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marcr
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Dec 23, 2009, 1:41 PM
Post #1 of 8
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Question about brakes
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If your replacing or machining your brake rotors do you have to replace the brake pads too? I only ask because my rotors are warped and i still have 8/32" of the friction material left on the brake pads and was hoping i can still reuse them.
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chickenhouse
Enthusiast
Dec 23, 2009, 1:54 PM
Post #2 of 8
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Re: Question about brakes
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Always good practice to replace pads with rotors and break them in together.
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marcr
New User
Dec 23, 2009, 2:16 PM
Post #3 of 8
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Re: Question about brakes
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is it required though? i mean 8/32" thats almost new pad thickness. It really isn't bad if i dont' replace the pads is it?
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chickenhouse
Enthusiast
Dec 23, 2009, 2:28 PM
Post #4 of 8
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Re: Question about brakes
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8/32- 1/4 inch. By the time you wear the glaze off the old pad to get them seated properly to your fresh rotors, which will require a lot of breaking, you may be down to 7/32. 6 or 8 months -5/32. Do they cost THAT much? Your call of course but I don't take cuts on brakes. Rotors needed turned because of pulsation. Maybe the pads caused it.
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Sidom
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/ Moderator
Dec 23, 2009, 9:09 PM
Post #5 of 8
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Re: Question about brakes
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What type of vehicle are we talking about here?
As CH said, it's usually a good idea to replace the pads if you are going to turn the rotors, saves you a lot of extra work. But to answer your question, you can just turn the rotors without replacing the pads.
Machining rotors is not required when replacing pads. Only if they're warped, grooved or scored is machining required. Some manufactors have TSB outs to not machine their rotors unless required.
There are a couple of things you are going to want to look at before getting the rotors turned. One, the pads (you already did). The next thing is the min. machining specs of the rotor and the actual specs of your rotor. If you are even close to min specs, it would be a better idea to replace the rotors. I've seen in the past that once a rotor gets warped, even when machined correctly the warpage comes back even on rotors with a lot of room left on them. If it's close I wouldn't even waste my money turning them, odds are you you'll have the same problem a few months down the road and be back at square one.
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marcr
New User
Dec 23, 2009, 10:51 PM
Post #6 of 8
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Re: Question about brakes
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they're off a plymouth neon.
I measured the rotor in 40 places and got an average thickness of 0.863" ; a minimum of 0.848" ; a maximum of 0.868" ; so thats a thickness variation of 0.0202"
If i knew any way of measuring runout i'd give you those numbers too. New rotors from advance or auto-zone are 0.871" thick so i think my current rotors are still near the beginning of their life which is why i'm leaning towards machining as opposed to replacement. New rotors run $40/rotor at AZ or advance, and i checked with midas they'll turn both of them for $22/rotor.
Discard thickness is 0.803"
The whole reason i bothered measuring them or anything is recently i've noticed a high speed vibration and a slight pulsating action in the pedal. As i said i suspect them to be warped some but i don't know how to measure runout.
(This post was edited by marcr on Dec 23, 2009, 11:00 PM)
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Sidom
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Dec 23, 2009, 11:08 PM
Post #7 of 8
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Re: Question about brakes
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Well looks like you've done your homework on these rotors.
Your specs are correct. .871" is new .803" is discard. Runout is .005"
Runout is measured with a dial indicator. The gauge is zeroed in the middle of the pointer travel, rotor secured & then rotated fully and the runout should not exceed .005", if it does then machining is required.
If you just have a slight pulsation at high speeds then more than likely they aren't warped too bad and can be machined..... Compare the price to turning as opposed to new ones, if the cost is close you decided. If you do have them turned, make sure to wash the rotors with soap in warm water & then dried before reinstalling. also keep the pads clean. If any oil or grease gets on the pads sand them, do not use brake clean or any other cleaner on the pads to try to remove the oil. The pad will act like a sponge & absorb the oil which can contribute to noise or hot spots later on down the road.......
The key to quiet brks is clean & free moving parts (and quality pads, but that goes without saying even though I just said it  )...........
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marcr
New User
Dec 23, 2009, 11:22 PM
Post #8 of 8
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Re: Question about brakes
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I don't have a dial indicator so i'll probably just ask them to check the runout when i drop them off to get turned. I doubt it would be that bad since this just started recently so they should be able to correct it.
I never knew that about pads that they can absorb brake clean, i always thought that was a good suitable way to clean them off, I'll keep that in mind in the future!
thanks for the help!
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