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Discussion Starter · #1 ·
Can anyone ELI5 how that rubber bumper on upper control arm works. Most explanations I found say that it prevents control arm from hitting your frame when you hit a bump / hole. But I can't really imagine how this bumper can touch anything in that area...

I'm going to replace upper arm soon, and I noticed that a good number of arms are sold without this bumper. I also checked my arm and found that bumper is gone, but still I can see a bolt there that was holding that bumper. I was driving like for a year at least, and I'm not even sure if I did any damage...

Please advise.


 

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That looks more like a mass damper - they help keep unwanted harmonics from happening.
 

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@zaharca It is a harmonic damper like @Sydtron stated.

Make sure you torque that arm down at your normal ride height position.

Here is what happened to mine wen it was 5/16 of an inch off from normal (didn't take the strut off to allow the correct positioning).

Damaged-upper-control-arm-bushing-mazda-6-ford-fusion.jpg

1 year later.
 

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Okay, since I didnt do it the first time... mainly because I didnt know what that meant either.


When your car is driving on the road all the suspension parts are in their normal positions. This means that the rubber bushings are not stretched one way or the other.
If you tighten the arms in a different position, other than the resting (road driving) position, the rubber will stretch to change from the position you tightened them down, to the position they are normally with the car sitting on the road. That stretch is fine if it is over bumps, but sitting in a stretched state for time, will cause them to tear prematurely. There are other reasons too but hopefully you get the idea.

On the other point, every thing that rotates, (engine, transmission, axles, wheels, etc) creates a vibration. That vibration varies depending on the rotation speed and material it's made of. The vibration will also produce sound (like the body of a drum does when the drum head vibrates after hitting it). As the tires roll down the highway they create vibrations that can be stopped (or reduced) by putting rubber in various locations. It is quite a science with numerous academic papers written on the subject. You have those little rubber absorbers all over the car, (suspension arms, cv-axles, motor mount, trans mount and more)
 

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Discussion Starter · #8 ·
@DrFeelGood Thanks for explanation. I had a general understanding how rubber mounts, bushing, etc. help with vibrations, but the purpose of this particular damper was not so evident for me.
@TalonTsi90 (y)
 

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If you want to dive into the subject, search "tuned mass damper" - plenty of papers and videos explaining how these things work, the active ones are crazy how they can suppress vibration.
 
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