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Discussion Starter #21
I still haven't gotten a chance to measure my rotors for runout, planning on doing so tomorrow on my friend's lift. I'll also check thrust arm bushings again as suggested.

I noticed a new symptom last night, when reversing in a parking garage I hit the brakes and heard clicking sounds coming from the front drivers side brakes as I stopped. I recorded this video and uploaded it to youtube to post here. It shows me braking while moving forward and braking while moving backwards which produced the most clicking sounds.

What could be causing the clicking sounds? It's almost certainly linked to the shaking issue. Control arm/bushing? I feel like it's coming from the brake caliper itself but take that with a grain of salt, just a feeling based on the metallic character of the sound. I feel like It doesn't sound exactly how worn suspension parts sound, like it seems way more metallic. Again, take that feeling with a grain of salt because I don't have much experience with suspension sounds.

You don’t have a warped rotor, as technically that doesn’t really happen- it’s a phrase used to describe lateral runout. You may have lateral runout caused by uneven deposits, lateral runout at the hub or bearing, lateral runout caused by poor manufacturing (uneven surface out of the box).

Or you may have a hot spot, where one area of the rotor has become overheated and has therefore changed in composition, it will become harder with a higher coefficient of friction on that spot- obviously that will cause shudder as the harder spot goes past the pad, the rest of the rotor also wears away more quickly, so now you have a hard “bump” on the rotor surface.

Lateral runout can be measured, hot spot will look like a dark stain on the surface.

I believe the temp at which cast iron starts to become malleable is around 1400f. Formula 1 cars will see 1200f on their brakes for brief periods. Given a road car will see much less, it’s highly unlikely you will ever get them hot enough to deform.
Gotcha, so I can conclude there isn't a hot spot on my rotors from what I can tell. More likely uneven deposits or the hub or bearing if I measure any when I get a chance.

My money is STILL on thrust arm bushings, even in spite of this. Last set I put on, I carefully had the weight on the car with all 4 corners up on ramps when I torqued them down, probably my 4th thrust arm job myself. One side leaked out all its oil within about 150 miles. I'm quite convinced (other similar reports) of some sort of manufacturing or quality defect with recent Lemforder parts. Go so tired of dealing with it I went to monoballs. Slightly degraded ride quality, but MUCH more controlled and best of all I'll probably never need to worry/wonder about them causing brake shimmy again! At any rate, go underneath the car and inspect the bushings for the telltale signs of any leakage; I suspect you'll find some. . .
Inspect the rubber very closely and look for any sign oil might have leaked. There were some early batches that the oil leaked out within the first month or two of service, so pockets for dirt where it should not be and when you wipe it off it sticks to itself rather than crumbles away. The issue has been resolved but maybe you got unlucky and got old stock that should have been sent back. Sorry don't remember which manufacturer it was for sure but I think it was lems with the new bushing installed.
Last time I was under the car I didn't notice anything but I didn't look very closely. I'll check again as soon as I get the car back on a lift. I didn't buy Lemforder brand thrust arms though, I think I bought Meyle or something else.

You can't test for runout with worn bearings, they will mimic runout. The first step in setting up is to force the rotor towards and away from the center of the car to look for play in the bearing. If there is you replace the bearings and try again.
I'll check that as well, so I just try to shake the rotor back and forth to check for any play right? If it has any play at all then that would probably be the problem!
 

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so I just try to shake the rotor back and forth to check for any play right? If it has any play at all then that would probably be the problem
No and if you are planning on doing it on a lift then no again. There are things you must do but I will cut to the chase. You should check every part in the suspension for play or out of tolerance, because if the wheel bearing is connected to things that move it will move.
The short story is isolate the bearing from the suspension in a spot and then set your dial indicator up so it will be the most protected from something else. I like to set the wheel on a jack stand that bears on bottom of the ball joints. That usually stabilizes even worn ball joints. Then I setup at the bottom dead center of the rotor. That does not isolate from movement in the steering but you can lock the steering. Then I stick a screw driver in the rotor at the top or bottom and with some force but not much push the rotor, read the gauge, pull the rotor read the gauge. Decide if that was good or if the steering helped make those readings.
There are better ways to do it but that works for me because best guess is usually good enough. That assumes you have done all the other things first. Suspension first, then steering, next bearings then run-out.
 

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I’m still leaning an issues with your rotors, calipers, or pads. Every shimmy I’ve dealt with at highway speeds has always been remedied by new rotors or replacing a bad caliper. Specifically, shimmy at highway speeds under very light breaking.

Did you have the shimmy before the brake work?
 

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Discussion Starter #25
I ordered two front wishbone straight control arms and sway bar links, they'll be here tomorrow so I'll replace them. Hopefully they fix the issue because I was already planning on replacing them but if not I'll have to keep searching for the culprit. Haven't measured runout yet, will likely do so while following sailor's advice tomorrow.

No and if you are planning on doing it on a lift then no again. There are things you must do but I will cut to the chase. You should check every part in the suspension for play or out of tolerance, because if the wheel bearing is connected to things that move it will move.
The short story is isolate the bearing from the suspension in a spot and then set your dial indicator up so it will be the most protected from something else. I like to set the wheel on a jack stand that bears on bottom of the ball joints. That usually stabilizes even worn ball joints. Then I setup at the bottom dead center of the rotor. That does not isolate from movement in the steering but you can lock the steering. Then I stick a screw driver in the rotor at the top or bottom and with some force but not much push the rotor, read the gauge, pull the rotor read the gauge. Decide if that was good or if the steering helped make those readings.
There are better ways to do it but that works for me because best guess is usually good enough. That assumes you have done all the other things first. Suspension first, then steering, next bearings then run-out.

I’m still leaning an issues with your rotors, calipers, or pads. Every shimmy I’ve dealt with at highway speeds has always been remedied by new rotors or replacing a bad caliper. Specifically, shimmy at highway speeds under very light breaking.

Did you have the shimmy before the brake work?
No shimmy before brake work. That's the one part I don't understand, why this started after doing brake work and didn't happen at all before. The rotors don't seem bent and no shaking under 40mph. Only thing I can think of is the brakes are slightly more responsive but there's no way just that would cause something this severe.
 

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That's the one part I don't understand
The brakes do vibrate, that is what all that rubber is for, to dampen and remove the vibration from the rest of the system. Every time you come to a stop and have to hold the brakes small amounts of brake dust or even the pad can transfer to the rotor, the hotter the rotor the worse that can be. It normally is removed the next stop. If you did not bed your brakes once you did the work then the transfer can be more than normal. Without a properly bedded in system the rotor will not have the protective coat that makes those deposits easily removed. If they are not removed, when you stop again and hold the brakes it is almost always at the spot where the deposits are so they get worse.
If the mating parts were not cleaned and the rotor does not sit perfectly flat on the hub, that might cause a vibration that the rubber cannot absorb. That would be the same as having a very serious runnout issue. If the slides are not working correctly then that would make even a small defect in the mating surfaces more severe.
 

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I still haven't gotten a chance to measure my rotors for runout, planning on doing so tomorrow on my friend's lift. I'll also check thrust arm bushings again as suggested.

I noticed a new symptom last night, when reversing in a parking garage I hit the brakes and heard clicking sounds coming from the front drivers side brakes as I stopped. I recorded this video and uploaded it to youtube to post here. It shows me braking while moving forward and braking while moving backwards which produced the most clicking sounds.

What could be causing the clicking sounds? It's almost certainly linked to the shaking issue. Control arm/bushing? I feel like it's coming from the brake caliper itself but take that with a grain of salt, just a feeling based on the metallic character of the sound. I feel like It doesn't sound exactly how worn suspension parts sound, like it seems way more metallic. Again, take that feeling with a grain of salt because I don't have much experience with suspension sounds.



Gotcha, so I can conclude there isn't a hot spot on my rotors from what I can tell. More likely uneven deposits or the hub or bearing if I measure any when I get a chance.




Last time I was under the car I didn't notice anything but I didn't look very closely. I'll check again as soon as I get the car back on a lift. I didn't buy Lemforder brand thrust arms though, I think I bought Meyle or something else.



I'll check that as well, so I just try to shake the rotor back and forth to check for any play right? If it has any play at all then that would probably be the problem!
I have the exact same sound comming from my front end, and the same shimmy at high speed 50 mph+. I tightened upper and lower control arm, there was little side to side movement in the upper thrustarm, but the ball joint was ok. I did the entire front and rear suspension just 6-7 month ago.
I have somewhat narrowed it down to pad-knockback, because I run 4 piston caliper front&back and a floating rotor setup.
And I did see/hear it while my mate was pressing the brakepedal, while the front wheel was off. But this does not correlate to the brake shimmy at 50mph+.

on stock caliper&rotor setup, there was no noise, so the fixed caliper+bigger rotor must mean any little play in control arms will manifest itself to an even bigger degree, than with floating calipers.

do you miss the caliper-spring? Or miss your pad shimmy backplates

I now assume the shimmy must come from the little play in the upper thrust arm, and that is why I have ordered powerflex lower and upper bushings (racing version) I would have considered monoball, but now I am trying powerflex.

I am eager to see, what you can conclude from this, your fix could be my remedy
 
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