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TSB 98-5A-4 Brake Vibration / Lug Nut Torque

ISSUE: The use of air impact tools to tighten wheel lug nuts can lead to overtightened and/or unevenly tightened wheel lug nuts. Air impact tools typically used for wheel lug nut removal and installation can generate up to 475 N-m (350 lb-ft) of torque. Overtightened and/or unevenly torqued wheel lug nuts may cause:
> Brake vibration
> Distortion of the wheel hub
> Distortion of the brake rotor
> Brake rotor runout
> Damage to the wheel
> Damage to the wheel nuts and studs

ACTION: All wheel lug nuts should only be tightened to specification using a torque wrench or by using the Rotunda ACCUTORQ 164-R0314 or equivalent on a 1/2" drive air impact tool. The "ACCUTORQ" lug nut sockets limit the torque of the air impact tool, preventing overtightening or uneven tightening of the wheel lug nuts. The torque limiting devices (regulators) on air impact tools will not reduce the output torque enough to prevent overtightening of the wheel lug nuts.

NOTE: REFER TO THE APPROPRIATE SERVICE MANUAL OR THE CHART IN «FIGURE 1» FOR THE CORRECT WHEEL LUG NUT TORQUE SPECIFICATION. THE CHART IN «FIGURE 1» ALSO PROVIDES THE CORRECT "ACCUTORQ" LUG NUT SOCKET TO USE.

The "ACCUTORQ" socket is intended for lug nut installation, not removal. When using the "ACCUTORQ" socket, the output torque of the air impact tool must be set to 217-339 N-m (160-250 lb-ft), usually this will be the lowest setting on the air impact tool.

The "ACCUTORQ" lug nut sockets are available through Rotunda Equipment. The four-piece set (164-R0314) fits most Ford Motor Company cars and light trucks. The tool set consists of four (4) lug nut sockets and a storage case. The set can be ordered by calling Rotunda Equipment at 1-800-ROT-UNDA (768-8632).

CAUTION: AIR IMPACT TOOLS SHOULD NOT BE USED TO TIGHTEN WHEEL LUG NUTS UNLESS THE "ACCUTORQ" LUG NUT SOCKET OF THE CORRECT SPECIFICATION IS USED.

NOTE: DO NOT USE AIR IMPACT TOOLS ON LOCKING WHEEL LUG NUTS. THEY ARE TO BE HAND-TORQUED ONLY.

OTHER APPLICABLE ARTICLES: NONE
SUPERSEDES: 97-17-6
WARRANTY STATUS: INFORMATION ONLY
OASIS CODES: 301000, 303000, 306000