Got a question for the brake gurus...

At what point does a brake caliper's performance start to deteriorate? I mean, is it an all or nonething affair, where they either work or fail? Or do the seals, pistons, and what not start to wear from all the high heat, rain, snow, ice, dust, and basic abuse that brakes ee every day.

For example: My SVT has a buncha miles on it, and even with new pads and rotors all around, it just doesnt feel as strong as it did in "days gone by." And yes, I replaced and bleed the fluid, used Bendix Ti pads, and lubed my slide pins.

I'm not looking for "you should have done this...have you tried that..." but rather, when is it time for rebuilt calipers or new ones?

TIA

Usually, no. Calipers tend to continue to work the same unless they start leaking. (or slide pins are bound up or whatever). But if you look at the caliper piston(s) and see that the dust boost and perhaps seals have deteriorated, you'll know that it won't be long before the seal starts leaking.

In your case, I'm inclined to believe you didn't get the system fully bled. Once air gets in the lines (for any of a number of reasons) it can be very difficult to get it completely bled again.

Another aspect is, that the friction level of the bendix pads may not be quite as high as the factory pads. Actual data for friction levels is rarely available, and when it is, it is wholly insufficient to caracterize the real friction profile seen on the vehicle.

I'll agree with most of that and I can speak from experience that the following will effect general performance:

Seals with debri in them.
Seals that are dry.
Sliders that are not properly cared for and lubed.
Pistons and or bores that are scored and not allowing smooth operation.
Pads that are binding up in the brackets which hold them.
Pads worn down too far and binding at an angle.
Glazed or oiled pads which no longer have the proper bite.

Most of this effects both the clamp and release of the piston and can lead to dragging or the opposite; too much pull back.

Pads that are of the lower Cf and or oiled/glazed are an obvious one.

We'll assume now that you are speaking of the fronts only? Don't overlook a problem in the rear that makes you think front either.