Posted by Mike on November 22, 19100 at 07:27:19:
In Reply to: Re: Share proper proceedure? nm posted by PeteL on November 22, 19100 at 05:18:56:
The steps to be followed are in the service manual. But I'm happy to share the secrets I've learned.
Squeal results from the pads being loose and/or contaminated or defective rotor finish. The first time you step on the brakes the force of the rotor sweeping across the pads is far greater than even the strongest man can generate. So, we must make sure the pads are tight and perfectly clean and the rotor must be correctly finished.
1) Buy replacement pads and caliper hardware, if required, from reputable manufacturers and be certain that they are correct for your specific application. On a GM truck, it makes no sense to buy hard pads in an attempt to reduce pad wear. The pads are the wear item, NOT the rotors. They are designed to operate that way. You can buy a lot of sets of pads for what a set of rotors will cost, especially on some of the K2500/K3500 trucks!
2) Check the calipers! It is unrealistic to ignore them when they have everything to do with brake performance. The caliper bolts and bushings must be perfect. If they are not they must be replaced. Use the correct grease; high-temp disc brake caliper bolt grease (nothing else!). Check the pistons and their bores and seals. Unless perfect, rebuild or replace the caliper. Clean the pad mounting surface on the caliper with brake cleaner.
3) If you need to turn the rotors, have it done by someone who will get it right. A dull tool bit in the lathe or too aggressive of a feed will cause a rough finish on the rotor which will squeal every time. Be sure to tell them to tell you what the lateral runout is after they are done. If they don't know, they could not possibly have done a decent job turning your rotors. The spec is in the book. This has nothing to do with squeal (it has everything to do with pedal pulsation) but is often missed. And of course, make sure the minimum thickness spec is honored. It's also in the book and it's even stamped on the rotor.
4) Whether the rotors are being reused as is, turned, or replaced, clean them with a rag and brake cleaner (use nothing else!) until you cannot get the any more dirt to show on the rag.
5) Wear latex gloves to handle the new pads. Any contamination, even from freshly washed hands, can make them squeal. Avoid touching the pad face! When assembling them, pay attention to the service manual but be sure to include all anti-rattle clips and shims, if used, and when bending the ears make sure they hold the pads tight. Starting the bend with a pair of pliers and finishing with a few taps from a hammer will ensure that they are tight. If you use "anti-squeal" be sure to follow the directions on the can.
6) When installing the lugs, follow the tightening pattern and torque specs and tighten in small, even amounts with a beam type torque wrench.
7) At a minimum, inspect and adjust the rear brakes. If the front pads wear very quickly, your rear self-adjusters may not be working. This can also cause weird ABS behavior. If so, adjust the rear brakes every oil change or so.
8) Make the first few stops with your new brakes very gently.