Rotors - Tech Tips

Rotor - Tech Tips

Rotor Bedding

All new iron rotors should be bedded-in before being used under racing conditions. Proper bedding-in will prepare the rotor surface, prolong the rotor's life and make it more resistant to thermal checking or cracking under severe braking conditions. Once the brake system has been tested and determined safe to operate the vehicle, follow these steps for the bedding of all new rotors. These procedures should only be performed on a race track, or other safe location where you can safely and legally obtains speeds up to 65 MPH, while also being able to rapidly decelerate.

  • Thoroughly inspect all brake system components before proceeding to track. Check all bolt connections, make sure mounting bolts and rotor bolts are properly lockwired, that brake pads are properly secured by retaining clips or cotter pins, that master cylinders and brake pedals are working properly, that brakes are properly bled with plenty of fluid, and that proper engagement of brakes occur when pedal is depressed.

  • Because the bedding process is different for rotors and pads, it is best to bed-in a new rotor (disc) using a used set of pads, preferably ones which will not create heat rapidly. Generating heat too quickly will thermal shock the rotors. Likewise, when bedding-in a new set of brake pads, use a used rotor. This new-used bedding process permits controlled bedding of each individual component.

  • Make sure that the rotor surfaces are free from oils, grease and brake fluid.

  • Close air ducts approximately 75% to expedite the bedding-in process.

  • Begin with a series of light decelerations to gradually build some heat in the brakes. Use an on-and-off the pedal technique by applying the brakes for 3-5 seconds, and then allow them to fully release for a period roughly twice as long as the deceleration cycle. If you use a 5 count during the deceleration interval, use a 10 count during the release to allow the heat to sink into the pads & rotors.

  • After several cycles of light stops to begin warming the brakes, proceed with a series of medium to firm deceleration stops to continue raising the temperature level in the brakes.

  • Finish the bedding cycle with a series of 8-10 hard decelerations from 55-65 MPH down to 25 MPH while allowing a proportionate release and heat-sinking interval between each stop. The pads should now be providing positive and consistent response.

  • If any amount of brake fade is observed during the bed-in cycle, immediately begin the cool down cycle.

  • Drive at a moderate cruising speed, with the least amount of brake contact possible, until most of the heat has dissipated from the brakes. Avoid sitting stopped with the brake pedal depressed to hold the car in place during this time. Park the vehicle and allow the brakes to cool to ambient air temperature.

Rotor Runout

Rotor runout should be adjusted as soon as you receive your Wilwood components. Wilwood rotors are precision machined to ensure the rotor surfaces are flat and parallel. Sometimes hubs, bearings or other components have runout that cause the rotor to runout. As a rule of thumb, allowable runout should be .005” - .008”. Adjust the runout by re-indexing the rotor or by placing shims between the rotor and hub, or hat. Runout should be rechecked regularly. You can assume the runout to be acceptable as long as you are not experiencing brake drag, pedal oscillation or excessive piston knock back.

Rotor Wear

Rotors will eventually start to show signs of wear; how fast depends on the type of racing, the frequency, and the brake usage. Grooving and/or cracking due to severe heat and thermal cycling indicate the rotor should be replaced. Note that surface checking itself is not a sign a rotor needs replacing as this can occur on iron rotors. Always replace rotor mounting bolts and lockwire whenever replacing rotors, taking care to inspect mounting hats or hubs for signs of abuse.

Wilwood Pre-Bedding Service

Getting track time for a proper pad and rotor bedding session can be difficult. Wilwood offers factory dyno-bedded pads and rotors on many of our popular competition pads and Spec 37 GT series rotors. Dyno-bedded parts are ready to race on their first warm up cycle. This can save valuable time and effort when on-track time is either too valuable or not available at all, Dyno-bedding assures that your pads and rotors have been properly run-in and are ready to go. Contact your dealer or the factory for more information on Wilwood Dyno-Bedding services.

Please contact your Wilwood representative for price and availability.

Contact Wilwood

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Phone: (805) 388-1188

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Version: 3.04 May 22, 2023
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