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warped rotors?
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Author:  75dartcustom [ Sat Aug 20, 2005 9:59 pm ]
Post subject:  warped rotors?
i put new calipers on my dart and she braked great for about 500 miles. then i went on a road trip and after 8 hours at 70 mph when i pulled off the highway i heard a terrible noise from my brakes. it was cyclical, meaning it happens faster when the wheels are moving faster and slows with them, so im almost positive its warped rotors.

rotors are supposed to be good to .940 inches but mine are at 1.00 inches. am i correct to assume this sound is rotors? do i have no choice but to replace them?

and what do they make that brake noise treatment out of that you find at the autoparts store. i won't have time to do the work for a couple weeks so it looks tempting.

also, has anyone done this? is it easy? any words of wisdom are appreciated before i jump into the project, assuming its neccesary.
Author:  sixty4dartgt [ Sun Aug 21, 2005 12:09 am ]
Post subject: 
My rotors on my 1997 Dodge 1500 warped after about 6 months. It has metallic pads which chew the rotors up. I know on Volvos you have to buy new rotors every time you do brakes.
I had a '85 Rustang in the early 90's that got warped rotors after I drove thru a bunch of puddles. I guess if they cool too fast it warps 'em.
Author:  slantvaliant [ Sun Aug 21, 2005 8:28 am ]
Post subject: 
Some designs are prone to warping, but deposits can do the same thing. If the pads weren't bedded well, they can leave stuff on the surface, making it thicker in spots. This can be checked with two dial indicators positioned opposite each other on the rotor.
The brake noise stuff I've seen is intended to quiet some of the vibration / squeal that occurs between the pads and calipers.
Author:  kesteb [ Sun Aug 21, 2005 3:40 pm ]
Post subject: 
Your '75 Dart will have the single piston, sliding calibers. The calibers have a tendency to sometimes stick. The noise you hear is nornal rotor, pad rubbing. The normal runout from the rotor/wheel bearings are suppose to move the pads away from the rotor. When the calibers stick, this dosen't happen. You may need to remove the calibers and clean up the mount points so they will slide correctly.

If your brakes squeal when stopping, this is caused by friction between the pads and the calibers. The "anti-squeal" spays, lubricates the contact area between the pads and calibers. A silicon based spray seems to work the best.
Author:  75dartcustom [ Mon Aug 22, 2005 8:35 am ]
Post subject: 
definately no squeal, this is a grinding sound. so what exactly are the mount points? its not the piston that is sticking, correct? the caliper is mounted on two bolts, those are torqued to 100ft/lbs per spec. so it shouldn't be sitting at any sort of an angle.

also, the sound doesn't always occur, its there, it dissapears for a few blocks, it comes back, and the grinding is pretty sick in the stomach feeling when you have a girl in the passenger seat.
Author:  guest [ Mon Aug 22, 2005 10:31 am ]
Post subject:  brake noise
I've found that certain brake pads, while working fine, sound terrible (grinding & squealing) - sanding the surface of the pad helped for a while, but the noise always came back. I went to a different brand and the problem went away and didn't return.
Author:  kesteb [ Mon Aug 22, 2005 6:13 pm ]
Post subject: 
Quote:
definately no squeal, this is a grinding sound. so what exactly are the mount points? its not the piston that is sticking, correct? the caliper is mounted on two bolts, those are torqued to 100ft/lbs per spec. so it shouldn't be sitting at any sort of an angle.
Intersting, I didn't realize that Chrysler used that type of caliber on '75 darts, certainly not the same that were used on my donor car.
Quote:
also, the sound doesn't always occur, its there, it dissapears for a few blocks, it comes back, and the grinding is pretty sick in the stomach feeling when you have a girl in the passenger seat.
Are you sure they didn't put a pad on backwards?
Author:  SlantSixDan [ Mon Aug 22, 2005 7:01 pm ]
Post subject: 
Quote:
Quote:
definately no squeal, this is a grinding sound. so what exactly are the mount points? its not the piston that is sticking, correct? the caliper is mounted on two bolts, those are torqued to 100ft/lbs per spec. so it shouldn't be sitting at any sort of an angle.
Intersting, I didn't realize that Chrysler used that type of caliber on '75 darts, certainly not the same that were used on my donor car.
Yep, single-piston sliders on A-bodies from '73-'76. (Four-piston fixed calipers from '65-'72). What did you find on your donor car, and what year was it?
Quote:
Are you sure they didn't put a pad on backwards?
This isn't possible on the '65-'72 setup, and I'm pretty sure it's not possible on the '73-up setup, either (pads are symmetrical).
Author:  Slant6Ram [ Tue Aug 23, 2005 6:40 am ]
Post subject:  Possible causes.
My experience has shown that the symtoms you're experiencing can frequently be indications of larger and more critical problems. The root of your problems may be just cheap quality brake pads, but I've also seen excessive heat caused by dragging/sticking brake pads or overworking front pads because the rear shoes are out of adjustment or otherwise not correct.

Check rear shoe adjustment, they should be as tight as possible without dragging once the drums are all the way on. You might have to grind the lip off the edge of an old drum to get it on when adjusted properly.
Verify that rear wheel cyclinders are not siezed by having someone lightly press the brakes with the drum removed. Make sure both shoes move, not just one. (yes, I've seen only one shoe siezed, and it makes a big difference in stopping)
Clean and lubricate all the sliding surfaces for the front calipers.

If your brake fluid is black as coal, it's a good bet that it needs replaced. I suck most of the old fluid out of the master with an old turkey baster and then bleed the system clean.

I once fixed a caliper problem completely, by bleeding the front brakes until all the old fluid was clear and clean.

Air in the rear lines will also overwork the front brakes. Bleeding will fix that unless one of the wheel cyclinders is leaking. If so, the breaks will appear dark and damp instead of dusty.

I suggest you plan a whole day worth of careful inspection, adjusting, bleeding, etc. Brakes are not something that fail gracefully, they usually seem to go when you need them the most. :shock:
Author:  '74 Sport [ Tue Aug 23, 2005 8:57 am ]
Post subject: 
What is the possibility that it might not be brakes, but rather wheel bearings? I haven't had bearings go out, but I rather imagine it would be a horrific sound. :shock:

Jerry
Author:  skraecken [ Tue Aug 23, 2005 11:56 am ]
Post subject: 
My experience is that the "squeal" is produced from the pad vibrating against the piston, in Sweden a common fix is a thin plate between the pad and the piston.
Author:  Slant6Ram [ Tue Aug 23, 2005 1:53 pm ]
Post subject:  Wheel bearing noise.
Quote:
I rather imagine it would be a horrific sound. Shocked
Yes it's a roar that increases with speed and changes depending on which way the road turns. Doesn't seem to apply to this situation because usually pressing the brakes makes that sound quiet down rather than increase in my experience because the shoes deaden the harmonics.

Now you'll know how to know. :wink:
Author:  kesteb [ Tue Aug 23, 2005 8:52 pm ]
Post subject: 
Quote:
Yep, single-piston sliders on A-bodies from '73-'76. (Four-piston fixed calipers from '65-'72). What did you find on your donor car, and what year was it?
Quote:
Are you sure they didn't put a pad on backwards?
This isn't possible on the '65-'72 setup, and I'm pretty sure it's not possible on the '73-up setup, either (pads are symmetrical).
The donor car was a '75 Dart Custom SE. The caliber sits on top/inside of the caliber brackets with a couple of bolts and some sheetmetal to hold them in place. The pads have tabs that slip over the caliber brackets and nestle down inside of the calibers. I have seen the same setup on f-bodys and 1/2 ton trucks. And yes it is possible to put the pads in backwards.
Author:  75dartcustom [ Mon Aug 29, 2005 10:44 pm ]
Post subject: 
there are a few things that puzzle me about this brake grinding sound:

1. i put in new calipers, new pads in front, dissasembled the rear brakes, cleaned them, reset them, put in new wheel cylinders, and bled the fluid until it was fresh, new, beautiful light amber color.

2. the thing braked with absolute perfection for the next 500 miles.

3. sometimes i get the grinding sound cold, sometimes i dont, sometimes i get it hot, sometimes i dont, sometimes its there as soon as i start up, it goes away for a while, it comes back, there seems to be no pattern to the sound whatsoever...

4. there is no squeak or squeal, nothing high pitched whatsoever...
Author:  75dartcustom [ Mon Aug 29, 2005 10:50 pm ]
Post subject:  Re: Possible causes.
Quote:
My experience has shown that the symtoms you're experiencing can frequently be indications of larger and more critical problems. The root of your problems may be just cheap quality brake pads, but I've also seen excessive heat caused by dragging/sticking brake pads or overworking front pads because the rear shoes are out of adjustment or otherwise not correct.
can anyone recommend a quality brand for brake pads?
Quote:
Check rear shoe adjustment, they should be as tight as possible without dragging once the drums are all the way on. You might have to grind the lip off the edge of an old drum to get it on when adjusted properly.
Verify that rear wheel cyclinders are not siezed by having someone lightly press the brakes with the drum removed. Make sure both shoes move, not just one. (yes, I've seen only one shoe siezed, and it makes a big difference in stopping)
Clean and lubricate all the sliding surfaces for the front calipers.
i will do all these
Quote:
If your brake fluid is black as coal, it's a good bet that it needs replaced. I suck most of the old fluid out of the master with an old turkey baster and then bleed the system clean.
fluid is about 600 miles old, typical half dirty color. it should be ok right? or should i bleed them anyway?
Quote:
I suggest you plan a whole day worth of careful inspection, adjusting, bleeding, etc. Brakes are not something that fail gracefully, they usually seem to go when you need them the most. :shock:
yes, i think my car needs a day of love and attention
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