E46Fanatics - View Single Post - Poly RTABS or Rubber OEM RTABS Lemforder
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Old 05-02-2013, 07:33 PM   #8
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Join Date: Mar 2006
Location: Southern California
Posts: 26,628
My Ride: Lexus
Originally Posted by Grande D View Post
For people who like the feel of rubber, the RTABs are the one place where it is acceptable to go poly. The NVH difference (RTABs only) is so small that if you didn't drive your car for a week in between you would not notice a difference.

Powerflex or AKG. AKG makes a part that is slightly softer than Powerflex and apparently cannot be distinguished from stock rubber. Stock rubber with limiters is more of a PITA than it's worth. Yes, I've tried that solution also.
Poly can be unpredictable in the RTAB location due to binding. Yes, this is according to Vorshlag. But if you understand how the BMW rear suspension is designed, there has to be play in that location. It's designed that way on purpose for street cars. BMW calls it elasto-kinematics (12th time I am mentioning this very word/term on these forums here @ e46fanatics.com) and is a huge part of the success story of world-renowned BMW 3-Series handling and stability.

Plus.. I wouldn't want to deal with the noise. I just think poly is often installed because it is "easier" to deal with than bushings. But in my opinion, they aren't.

I doubt the BMW M3 CSL is buzzing around the Nurburgring with poly RTABs. In fact, I know they're not. They use standard M3 part# 33326770817. It's preference, of course, but I'm saying don't think that it automatically will make your car grip harder or drive faster cause it won't.

Just don't get the obsession with poly when BMW designed the entire suspension to be elastic, including the hardcore M3 CSL. I just think that money is better spent elsewhere like on the CSL-specific rear lower control arm that uses a spherical bearing on its inner pivot rather than a bushing. The same can be had with aftermarket control arms that have a bearing like TMS. Now that I'm sure would give you some "feel"
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