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Old 05-02-2013, 07:43 PM   #9
Grande D
Registered User
Join Date: Dec 2006
Location: Redwood City
Posts: 3,434
My Ride: E36 M3
Originally Posted by Mango View Post
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 @ 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"
Never said it made the car faster. But I do think you're over-thinking it. Plenty of respected people who've made track cars out of their M3s use poly, so they must see some advantage or they would not do it. Neither is wrong, but I do not think stock or limited stock RTABs are worth the effort at all. Two people I know who did stock RTABs with limiters agree with me.

Properly greasing them is key, you can't use the supplied grease. You have to use copper anti-sieze.

Having said that, I've never heard a single noise from either car with the PF RTABs. If you want softer, buy the AKG Poly RTABs which have roughly the same deflection characteristics as the OEM RTABs (based on eyeballing them both).

Furthermore, the CSL is still a compromise. It's not a race car no matter how great it may be.

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