How to Properly Measure Rotor Runout

welcome to the total brake job brought to you by win here this video will show you how to measure and correct rotor run-out measuring rotor run-out only takes about a minute when assembling new brakes run-out is defined as the amount of lateral or side-to-side movement of the brake rotor as it rotates 360 degrees the specification is usually referred to as total indicated run-out total indicated run-out is defined as run-out measured on the vehicle or installed run-out total indicated run-out includes all factors that can influence the amount of run-out run-out can be in the hub flange the brake rotor or it can be caused by improper wheel nut torque all of these factors add up to give the rotors total indicated run out the average allowable total indicated run-out specification for most late model vehicles is two thousandths of an inch or point zero five millimeters this is the maximum allowed run-out generally does not cause pulsation run-out causes thickness variation that leads to pulsation thickness variation is the main cause of pulsation let's say the vehicle had three thousandths of an inch or point zero seven six millimeters of total indicated run-out when measured at the outside face of the rotor if this vehicle is riding on 205 55 our 16 tires in one mile 1.6 kilometers the high spot with three thousandths of an inch point zero seven six millimeters of run-out goes past the brake pads about eight hundred and thirty six times over six thousand miles or ten thousand kilometers that spot on the brake rotor will go past the brake pads more than five million times every time the spot passes the brake pads a little bit of the brake pad material is removed over five million revolutions enough material is deposited on the brake rotor to create a thickness variation that can be felt by the driver as a brake pedal pulsation correcting run-out is imperative to performing a complete brake job if you'll be machining the brake rotor mark the brake rotor and wheel hub for reassembly marking its current location will help prevent any run-out caused by stacking tolerances it's extremely important to remove any rust or corrosion from the hub flange face we recommend using an abrasive pad and a hub cleaning tool for cleaning around the wheel studs you should never remove more material than needed or produce sparks while cleaning the hub face be sure both the inboard and outboard mounting surfaces are free of rust and debris prior to machining or reusing the rotor to check run-out mount the dial indicator to a fixed point on the steering knuckle the needle of the dial indicator should be perpendicular to the brake rotor measurement should be taken 1/2 an inch or 13 millimeters from the outer edge of the brake rotor lift and release the needle off the brake rotor a couple of times to ensure good contact next find the lowest point in the rotor and set the dial indicator to zero rotate the brake rotor one full revolution to ensure the dial indicator is still set to zero now rotate the brake rotor to find the high spot this is the total indicated run-out in this case it is six thousandths of an inch or 0.15 millimeters mark the high spot on the brake rotor try and reposition the brake rotor 180 degrees on the hub if repositioning the brake rotor does not bring the run-out within the manufacturers specification you'll need to install a correction shim a correction shim can only be used if the run-out is seven thousand seven point one seven seven millimeters or less follow the shim manufacturers installation instructions run out more than 7 thousandths of an inch or 0.1 7 7 millimeters indicates you will need to check for debris trapped between the brake rotor and hub if no debris is present check the run out on the hub flange and replace as necessary one of the most important yet overlooked steps is the proper torque of the wheel nuts please consult the service manual for the torque specification of your vehicle using an impact wrench to tighten the wheel nuts is perfectly acceptable as long as they are not tightened to the full torque specification at this time we are merely tightening the wheel nuts to about 80% of the final torque value this is enough to hold the wheels in place until the final torque to the manufacturers specification with a torque wrench turn your impact gun to the lowest possible setting with the torque stick never touch the torque stick when tightening as the torque stick acts much like a tuning fork and uses vibration holding or even touching the torque stick while tightening will change the torque value and will over tighten the wheel nuts once the vehicle is on the ground set your torque wrench to the manufacturers specification and be sure to always use a star or crisscross pattern when you are tightening the wheel nuts this presentation is by no means representative of all braking systems or brake problems this is merely a guide for measuring and correcting rotor run-out brake components should be installed by a trained technician any improper installation of brake components may cause a serious safety issue or an accident please consult the appropriate service manual for detailed instructions and specifications

Channel: Winhere Brake Parts, Inc.

Views: 26,702

Rating: 4.8128657 out of 5

Keywords: Brakes, Rotor, Run out, Discs, Pulsation, Warped

Id: t_IZzyQcBPA

Length: 6min 29sec (389 seconds)

Published: Wed Sep 23 2015