Rotor Runout: Cause and Correction

Rotor Runout: Cause and Correction
The vehicle owner may say that under light braking the vehicle pulses to a stop or under heavy braking the vehicle shudders. Technical service bulletins ( TSBs ) often describe these symptoms as a “ judder. ” There are only two causes for judder — lateral runout and magnetic disk thickness pas seul on the rotor ’ s friction coat. Click hera to Read More ad

What could have caused the lateral pass runout ? The causes of the condition range from lugs that were all over or raggedly torqued to common corrosion between the hub and rotor .
There are other causes, such as the rotor machined to less-than-minimum thickness and overheating. Correcting the condition requires the machine or refilling of the rotor. Whether you are turning a rotor on or off the vehicle or replacing it, cooking is the samara to success .
The greatest cause of lateral pass runout comebacks is not poor OEM technology or low-quality aftermarket parts, it is ignorance and carelessness. Don ’ t take this the wrong way, but some of your instincts and methods of operation could be costing you. By no means, is this written from from the perspective of talking down to the technician, it is barely some self-introspection can even help the best technician. Take the clock to perform a diagnostic on yourself. You might be surprised .
Rotor Runout: Cause and Correction You are Only as Good as Your Tools
Both on-the-car or off-the-car bracken lathes are preciseness machines that that must be maintained and treated with big manage. Dirt and alloy chips can shorten the biography couple of any lathe and lead to comebacks .
When was the last time you checked the runout of the spindle and cutting head ? Remember, the cut is alone deoxyadenosine monophosphate true as the arbor, spindle and adapters. ad Some of the TSBs check information on checking runout of the lathe arbor and clamps. But, your best source of information is the manual that came with the lathe. If you can not find it, it may be online in PDF format. even if your bench lathe is arsenic old as dirt, person can sell you the parts to fix it .
look at the condition of your adapters. A weekly houseclean and lubrication should be performed. The adapters should be trued to the arbor on a monthly basis. After they are trued, all nicks and burr should be removed with a fine emery fabric. Coat the adapters with a light coat of oil. ad What about cutting bits ? This topic is an article on its own. For some technical school, proper cutting act manage is fair arsenic unmanageable as putting the toilet seat down or putting a new roll of toilet newspaper back on the roller .
On-the-Car Runout
Today, you can purchase an on-the-car brake lathe that, after it has been attached to the vehicle, will mechanically properly compensate for runout. It is promptly and easy .
Rotor Runout: Cause and Correction But, wait a moment, most manufacturers have written across-the-board bulletins on the proper methods of turning brake rotors. All of the bulletins begin with the proper cooking and measurement of the components before turning the rotor. Most dealers are required to have a runout compensating on-the-car bracken lathe by the OEMs, and the OEMs are paying the guarantee time. so why would they begin a TSB with this “ extra ” assay before turning the rotor ? Simple, it is a quality check that helps to eliminate runout problems that could actually be made worse by turning the rotor .
Rotor Runout: Cause and Correction Turning a rotor is a preciseness operation that requires a clean and rust-free mounting surface. There are tools available to clean the bear flange and rotor mount surfaces. They can range from rotating harsh to hood sandblasters. Vented rotors can be a beginning of corrode that can range from dust to chunks coming from the vent passages. It is a good mind to knock loose the rust with a telegram brush to prevent it from getting on mounting surfaces and turning equipment .
once the rust has settled, pull out your dial bore and go to work. The spindle of a bench lathe is basically the steering wheel carriage when cutting on-the-car. The maximal endplay for a bear is 0.004 ” ( 0.100 millimeter ). This is a estimable reason to check flange runout and endplay before installing the lathe arranger. ad The rack wear is the heart of the assembly. If the hold flange has a runout, that runout will be magnified at the rotor clash come on. A runout of 0.0005 column inch ( 0.00254 millimeter ) at the bearing flange could result in a 0.001 column inch ( 0.025 millimeter ) runout at the rotor clash airfoil. The maximum allowable runout at the rotor clash open is 0.002 column inch ( 0.050 millimeter ) as stated by most manufacturers .
Rotor Runout: Cause and Correction Shimming the Rotor
Flange runout can be corrected with tapered shims that are available to correct a runout of 0.003inch ( 0.075 millimeter ) to 0.009 edge ( 0.230 millimeter ) A runout of more than 0.005 inch ( 0.125 millimeter ) at the have a bun in the oven flange can not be corrected by the use of a shim. The combination of rotor and hold flange could prevent the rotor from being turned. Checking bearing flange runout should be performed after clash surface runout. Changing the rotor position 180º on the bearing can check flange runout. If the high blemish changes 180º, the rotor could be oklahoma or fix to turn after the bear is shimmed .
Components should be marked as you perform an inspection of the fabrication. Check the charge endplay. Mark the relation of the rotor to the bear flange. Mark the rotor gamey and low runout spots on the rotor clash coat. The low blot marked as zero and the senior high school spot as 0.XX ”. Mark the high and low runout spots on the behave flange with the same method acting and the rotor friction surface. ad once you have collected the datum, the follow comparisons should be made. If the endplay exceeds manufacturer ’ sulfur specifications, replace the bearing and recheck runout. Compare bearing flange to rotor runout stead. If the shim can not correct the runout, the bearing should be replaced. Check the rotor thickness. The minimum dimension should be stamped or cast into the rotor. There has to be enough thickness to cover the runout without going below the minimum thickness .
Rotor Runout: Cause and Correction Hub and Rotor Interaction
How the rotor interfaces with the hub can determine runout. Think of the rotor as the peanut butter in a peanut butter and jelly sandwich and the hub and rack as the slices of bread. If you push down on one corner, the peanut butter will shoot out the opposition corner. If you tighten lugsail nuts in a circular model, stress is placed on the rotor hat incision and bearing flange unevenly .
All wheels should be mounted by using a crossing blueprint to tighten the lugs .
Rotor Runout: Cause and Correction Pulling it Together
Most cognition and learn for technicians about trueing rotors is picked up in bits and pieces from respective sources and failures. It is learning with preceptor ’ t and very little do ’ mho. Below, is a list of how it should be done for installing modern rotors and machining old rotors .
Installing New Rotors

  1. Check bearing end play : end play is an indication of bearing condition and allowance .

  2. Clean the bear flange : airfoil should free of debris for a thoroughly dial indicator reading .

  3. Check bearing flange runout : flange run out is magnified at the rotor clash surface .

  4. Install new rotor : Torque the rotor on the flange to check conjunction to the knuckle .

  5. Check newfangled rotor runout : It ’ s a double check before installing the wheel .

Rotor Runout: Cause and Correction Turning Rotors (off vehicle)

  1. Check lateral runout : set high and low spot, a shim possibly required to correct the runout.

  2. Check rotor thickness : comparison to runout for minimum thickness before and after turning .
    Rotor Runout: Cause and Correction

  3. Clean the wear flange .

  4. Clean the rotor to bearing mounting coat .

  5. Check bearing end toy : should be no more than 0.004 inch ( 0.100mm ) .

  6. Check bearing flange runout : change rotor placement on bearing .

  7. fomite .

  8. Check turned rotor runout and thickness : it ’ s a double match before installing the bicycle .

Turning Rotors (on vehicle) ad

  1. Check rotor thickness .

  2. Check bearing end bid .

  3. Check lateral pass runout .

  4. uninfected wheel and rotor mounting surface .

  5. Mount lathe according to manufacturers instructions .

  6. machine the rotor .

  7. Check turned rotor runout and thickness .

The steps above may look simple, but used as a frame work for basic brake repair they can go a long ways to ensuring quality and reducing comebacks .
But, a holocene General Motor ’ s TSB takes it to the next level. The bulletin makes two critical points :
GM Bulletin 00-05-002D:
If performing act brake service for careworn pads entirely, and the rotors are not damaged and standard within stipulation, DO NOT REFINISH ROTORS. ad

  • Remove the old rotor ( south ) .

  • measure the rotor for original thickness using a brake micron .

  • Reference the minimum thickness specification stamped on the buttocks of the rotor or SI for Minimum Thickness specification/other. In most cases, the rotor should be refinished unless the measurement taken makes it obvious that refinishing the rotor would take the measurement under the Minimum Thickness specification ( then substitution is necessary ) .

  • Record the ORIGINAL rotor thickness measurement on the repair order hard copy .

  • Clean all of the checkmate surfaces between the hub, the rotor and the rack using the J 42450A — Wheel Hub Cleaning Kit if rotors are not to be refinished .

Important: Cleaning all entangle surfaces and making them exempt of corrosion, burr and other debris ( which includes removal of Hubless rotors ) is critical and MUST be performed whether using an On-Car or Bench Lathe Refinish Procedure. ad Be certain to follow the appropriate refinish procedure listed below for the type of lathe you are using .
Important: only replace the rotors if they do not meet the Minimum Thickness specification .
Important: only remove the necessary amount of substantial from each side of the rotor and note that equal amounts of material do not have to be removed from both sides on any brake system using a floating caliper .
crucial : anterior to making the hack, install the commend clip-on style disk silencer supplied with the lathe. use of this silencer is critical to prevent chew the fat from occurring during the cut.

ad There is an old saying “ No training leads to poor people performance. Brakes are one of the most significant safety systems on the vehicle .

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Category : Car Brakes