brake squeal after changing rotors

[Sunliner]

we have a 2004 Sienna LE.
I noticed it shuddering when braking so last month I changed rotors. That eliminated the shuddering, but now the darn thing squeals when the brakes are applied. I just did the pads about a year ago, and there's still a lot of material left on the pads.
I was very careful not to drop any shims when I moved the calipers to do the rotors, and torqued everything back down according to the book. don't know how I made this happen...

[wiswind]

Brake Squeal is a tough one.
It is the result of a "harmonic" between the different brake components.
IDEALLY one would replace the pads & rotors together......as the pads are certain to be somewhat molded to the surface of the rotors.
When I do a brake job, (not nearly as many as a real mechanic does.....so my sample size is very small) I notice that there are ridges in the rotors......not completely smooth.....and I imagine that the new rotors with the old pads has you rubbing hard on the ridges in the old pads on the new & smooth rotors.
You could have a simple matter of the pads/rotors wearing in together to become more quiet....or a longer lingering problem, as far as the noise is concerned.

[FishFind]

He got it.

[jdmccright]

I use CRC Disc Brake Quiet on the backs of all my pads when I do brake jobs. It's red and comes in a squeeze bottle. I apply it over the entire back of the pad to completely cover the shim past the edges. Let it set while I finish cleaning/lubing the rest, then install the pads while its tack dry. I've never had squealing brakes.

If you're reusing pads for new rotors, you can smooth them by running them over 100-grit sandpaper laid on flat concrete. Most new rotors are already surfaced with a criss-cross pattern for immediate use.