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      10-01-2016, 09:24 AM   #2
fmorelli
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Drives: Atacama Yellow 35i
Join Date: Mar 2016
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Well what BMW calls the "wishbone" in the front of our cars (lower control arm, if you wish), 31126786203/4 (left/right) have rubber inner joints on the E89. The E92 M3 has a ball joint. Simply you are going to get less deflection with the ball joint. Note, the arm is not the same wishbone design. Anyway, any time changing structural suspension parts should follow with an alignment. One other note (search threads here) is that you will have to fashion a mount for the passenger-side wishbone mount for the self-leveling lights - totally different on E89 than E92 (thanks BMW). It's not rocket science - forum search will help.

In my case (so this is the, "in my opinion" part), I decided to leave the stock tension strut (if you are an old BMW guy, older models had a "thrust arm" - same basic function except thrust arms come from behind the car and the tension strut on modern BMWs comes from the front). In my case rather than use the E92, I chose to press out the rubber bushing and go with a spherical bearing from AKG. A good alternative is the E92 tension strut for the M3.

Since you are asking about suspension, remember the rear of the car is very E46-like. The rear hub carrier has two suspension mount points (for upper and lower control arm). E46 regular cars were outer rubber bushing. E46 M3 were both ball joints. E89 arms have an upper ball joint and lower arm rubber bushing at the hub carrier. I changed out the lower rubber bushing to a ball joint. As for the inner bushings, they are rubber sleeve and can be replaced, but my suspension guy says the rubber sleeve is so thin that for even serious street use he says it is a waste of time to do the inner bushings.

In the rear, one other thing is the RTABS. With the E46 many run RTAB Limiters. On the Z4, the RTAB is 4mm wider than the E46, so the only real way to run limiters is to push out the RTABs for the E46 M3 RTABs and then install limiters.

You can do all of this yourself if you are handy and can get tools to press bushings in and out. Conversely any good independent BMW shop does this stuff frequently and can do so without much headache.

BMW Factory E46 M3 RTABs or Meyle HD work fine. Limiters can be had (shop around) - I buy mine from FCPEuro. Ball joints I would recommend BMW Factory or Lemforder. Except for the AKG spherical bearing, all my parts come from FCPEuro - those guys rock, fast, good prices—I have ordered probably between 2-3,000 parts from them, never once got the wrong thing. That's for folks in the USA.

Generally speaking the Z4 has been criticized for being too soft as a sports car. The suspension work really helps clean that up, and its responsiveness. The rest is subjective. I'll let those with lots of E89 before/after experience speak to the difference.

Hope this helps,

Filippo
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2011 35i MT Atacama ... lots of bits. Full Öhlins TTX custom suspension. Build thread.
Build sheet. Currently finishing suspension, fuel, ignition system with Barry Battle @ 3DMMotorsport.
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