Brake pad recomendations needed
08-26-2011, 04:06 PM
#31
Senior Member
Join Date: 07-05-2008
Location: Akron Ohio
Posts: 5,464
Yep you too can not properly service the rotors and brakes and complain about no full contact with the rotors with the pads and the inability of not stopping.
The fact is you can change your oil and skip the filter too but that does not mean it is the proper thing to do. In time you will pay for it one way or the other.
Might note he complained of rust on the rotor. Well that is not from ceramic pads!
If you don't service the brakes right you really don't know what you are leaving on the table. I see this all the time when someone buys a Holley or Edelbrock carb. They had a bad one on the car and bolt a new carb on finding a great improvment over what they had. If then they only rejetted or put the proper metering rods in they would be shocked at how much better they would see their car run.
Did they have to rejet? No! but if they did they would enjoy the full benefit of a properly tuned carb and get max power and milege out of it. Same goes for Brakes. If you don't service them right you leave the door open for poorer performance and often future issue that you may not see till a few thousand miles later. The bottom line is they don't tell you to cut or replace your rotors just to sell you new one. They do it to make sure you have a proplerly operating system that is giving all it can give.
Sorry there are short cuts to take but brakes are not one of them for me. I have seen too many cars with poor brakes and I wonder who they may take out someday.
I loved the guy I had once who had the drum worn away till all that was left was the flang between the wheel and axle. His reply was oh that is why it does not stop very good?
The fact is you can change your oil and skip the filter too but that does not mean it is the proper thing to do. In time you will pay for it one way or the other.
Might note he complained of rust on the rotor. Well that is not from ceramic pads!
If you don't service the brakes right you really don't know what you are leaving on the table. I see this all the time when someone buys a Holley or Edelbrock carb. They had a bad one on the car and bolt a new carb on finding a great improvment over what they had. If then they only rejetted or put the proper metering rods in they would be shocked at how much better they would see their car run.
Did they have to rejet? No! but if they did they would enjoy the full benefit of a properly tuned carb and get max power and milege out of it. Same goes for Brakes. If you don't service them right you leave the door open for poorer performance and often future issue that you may not see till a few thousand miles later. The bottom line is they don't tell you to cut or replace your rotors just to sell you new one. They do it to make sure you have a proplerly operating system that is giving all it can give.
Sorry there are short cuts to take but brakes are not one of them for me. I have seen too many cars with poor brakes and I wonder who they may take out someday.
I loved the guy I had once who had the drum worn away till all that was left was the flang between the wheel and axle. His reply was oh that is why it does not stop very good?
Last edited by hyperv6; 08-26-2011 at 07:25 PM.
08-26-2011, 10:15 PM
#32
Senior Member
Join Date: 05-24-2010
Location: SE Wisconsin
Posts: 104
My rusty rotors happened with the original, from the factory equipment on my Envoy at the 40K mark. I bought the truck new. All 4 rotors had rust forming at the inside and outside edges of the pads, about 1/4" inboard of the pads. Pads were only 50% worn.The pads were not agressive enough to remove the rust during braking and the uneven rusty surface caused vibration. I put on "new" rotors and "new" ceramic pads and the same thing happened at the 60K mark. Pads had lots of life left. Pulled the rotors, sanded off the rust, scuffed the rest and put in some good semi-metallic pads. 30K later, it stops better than new and there is no rust under the pads. Maybe someone else can explain why this happened with the ceramics, but not the semi-metallics. Both the factory and my correct replacement brake jobs sucked with ceramics.
08-27-2011, 07:24 AM
#33
Senior Member
Join Date: 07-05-2008
Location: Akron Ohio
Posts: 5,464
Rotors rust unless they are coated. Anyplace where a pad contacts it wears off no matter the material.
If the last set corrected it you either got better alignement with the new parts or the pads had a larger contact area.
The rust would come off no matter if they were organic, metalic, carbon or ceramic. It cleans the surface and no pad is that soft or as you said gental
If the last set corrected it you either got better alignement with the new parts or the pads had a larger contact area.
The rust would come off no matter if they were organic, metalic, carbon or ceramic. It cleans the surface and no pad is that soft or as you said gental
08-27-2011, 08:52 AM
#34
Member
Join Date: 11-16-2008
Location: NJ
Posts: 68
Some rotors, particularly the OEM ones on Trailblazer/envoy and Silverado/sierra are very prone to rust. They seem to rust from the inside out almost, near the edges. The rotors get "soft" in that area and virtually no pad will clean them up once this happens.
I also see the problem of vehicles (usually GM trucks and Wbody cars) when the rust gets so bad there will literally only be a one inch wide section of rotor that has anything resembling a clean braking surface. Its the result of a combination of drivers who are very easy on their brakes, the location of vehicle (snow belt, The shore,) and pads that don't have an aggressive enough bite to properly clean of the levels of corrosion. And debris that can form in these areas in a matter of several hours, combine that with the fact that these "light beakers" also seem to be the people which most readily complain about any brake noise and it becomes a vicious cycle...you can't put on aggressive pads because they complain about the noise, you then put gentle ceramic pads on and they don't clean the rotors properly. Ill have to take pics of some the absolutely horribly rusted rotors that come through my shop, all from people with gentle braking habits and non aggressive pads.
I also see the problem of vehicles (usually GM trucks and Wbody cars) when the rust gets so bad there will literally only be a one inch wide section of rotor that has anything resembling a clean braking surface. Its the result of a combination of drivers who are very easy on their brakes, the location of vehicle (snow belt, The shore,) and pads that don't have an aggressive enough bite to properly clean of the levels of corrosion. And debris that can form in these areas in a matter of several hours, combine that with the fact that these "light beakers" also seem to be the people which most readily complain about any brake noise and it becomes a vicious cycle...you can't put on aggressive pads because they complain about the noise, you then put gentle ceramic pads on and they don't clean the rotors properly. Ill have to take pics of some the absolutely horribly rusted rotors that come through my shop, all from people with gentle braking habits and non aggressive pads.
08-27-2011, 11:57 AM
#35
Senior Member
Join Date: 05-24-2010
Location: SE Wisconsin
Posts: 104
Thanks Maven for backing me up on this one. I'm not a light braker but I do live in WI where we have lot's of salt on the road. Hperv6, I can say without question that the pads did NOT remove the rust on the inside/outside edges of the pads. In fact the rust wore the pads away on those edges, leaving a 1/4" x 1/8" deep groove on the inside/outside edges of the pads. Did it from the factory and with a full set of replacement parts. The semi-metallic pads are more agressive and do not do it. They do not make more noise from what I can tell, just a bit more dust to clean up. This is the only vehicle in my 34 years of driving that has done this. It is also the only one w/ceramic brakes.
Might be the perfect storm in my case.
Might be the perfect storm in my case.
08-27-2011, 09:01 PM
#36
Senior Member
Join Date: 07-05-2008
Location: Akron Ohio
Posts: 5,464
The rotors do not get soft. What happens is the caliper is either not traveling all the way on the mounts or the pad is not making full contact for another reason. I the pad was making contact the rotor would clean no matter what type pad.
GM trucks and the W bodys have had this issues. The older W bodies had major issues on the rear disc. The pins would corrode or the surface of the rear pins would get to the point that they would not let the caliper slide. The piston would still make the front pad contact but the rear pad would never touch. The rotor then would rust as nothing was cleaning it since the pad never made contact. Note this also would make degrade brake performance.
This is not something I made up and GM even had a TSB out for new pins that would correct the problem. I had a 1990 GP that had this issues. My buddy who was in a GM service department told me what I needed and gave me the TSB years ago.
It is plan and simple if the pad touches the rotor no rust if it is not making contact something is holding the pad off or misaligned to not clean the rotor off.
Any pad no matter the material will clean a rotor of. It is like a lathe and takes a little of the rotor surface every time the brakes are used if it comes in contact.
Another cause is a damaged rotor where the metal has been damage due to cracks or debri that may have gotten under the pad.
Metalic linings are ok but they are not the best anymore. They are like carburators vs Fuel Injection, they get the job done but just not state of the art.
Installed properly any brake pad will function properly. If there is an issue this rust issue will happen anyways. Odds are you corrected the issue when you change the pads and installed the new pads. It was your work that fixed it not the pads.
GM has had a history of caliper and mount issues that have cause issues on many trucks and cars. The Envoy, Trailblazer and W bodies are not the only ones.
Note GM was blaming acid rain for some of the issues but I think it was mostly bad caliper pins or mounts. Once they were replaced that fixed it.
GM trucks and the W bodys have had this issues. The older W bodies had major issues on the rear disc. The pins would corrode or the surface of the rear pins would get to the point that they would not let the caliper slide. The piston would still make the front pad contact but the rear pad would never touch. The rotor then would rust as nothing was cleaning it since the pad never made contact. Note this also would make degrade brake performance.
This is not something I made up and GM even had a TSB out for new pins that would correct the problem. I had a 1990 GP that had this issues. My buddy who was in a GM service department told me what I needed and gave me the TSB years ago.
It is plan and simple if the pad touches the rotor no rust if it is not making contact something is holding the pad off or misaligned to not clean the rotor off.
Any pad no matter the material will clean a rotor of. It is like a lathe and takes a little of the rotor surface every time the brakes are used if it comes in contact.
Another cause is a damaged rotor where the metal has been damage due to cracks or debri that may have gotten under the pad.
Metalic linings are ok but they are not the best anymore. They are like carburators vs Fuel Injection, they get the job done but just not state of the art.
Installed properly any brake pad will function properly. If there is an issue this rust issue will happen anyways. Odds are you corrected the issue when you change the pads and installed the new pads. It was your work that fixed it not the pads.
GM has had a history of caliper and mount issues that have cause issues on many trucks and cars. The Envoy, Trailblazer and W bodies are not the only ones.
Note GM was blaming acid rain for some of the issues but I think it was mostly bad caliper pins or mounts. Once they were replaced that fixed it.
08-27-2011, 09:47 PM
#37
Senior Member
Join Date: 07-19-2008
Location: Somewhere
Posts: 183
As Hyper said - turning or new rotors should be considered a must with a new set of pads.
08-27-2011, 10:45 PM
#38
Member
Join Date: 11-16-2008
Location: NJ
Posts: 68
The rotors do not get soft. What happens is the caliper is either not traveling all the way on the mounts or the pad is not making full contact for another reason. I the pad was making contact the rotor would clean no matter what type pad.
GM trucks and the W bodys have had this issues. The older W bodies had major issues on the rear disc. The pins would corrode or the surface of the rear pins would get to the point that they would not let the caliper slide. The piston would still make the front pad contact but the rear pad would never touch. The rotor then would rust as nothing was cleaning it since the pad never made contact. Note this also would make degrade brake performance.
This is not something I made up and GM even had a TSB out for new pins that would correct the problem. I had a 1990 GP that had this issues. My buddy who was in a GM service department told me what I needed and gave me the TSB years ago.
It is plan and simple if the pad touches the rotor no rust if it is not making contact something is holding the pad off or misaligned to not clean the rotor off.
Any pad no matter the material will clean a rotor of. It is like a lathe and takes a little of the rotor surface every time the brakes are used if it comes in contact.
Another cause is a damaged rotor where the metal has been damage due to cracks or debri that may have gotten under the pad.
Metalic linings are ok but they are not the best anymore. They are like carburators vs Fuel Injection, they get the job done but just not state of the art.
Installed properly any brake pad will function properly. If there is an issue this rust issue will happen anyways. Odds are you corrected the issue when you change the pads and installed the new pads. It was your work that fixed it not the pads.
GM has had a history of caliper and mount issues that have cause issues on many trucks and cars. The Envoy, Trailblazer and W bodies are not the only ones.
Note GM was blaming acid rain for some of the issues but I think it was mostly bad caliper pins or mounts. Once they were replaced that fixed it.
GM trucks and the W bodys have had this issues. The older W bodies had major issues on the rear disc. The pins would corrode or the surface of the rear pins would get to the point that they would not let the caliper slide. The piston would still make the front pad contact but the rear pad would never touch. The rotor then would rust as nothing was cleaning it since the pad never made contact. Note this also would make degrade brake performance.
This is not something I made up and GM even had a TSB out for new pins that would correct the problem. I had a 1990 GP that had this issues. My buddy who was in a GM service department told me what I needed and gave me the TSB years ago.
It is plan and simple if the pad touches the rotor no rust if it is not making contact something is holding the pad off or misaligned to not clean the rotor off.
Any pad no matter the material will clean a rotor of. It is like a lathe and takes a little of the rotor surface every time the brakes are used if it comes in contact.
Another cause is a damaged rotor where the metal has been damage due to cracks or debri that may have gotten under the pad.
Metalic linings are ok but they are not the best anymore. They are like carburators vs Fuel Injection, they get the job done but just not state of the art.
Installed properly any brake pad will function properly. If there is an issue this rust issue will happen anyways. Odds are you corrected the issue when you change the pads and installed the new pads. It was your work that fixed it not the pads.
GM has had a history of caliper and mount issues that have cause issues on many trucks and cars. The Envoy, Trailblazer and W bodies are not the only ones.
Note GM was blaming acid rain for some of the issues but I think it was mostly bad caliper pins or mounts. Once they were replaced that fixed it.
You are 100% correct regarding the pin and caliper movement freedom issues, HOWEVER, this is not the only cause of the pads not cleaning the rotors. If every pad that didnt clean a rotor was due to caliper/pin stickage then you would never see the issues where the only braking surface is down the center of the pad.....how can a pad not apply pressure on the inner and outer edges but still apply it in the center?
Unless youre going to tell us that pads wearing with no discernible taper or wedge is due to some pad defect, and that taper and wedge are related to improper caliper movement/clamping, now you have effectively ruled out the environment as a possible cause of brake issues. Unfortunately this just isnt way things work. Corrosion does in fact cause brake concerns, it isnt merely a side effect of an improperly functioning friction/disc interface.
Also the rotors due in fact get soft/spongy from the corrosion, once the corrosion grabs hold it turns the iron into iron oxide........ iron oxide is bigger than iron.......it takes up more space but with the same amount of iron.....this means more space between the iron because of the oxygen....see where I am going here?.......
08-28-2011, 07:20 AM
#39
Senior Member
Join Date: 07-05-2008
Location: Akron Ohio
Posts: 5,464
If the pads always cleaned off the rust no matter what like they were a lathe, then there would never be rusted sections of rotor. But this isnt the case, corrosion occurs even from a simple overnight rest and the brake pads simply can not clean it all off. and the rust propagates
You are 100% correct regarding the pin and caliper movement freedom issues, HOWEVER, this is not the only cause of the pads not cleaning the rotors. If every pad that didnt clean a rotor was due to caliper/pin stickage then you would never see the issues where the only braking surface is down the center of the pad.....how can a pad not apply pressure on the inner and outer edges but still apply it in the center?
Unless youre going to tell us that pads wearing with no discernible taper or wedge is due to some pad defect, and that taper and wedge are related to improper caliper movement/clamping, now you have effectively ruled out the environment as a possible cause of brake issues. Unfortunately this just isnt way things work. Corrosion does in fact cause brake concerns, it isnt merely a side effect of an improperly functioning friction/disc interface.
Also the rotors due in fact get soft/spongy from the corrosion, once the corrosion grabs hold it turns the iron into iron oxide........ iron oxide is bigger than iron.......it takes up more space but with the same amount of iron.....this means more space between the iron because of the oxygen....see where I am going here?.......
You are 100% correct regarding the pin and caliper movement freedom issues, HOWEVER, this is not the only cause of the pads not cleaning the rotors. If every pad that didnt clean a rotor was due to caliper/pin stickage then you would never see the issues where the only braking surface is down the center of the pad.....how can a pad not apply pressure on the inner and outer edges but still apply it in the center?
Unless youre going to tell us that pads wearing with no discernible taper or wedge is due to some pad defect, and that taper and wedge are related to improper caliper movement/clamping, now you have effectively ruled out the environment as a possible cause of brake issues. Unfortunately this just isnt way things work. Corrosion does in fact cause brake concerns, it isnt merely a side effect of an improperly functioning friction/disc interface.
Also the rotors due in fact get soft/spongy from the corrosion, once the corrosion grabs hold it turns the iron into iron oxide........ iron oxide is bigger than iron.......it takes up more space but with the same amount of iron.....this means more space between the iron because of the oxygen....see where I am going here?.......
Nearly every rotor get surface rust over night or after a wash. that is nothing new or uncommon. As long as the pad makes contact it will clean it off at the first stop. If that area is not making poper contact nothing will clean it off and the rust will build.
Pans can wear at odd angle etc due to the caliper not functioning properly. The piston can push the pad but **** a floating caliper into odd angles and wear pads on even. The can also wear out one side and leave the other pad not even making contact or little contact as in the case of the W cars.
I get calls all the time just from people upset that the Cadium or anodized surface of their rotors get wiped off in the first few stops no matter the pad material.
So if you don't believe two litle pads in full contact with a rotor can not clean a rotor brake surface. The heat and pressures of any car on such a small abrasive pad surface will wipe about anything out including rust.
But believe as you like.
08-28-2011, 07:32 AM
#40
Senior Member
Join Date: 07-05-2008
Location: Akron Ohio
Posts: 5,464
Here is one of the items I have found from my GM files that applies to the older truck issue. It also applies to many of todays issues on the new cars. Things have really not changed much over the years with regular brakes systems. Now with the many new multi piston calipers and ceramic rotors it is a whole different ball game. This is a nice guide to help fix several common issues.
Too few really understand what all is involved there is much more to brakes than just changing pads. Modern cars are a little more sensitive than the older cars and you need to follow proper direction to have long term trouble free brakes. I can rember you were lucky to get 25K-30K Miles out of front disc pads.
Today My GTP will wear the front and rear even to going on 70K miles with mostly city driving. I really love the new Bosch electric proportioning system on that car. More should have it.
Anyways here is some good basic principals for brakes that apply to most models and makes not just GM trucks.
General Motors Service Bulletin Warranty Administration
File In Section: 05 - Brakes
Bulletin No.: 00-05-22-002
Date: February, 2000
Brake Rotor Warranty Service Procedure
Models: 1995-2000 Passenger Cars and Light Duty Trucks
This bulletin outlines GM's standard procedures and guidelines for brake rotor service and brake wear.
Important: Certain conditions may apply to individual vehicles regarding specific repairs which differ from those outlined in this bulletin. Refer to those specific repairs in applicable bulletins.
Original equipment rotor surfaces are ground to ensure smooth finish and parallelism between mounting and friction surfaces. New rotors SHOULD NOT be resurfaced before installation. When rotor turning is necessary, it is essential that you use a high quality brake lathe. Rotors, when remounted on the hub, should have less than 0.080 mm (0.003 in) lateral runout. Brake rotors should only be turned when one of the following rotor surface conditions exist:
1. Severe scoring - depth in excess of 1.5 mm (0.060 in).
2. Pulsation concerns from:
* Lateral runout in excess of 0.080mm (0.003 in).
* Thickness variation in excess of 0.025 mm (0.001 in).
* Excessive corrosion on rotor braking surfaces.
Rotors are not to be resurfaced in an attempt to correct the following conditions:
Noise/squeal
Cosmetic corrosion
Routine pad replacement
Discoloration/hard spots
Explanation of Brake Rotor Warranty Service Procedure
Rotor refacing during normal pad replacement is not necessary.
Rotor refacing for cosmetic corrosion is unnecessary. Clean up of braking surfaces can be accomplished by 10-15 moderate stops from 62-75 km/h (35-40 mph) with cooling time between stops.
Rotor service is ineffective in correcting brake squeal and/or premature lining wear out and should not be used to address these conditions unless specifically directed by a service bulletin.
When installing new rotors, DO NOT reface them. If a new rotor has more than 0.080 mm (0.003 in) lateral runout when properly mounted on the hub, it may be machined using an approved on-car lathe. Ensure bearing flanges and rotor mounting surfaces are free of corrosion when installing rotors to prevent inducing lateral runout. Use Kent Moore tool J-42450A to clean the corrosion around the wheel studs.
Always mark the position of the rotor on the hub before removal and reinstall the rotor in the same position. Rotors with perceived hard spots or discoloration should not be serviced. These conditions are normal. Installation of new rotors does not require pad replacement. Do not replace pads unless their condition requires it. It is not necessary to replace rotors in pairs. Rotors may be replaced individually. However, caution should be exercised, as a variance in surface finish may cause a brake pull condition.
A torque limiting socket or torque wrench must be used to insure that the wheel nuts are tightened to specification. This should be done In 3 steps using the star pattern:
1. Hand tighten all 5 lug nuts using the star pattern.
2. Tighten all 5 nuts to approximately 1/2 spec. using the star pattern.
3. Tighten all 5 nuts to full spec. using the star pattern.
Never use lubricants or penetrating fluids on wheel studs, nuts or mounting surfaces. Wheel nuts, studs, and mounting surfaces must be clean and dry.
Brake Service Techniques
1. Clean and lubricate all rnetal-to-metal contact points (i.e. caliper to knuckle, pad to knuckle, etc).
2. Clean and lubricate slide pins, if applicable.
3. Set correct clearances (i.e. caliper to knuckle, etc), if applicable.
4. Clean rotor and hub mounting surfaces. Use Kent Moore tool J-42450 to clean around the wheel studs.
5. Verify lateral runout of the rotor with a dial indicator (rotor held on hub with 3 or more wheel nuts and washers).
Important: Refer to the appropriate Service Manual for more specific procedures-
Pulsation
Important: Brake pulsation is often caused by factors outside customer control. In these instances, the repair is covered under the GM New Vehicle Warranty. Brake pulsation concerns may result from two basic conditions:
Pulsation is caused by brake rotor thickness variation. Thickness variation causes the piston in the brake caliper to "pump" in and out of the caliper housing. This "pumping" effect is transmitted hydraulically to the brake pedal. 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 0.080mm (0.003 in). Pulsation that is the result of excessive lateral runout usually develops in 4800 -11300 kilometers (3000 -7000 miles). 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 kilometers (3000-7000 miles) 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.
Too few really understand what all is involved there is much more to brakes than just changing pads. Modern cars are a little more sensitive than the older cars and you need to follow proper direction to have long term trouble free brakes. I can rember you were lucky to get 25K-30K Miles out of front disc pads.
Today My GTP will wear the front and rear even to going on 70K miles with mostly city driving. I really love the new Bosch electric proportioning system on that car. More should have it.
Anyways here is some good basic principals for brakes that apply to most models and makes not just GM trucks.
General Motors Service Bulletin Warranty Administration
File In Section: 05 - Brakes
Bulletin No.: 00-05-22-002
Date: February, 2000
Brake Rotor Warranty Service Procedure
Models: 1995-2000 Passenger Cars and Light Duty Trucks
This bulletin outlines GM's standard procedures and guidelines for brake rotor service and brake wear.
Important: Certain conditions may apply to individual vehicles regarding specific repairs which differ from those outlined in this bulletin. Refer to those specific repairs in applicable bulletins.
Original equipment rotor surfaces are ground to ensure smooth finish and parallelism between mounting and friction surfaces. New rotors SHOULD NOT be resurfaced before installation. When rotor turning is necessary, it is essential that you use a high quality brake lathe. Rotors, when remounted on the hub, should have less than 0.080 mm (0.003 in) lateral runout. Brake rotors should only be turned when one of the following rotor surface conditions exist:
1. Severe scoring - depth in excess of 1.5 mm (0.060 in).
2. Pulsation concerns from:
* Lateral runout in excess of 0.080mm (0.003 in).
* Thickness variation in excess of 0.025 mm (0.001 in).
* Excessive corrosion on rotor braking surfaces.
Rotors are not to be resurfaced in an attempt to correct the following conditions:
Noise/squeal
Cosmetic corrosion
Routine pad replacement
Discoloration/hard spots
Explanation of Brake Rotor Warranty Service Procedure
Rotor refacing during normal pad replacement is not necessary.
Rotor refacing for cosmetic corrosion is unnecessary. Clean up of braking surfaces can be accomplished by 10-15 moderate stops from 62-75 km/h (35-40 mph) with cooling time between stops.
Rotor service is ineffective in correcting brake squeal and/or premature lining wear out and should not be used to address these conditions unless specifically directed by a service bulletin.
When installing new rotors, DO NOT reface them. If a new rotor has more than 0.080 mm (0.003 in) lateral runout when properly mounted on the hub, it may be machined using an approved on-car lathe. Ensure bearing flanges and rotor mounting surfaces are free of corrosion when installing rotors to prevent inducing lateral runout. Use Kent Moore tool J-42450A to clean the corrosion around the wheel studs.
Always mark the position of the rotor on the hub before removal and reinstall the rotor in the same position. Rotors with perceived hard spots or discoloration should not be serviced. These conditions are normal. Installation of new rotors does not require pad replacement. Do not replace pads unless their condition requires it. It is not necessary to replace rotors in pairs. Rotors may be replaced individually. However, caution should be exercised, as a variance in surface finish may cause a brake pull condition.
A torque limiting socket or torque wrench must be used to insure that the wheel nuts are tightened to specification. This should be done In 3 steps using the star pattern:
1. Hand tighten all 5 lug nuts using the star pattern.
2. Tighten all 5 nuts to approximately 1/2 spec. using the star pattern.
3. Tighten all 5 nuts to full spec. using the star pattern.
Never use lubricants or penetrating fluids on wheel studs, nuts or mounting surfaces. Wheel nuts, studs, and mounting surfaces must be clean and dry.
Brake Service Techniques
1. Clean and lubricate all rnetal-to-metal contact points (i.e. caliper to knuckle, pad to knuckle, etc).
2. Clean and lubricate slide pins, if applicable.
3. Set correct clearances (i.e. caliper to knuckle, etc), if applicable.
4. Clean rotor and hub mounting surfaces. Use Kent Moore tool J-42450 to clean around the wheel studs.
5. Verify lateral runout of the rotor with a dial indicator (rotor held on hub with 3 or more wheel nuts and washers).
Important: Refer to the appropriate Service Manual for more specific procedures-
Pulsation
Important: Brake pulsation is often caused by factors outside customer control. In these instances, the repair is covered under the GM New Vehicle Warranty. Brake pulsation concerns may result from two basic conditions:
Pulsation is caused by brake rotor thickness variation. Thickness variation causes the piston in the brake caliper to "pump" in and out of the caliper housing. This "pumping" effect is transmitted hydraulically to the brake pedal. 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 0.080mm (0.003 in). Pulsation that is the result of excessive lateral runout usually develops in 4800 -11300 kilometers (3000 -7000 miles). 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 kilometers (3000-7000 miles) 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.
Last edited by hyperv6; 08-28-2011 at 10:21 AM.