METRIC WHEELNUT FASTNERS INFORMATION

TO: ALL CHEVROLET DEALERS

CAUTION:

Many Chevrolet passenger vehicles use metric wheel nuts and studs. These are not interchangeable with customary (inch) wheel nuts and studs. If one (1) is forced as replacement for the other, damage to stud/nut threads will occur, which could allow wheel to come off while vehicle is moving, possibly causing loss of control, personal injury, and property damage. .

With exception of Chevette, metric wheel studs will have the letter "M" stamped into threaded end and the word "metric" on head (see Figure 1).

Metric wheel nuts are blue in color and have the word "metric" stamped into their face, with these exceptions:

o Early model year Chevettes.

9 Capped or chrome styled nuts.

All metric wheel nuts on Chevrolet passenger vehicles have a thread size of M12xl.5 and require a 19mm (or 3/4 inch) socket. Customary (inch) wheel nuts can have a thread size of either 7/16-20 or 1/2-20, requiring a 3/4 inch (or 19mm) socket or a 13/16 inch socket, respectively.

The following chart shows Chevrolet's conversion to metric wheel nuts by carline:

WHEEL NUT THREADS

Model Year

Carline 1976 1977 1978 1979 1980 1981 1982

Impala, Caprice, Corvette I I I I I I I Camaro I I I I I I M*

Monza I I I I I -

Malibu, Monte Carlo I I I I I I M*

Cavalier, Celebrity - - - - - - M*

Nova I I I I - - Citation - - - - m m M* Chevette m m m m m m M*

I = Customary (Inch) Wheel Nut Threads M = Metric Wheel Nut Threads

See Aluminum Wheel Section

ALUMINUM WHEELS

On Chevrolet's passenger vehicles with original equipment aluminum wheels, special styled wheel nuts are used. All models prior to 1982 used a solid chrome flanged nut (Figure 2). During that period, the nut could have had either metric or customary (inch) threads, depending on its model usage. Beginning with those 1982 models marked with an asterisk (*) in the chart, metric thread capped conical nuts are used (Figure 2). The 1982 Corvette continues to use customary (inch) chrome flanged nuts.

CAUTION:

To reduce the risk of a wheel coming off while vehicle is moving, possibly causing loss of control, personal injury and property damage, do not use a flanged nut in place of a conical nut or a conical nut in place of a flanged nut. Contact surfaces on the wheel are designed differently to accommodate different design nuts (see Figure 2).

Both of the above styled nuts can be used with the steel spare wheel (see Figure 3).

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.