New rear brakes/rotors.. grinding - A Theory

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Apr 7, 2019
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Just a theory..
After reading many posts with regard to the mysterious grinding following new rear brake/rotor install, and trying to figure out the source of mine.. I may have a solution for those still scratching their heads. There are so many variables involved that it's hard to say what is causing the issue, let alone determine the proper action. I installed new OEM rear rotors, remanufactured OEM calipers, and those fancy Napa pads. Immediately following there was a new metal on metal grind/rub.. heard mostly from the passenger side. I removed the complete install numerous times, inspected pad spring clips, straightened the dust shield, and removed the parking brake all together. I noticed there was a mark on the inside of the rotor where the parking brake backing plate lip would possibly touch.. so i shaved down the lip. Each time I bolted up the wheel and drove it, and it always seemed the same or got worse.

Now, if you are like me and have an 'all previous owner neglected' LC.. one which you are removing original factory parts from.. then it is safe to assume that the vehicle had rarely [if ever] been jacked from the rear diff. That being said, my theory is that the never seen stress [in 20 years] is straining the rusted and never greased drive shaft or u-joints. When it occurred to me that the sound is more of a pulse rather than a solid sound I greased the shaft and joints and the sound is 90% gone [I ran out of grease, and the shaft wasn't full].

Could it be a coincidence, absolutely! It is possible to have finally smoothed what may have been rubbing the rotor.. but all of these tests were isolated and I am fairly certain the driveshaft was the issue. Anyhow, I hope this helps those at the end of their rope. Lube your shafts boys.

*Update: just drove it some more, and though all straight line driving is noise free, it re-engages upon turns. Took 4 right turns and then 4 left, all the same. Sound lasts as long as it takes for the vehicle to level out [5 seconds]. Also, never has the sound occurred in reverse.. even 25+ yards. So, still just a theory.
 
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abuck99

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After replacing rear rotors, pads, and all ebrake hardware (all OEM Toyota parts) I found I had a rub-scraping noise only on turns (coasting through a turn), not in straight line. I attributed this to a very narrow tolerance inside edge near where the shoes sit of the new rotor; rubbing on the e-brake backing plate (not the dust shield) red arrows. I think also a little lash in the axle presents it self here in side to side motion. Over time the rub goes away as rotor hub wears in. Nothing to be overly concerned about- just a little annoying.

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Last edited:
Joined
Apr 7, 2019
Messages
18
Location
USA
After replacing rear rotors, pads, and all ebrake hardware (all OEM Toyota parts) I found I had a rub-scraping noise only on turns (coasting through a turn), not in straight line. I attributed this to a very narrow tolerance inside edge near where the shoes sit of the new rotor; rubbing on the e-brake backing plate (not the dust shield) red arrows. I think also a little lash in the axle presents it self here in side to side motion. Over time the rub goes away as rotor hub wears in. Nothing to be overly concerned about- just a little annoying.

View attachment 1950827View attachment 1950834
yep.. thats the rim I was filing and grinding smooth. Such a tight tolerance, definitely annoying when the circumference has flaky rust.
 
Joined
Apr 7, 2019
Messages
18
Location
USA
After replacing rear rotors, pads, and all ebrake hardware (all OEM Toyota parts) I found I had a rub-scraping noise only on turns (coasting through a turn), not in straight line. I attributed this to a very narrow tolerance inside edge near where the shoes sit of the new rotor; rubbing on the e-brake backing plate (not the dust shield) red arrows. I think also a little lash in the axle presents it self here in side to side motion. Over time the rub goes away as rotor hub wears in. Nothing to be overly concerned about- just a little annoying.

View attachment 1950827View attachment 1950834
Do you recall about how long it lasted? Granted, I haven't driven too much due to the work I have been doing.. but it is definitely getting on my nerves. Thx
 
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I had a similar problem with turning that was resolved by grinding down that inner lip (red arrows) where it seemed to be rubbing the rotor.
 
Joined
Apr 7, 2019
Messages
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I had a similar problem with turning that was resolved by grinding down that inner lip (red arrows) where it seemed to be rubbing the rotor.
Yeah, I have abandoned my initial theory.. though I think it would apply in some situations. The 10K mile wear down period mentioned is not an option for me, as I don't do enough driving.. I would be dealing with it for over a year.
I have painted the lip to see where the contact is happening, and will continue grinding in small increments. I wonder how much [if any] of the lip is needed by the parking brake.. I can't really say because I have removed it. I'm hoping that most if not all centering of the parking brake is accomplished with the springs. Do you recall how mush you took off?
 

abuck99

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I think that little lip just helps to keep debris from getting into the hub. Your idea of painting the edge is a good solution. Keep us posted what you find out.
 
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Finally.. took the grinder to it one more time, as well as a 3lb hammer.. problem solved. the first 2 images below show the wear pattern..lol, I'm not sure the paint was even necessary. You can see how deep it was cutting, not just the lip [from 4-8 o'clock] but 2mm deep in the proud surface rectangles. Flattened all fairly flush, and gently pounded the edge back about 1mm. Went for a drive and took some really hard turns, no issues! What a nightmare.

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The grind:
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