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.

The improper use of impact wrenches on wheel nuts greatly increases the likelihood of pulsation after wheel service.

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 will consistently deliver machined rotors that meet GM specifications (lateral runout less than 0.080 mm (0.003 in) and is the only on-car brake lathe that is currently recommended by GM. The use of this on-car rotor turning technology has proven to significantly reduce the repeat occurrences of brake pulsation.

*We believe this source 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 kilometers (3000-7000 miles) 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:

- 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.

- If the customer had the wheel service done outside of our dealer network. normally GM would not offer 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 ran 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 silicon 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.




Squeak/Squeal Noise

Occurs with front semi-metallic brake pads at medium speeds when light to medium pressure is applied to the brake pedal.

Occasionally a noise may occur on rear brakes during the first few stops or with cold brakes and/or high humidity.

Grinding Noise

Common to rear brakes and some front disc brakes during initial stops after the vehicle has been parked overnight.

Caused by trace corrosion on the metal surfaces during vehicle non-use. Usually disappears after a few stops.

Groan Noise

A small groan may be heard when stopping quickly or moving forward slowly from a complete stop. This is normal.



Brake Wear

Several factors impact brake lining wear and should be taken into account when reviewing related issues. The following are conditions that may accelerate brake lining wear.

- Heavy loads
- High temperatures
- Towing
- Mountainous terrain
- City Driving
- Aggressive driving
- Driver braking characteristics (left foot)

The following are conditions that rnay extend brake lining wear:

- Light loads
- Highway driving
- Conservative driving
- Level terrain

 

Just had to replace two thrashed rotors yesterday. I at 16K went with "lifetime" pads. Big mistake! three years later and two turnings. trashed! pads were still OK, (I am pissed at myself for letting it get this bad). New rotors give the steering that confident heaviness. I went with a slightly thicker, and harder rotor from NAPA. Feels much better than the stock rotor.... then again, I was about .05" past salvageing them. almost 1/4" just gone! I also went back to an organic A/C Delco pad. I'm not too happy about having to change them out every 12-15K, but I'll take that over a shimming steering wheel any day.

 

Hyperv6, So how do you explain my pads being grooved from the rust? Not the rotors, the pads. In your explanation the pads should always remove the rust. Not so! The rust actually ate away the pads and caused groves in the pads. Also, this occurred on all 4 brakes on both sides of the rotors. 8 surfaces in all. So ALL of my brakes were out of whack?

At 40K I put on new rotors with new ceramic pads. 20K later the same rust problems occurred. I sanded off the rust from the old rotors and put on semi-metallics. 30K later there is no rust under the rotors. My problem should have reappeared if everything was out of whack, but it didn't. I only changed the pads and fixed the problem.

 

Rust can and will eat away at metalic pad just as well as ceramic or carbon fibrer.

You fixed your problem but you did it with the work you did to change the pads it was not the pads themselves.

I have seen many times metalic pads do the same thing you blame on the Ceramic pad for.

Believe what you want but find a auto mfg or brake mfg that agrees with you and then you may convince me otherwise.

Rust forms due to poor contact or the lack of contact. Grooves often are done with dirt and debrie or in many cased metal bits in a cheap metalic pad can make some deep grooves.

A metalic pad only has metal bits in a bonding carbon to help absorbe the heat. The metal is a cheap way to remove heat and keep brakes from fading. Today they are using more modern materials for the heat transfer.

Note the real name is semi metalic pads. That is because they are only semi metalic as in bits and pieces. The rest of the material bonding carbon is just to hold it to gether and provide the friction to stop. If it were just a carbon filler the it would heat up faster as the cheaper bonding material has poor heat transfer.

It would really help to see pictures but I understand as I don't take pictures of my brakes either. There are several causes but not being semi metalic pads is not one of them.

I have seen were cheap semi metalic pads have if anything gooved rotors with large chunks of metal. Once the metal bit is gone the goove has no contact and it can rust as nothing is touching it. So in many ways I have also seen semi metalic pads cust similar things.

I still say it is a failure in the system not the materials. You just corrected it witht he act of changing the pads not the pad material.

 

Hunh? All 8 rotor surfaces of my original ceramic brakes go bad with surface rust. All 8 go bad with replacement ceramic pads and new rotors. I clean up and reuse the replacement rotors and put new semi-matallic pads on and the problem dissappears. I have 10K more miles on the semi-metallics than I did on the ceramics before they went bad and the semi's still look great. That is 16 bad surfaces w/ceramics vs. 0 bad w/semis'. It's the act of replacing the pads, not the material? Not a fricken chance.

Look up brake pads on many sites and you will see that the advantages they list for ceramics is that they are low dusting and extremely easy on the rotors. I'm not saying that they don't work great in some applications, but in my application they didn't.

BTW, I did talk to an engineer at Bendix. He said that there are many different formulations of ceramic pads but was not overly surprised at my situation. He suggested a more aggressive semi-metallic pad in my situation
if I was willing to live with more brake dust.

 

I do agree with the different formulas of pads of all types. If you had some crap pads you get crap results no matter the material.

As many here will agree you get what youy pay for most times.

Note EBC used Kevlar in their best pads. Other claim to but up to a short while Dupont only sold to EBC. The funny thing is Dupont is the only offical supplier.

IF pads are made in China or some other 3rd world country the quality can vary. Best to know what you buy. A big brand name is not always the safe way either.

I know with dealing with my one brake supplier he said the rotors are mostly good but if they are wrong no one speaks english all of a sudden.

 

It just strange that it happened with the original Delco pads and Raybestos replacements. I was not impressed with the Raybestos pad as 3 of the 8 pads had seperated from the backing plates after only 20K miles.

I rememeber buying rotors for my wifes Z-24. $10 each to turn them or $16 each new. Yeah, they were from China....

 

I don't know what to tell you as I still think there is an issue in the system somewhere. I it is hard to see over the computer. In all the years I have delt with brakes they clean off no matter what material if they are used. ID not the pad gets ate up in no time. The only real causes I have seen are no contact or where a car or truck sat outside for years and you try to get it going gain. Even then they clean up pretty easy mosty times.

Its sad but almost all rotors are now from China or India. Most are really pretty good but at times there are some spec issues and they get a poor grade of metal. You have a one in 100 shot at a bad one but you just don't know till it is too late. Price often is not a factor. A good known name brand is often the best bet. At least you have someone to hold accountable.

 

Are any rotors made in the USA anymore? if not, anywhere other than China

 

Very few are made here. Like I said before most are China or India.

India is now suppling more and more auto parts.