Wheel disc deformation is one of the most insidious faults, which drivers often confuse with imbalance or suspension problems. "Eight" (or disc radial runout) not only worsens handling, but also accelerates wear of rubber and wheel bearings, and in critical cases can lead to tire rupture at high speed. In this case, the disc may look perfectly smooth externally, but symptoms appear only when moving.

In this article we will analyze unique characteristics of the “eight”, which do not coincide with imbalance or “ovoidity” of the tire, and also learn to distinguish them from other faults. You will learn how to check a wheel without special equipment, what tests to do on the go, and why even a new disk can go “figure eight” after the first hit in a hole. The material is useful for both beginners and experienced car owners - after all, 60% of wheel runouts go unnoticed until the suspension components are critically worn.

What is the “eight” on the wheel and why is it dangerous?

The term "eight" is a colloquial name radial runout of the diskwhen its rim is deformed along the vertical axis, taking the shape of a number 8. Unlike axial runout (when the disk “walks” left and right), radial leads to the fact that when rotating the wheel either “rises” or “sags” relative to the axis of rotation. This creates cyclical shocks to the suspension and steering.

The main reasons for the appearance of the “eight”:

  • 🚗 Hitting obstacles: curbs, holes, rails. Even one strong hit in a pothole at a speed of >40 km/h can deform the disc.
  • ⚙️ Incorrect bolt tightening: distortions during wheel installation (especially on alloy wheels).
  • ❄️ Thermal deformation: sudden cooling of a hot disk (for example, after braking in a puddle in winter).
  • 🔧 Manufacturing defect: Cheap stamped or cast wheels often have hidden metal stresses.

Why is the “eight” dangerous:

  • 🔥 Overheating of wheel bearings: due to uneven load they fail 3-5 times faster.
  • 🛞 Uneven tire wear: The treads wear off in patches, which reduces grip on wet roads.
  • 🚨 Loss of controllability: at speeds >80 km/h the car begins to “steer” to the side, especially when braking.
📊 How often do you check your wheels for runout?
Every season
After strong blows
Only with vibrations
Never

5 Visual Signs of a Figure Eight Without Tools

It is not always possible to visit a tire shop or use balancing stand. Here's how to identify a defect "by eye":

1. Uneven gaps between the disc and the brake caliper

Rotate the wheel by hand (the car should be on a jack or lift) and look at the gap between the disc and the caliper. If it either increases or decreases, this is a sure sign of radial runout. For clarity, you can bring it to the gap sheet of paper: with the “eight” it will either be clamped or released.

2. Tire “bouncing” when rotating

Remove the wheel and place it on a flat surface (such as the garage floor). Spin it and watch the sidewall of the tire. If the disc is deformed, the rubber will rise and fall relative to the plane. This method works even for a tire with a residual pressure of 0.5–1 atm.

3. Traces of friction on the inside of the disc

This is especially true for alloy wheels. With a figure eight, the rim periodically touches the brake pads or suspension elements, leaving scratches or abrasions. Pay attention to the inner side of the disk near the hub - traces of contact are most often visible there.

4. Uneven tread wear

If “spots” with a more erased pattern appear on the tire (especially on the sides), this may indicate runout. Difference from imbalance: with a figure eight, wear is localized in 1-2 places around the circumference, and not across the entire tread width.

5. Steering wheel vibration at low speed

The imbalance usually appears at speeds >60 km/h, and the “eight” makes itself felt already at 20–40 km/h. If the steering wheel shakes like you're driving on a washboard, check the front wheels.

Rotate the wheel and observe the gap at the caliper|

Place the wheel on the floor and check the tire hop|

Inspect the inside of the disc for scratches|

Check the steering wheel for vibration at 30–40 km/h |

Compare tread wear on all wheels -->

Test on the go: how to distinguish a figure eight from an imbalance

Many people confuse disk runout with wheel imbalance or tire deformation (“ovoid”). Here's how to tell them apart:

Sign "Eight" (disc beat) Imbalance Tire deformation (“egg”)
Steering wheel vibration At any speed, increases when braking Only at speeds >60 km/h Most often at speeds of 80–100 km/h
Body vibration Sharp, “blows” to the suspension Smooth like a shiver Rhythmic, coincides with the rotation of the wheel
Rubber wear Local "spots" on the tread Smooth but accelerated Wavy all around
Sounds when driving Cyclic clicking or knocking noises Hum or low frequency noise Popping sounds when hitting bumps

Practice test:

  1. Accelerate to 60–80 km/h on a flat road.
  2. Evaluate the nature of vibration:
    • If she rhythmic and coincides with the revolution of the wheel → “eight” or “egg”.
    • If constant and increases with speed → imbalance.
  • Slow down lightly:
    • The vibration has increased → the problem is front wheels.
    • Vibration has not changed → check rear.
      • 💡

      If the vibration occurs only when braking, the cause may be deformation brake disc, not wheeled. Check its thickness with a caliper - a difference of more than 0.05 mm between the edges indicates a “figure eight” brake disc.

      Accurate diagnosis: instrumental methods

      To confirm the figure eight 100%, you will need measuring instruments. Here's what you can do yourself:

      1. Using a dial indicator

      This is the most accurate way. Algorithm:

      1. Remove the wheel and secure it to slipway or a flat surface.
      2. Install the indicator on a stationary part (for example, on the hub) so that its leg touches the rim of the disc.
      3. Spin the wheel slowly. If the indicator needle deviates by more than 0.5 mm, the disk is deformed.

    Norm for:

    • 🚘 Stamped discs: up to 0.3 mm.
    • 🔄 Cast/forged wheels: up to 0.15 mm.

    2. Check on a balancing stand

    At modern stands (for example, Hofmann Geodyna or Corghi Artiglio) there is a function for measuring disc runout. Ask the technician to enable the mode «Radial Runout» - it will show the amount of deviation in millimeters. Runout >0.7 mm is considered critical.

    3. Laser level or ruler

    Hang the wheel on a wire or use rotating stand. Point the laser beam at the rim and mark with chalk the points where the beam “goes” beyond the rim. The difference between the maximum and minimum distance is the amount of runout.

    What to do if there are no tools?

    If you only have a ruler at hand, place it on the rim of the disc and slowly spin the wheel. Gaps of more than 1–2 mm between the ruler and the disk at different points indicate a figure eight. This method is less accurate, but will help identify gross deformations.

    When can a figure eight be fixed, and when can a disk only be scrapped?

    Not every deformation can be eliminated. Here are the criteria:

    The disk needs to be repaired if:

    • ✅ The runout does not exceed 1.5 mm (for stamped ones) or 1.0 mm (for cast ones).
    • ✅ No cracks or through damage.
    • ✅ The deformation is localized on the rim, not on the hub part.

    The disk is only a replacement if:

    • ❌ Beating >2 mm (even after rolling it will return after 1–2 thousand km).
    • ❌ There are cracks, especially in the places where the spokes are attached (for alloy wheels).
    • ❌ The landing plane under the hub is deformed.
    • ❌ The disc has already been rolled more than 2 times.

    Repair methods:

    • 🔨 Rolling on a machine: Suitable for stamped discs. Cost - from 800 rubles. per wheel.
    • 🔥 Heating and straightening: used for cast wheels, but is risky (may damage the metal structure).
    • 🛠️ Argon welding: To repair cracks, but does not correct runout.
    💡

    After straightening, cast wheels lose up to 30% of their strength. If the disk was deformed in an accident or a strong impact, its repair is unsafe - it is better to replace it.

    What happens if you drive with a G8: consequences for the car

    Many drivers ignore wheel beating for years, attributing vibrations to “crooked roads.” Meanwhile, the defect causes systemic damage to the car:

    1. Suspension

    • 🔧 Wheel bearings: they fail on average after 15–20 thousand km (instead of 100 thousand km under normal conditions).
    • 🛢️ Shock absorbers and struts: leak due to constant micro-impacts.
    • 🔗 Silent blocks and balls: loosen 2–3 times faster.

    2. Steering

    • 🚗 Steering rack: backlash appears, wear of the gear pair increases.
    • 🔄 Power steering/electric power steering pump: works with increased load, which leads to overheating.

    3. Brake system

    • 🛑 Pads and brake discs: wear unevenly, “beating” appears when braking.
    • 🔥 Brake hoses: vibrations accelerate their cracking.

    4. Tires

    • 🛞 Local “bumps” on the tread: appear after 5–10 thousand km.
    • 💥 Risk of rupture: If you hit a pothole at a speed >80 km/h, the tire may burst.
    💡

    If you notice that after replacing the wheels with new ones the vibration has not disappeared, check mounting surfaces on the hub. Often, after a long drive with the V8, they also become deformed and require sharpening.

    Prevention: how to avoid figure eight on wheels

    Preventing disc deformation is easier than eliminating its consequences. Here are proven methods:

    1. Proper driving in potholes

    • 🚦 When driving over bumps don't slow down - this increases the load on the disk.
    • 🛣️ If you can’t go around the hole, slow down to 20–30 km/h and drive on “straight” wheels.

    2. Tire pressure monitoring

    • 💨 Underinflated tires increase the risk of disc deformation upon impact.
    • ⚠️ The optimal pressure is indicated in car instructions or on a sticker in the doorway.

    3. Correct installation of wheels

    • 🔧 Tighten the bolts criss-cross with the torque specified in the manual (usually 90–120 Nm).
    • 🛠️ Use torque wrench - over-tightening is just as harmful as under-tightening.

    4. Select disks

    • 🔄 It is better to use for winter tires stamped wheels - they are softer and break less when impacted.
    • 💎 Choose alloy wheels from thickened knitting needles (for example, models from BBS or OZ Racing).

    5. Regular diagnostics

    • 🔍 Check the wheels for runout every season when changing tires.
    • 📏 After a strong impact, measure the geometry of the disk even if everything is visually normal.
      • ⚠️ Attention: If you often drive on dirt roads or rough roads, install wheels with negative offset (ET) - they are less susceptible to deformation under lateral loads.

      FAQ: Frequently asked questions about the G8 on wheels

      Is it possible to drive with a disc runout of 1 mm?

      Technically possible, but not advisable. A runout of 1 mm already creates an increased load on the suspension and accelerates tire wear. If it is the front wheel, vibrations on the steering wheel will be noticeable at speeds >50 km/h. It is recommended to roll the disc on a machine.

      How to distinguish a figure eight from a crooked brake disc?

      When beating brake disc The vibration only appears when braking and disappears when coasting. The "eight" wheel rim vibrates constantly, and when braking it intensifies. Also inspect the brake disc - if there are signs of blue spots (overheating), it is definitely deformed.

      Is it true that alloy wheels cannot be rolled?

      This is a myth. Alloy wheels you can roll, but only on specialized equipment with temperature control. Regular “hot” rolling on a stamping machine will ruin them. It is better to contact services where there are heated hydraulic presses (for example, 3D editing).

      Why is there still vibration after balancing?

      The reasons may be:

      1. Balancing was done without taking into account the disc runout (you need to use a stand with a function «Runout Compensation»).
      2. Deformed hub landing plane (groove required).
      3. Worn out silent blocks or ball joints, which mask the runout.
      4. The tire has hidden cord defect (“egg”), which is not visible externally.

      Ask a technician to check the disc for runout up to balancing.

      How much does it cost to repair a V8?

      The cost depends on the type of disk and region:

      • 🔨 Rolling a stamped disc: 800–1,500 rub. per wheel.
      • 🔥 3D editing of a cast disk: 2,000–4,000 rub. (depending on complexity).
      • 🆕 New stamped disc: from 1,500 rub. (for example, KFZ or TREBL).
      • 💎 New alloy wheel: from 5,000 rub. (brands Replica, Dezent).

      Economically, repairs are justified if the cost of the work does not exceed 50% of the price of a new disk.