Wheel Mounting Surface Check

Replace any wheels that are bent or dented, or have excessive lateral or radial runout. Wheels with runout greater than specified may cause objectionable vibrations.

Fig 1: Checking Wheel Mounting Surface
Courtesy of GENERAL MOTORS CORP.
1. Thoroughly clean the wheel mounting surface with a clean shop towel and denatured alcohol, or equivalent.
2. Use a straight edge 203-229 mm (8-9 in) long. Place the straight edge on the wheel inboard mounting surface. Try to rock the straight edge up and down within the mounting surface.
3. For aluminum flat-mount wheels, repeat the procedure in step 2 on at least 3-4 different positions on the inboard mounting surface.

   If you can rock the straight edge, the mounting surface is bent and you must replace the wheel.

4. Inspect the mounting wheel/nut holes for damage caused from over-torquing the wheel/nuts. Inspect for collapsed wheel/nut bosses. Inspect for cracked wheel bosses.
Fig 2: Inspecting Wheel Inboard Mounting Surface
Courtesy of GENERAL MOTORS CORP.
5. For steel wheels, repeat the procedure in step 2 on at least 3-4 different positions on the inboard mounting surface.
   • The outer mounting ring is designed to be raised slightly above the inner mounting ring.
   • If you can rock the straight edge, the mounting surface is bent and you must replace the wheel.
Fig 3: Inspecting Mounting Wheel/Nut Holes For Damage
Courtesy of GENERAL MOTORS CORP.
6. Inspect the mounting wheel/nut holes for damage caused from over-torquing the wheel/nuts. Inspect for collapsed wheel/nut bosses. Inspect for cracked wheel bosses.
NOTE: The use of non-GM original equipment wheels may cause:
• Damage to the wheel bearing, the wheel fasteners and the wheel
• Tire damage caused by the modified clearance to the adjacent vehicle components
• Adverse vehicle steering stability caused by the modified scrub radius
• Damage to the vehicle caused by the modified ground clearance
• Speedometer and odometer inaccuracy
IMPORTANT:
• Replacement wheels must be equivalent to the original equipment wheels in the following ways:
  • The load capacity
  • The wheel diameter
  • The rim width
  • The wheel offset
  • The mounting configuration
• A wheel of the incorrect size or type may affect the following conditions:
  • Wheel and hub-bearing life
  • Brake cooling
  • Speedometer/odometer calibration
  • Vehicle ground clearance
  • Tire clearance to the body and the chassis
7. Replace the wheel if the wheel is bent.
8. Replace the wheel if the wheel/nut boss area is cracked.

Identify steel wheels with a 2 or 3-letter code stamped into the rim near the valve stem. Aluminum wheels have the code, the part number, and the manufacturer identification cast into the back side of the wheel.