True cause of brake pulsation!

[NorthstarAJ]

This will bee a long thread and I have a Lot of info on it.

Brake pulsations are caused by Lateral run-out not a warped rotor. If your caliper can slide you will never feel a warped rotor.

Lateral Run-out: Hmmm

This is a Big deal at GM currently

I will start with another website. I will need some time compiling data.

This is not the same video. Hmmmm. I will have to down load it from my Tivo

Fro now http://www.brakealign.com/pages/diagram.htm

[BodybyFisher]

I know we have been through this topic here also, I would say its as passionate a subject as oil is here.

http://caddyinfo.ipbhost.com/index.php?sho...thick+variation

Stoptech has some interesting white papers on rotors, pulsing, lateral runout and my favorite thickness variation and material transfer.

http://www.stoptech.com/tech_info/tech_white_papers.shtml

[bowtie123]

Heres a interesting article on warped rotors.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

[BodybyFisher]

Heres a interesting article on warped rotors.

<a href="http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml" target="_blank">http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml</a>

I know I love that article..that is the article where they say that rotors dont warp, that its a wrong term that the shutter is caused by brake material transfer that causes thickness variation.

[NorthstarAJ]

Heres a interesting article on warped rotors.

<a href="http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml" target="_blank">http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml</a>

I know I love that article..that is the article where they say that rotors dont warp, that its a wrong term that the shutter is caused by brake material transfer that causes thickness variation.

On a normal production car we see that the thickness variance becomes to great do to Lateral run-out and corrosion.

[growe3]

Regarding the break-in procedure stated in the Stop Tech article, I must disagree.

I have replaced many disc and drum brakes on my own vehicles, friends vehicles, and when I used to do shop work. Harsh break-ins have never been necessary, and often caused vibrations. The only way I found to fix them after this, was to resurface the rotors or drums. I didn't realize it at the time (many years ago), but I was removing the uneven pad or shoe deposits.

I normally use Raybestos or Bendix, street, high performance replacement parts.

On one of my STS's I followed the Stop Tech method of break-in. While all seemed well at first, I noticed that after a few days I could feel some vibrations that shouldn't be there when braking. It got worse during the next month, and I finally took the rotors off, had them resurfaced (just enough to get back to clean metal), and broke them in again as directed in the Cadillac manual. No more vibrations. I have since done several other vehicles in the same manner with great results. I doubt that you really need a "break-in" anymore. Most people will break them in, with normal stop and go driving.

Please note that I speak from experience on high performance, and stock "street" vehicles, full race vehicles are a different ball game. Full race brakes do not belong on the street, they will never stay hot long enough to work properly. Semi-metallics and ceramics designed for the street, are the best all around choice; in my opinion.

See attached Burnishing instructions from my 93 Cadillac Seville/El Dorado manual, it is the same procedure in my 04 Cadillac Deville manuals. I have noted similar procedures in many other OEM manuals.

Please see attached image of Brake Burnishing procedure (sorry for the 64k image quality).

-George

[BodybyFisher]

Its funny you say this, because I have never done any special breakin process, I am just careful not to do any panic stops for the first ride I take and then come home and let it cool.

The guru described a more aggressive break in procedure than described in your manual, similar to the stoptech procedure. I recall 10 hard stops in a row just short of lock up from about 50 down to a rolling stop without letting the pads sit in one spot on the rotor, then let it cool.

[BodybyFisher]

Double Post< can prune

[bowtie123]

I brought a new Corvette in 1965.

I believe this was the first year of a successful

four wheel disc brake system on a standard production car.

14 years later, when I sold the car with 217,000 miles on it,

it still had the original rear pads and all four original rotors,

which had never been turned.

I never had any pulsation problems with these brakes.

Whats the difference with todays systems that start to create

pulsation after 15,000 miles?

I had a '89 Fleetwood coupe that still had drum brakes on the rear.

Amazing after 24 years, and on a Fleetwood no less.

[BodybyFisher]

I brought a new Corvette in 1965.

I believe this was the first year of a successful

four wheel disc brake system on a standard production car.

14 years later, when I sold the car with 217,000 miles on it,

it still had the original rear pads and all four original rotors,

which had never been turned.

I never had any pulsation problems with these brakes.

Whats the difference with todays systems that start to create

pulsation after 15,000 miles?

I had a '89 Fleetwood coupe that still had drum brakes on the rear.

Amazing after 24 years, and on a Fleetwood no less.

This is so true. Those rotors looked tempered and they were heavy. These rotors look un-tempered and they just wear. Throw aways as has been said. I am thinking of trying drilled rotors to see if I can improve the breaking system on this car.. I think they went to a bigger rotor after my year, but I always forget what the change was.

[growe3]

Its funny you say this, because I have never done any special breakin process, I am just careful not to do any panic stops for the first ride I take and then come home and let it cool.

The guru described a more aggressive break in procedure than described in your manual, similar to the stoptech procedure. I recall 10 hard stops in a row just short of lock up from about 50 down to a rolling stop without letting the pads sit in one spot on the rotor, then let it cool.

Hmm..don't quite what no what you mean by "Its funny you say this...." Your description of just drive after you put them on is probably fine, that is pretty much what I have come to do.

I have a lot of respect for the Guru, and the information that he shared with us, but in this particular case, I will have to go with my experiance, and the OEM reccommendations; they are working very well for me.

-George

[BodybyFisher]

I am sorry for not being clear, when i say its funny you say this, its because, I don't believe it any special aggressive burnishing either. I have found that when I have a pulsing, doing an aggressive burnishing only makes it worse.

[Ranger]

I must confess, that of all the brake jobs I have done, I do not burnish or break them in either.

[wiz6728]

me i just put them on make sure the rears r adjusted (if drum)& drive & just take it easy for the first 100 mile

[coolnesss]

I brought a new Corvette in 1965.

I believe this was the first year of a successful

four wheel disc brake system on a standard production car.

14 years later, when I sold the car with 217,000 miles on it,

it still had the original rear pads and all four original rotors,

which had never been turned.

I never had any pulsation problems with these brakes.

That just is because you were driving it correctly - 'Vettes were best when accelerating, not while braking. Kudos!

[NorthstarAJ]

Part 1 -- Background, Measuring, and Cleaning

Earlier this year, bulletin 00-05-22-002D was released for the purpose of updating and centralizing all of GM’s standard brake service procedures and policy guidelines for brake rotor and brake pad service and wear (fig. 1). If you haven’t already done so, refer to this bulletin before performing your next GM brake service.

Over the next few months, TechLink will provide several brake articles featuring information from this bulletin, and in some cases expanding on it. You must observe the practices contained in the bulletin and in SI.

WHAT CONSTITUTES A SUCCESSFUL BRAKE SERVICE?

Five steps must be performed to complete a successful brake service.

1. Measure and document rotor thickness -- specifications in SI

2. Clean hub, rotor and wheel mating surfaces

3. Perform proper rotor refinish and documentation

4. Measure, document and correct lateral run out (LRO)

5. Reassemble with proper torque and document final rotor thickness

NECESSARY AND UNNECESSARY BRAKE SERVICE

Rotors

Contrary to general understanding, many rotors can be resurfaced rather than replaced. Rotors should not be replaced for “lot rot.” In a recent study, low mileage rotors were cleaned up with minimum of 77% of life remaining.

Rotors should not be replaced for pulsation. In a recent study, rotors under 12,000 miles (19,000 km) were cleaned up with minimum of 70% of life remaining.

TIP: Replacement for rotor flaking should be handled on a case by case basis.

Pads

Pads should not be replaced unless excessively worn, contaminated or damaged (fig 2).

http://216.182.211.32/techlink/images/issu...s/3x3/fig2s.jpg

TIP: If replacement is necessary, always replace disc brake pads in axle sets using OEM pads if repaired under warranty.

Brake pad replacement necessary under warranty:

- Substantial premature pad wear (see specific pad specifications/gaps/wear sensor information in SI).

- Damaged pad friction surfaces (cracks, fractures, separation from mounting plates or other issues that could impair brake performance).

- Uneven vehicle side-to-side/premature pad wear due to caliper issue requiring repair issue.

- Pad material contamination (oil, grease, etc.)

TIP: If pad replacement for one of these causes is performed, also perform and document repair to correct the cause of the concern.

Brake pad replacement unnecessary under warranty:

- Pads generally should not be replaced for noise concerns, unless specifically directed by a Bulletin addressing customer’s concern

- Pads should not be replaced just because rotors are being serviced.

DEFINITIONS OF CORROSION

Corrosion is caused by normal oxidation (rust) that is not cleaned off of the rotor by the pad but is impacted into the rotor.

Corrosion may cause owner complaints of pulsation or noise.

Corrosion may range from very light to heavy scaling.

Light Corrosion

Rusting on the rotor braking surfaces may occur when a vehicle is not driven for extended periods. Light surface rust is often cosmetic and can be eliminated during a few normal driving stops.

Perform 15 moderate stops from 35-40 mph (62-75 km/h) with cooling time between stops.

Light “Delamination”

“ Delamination” looks like a layer of paint flaking off the rotor. This layer is composed of rust and pad material. “Delamination” is NOT rotor surface degradation. Light flaking can normally be corrected by refinishing the rotor.

TIP: Pads generally do not require replacement for this condition.

Heavy Corrosion / Delamination

Heavy corrosion is characterized by rust scaling and deep pitting. This type of rotor corrosion may be too deep to machine and may require replacement of the rotor.

WHEN SHOULD A ROTOR BE REPLACED?

A rotor should not be replaced or refinished for:

- Noise/squeal

- Cosmetic corrosion

- Routine pad replacement

- Discoloration/hard spots

A rotor should be refinished for:

Severe scoring -- depth in excess of 0.060 inch (1.5 mm).

Pulsation concerns from:

- Thickness variation in excess of 0.001 inch (0.025 mm).

- Excessive corrosion on rotor braking surfaces.

BRAKE PULSATION

Pulsation is caused by thickness variation. Thickness variation is caused by corrosion or rotor lateral run-out.

Remember, a caliper floats in the steering knuckle. Parallel surfaces (no thickness variation) will NOT produce brake pulsation even with 0.010 inch (0.25 mm) or more lateral run-out.

Wear-induced thickness variation usually occurs 2,000-10,000 (3,200-16,000 km) after miles after rotor service. Lateral run-out can be cut into the rotor with an improperly maintained brake lathe.

On brake apply, a rotor with thickness variation will push the brake pads apart resulting in hydraulic movement through brake piping to the master cylinder and to the brake pedal.

CRITICAL DIMENSIONS OF A ROTOR

Here are some details about measuring a rotor.

TIP: Thickness measurements should be done with a brake micrometer (fig. 3), which has a pointed anvil and a deep throat.

Brake Rotor Thickness

SI provides three dimensions:

- New (original)

- Minimum after machining

- Discard (fig. 4)

TIP: If you subtract the minimum thickness after refinishing from the new thickness, the result is the amount of useful rotor life left.

TIP: Brake rotor thickness should be checked a final time just before you put the wheel back on the vehicle.

Rotor Thickness Variation

TIP: This measurement is used when addressing brake pulsation concerns.

The rotor should be measured in at least four places in the pad contact surface area.

SI calls for correction if the thickness variation exceeds 0.001 inch (0.025 mm).

Brake Rotor Scoring

Scoring greater than 0.060 inch (1.5 mm) requires correction. Scoring greater than 0.060 inch (1.5 mm) after machining requires rotor replacement.

Lateral Run-Out

Install a dial indicator, following SI procedures. Generally, the indicator is attached to the steering knuckle, with the plunger contacting the rotor braking surface at a right angle, and 0.25 inch (6.35 mm) from the outer edge (fig. 5).

On most GM passenger cars, if LRO is 0.002 inch (0.050 mm) or less, no correction is necessary. If LRO is over 0.002 inch (0.055 mm), correction is required.

TIP: An exception is the N-car specfication of 0.0015 inch (0.038 mm). Always check SI for specifications for the vehicle you’re working on.

CLEANING BRAKE COMPONENTS

One of the causes of excess lateral run out is foreign material between mating surfaces of rotor, hub, and wheel (fig. 6). These include debris, corrosion, flaking and grease.

You need to obtain clean metal-to-metal contact to get repeatable results. Pits aren’t so much of a problem as raised surfaces.

Clean rotor to hub mating surfaces using J-42450 Wheel Hub Resurfacing Kit. The configuration of the tool permits it to fit over the mounting stud, to remove corrosion that cannot be reached by other methods (filg 7).

And, 80-grit abrasive discs and holder are available in the J-41013 Wheel Hub Cleaning Kit. This is useful in cleaning mounting surfaces in general (fig. 8).

[NorthstarAJ]

Part 2 -- Refinishing and Lateral Run-Out (LRO) Correction

There are five steps which must be performed to complete a successful brake service.

1. Measure and document rotor thickness and thickness variation (fig. 1).

2. Clean hub, rotor and wheel mating surfaces of all rust and debris to shiny surfaces.

3. Perform and document proper rotor refinish using either on-car or off-car lathe following the manufacturer’s directions.

4. Measure, document and correct existing lateral run-out (LRO) with Brake-Align correction plates.

5. Document final rotor thickness, reassemble wheel to hub with proper torque, and burnish the refinished rotors to the pads.

The first two steps were covered in Brake Service, Part 1 (TechLink, December 2004). The present article explains the remaining steps: rotor finishing and measuring, correcting LRO, final assembly and documentation.

TIP: Refer to bulletin 00-05-22-002F for GM’s standard brake service procedures. Another excellent information resource is Service Know-How Course 5040.01B -- Brake Pulsation Due to Lateral Runout.

IMPORTANT: These procedures and discussion are highlights of proper brake rotor service and are presented for general information. They are not comprehensive or specific to a certain model/year vehicle and are not intended as such. Always refer to procedures in SI, applicable factory service manuals and applicable Service Bulletins for complete procedures and specifications for the year and model vehicle you are working on.

ROTOR FINISHING

Critical characteristics of a brake rotor include:

- Surface finish

- Parallelism

- Perpendicularity to hub centerline

- Flatness

- LRO

Of these, only LRO and flatness can be measured; the brake lathe must provide the other characteristics.

On-Car vs. Off-Car Lathe

The purpose of machining a rotor is to produce two parallel surfaces with minimum LRO. Both types of lathe will do this, and both methods have considerations.

On-Car (fig. 2)

- Portable

- Compensates for LRO

- Cuts captured rotors (TechLink Jan. 2004)

- Non-directional finish

- Requires more training

Off-Car (fig. 3)

- Easier to set up

- Stationary location

- Substantial disassembly (or impossible to use) on captured rotor vehicles

- Does not compensate for LRO

TIP: Before machining a rotor on either kind of equipment, the hub and wheel sides of the rotor mounting flange must be cleaned to shiny metal on both sides.

Lathe Use and Inspection

A later article will present much greater detail about the critical care of both types of lathes. But before turning a rotor on any type of lathe, take the following into account.

Lathe Safety

- Lathe’s electrical cord, motor, switches, light(s) and belt(s) (as applicable) in good working condition

- Lathe clean and free of debris, rust and chips

- Safety shields, vibration dampers, other attachments clean and in good working order

- Cutting tools sharp and in good condition

- Operator wearing proper personal protection equipment

Correct any shortcomings before proceeding.

Lathe Inspection

Carefully inspect the bell clamps or adapters you are going to use. Their machined surfaces should be clean, free of rust and grease and not have any nicks or damage present. Any dirt or rust should be cleaned off and any nicks or damage should be removed with a stone. If the damage or rust is significant, the bell clamp or adapter should be verified and/or corrected before use. See TSB 00-05-22-002F or the Brake Pulsation Due to Lateral Runout Service Know-How video and booklet for details.

Inspect the lathe arbor (Off-Car) and lathe arbor shoulder (both On and Off-car) for any nicks, dirt or damage. Clean or repair as necessary as indicated above.

Verify that the adjustment and locking features of the lathe work smoothly and correctly. Verify the cutting head (Off-Car) moves freely in its ways without excessive slop. If necessary, disassemble and remove any chips, dirt or debris which prevent this and perform adjustments as indicated by the lathe manufacturer.

Vehicle/Hoist Inspection (On-Car Only)

Insure that the hoist supporting the vehicle is in good condition and supports the vehicle solidly

Make sure the vehicle’s wheel bearings, drive axle and suspension components (as appropriate) are in good condition without excessive play, damage or wear. Repair/replace components as necessary BEFORE attempting to turn a rotor on an On-Car lathe.

TIP: Failure to support a vehicle on a sturdy hoist may result in the On-Car lathe not being able to self compensate itself. If this occurs, move the vehicle to a suitable hoist or secure it fore/aft with jackstands as appropriate.

Rotor Cutting

Once the lathe equipment is verified to be in good operating order, cut the rotor to achieve a good finish according to the lathe manufacturer’s instructions.

Always do the math ahead of time, BEFORE beginning to cut. Properly measure the rotor with a brake micrometer to determine what your bottom depth is and how much rotor surface to remove. Remove only as much material as needed to obtain a smooth, even rotor surface. Make the cut in one pass, if it is within the lathe’s capability.

TIP: Equal amounts of material do not have to be removed from both sides of the rotor on a floating caliper system.

TIP: On a rotor surface with rust buildup, insure that the cut is deep enough to cut metal. Dragging the tool across rust will dramatically shorten its useful life.

Rotors generally can be turned and should NOT automatically be replaced for:

- Low mileage rust conditions (lot rot)

- Brake pulsation due to rust buildup or thickness variation induced from excessive LRO

- Minor rust accumulation which is flaking off

Refer to Brake Service, Part 1 (TechLink, Dec. 2004) as well as Bulletin 00-05-22-002F for more information.

Final Rotor Finishing and Cleaning

The rotor surface must have a non-directional finish. Follow the lathe manufacturer's recommendation for applying a non-directional finish using moderate pressure. If the lathe is equipped with a non-directional finishing tool, use 120 grit aluminum oxide sandpaper. If the lathe is not equipped with a non-directional finishing tool, use a sanding block and 150 grit aluminum oxide sandpaper.

Rotor Measurement

Before removing the rotor from the lathe (or on-car lathe from the rotor), be sure the rotor thickness is at or above the Minimum Thickness After Machining (sometimes called Minimum Machine) thickness specification in SI. (fig. 4)

Discard a rotor that is not at or above minimum machine thickness. It cannot safely be placed back on a vehicle.

Remove all machining debris from the rotor surfaces to insure quiet brake operation. Failure to remove all minute metallic machining residue will result in significant brake squeal with some brake pad compounds.

The best method is thorough scrubbing with hot, soapy water. If you use an environmentally friendly hot tank washer, use brake cleaning spray to remove residual oil from the rotor surfaces.

MEASURING AND CORRECTING LATERAL RUN-OUT

TIP: Before installing the rotor to the hub, be sure there is no debris on the rotor or hub mating surfaces.

TIP: When installing a rotor on a hub, hold the rotor at the 5 o’clock and 8 o’clock positions to avoid dropping any residue from inside the rotor cooling vanes into the hub/rotor interface area.

Hold the rotor flat to the hub. Install J 45101-100 conical washers (A) and lug nuts ( and finger tighten (fig. 5). Torque the lug nuts to SI specifications using a star pattern.

A Conical washer

B Lug nut

TIP: Conical washers simulate the clamping load of the wheel on the rotor/hub interface to make an accurate LRO measurement.

TIP: Print the brake specifications from SI as handy reference during the repair. Attach it to the repair order as a permanent part of the vehicle history file to substantiate the specifications you were working with.

LATERAL RUNOUT (LRO) CORRECTION

IMPORTANT: Over time, excessive LRO causes thickness variation which causes brake pulsation. See the December 2004 TechLink as well as 00-05-22-002F.

This procedure involves placing a machined, tapered correction plate between the rotor and hub.

Install a dial indicator J 45101 (or equivalent) to the steering knuckle and position the indicator button so it contacts the brake rotor friction surface at a 90° angle, approximately 0.5 inch (13 mm) from the outer edge of the rotor (fig. 6).

With the dial indicator installed, rotate the rotor until the lowest reading is displayed on the indicator dial and set the dial to zero. Rotate the rotor until the highest reading is displayed on the dial. Mark the location of the high spot relative to the nearest wheel stud, or studs. Mark the studs and rotor (fig. 7) to allow you to reinstall the rotor to the hub in the same index location. Record the amount of measured LRO on the repair order for the corner of the vehicle you are working on.

Refer to LRO measurement procedures in SI. On most passenger cars, if LRO is greater than 0.002 inch (0.055 mm), correction is required. P-90/N-car specification is 0.0015 inch (0.038 mm). Always consult SI for the specifications for the model/year vehicle your are working on.

Select and document the appropriate correction plate. Use the Brake-Align application chart supplied with the plates. Brake-Align plates are numbered XXX-XX, where the first three numbers represent the type of hub they fit and the last two numbers represent the correction value in thousandths of an inch (03 gives 0.003-inch correction, 06 gives 0.006-inch correction and 09 gives 0.009-inch correction). Brake-Align plates come in only these three thicknesses. Select the appropriate correction plate as indicated below.

You are trying to get the total LRO as close to zero as possible. Because you are compensating a rotating device, it doesn’t matter if the values go positive or negative.

EXAMPLE: If the runout is 0.005-inch, the 0.006-inch plate would give you -0.001-inch LRO after installation. The 0.003-inch plate would bring you to +0.002-inch (which might be within spec) but the 0.006-inch plate minimizes the total LRO and gives a better repair.

With the rotor removed, install the plate (A) on the hub with the V-notch ( at the high point previously marked © (fig. 8).

A Plate

B V-notch

C High point mark

TIP: Brake-Align plates have a double wheel lug pattern of mounting holes to allow positioning the V-notch at a lug location or in between lugs, depending on the location of the high spot mark.

Install the rotor, observing the index marks you made earlier.

Hold the rotor flat to the hub, add a conical washer and finger-tighten the first lug nut. Repeat with the other lug nuts. Tighten to the specified torque, in a star pattern.

Confirm that LRO is within specification using the measurement procedure above.

Measure the final rotor thickness for that rotor in that position on that vehicle and record on the repair order.

Install the caliper and pads. Pad inspection and replacement guidelines were covered in part 1 and bulletin 00-05-22-002F.

Remove the lug nuts and conical washers; re-install the wheels, using the recommended lug torque and procedure.

Depress the brake pedal several times to take up changes in component clearance due to rotor refinishing and to secure the rotor in place.

Verify and adjust the brake fluid level in the master cylinder reservoir.

Brake-Align Tips

Brake-Align plates save you time. Using them is an approved repair procedure and they should be used to correct brake rotor LRO when it exceeds the specification. Brake-Align plates, properly used, give you repeatable, exact LRO correction results quickly.

TIP: The LRO Indexing Correction procedure in SI is valid to correct minor LRO variation. But you may need to bolt and un-bolt the rotor from the hub 4 or 5 times to get the lowest LRO measurement, which still may or may not be within the vehicle’s maximum LRO specification.

The most commonly used plates are the 0.003-inch and 0.006-inch. If rotor LRO measurements indicate the need for a 0.009-inch plate, determine EXACTLY where that LRO is coming from. First, remove the marked/indexed rotor from the hub and check the hub lateral surface for LRO with a dial indicator in the same method as above for checking the rotor. Place the indicator tip just outboard of the lug circle. Generally, most hub outer edges are approximately half the distance from the centerline of the axle to the area you were checking on the rotor. Using some geometry, it would be logical to expect this value to be approximately half of what you were seeing at the rotor, if 100% of the runout is in the hub.

EXAMPLE: You measured 0.011-inch LRO on the rotor. You disassembled the rotor from the hub and measured the outer edge of the hub and found 0.001-inch LRO. This would indicate that approximately 0.002-inch of your 0.011-inch total LRO is due to hub LRO.The rest is LRO in the rotor itself. If you have just cut that rotor, you need to take a very close look at your cleaning process and your lathe equipment.

TIP: Never re-use a Brake-Align correction plate. Never stack more than one Brake-Align correction plate on an individual hub.

FINAL DOCUMENTATION

At this point you should have performed the following measurements and recorded them on the repair order (or diagnostic worksheet as appropriate):

- Initial rotor thickness

- Rotor thickness variation measured in at least four equal places around the circumference of the rotor (if customer concern was brake pulsation)

- Final rotor thickness after machining (if rotor was turned)

- Assembled rotor lateral runout measured and recorded in thousandths of an inch so it can be coded for warranty purposes

- Brake-Align correction plate used (XXX-XX format)

- Final rotor thickness installed on the vehicle in its final position (left/right/front/rear)

BURNISHING PADS AND ROTORS

CAUTION: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.

Burnishing the brake pads and brake rotors is necessary to ensure that the braking surfaces are properly prepared after disc brake system service.

Perform this procedure whenever the disc brake rotors have been refinished or replaced, and/or whenever the disc brake pads have been replaced.

Select a smooth road with little or no traffic. Accelerate the vehicle to 48 km/h (30 mph).

Use care to avoid overheating the brakes while performing this step.

Using moderate to firm pressure, apply the brakes to bring the vehicle to a stop. Do not allow the brakes to lock. Repeat until approximately 20 stops have been completed. Allow sufficient cooling periods between stops to properly burnish the brake pads and rotors.

- Thanks to North Central Region Service Engineers and Field Warranty Specialists

[NorthstarAJ]

Question

If you machine just the left front rotor and not the right front. Will the car pull when braking and in what direction?

[Ranger]

Question

If you machine just the left front rotor and not the right front. Will the car pull when braking and in what direction?

My guess would be yes. Probably pull to the left.

[BodybyFisher]

Interesting question. The machining helps the new pads 'seat'. If you replace the pads on one side and machine the rotor because its rough, and you replace the pads on the other side and you DON'T machine the rotor, you have a mis match in the way the pads are 'seated'. I believe that what is done to one side should be done to the other.

However, IF, you don't touch one side, and replace the rotor and pads on the other side, once the new pads 'seat', it will NOT pull. I believe seating it important.

By the way, thanks for posting this information, I will be reading it later, brakes are a touchy subject for me. Mike

[NorthstarAJ]

Interesting question. The machining helps the new pads 'seat'. If you replace the pads on one side and machine the rotor because its rough, and you replace the pads on the other side and you DON'T machine the rotor, you have a mis match in the way the pads are 'seated'. I believe that what is done to one side should be done to the other.

However, IF, you don't touch one side, and replace the rotor and pads on the other side, once the new pads 'seat', it will NOT pull. I believe seating it important.

By the way, thanks for posting this information, I will be reading it later, brakes are a touchy subject for me. Mike

It will pull to the RIGHT

Test place a sheet of sticky back sand paper down, push your hand down and rub across it.

Next

Place a sheet glass down, push down and attempt to slide your hand.

Not going to happen.

Good brake lathes and operators get a near mirror finish.

Physics?

[JasonA]

So wasn't Ranger correct? Won't it pull to the left? If the left rotor was finished and the right side wasn't...why would it pull to the right? You'll have a better surface on the left, causing the car to pull to the left.

[BodybyFisher]

Interesting question. The machining helps the new pads 'seat'. If you replace the pads on one side and machine the rotor because its rough, and you replace the pads on the other side and you DON'T machine the rotor, you have a mis match in the way the pads are 'seated'. I believe that what is done to one side should be done to the other.

However, IF, you don't touch one side, and replace the rotor and pads on the other side, once the new pads 'seat', it will NOT pull. I believe seating it important.

By the way, thanks for posting this information, I will be reading it later, brakes are a touchy subject for me. Mike

It will pull to the RIGHT

Test place a sheet of sticky back sand paper down, push your hand down and rub across it.

Next

Place a sheet glass down, push down and attempt to slide your hand.

Not going to happen.

Good brake lathes and operators get a near mirror finish.

Physics?

Physics? So where is it that you work, Crest Cadillac, Brookfield, Wi? Do they condone you to use their proprietary equipment/software for experimentation and removing the speed limiter?

You made this statement:

I have had my tuning thread over on another forum and I guess I need to go back a little bit and explain some things.

I have some GM software used to alter the programs. This for me is very time consuming and I have troubles at the end getting it to finalize.

I have found a way with that program to copy a portion and paste it into another program.

This will change shift points, torque, Power Enrichment, spark, max speed, Trans pressure, and emission devices.

Now this is all within GM standards so this way it is all GM and will never damage an engine. I have worked over my program in my Turd, but if it breaks it is mine. If I break your car I now have a problem.

Yes I am taking the safe way out.

Well that is not entirely true is it, some member stopped by to say that you did some work to his NS. Did you have him sign a disclaimer?, see an attorney to find out how to make what you are doing legal. Does GM make you sign anything regarding making changes outside of the shop? I would be surprised if they didn't. Someone blows an engine and shows up at Crest, I am sure Crest will fix it and you will be finding a new job. Have you considered these issues?

I guess in your free time a GM tech can do anything he wants, its a free world and the liability would be yours not theirs. However, its interesting to note what attorney's these days consider a liability, heck Mc Donalds got sued for someone getting burned by coffee. Now, a GM tech removes a speed limiter off of a NON STS/ETC, NON Z RATED vehicle, put the driver at potential risk due to an inferior suspension, hmm, sounds like you should be consulting an attorney with the kind of work you do on the side. Have you told your supervisor at Crest you are doing this kind of experimentation? I would if someone gets killed, well you understand.

If you have something to add, by all means add it, but being sarcastic, critical, preaching or thinking you are going to school us, is in bad form, you are only 39 so you really don't understand what humility means yet. Its a hard lesson.

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It's a moot point for me, I do brakes in pairs. What I do to one side I do to the other side. This is something you need to consider in dealers as they will only do one side (inferior work doing one side if you ask me). As a DIY, I always replace in pairs and always resurface or replace the rotors in pairs, end of problem.

If the rotor does not meet this spec after refinishing it needs replacing

Rotor Maximum Allowable Thickness Variation

(0.025 mm) or 0.001 in

As far as the mirror finish, I hope you mean BEFORE the non-directional finish is applied because once its applied there is nothing mirror about it. I insist upon having a non directional finish, it helps the new pads seat, after a day, I have a MIRROR finish when the pads burnish the rotor.

Document ID# 657002

2002 Cadillac Seville

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Brake Rotor Refinishing

Tools Required

J 41013 Rotor Resurfacing Kit

J 42450-A Wheel Hub Resurfacing Kit

The disc brake rotors do not require refinishing as part of routine brake system service. Do not refinish disc brake rotors in an attempt to correct the following conditions:

Brake system noise - squeal, growl, groan

Uneven and/or premature disc brake pad wear

Superficial or cosmetic corrosion/rust of the disc brake rotor surface

Scoring of the disc brake rotor surface less than the maximum allowable specification

Disc brake rotors should only be refinished if the following conditions exist:

Excessive corrosion/rust and/or pitting

Cracks and/or heat spots

Excessive blueing discoloration

Scoring of the disc brake rotor surface in excess of the maximum allowable specification

Lateral runout in excess of the maximum allowable specification

Thickness variation in excess of the maximum allowable specification

Inspect each of the disc brake rotors and determine if the rotors can be refinished and remain above the minimum allowable thickness after refinish specification:

Inspect the thickness of each of the disc brake rotors. Refer to Brake Rotor Thickness Measurement

Inspect each of the disc brake rotors for excessive surface wear and/or lateral runout. Refer to Brake Rotor Surface and Wear Inspection .

If the rotors can be refinished, proceed with the rotor refinishing procedure.

Important

Failure to clean the corrosion from the wheel bearing flange, brake rotor mating surface, and brake rotor mounting face may result in increased lateral runout of the brake rotor and brake system pulsation.

Use the J 41013 in order to thoroughly clean any corrosion from the wheel bearing flange.

Use the J 42450-A in order to thoroughly clean any corrosion/rust from the brake rotor mating surface and mounting face.

Mount the brake rotor to the brake lathe according to the lathe manufacturer's instructions, ensuring that all mounting attachments and adapters are clean and free of debris.

Ensure that any vibration dampening attachments are securely in place.

With the brake lathe running, slowly bring in the cutting tools until they just contact the brake rotor friction surfaces.

Observe the witness mark on the brake rotor. If the witness mark extends approximately three-quarters or more of the way around the brake rotor surface on each side, the brake rotor is properly mounted to the lathe.

If the witness mark does not extend three-quarters or more of the way around the brake rotor, re-mount the rotor to the lathe.

Following the brake lathe manufacturer's instructions, refinish the brake rotor.

After each successive cut, inspect the brake rotor thickness. Refer to Brake Rotor Thickness Measurement .

If at any time the brake rotor exceeds the minimum allowable thickness after refinish specification, the brake rotor must be replaced.

After refinishing the brake rotor, use the following procedure in order to obtain the desired non-directional finish:

Follow the brake lathe manufacturer's recommended speed setting for applying a non-directional finish

Using moderate pressure, apply the non-directional finish:

If the lathe is equipped with a non-directional finishing tool, apply the finish with 120 grit aluminum oxide sandpaper

If the lathe is not equipped with a non-directional finishing tool, apply the finish with a sanding block and 150 grit aluminum oxide sandpaper

After applying a non-directional finish, clean each friction surface of the brake rotor with denatured alcohol or an equivalent brake cleaner

Remove the brake rotor from the brake lathe.