Brake Gurus - need your advice

So I needed new brakes, did some research and decided to go with Centric Premium rotors and EBC green 6000 pads. Install went smooth but I have the dreaded brake squeal. I did apply thin layer of CRC disc brake quiet to the back of the pads but I opted not to install the shims. I only have 26 miles on the new brakes so bedding isn't nearly complete. I am following manufacturers suggestion on bedding in to complete 200 miles of urban driving then perform final bedding in procedure.

Should I wait to complete the full bedding in procedure or should I install the shims. If I install the shims, do I need to clean off all the CRC brake quiet? Do I apply brake quiet to the back of the shims?

The new brakes feel good and solid with improved braking at slower speeds so I am happy with my purchase so far

You did pads and rotors at the same time - finish bedding, first. Typically, you don't want to to new pads on new rotors - you can get heat-checking from that. I usually will have the rotors turned (and I tell the shop to take the bare minimum off to clean it up - they understand. I've gone and picked them up with a total of .001" knocked off, just to freshen up the surface. It's nice having shops that understand your quirks, and you'll get that with the mom-and-pops and local chains more than you will with the big nationals...)

Part of the squeal will be the outgassing of the friction material - the gas comes out of the working surface (mostly) and forces the pad away from the rotor. The hydraulic pressure forces the pad into the rotor. It's best described as "slip and stick" - and it's the same thing that lets you make a water glass 'sing' using your fingertip around the rim.

Finish bedding everything in, and then you can do the shims if they're still noisy. If it comes to that, I'd say to strip the back of the pad and reapply the glop, stick the shim on, then another thin layer of glop (both thin layers. The Permatex spray stuff works quite well, when you need it.) That's usually how I've done shims, and it's worked well for me.

The problem with new pads on new rotors is that the rotors haven't been heat-soaked or heat-cycled yet, and the "slip-and-stick" from the pads outgassing damn sure will heat things up more than normal! New rotors often get heat-checked with new pads, and you'll be replacing the rotors in six months. In the very worst case, the rotors can rupture on you (I did have a rotor actually crack right across the hat once upon a time - I was dating a woman who drove an automatic with both feet, and wondered why I had to do four wheels' worth of brakes on her car every six months...)

If the pads came with shims I would highly recommend using them. EBC also uses a break-in compound that may take a while to wear off. They recommend a few hundred miles of easy breaking and up to 1000 miles before the noise goes away.

Thanks for the info fellas - didn't know about the heat checking thing but it makes sense. I really didn't have much choice since my old rotors had pitting deep enough to hold some pockets of rust - even through the midsubstance of the rotor where the pads were gripping. I don't know what caused this but I had some type of braking issue. I'll use the brakes sparingly and try to break them in easily so they don't overheat and crack - you say that can crack the hat, HOLY SH*T!

If I need new rotors in a few months, so be it - a $56 mistake. A mistake that I won't make again. Thanks again for the info

I have to wonder how it is that new vehicles come with new pads and rotors...

I personally have never, in over 4 decades of experience, had an issue with all new parts. When I put new pads on old rotors, just did that on the 98, I remove the glazed surface from the rotor to get the pads to seat. If needs be it gets turned. Otherwise scotchbrite will take off the glaze without removing much material. I also replace the hardware i.e. the pins the calipers ride on.

o-gauge-steamer said:

I have to wonder how it is that new vehicles come with new pads and rotors...

I personally have never, in over 4 decades of experience, had an issue with all new parts. When I put new pads on old rotors, just did that on the 98, I remove the glazed surface from the rotor to get the pads to seat. If needs be it gets turned. Otherwise scotchbrite will take off the glaze without removing much material. I also replace the hardware i.e. the pins the calipers ride on.

Click to expand...

They do, and most people don't push their vehicles that hard.

A lot of what I've learned comes from having done amateur race work (bracket and some truck/tractor pull,) so the principles are a bit different. Considering I'm a rather more, er, "spirited" driver than most, I've stuck to the race work - and it's served me well.

The description on why new brakes squeal like they do is accurate, and that's why I've never felt good putting new rotors on with new pads (even though the factory did it.) When I'd set up a strip car, it was usually with custom work - and I could get pads "pre-bedded" by the factory. Sometimes get the rotors "pre-bedded" as well - the heat-soaking involved removed internal stresses.

One of these days, I'd like to see if new rotors/drums would benefit from being heat-soaked in the kitchen oven after the Cosmoline has been stripped off (you don't want to heat that stuff up! Yech...) and allowed to cool, but it would probably be an overnight process. Kitchen oven won't get hot enough to "bed" brake pads - most of the ovens top out at 500*F, and outgassing doesn't get started until 600-700*F.

Time was when performance production vehicles would come from the factory with pre-bedded brake pads - and that was done the same way that Wilwood or Baer would do it - they'd put them in a caliper, on a dyno, against a rotor, and run them through a specific cycle of speed and brake applications until the material would settle down and stop outgassing. This would enhance rotor break-in. I'd be highly doubtful they did that anymore - it's an extra process, costs money, and how many people are willing to drive an F-body or Fox properly anymore? Not from what I've seen...

Just a quick update, only 96 "urban miles" since the brake install so I haven't performed the final bedding procedure yet. At about 80 miles, I noticed that the brake squeal had stopped. Guess I don't need to install the shims. Braking has improved dramatically already.