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  #1  
Old 08-03-2009, 08:02 PM
RML RML is offline
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How do I clean up these rotors?

I am changing the brake pads on my 84 300D. The rotors have some wear as evidenced by the lip of metal on the outside edge. I was just going to replace them but instead invested in a calipers so I could see what I have left. The limit is 10.6 mm and they are well within the service limit, measuring 11.5 mm. I would like to file that lip off so I inserted one lug nut in the hub, attached a socket with an extension, and had a helper, my son, spin the wheel around while I held a file to the lip on the spinning brake disc. This works but will be awfully slow going, not to mention that there is an inner lip as well, and another wheel to do on the other side.

So I am thinking that if I could hook up the hub to an electric drill this would go alot faster. I would prefer not to have to remove the hub and rotor from the spindle, as it looks as though the PO had the bearings packed relatively recently. Has anyone devised an effective way to turn the hub and rotor so as to clean up the rotor while it is still on the car?

I know, maybe I am just being too cheap and should go for new brake discs. But I would be interested to know what else had been done out there in the DIY universe.

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  #2  
Old 08-03-2009, 08:22 PM
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No, no need to replace parts unnecessarily. I wouldn't worry about that lip, many, many folks don't.
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  #3  
Old 08-03-2009, 08:28 PM
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I wouldn't worry about the lip either - if you are really concerned I'd just take them into a shop to have them turned for about $10. Then again brand new rotors aren't much more than that for these cars.
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  #4  
Old 08-03-2009, 09:57 PM
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I always assumed the lip would cut the sensor wire and give me a premature pad replacement due light.
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  #5  
Old 08-03-2009, 10:43 PM
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Quote:
Originally Posted by Cr from Texas View Post
I always assumed the lip would cut the sensor wire and give me a premature pad replacement due light.
It does. It did on my SD....then I ignored it too long (light had gone out) and the pad nearly wore to the point of 0 material left.

I just put on new rotors....they're really not that expensive...
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  #6  
Old 08-03-2009, 10:46 PM
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Quote:
Originally Posted by Cr from Texas View Post
I always assumed the lip would cut the sensor wire and give me a premature pad replacement due light.
It doesn't seem like the sensor wire should be that close to the edge of the rotor.
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  #7  
Old 08-03-2009, 10:51 PM
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Originally Posted by pawoSD View Post
. . . I just put on new rotors....they're really not that expensive...
I don't mind spending the money when I have to but it seems premature. Also, replacing the rotors means pulling the hub off, which means messing with the bearings and the retaining nut on the spindle. Not that this is all that complicated, I just didn't want to get into it on this go around. There are other maintenance items on the list that I would rather be doing.
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  #8  
Old 08-03-2009, 10:58 PM
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I have definitely witnessed the same lip and felt it needed to be removed before even thinking of turning the key.

I have used 4" grinders in the past, but the rotors were always off the car. I am sure there is a spot where you can access both sides of the rotor without hitting the dust shield.

Take a practice run first on the outer lip just to get a good sense of how quickly material will be removed from the rotor. Then start glancing it with simple, well timed strokes... you'll find a speed that suits the proper removal of the lip and you'll become comfortable enough to do the inner lip.

There is no reason to set up some kind of rotating device. Just keep the rotor in place while you are working on a particular section.-----*you can weigh it down with a C-clamp clamped to the rotor surface... the weight will stop the rotor from turning..)
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Old 08-03-2009, 10:59 PM
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This just came to me. If I got a spare dust cover from the junk yard, I could drill a hole in the dome, put a bolt through, tighten it down with a nut, and spin the hub by inserting the bolt into the drill chuck while the dust cover is on the hub. I would of course have to remove the radio supression spring from inside the cap while I am doing this procedure.

My son thinks this would be a big load on the drill. I am sure I could rig up something coming off my grinding wheel, which I belive has a more powerful motor.
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  #10  
Old 08-03-2009, 11:06 PM
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Originally Posted by jt20 View Post
I have definitely witnessed the same lip and felt it needed to be removed before even thinking of turning the key.

I have used 4" grinders in the past, but the rotors were always off the car. I am sure there is a spot where you can access both sides of the rotor without hitting the dust shield.

Take a practice run first on the outer lip just to get a good sense of how quickly material will be removed from the rotor. Then start glancing it with simple, well timed strokes... you'll find a speed that suits the proper removal of the lip and you'll become comfortable enough to do the inner lip.

There is no reason to set up some kind of rotating device. Just keep the rotor in place while you are working on a particular section.-----*you can weigh it down with a C-clamp clamped to the rotor surface... the weight will stop the rotor from turning..)
I am concerned that with the rotor not turning, and working on one spot at at a time, there might be an uneven heat buildup which could cause the rotor to warp. Maybe I am under estimating the capacity for the rotor to transfer the heat away. I just know that when I have taken tools to the grinder to sharpen them, they can get awfully hot at the area I am grinding.
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  #11  
Old 08-03-2009, 11:10 PM
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I think you will be surprised at how quickly that lip comes off with some glancing blows from a 4" grinder.

I was able to hold a much smaller one steady by the bell as I ground it on a plastic surface.

...perhaps yours is worse than I imagine.
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  #12  
Old 08-03-2009, 11:31 PM
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Quote:
Originally Posted by RML View Post
I am concerned that with the rotor not turning, and working on one spot at at a time, there might be an uneven heat buildup which could cause the rotor to warp.
I am beginning to recall making several passes over the entire rotor before I was done...

Maybe that's a valid concern.
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  #13  
Old 08-03-2009, 11:37 PM
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Quote:
Originally Posted by jt20 View Post
I think you will be surprised at how quickly that lip comes off with some glancing blows from a 4" grinder.

I was able to hold a much smaller one steady by the bell as I ground it on a plastic surface.

...perhaps yours is worse than I imagine.
The smooth surface of the rotor where the brake pads hit measures 11.6 mm. The lip measures 11.8 mm. So there is a 0.2 mm difference or 0.1 mm on each side. It sure feels deeper than this but that is what it measures.

My biggest concern is that I was not able to get the brake pads out because they were getting hung up on the lip. I was not able to easily pull the caliper off either. I finally opened up the bleeder and pushed the pads back enough so they could clear the lip. I would rather not have to deal with this next time, when it will be a bit worse.
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  #14  
Old 08-03-2009, 11:58 PM
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Another idea is that the grinder WILL spin the rotor to some degree.. that might work to your benefit.


I'm quite sure that some of that lip is comprised of iron oxide... aka rust. You'll get through that.

I am actually shocked to read that so many others just put the new pads and wait for them to wear in.... you're only working with 5% - 10% of the working brake surface on those lips... scary!!

And isn't it quite possible that you could crack the pad material in half despite the metal backing?
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  #15  
Old 08-04-2009, 12:42 AM
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I am going to give the grinder a try and expect that it will get the rotor spinning as well, as you say. We'll see what happens.

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84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
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