. For example:
- 🔄 For VW Golf 7 (CO 57.1 mm) and a disk with a CO 66.6 mm need a ring
57.1→66.6. - 🔄 For Toyota Corolla E210 (CO 60.1 mm) and disc with CO 73 mm - ring
60.1→73.
The rings are made of aluminum or plastic. Aluminum is more expensive (from 1,500 rubles per set), but withstand loads during emergency braking. Plastic (from 500 rubles) is suitable only for temporary use.
How to check the quality of the center ring
1. Check the absence of backlash when installed on the hub (tolerance - no more than 0.05 mm).
2. Make sure the ring does not deform when the bolts are tightened (especially for plastic bolts).
3. Aluminum rings should not have cracks or burrs that could damage the disc.
Method 5: Checking the labeling of the disc
On the back of most disks is marked, where the CO is indicated. Look for the signs:
CB 67.1- Central Bore 67.1 mm.DIA 57.1- diameter of the central opening 57.1 mm.HUMP H2- the presence of a hump (does not affect the CO, but is important for centering).
Example of full disk marking AEZ Dubrovnik:
AEZ 8.5Jx19 H2 5/112 CB 66.6 ET45
Here. CB 66.6 - That's the CO. If the marking is erased, use a bar (see para. Method 1).
⚠️ Attention: On Chinese discs (e.g., Replay or Dotz) CO may be rounded (e.g. 66 instead of 66.6 mm). Always check the exact size with the seller.
Typical errors in the measurement of CO
Even experienced tire tyre masters make mistakes that lead to vibration or damage to the hub. Here are the most common:
- 🔴 Hump measurement: They capture the protrusion inside the hole, not the flat part. The result is an overestimated value of the CO.
- 🔴 Ignoring cone: If the hole expands to one side, only the upper diameter is measured.
- 🔴 Confusion with PCD: Take the diameter of the fastening holes (for example, 112 mm in PCD 5×112) for the CO.
- 🔴 Round-up of values: For example, indicate 57 mm instead of 57.1 mm, which is critical for the Volkswagen or Audi.
- 🔴 Ignorance of centre rings: Buy a disk with a CO 66.6 mm for a car with a CO 57.1 mm, but forget about adapters.
Critical error: Use of discs without a humpe on cars where it is provided by the design (for example, BMW E60). The humpe fixes the disc on the hub, preventing micro-displacement during braking.
If after installation of the disk there was a vibration at a speed of 90-110 km / h, in 90% of cases the problem is in the discrepancy of the CO or PCD. First, check the centering of the disc on the hub!
FAQ: Frequent questions about CDs
Can I drive if the disk is 1 mm larger than the hub?
Nope. Even a difference of 0.5 mm leads to an imbalance, which at speed manifests itself as a vibration of the steering wheel. For temporary driving (for example, before tire fitting) can be used centreringBut you can not constantly operate such a disk - this will accelerate the wear of the hub bearing.
How do you know if the vibration is due to CO and not because of imbalance?
Vibration from the wrong CO:
- It's showing up at speed. 60–120 km/h It gets worse when you're overclocked.
- Feels in the steering wheel and pedals, not just in the body.
- It does not disappear after balancing the wheels.
The imbalance usually gives a vibration to the speed (for example, only 90 km/h) and disappears after balancing.
What if the disk is smaller than the hub?
A disc with a smaller CO will not physically fit on the hub. The only solution is to lathe the hole on the lathe to the desired diameter. However, this will weaken the design of the disk, so it is better to choose another disk or use it. sling-ring (if the difference is minimal)
How to check the CO without removing the wheel?
If the disk is installed on the car, you can measure the CO bolthole:
- Remove the cap (if any).
- Insert a bar or ruler through the fastening hole to the opposite edge of the CO.
- Measure the distance from the edge of the hole to the opposite wall of the CO, multiply by 2.
The method is less accurate (±1 mm), but will help to identify gross inconsistencies.
Which disks have the largest CO?
The largest central holes are found at:
- Mercedes-Benz Sprinter - 98.5 mm.
- Ford F-Series (American pickup trucks) - 87.1 mm.
- Toyota Land Cruiser 200 - 93.1 mm.
For such cars, only specialized wheels or universal models with adapters are suitable.