How much should brakes stick?


#1

I was replacing a tire on my 1991 F150, and noticed that the front disc brakes hold on the rotors a little bit. Not enough so that I couldn’t turn the rotor by hand, but enough so that I could hear the discs rubbing against the rotor as it turned.

Concerned as I am about good gas mileage, I grabbed a high quality silicone lubricant and sprayed those puppies down to really reduce the friction…JUST KIDDING!!! No, I talked to my dad about it and he figures its normal. Apparently not all pots fully-retract after every braking application? But he’s not 100%, so I thought I’d check around. Is this normal behavior? Or perhaps a sign that I need to change the brake pads or service the brakes?


#2

This sounds normal. What do the brake pads look like? Are the rotors smooth or do they have gouges in them?


#3

You might want to remove the caliper from the caliper bracket, and feel how smoothly the caliper mounting pins slide. It’s those things with small rubber bellows.

Tester


#4

Sounds normal.
Calipers, once the pressure is removed from the caliper fluid by removal of the pressure on the pedal, only have one force causing the piston to retract, and it’s a small one. It’s only a rubber ring around the piston that distends when the fluid pressure pushes the piston forward, then pulls the piston back just a bit as it returns to its molded shape. It isn’t perfect, and since neither the disc or the pads are perfectly flat and parallel, a bit of remaining drag isn’t unusual.

I liked Tester’s suggestion. While a small bit of drag isn’t abnormal, if the slides aren’t sliding freely they’ll just contribute to the resistance against the rubber ring and making sure they slide free is prudent.


#5

This is normal. As stated above, make sure the caliper slides are working properly.
Also, if the pads are worn evenly the caliper piston should be okay. If the pads are obviously worn unevenly then the piston might be sticking.


#6

I believe that model truck was using shielded rubber pins to hold the caliper in place.

Those pins should be replaced whenever they are removed and they require being coated with brake grease when installed. If there is any question as to their condition replace them. Pinch the protruding end of the pin and tap it back into the groove until it is flush with the caliper and then use a punch or chisel to push it out the back. Lubricate the new pins and tap it in until the tabs snap outward at the back.


#7

I’d just put it in Neutral on a grade and see how freely the truck coasts.


#8

I recall that the Ford factory spec was that if it rolls all the way to the bottom of the hill it’s perfect. Who could ask for anything more?


#9

Rod Knox: ha! She’ll get you to the bottom of any hill, no matter how steep! No worries.

Thanks for the feedback, guys. Brake pads looked fine, just a bit thin. I mean to go back and measure them soon. Rotors likewise looked fine. I’ll make a note to test the caliper brackets next time I’ve got the wheel off. Thanks again!


#10

Sounds normal to me too.


#11

Agreed.
The misconception of a newbie to disc brakes is that there would be free air space between the pad and rotor like the old drum brake shoes.
not so
just a release of pressure.


#12

Some brakes retract the pistons more than others. The design of the seal and the seal groove are used for this. It is used to improve MPG’s. Reduced contact = less drag = better MPG’s.

It causes other problems, long pedal free travel for one. Fix that with a bigger master cylinder bore and you need more power assist which can lower MPG… Vicious circle!