front disk brake questions
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front disk brake questions
Tonight I had my '99 SCab 4x4 Off-Road on jackstands to inspect the brakes. Once I got the tires off, I started poking around, and noticed that the discs were very hard to turn. The brake pads were in contact with the discs, despite the brake pedal not being depressed. My question is, is this normal? Or should the discs be free to spin when the brakes are not being applied? It seems that this could be helping me only get about 12 mpg in town. Also, if the front discs are supposed to spin freely when the brakes are not being used, is there any way to adjust them so that they do spin freely? It just seems to me that this would be very inefficient for the drivetrain to have to overcome brakes that are basically already resisting rotation, even before the brake pedal is ever pressed.
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From: Bridgewater, NJ
The pads contacting the rotor are a normal thing, but it should not be very difficult to turn the rotors. Exactly how hard is it to turn them? Does it take two hands? There is no adjustment on disc brakes to make them not contact the rotor, their default position is to only relax slightly after the pedal is released. There are a few possibilities for calipers getting stuck, one of which is that the piston inside the caliper is rusty or has a lot of dirt build up and cannot retract. The other is that the pins which the caliper bolts go into are seized, which will keep one pad contacting the rotor at a higher pressure than normal at all times.
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From: South of KCMO.
Whenever I replace my brake pads, I put one or two lugnuts back on the lug bolts to snug the disk back against the hub. This keeps the disk straight when I install the new pads. Maybe if you tried this and turn your disk to check for rubbing? I would think if your brakes were rubbing that much, your wheels would get hot. Have you smelled hot wheels or tires after you park the truck?
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I have not smelled anything, but on a hot day after I drive around town for any extended period of time (stop and go for more than about 15 - 20 minutes), the brakes begin grumbling real bad when I apply them and don't feel like they're working quite as well as they should. It definitely takes two hands to turn the rotors without the tires on, hell it almost takes two hands with the tires on the truck but off the ground. The pads are in great shape though - so, I'm not sure what's going on. I did grease the zerks on both calipers once I found them, hadn't ever noticed them before. This was all last night - drove it around town all day today so I'll pull the tires again and see if the grease helped out any to maybe loosen up the pistons. Thanks for input, more would be greatly appreciated guys.
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Joined: Jul 2004
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From: Syracuse
Make sure the slippers that the pads slide on are not corroded underneath on the bracket. If the pads don't slide freely on the bracket, they won't retract well. I use anti-seize on anything that moves, or that you want to remove again.
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From: South Texas
Originally Posted by truckalpers
I did grease the zerks on both calipers once I found them, hadn't ever noticed them before. This was all last night - drove it around town all day today so I'll pull the tires again and see if the grease helped out any to maybe loosen up the pistons. Thanks for input, more would be greatly appreciated guys.
I hope you are kidding! Grease+brakes=BAD NEWS!!
Did you actually get any grease into the brake bleeding valve? I doubt the grease made it in, unless you opened the valve first? Step back from the truck and put the tools down
I would take your truck to a brake shop and get ready to spend some money!
Last edited by triton_2002; Jun 23, 2005 at 04:26 PM.
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I would go with what Marcus6679 said, and are both the left and right side hard to turn?? if so you may have a bad brake differerentiating valve (probably spelled that wrong) or something elsein the brake system, make it easy bleed the brake system with new fluid and see if that helps.
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From: Southern USA
don't drive it unless you really have to, and only very short trips around town. i would stongly recommend taking off those 2 small bolts that hold the caliper to the backplate/braket an remove the caliper assy. this is very easy. i think there 13 mm screw heads. if the caliper is difficult to get off, then you got stuck pistons or that diff.valve is bad as another poster said. when you get the caliper off, take a c-clamp as most mechanics do, and position the clamp so you can lightly apply pressure to move the pistons inward. i think you'll find at least one is stuck. do you do much off road mudin'? i've replaced many pads (but not on 4 x 4's) and have never seen a caliper frozen on the rails, although that does need to be checked. You will notice this obviously when you remove it. Ford used to have real problems back in the 80's-early 90's with phenolic pistons. a guy at work had one froze up on a trip and it almost caught on fire. Not sure what kind of pistons they have today. are you sure water or sludge hasnt got into the wheel brgs? remove center cap and inspect brgs while your at it. didn't mean to get long winded....paul
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No, Paul you aren't getting long winded, I appreciate the help. Boy do I feel like an idiot greasing the "zerk" fittings. I won't do that again, though I don't think I actually got any grease in there as it all just squirted out as soon as I started pumping, but it is kinda funny that my grease gun slipped right on there, you'd think they'd make 'em different for idiots like me.
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As a Design Engineer, a frequent topic of discussion was trying to make things "idiot proof". There is general agreement among us that when something is finally made "idiot proof", along comes a new improved idiot! 
