New brake pad/rotor question

J Smith · 02-10-2005, 07:23 PM

I just finished rebuilding my brakes. Calipers rebuilt, new lines, new MC, fresh fluid.

My question is how much drag should the pad have on the rotor when first installed? I can hear the pad touching the rotor when I spin it, and there is enough friction to keep the rotor from spinning freely, but it's not so much where it takes any real effort to spin the wheel. Am I making sense?

Also, is there anything special I should do (braking) during the first couple hundred miles to make sure the pads/rotors "break in" correctly?

Thanks.

Zeke · 02-10-2005, 07:35 PM

You're gonna get a lot of answers, but tell us what pads you installed. Some require agressive break in. Others less so.

AFIK, the pads lightly drag on the rotors at all times. But, the time to recheck that is after a few stops. If the pads aren't "right there," you will have a long pedal.

The only pads that I know of that completely back off the rotors are on NASCAR superspeedway cars. They are looking for a tenth of a HP, or to save one.

J Smith · 02-10-2005, 07:40 PM

Ferodo pads.

I didn't have the pads "right there" when I first installed them and had the long pedal. Got them closer, to the point it was tough to slide the caliper over the rotor, now the brake pedal feels much better.

Zeke · 02-10-2005, 07:58 PM

Well, that's fine. You can install the pads on spread out pistons. First pedal will bring them into contact with the rotors. At this point, you want to recheck the BF level.

Inside each pistion is a long post (shaft) and the spring gizmo that slides over it acts to back off the pads after each clamping down or braking. They only back up a tiny bit, and there's enough slop in the way they hang that they will always rub. And, that's why the 20 degree orientation on the pistons and the slight bevel you were supposed to put on the leading edge of each pad (so they don't squeal).

As they wear, the spring/return advances down the shaft towards the center of the caliper. This is a reason you want to first install the pads on pistons "opened" up a bit. Not to mention ease of installation.

You know, there are guys around here that know a lot more than I do about brakes. Maybe I ought to climb in the backseat.