Rotor Preparation
No one talks about brake rotor prep, but it's a really big deal. You can't just take a brand new rotor out of the box and throw it at the car. Even worse is to take a used brake rotor and install new brake pads without any rotor preparation. This is just asking for trouble. You run a huge risk of brake squeal, and you're not getting the maximum effectiveness out of the new brake pads.
Most suppliers of bench lathes and on-car lathes say sanding after turning isn't necessary as long as proper feed rates and sharp lathe bits are used. The finish should be within specifications and cause no problems.
Proponents of sanding claim that sanding improves the finish by making rotors smoother. Sanding knocks off the sharp peaks as well as torn and folded metal left on the surface by the lathe bits. Sanding may improve the surface finish 2 to 5 microinches. This will give you better pedal feel, quicker pad seating, and improved overall brake performance.
Proponents of sanding claim that sanding improves the finish by making rotors smoother. Sanding knocks off the sharp peaks as well as torn and folded metal left on the surface by the lathe bits. Sanding may improve the surface finish 2 to 5 microinches. This will give you better pedal feel, quicker pad seating, and improved overall brake performance.
I sand brake rotors all the time. Any number of people will tell you it's unnecessary, but I've installed thousands of brakes on a wide variety of cars, and I can count the number of noise problems I've had on one hand.
Rotors can be sanded in various ways. One is to apply a non-directional finish with 80- to 120-grit sandpaper on a flat sanding block. Hold a pair of sanding blocks against the brake rotor for about 60 seconds while the rotor is turning at normal speed on the lathe (assuming you have a machine for turning brake rotors in your home garage).
For the rest of us the most common method is to use an abrasive pad on a drill. This technique is risky because it's difficult to do an even job, and metal buildup on the pad may actually make the surface rougher unless a fresh sanding pad is used for each side of the rotor.
If you do sand, do it carefully, evenly, and remember that you're not trying to remove metal. A minute or less on each side should be enough. You'll see the scratches develop as you use the sanding disc. You really don't want to remove any material; just simply scratch the surface.
If you do sand, do it carefully, evenly, and remember that you're not trying to remove metal. A minute or less on each side should be enough. You'll see the scratches develop as you use the sanding disc. You really don't want to remove any material; just simply scratch the surface.
Sanding becomes even more critical when installing new brake pads on old rotors. The surface of the brake rotor is coated with the old pad material. When you install new brake pads, the new friction material won't contact the rotor but will make contact with the old pad material. You want your new pad material to contact the steel of the brake rotor. Sanding the rotor surface assures that this will happen.
Cleaning Brake Rotors
Very few people take the time to clean or wash a rotor before installing it on the car. Washing a brake rotor with hot soapy water can remove bits of metal that might otherwise end up embedded in the new pads. I finish this washing process with brake clean. If I rub a white paper towel on the rotor surface and dirt shows on the towel, the rotor isn't clean enough.
Very few people take the time to clean or wash a rotor before installing it on the car. Washing a brake rotor with hot soapy water can remove bits of metal that might otherwise end up embedded in the new pads. I finish this washing process with brake clean. If I rub a white paper towel on the rotor surface and dirt shows on the towel, the rotor isn't clean enough.
Break in New Brake Rotors
Some people call it rotor seasoning. I call it a break-in procedure. Gradually heating the brake rotor means that the crystalline matrix will reconfigure to relieve internal stresses. After these stresses are relieved the rotor is ready to accept the heat of normal braking. Heating the rotors before they're fully seasoned can result in material deformation due to the unrelieved internal stresses in the material. This deformation can cause a vibration from the brakes.
Some people call it rotor seasoning. I call it a break-in procedure. Gradually heating the brake rotor means that the crystalline matrix will reconfigure to relieve internal stresses. After these stresses are relieved the rotor is ready to accept the heat of normal braking. Heating the rotors before they're fully seasoned can result in material deformation due to the unrelieved internal stresses in the material. This deformation can cause a vibration from the brakes.
Now perform four medium-hard-effort partial stops (about 75 percent) from 60 mph down to 15. Once again, follow this with 10 minutes of driving with little to no braking to cool the rotors. Now park the car and allow the brakes to cool overnight. You're almost done with the rotor bedding procedure.
One final note for those of you who run track events. Rotors need to be gradually elevated to operating temperatures before any severe use. Use the first lap of a session to warm the brakes as well as the engine, transmission, and tires.
On the next day, go back to your safe location where the brakes can be brought up to temperature. Once the brakes are warmed to normal operating temperature, perform four medium-effort partial stops from 60 mph down to 15. Follow this with five minutes of freeway driving with little to no braking to cool the rotors. Now make four medium to hard partial stops from 60 mph down to 15. Follow this with 10 minutes of freeway driving with little to no braking to cool the rotors.
Finally, make six hard partial stops from 60-plus mph down to 15 mph or until the rotors have reached an operating temperature of between 900 and 1,100 degrees F. If your Corvette doesn't have ABS, try to do this without locking a wheel. Follow this with 10 minutes of driving with little to no braking to cool the rotors.
When you come off the racetrack at the end of your session, drive around the pit area a couple of times to let your rotors cool. Race cars are normally placed on jack stands, or the air jacks are used, to get the same cooling effect. At track events, slowly doing a couple of laps around the pit area works nicely. Also, never use the parking brake at a track event. If you normally use the parking brake, put some duct tape on the handle to remind you not to use it at the track. The last thing you need to do is place a red-hot brake pad against a red-hot brake rotor.
Check Rotor Quality
Compare the thickness of the rotor plates to an OE or premium-quality rotor. If you really want to have fun, weigh the cheap rotor on a scale and compare it with a known high quality brake rotor. If the weight and plate thickness are significantly below the OE or a premium-quality rotor, buy a different rotor.
Measure run out in the rotor and wheel bearing with a dial indicator. On most vehicles, lateral run out greater than 0.002 inch will generate a pedal pulsation problem. Also, check the thickness of the rotor with a micrometer. The minimum thickness will be cast into the rotor.