Tahoe 4WD V8-393 6.5L DSL Turbo VIN S (1995)
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Thickness variation on a new rotor will be virtually undetectable. But if the rotor (as installed on the vehicle) has lateral runout, it is likely that
thickness variation will develop. Pulsation caused by thickness variation will develop on new vehicles when the tolerances of the hub and rotor
stack up with lateral runout in excess of .055 mm (.002 in). Pulsation that is the result of excessive lateral runout usually develops in
4800-11300 km (3000-7000 mi).
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Thickness variation can be induced when uneven torque is applied to wheel nuts (lug nuts). Improper wheel tightening after tire rotation, spare
tire usage, brake inspection, etc. can be the cause of pulsation. Again, it usually takes 4800-11300 km (3000-7000 mi) after this event for the
condition to surface. The owner or driver does not usually make the connection between the service event and the awareness of the pulsation.
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The proper usage of torque wrenches and/or torque sticks (torque limiting sockets) will greatly reduce or eliminate the pulsation conditions
after wheel service events.
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The improper use of impact wrenches on wheel nuts greatly increases the likelihood of pulsation after wheel service.
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GM highly recommends the use of on-car brake rotor turning as a method of eliminating the stack up of lateral runout which is a potential
source of brake pulsation. GM has identified superior equipment through testing and evaluation. The *Pro-Cut PFM900 or Hunter 0CL360
will consistently deliver machined rotors that meet GM specifications (lateral runout less than .055 mm (.002 in) and are the only on-car brake
lathes that are currently recommended by GM. The use of this on-car rotor turning technology has proven to significantly reduce the repeat
occurrences of brake pulsation. If on-car brake rotor turning equipment is not available, refer to Corporate Bulletin Number 01-05-23-001A
for brake rotor lateral runout correction procedure.
*
We believe these sources and their equipment to be reliable. There may be additional manufacturers of such equipment. General Motors does
not endorse, indicate any preference for or assume any responsibility for the equipment from this firm or for any such items which may be
available from other sources.
The following are examples of pulsation conditions and reimbursement recommendations:
1. If a customer noticed the condition after 4800-11300 km (3000-7000 mi) and it gradually got worse, normally the repair would be covered. The
customer may tolerate the condition until it becomes very apparent.
2. If a customer indicated they had wheel service, ask who performed the service. Then:
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If a dealer performed the service, consider paying for the repair and then strongly reinforce the use of torque sticks at that dealer. Two common
size torque sticks cover 90% of all GM products. Each technician needs to use torque sticks properly every time the wheel nuts are tightened.
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If the customer had the wheel service done outside of our dealer network, normally GM would not otter any assistance.
Customer assistance concerning brake pulsation and brake wear should always take into account the individual circumstances on a case by case basis.
The recommendations mentioned previously should only be used as a general guide. REMEMBER THAT CUSTOMER SATISFACTION IS
CRITICAL TO GM AND THAT OFTEN IT IS IN GM'S BEST INTEREST TO SATISFY AND EDUCATE THE CUSTOMER CONCERNING
FUTURE BRAKE SERVICE.
ROTOR GROOVING
Excessive grooving can be caused by foreign material in contact with the rotor, but most often rotor grooving is the result of normal brake wear. Do
not resurface rotors for light grooving. Resurface rotors only when grooves of 1.5 mm (0.060 in) or deeper are present. A dime may be used to
determine disc brake groove depth. Place a dime in the groove, with Roosevelt's head toward the groove. If the dime goes into the groove beyond the
top of his head, the groove exceeds 1.5 mm (0.060 in) and the rotor should be serviced. In Canada, if any portion of the letters of "Canada" are
covered, the rotor should be serviced. If the groove is too narrow for the dime to be inserted, it is not a cause for concern.
HIGH PEDAL EFFORT
Follow the Service Manual diagnostic procedures for this condition. Service (replace or resurface) rotors if they have been recently resurfaced. The
surface finish may be out-of-specification.
LIGHTLY RUSTED ROTORS
Light surface rust on rotor braking surfaces is often cosmetic and can be eliminated during a few normal driving stops. Rusting may occur when a
vehicle is not driven for extended periods. Rotors with surface rust on unsold new cars can usually be burnished clean by performing 15 moderate
stops from 62-75 km/h (35-40 mph) with cooling time between stops.
FACTS ABOUT BRAKE NOISE
Brake noise is normal and differences in loading, type of driving, or driving style can make a difference in brake wear on the same make and model.
Depending on weather conditions, driving patterns and the local environment, brake noise may become more or less apparent.
Brake noise is caused by a "slip stick" vibration of brake components. While intermittent brake noise may be normal, performing 3-4 aggressive stops
may temporarily reduce or eliminate most brake squeal.
If the noise persists, a brake dampening compound may be applied to the back of each pad. Use Permatex Disc Brake Quiet # 126hb, or equivalent.
Also, clean and lubricate all metal-to-metal contact areas between pads, pad guides, caliper and knuckles with a thin layer of high temperature silicone
grease. This allows parts to slide freely and not vibrate when moving relative to each other.
The following noises are characteristic of all braking systems and are unavoidable. They may not indicate improper operation of the brake system.
