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> Annoying grinding noise after new pads
andreic
post Jul 6 2018, 04:36 PM
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I installed new brake calipers and pads in the front on my 1.7L 914 (1972) after I discovered that one of the calipers was sticking. The calipers were high quality rebuilds from PMB.

Now I have this super annoying grinding noise whenever the car is moving. The noise is like something is grinding against the pads. It is there no matter if I press on the brake (hard or soft or at all), but it gets a bit louder if I step on the brake.

I suspect that the new pads are a bit wider than the old ones. When looking at my disks again today I noticed that there is some surface rust on them, about the first 1/4" both from the outside edge and from the inside. I know I should have had my brake disks turned when I changed the calipers, but did not do it.

My question is: will this annoying noise go away with a bit more driving, after the pads wear out a bit, or do I need to remove the calipers again, take the brake disks off to be turned, and reinstall everything?

Sorry for the low quality pic...Attached Image
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Spoke
post Jul 6 2018, 05:53 PM
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Sounds like you went top shelf with restored calipers from Eric with new pads. Those rotors should be replaced with new ones. I wouldn't turn any rotor these days as new rotors aren't that expensive and turned rotors are now that much thinner.

Replacing rotors also gives a good look at the bearings too. Maybe replace those as well and have all new rotating and brake components up front.
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porschetub
post Jul 6 2018, 08:54 PM
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QUOTE(Spoke @ Jul 7 2018, 11:53 AM) *

Sounds like you went top shelf with restored calipers from Eric with new pads. Those rotors should be replaced with new ones. I wouldn't turn any rotor these days as new rotors aren't that expensive and turned rotors are now that much thinner.

Replacing rotors also gives a good look at the bearings too. Maybe replace those as well and have all new rotating and brake components up front.

Let the pads bed in to the rotors or if not in spec replace them ,can't remember the wear limit think its like just over one millimeter from new thickness...don't quote me.
A lot of folks are unware the small amount the calipers move toward the disk,the piston seals dictate that.
I'am never to fussed about decent worn solid rotors with a pad replacement but vented ones are a safety issue cause they can fall in half (IMG:style_emoticons/default/sad.gif) .
Recently did all the disks and pads on my Audi now that is not cheap ,not much left from 900NZD fitted ,a powerful/heavy car the 914 couldn't be more different.
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HalfMoon
post Jul 7 2018, 08:09 AM
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Venting clearances set, right?
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PanelBilly
post Jul 7 2018, 08:39 AM
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I’ve always taken new rotor to the machine shop and had them turned first. I figure it’s best to start with a straight surface and I do t think you get that out of the box
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rhodyguy
post Jul 7 2018, 09:55 AM
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More often than not, the rotor runout is less than minimum spec after turning. Redo...with new bearings. Then you can forget them til next time.
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Chris914n6
post Jul 7 2018, 11:47 AM
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I once picked up an early 911 that just had brakes done, by a reputable shop. Grinding the whole way home. Found one of the pads was put in backwards....
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Jeff Hail
post Jul 7 2018, 12:49 PM
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Double check the pushrod adjustment from the pedal to the master cylinder. The pushrod nose should have 0.040 (1mm) between the m/c piston. Rock the brake pedal back and forth gently, should have tiny bit of movement. If no movement rod is too long, excessive its short.
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porschetub
post Jul 7 2018, 05:04 PM
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QUOTE(HalfMoon @ Jul 8 2018, 02:09 AM) *

Venting clearances set, right?


No ventin clearance for the front ,Jeff made a valid point about the cylinder pushrod I didn't think about that,mine was wound off and I needed to remove play in the pedal even with new disks and pads perfect now.
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porschetub
post Jul 7 2018, 05:08 PM
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QUOTE(Chris914n6 @ Jul 8 2018, 05:47 AM) *

I once picked up an early 911 that just had brakes done, by a reputable shop. Grinding the whole way home. Found one of the pads was put in backwards....


(IMG:style_emoticons/default/WTF.gif) ha ha did that once but only had myself to blame ,my wife needed her car in a hurry and I rushed the job .
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andreic
post Jul 12 2018, 06:02 PM
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I don't know, maybe I had a bad day and I put the pads in backwards. But I don't think I had such a bad day to put them in backwards on both wheels... Still, I'll check tomorrow.

(The car makes the same exact noise when spinning either the passenger or the driver's side wheel...)
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mb911
post Jul 13 2018, 05:36 AM
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Its gotta just be the built up rust on the rotors. It will go away with driving a little bit.. Same thing went on with my sons 944.
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HalfMoon
post Jul 13 2018, 08:06 AM
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QUOTE(porschetub @ Jul 7 2018, 07:04 PM) *

QUOTE(HalfMoon @ Jul 8 2018, 02:09 AM) *

Venting clearances set, right?


No ventin clearance for the front ,Jeff made a valid point about the cylinder pushrod I didn't think about that,mine was wound off and I needed to remove play in the pedal even with new disks and pads perfect now.


Opps. Duh me. Now I see he had said it was a front pad replacement.
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