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      05-09-2014, 09:39 AM   #39
wmandra
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Drives: 2010 328i, 2014 Z4
Join Date: Jan 2010
Location: NJ, USA

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Just wanted to post a quick update of where the current suspension setup is and some changes that are coming....

Finally went ahead and replaced the front upper strut mounts with Vorshlag camber plates and decided to try out some new alignment settings:

Front Camber: -2.5
Front Caster: +8
Front Toe: 0.00

Rear Camber: -2
Rear Toe: 0.32 (toe-in)

I ran this setup this past weekend at the track for testing and we're moving in the right direction. Initial turn-in in sharp and the car feels like its rotating right underneath the drivers seat going through the turns. I feel fairly confident these specs are the ones I'll be running for the rest of the season.

That said, there's still some room for improvement. I'm currently looking at replacing the AST dampers with MCS units and converting the rear to a true coilover. The current issue is that the OEM design in the rear definitely has some issues. With the spring mounted in the OEM location the effective Wheel Rate is only 55% of the actual spring rate and since the bottom of the spring sits on the wishbone which is then attached to the subframe, every time the spring needs to compress its pulling the subframe away from the body. This significantly limits the maximum amount of rear spring that can be used as too high a spring rate will end up damaging the subframe.

Moving the rear spring to a coilover setup will increate the Wheel Rate to about 83% of the spring rate and remove the stress from the subframe. This also brings the rear closer in line with the front Wheel Rate of 96%. Using the same 672# springs will increase the effective rear spring rate from 396# to 558# and bring the rear spring frequency more in line with the front. Right now wheel rates are 2.306Hz front and 1.626Hz rear, after the coilover conversion the rear rate will increase to 2.454Hz.

In addition to the coilover swap, I'm also considering replacing the M3 front control arms with a set of spherical front race arms from Bimmerworld (http://store.bimmerworld.com/bimmerw...ion-p2100.aspx) but still undecided on that.
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Driver, Ratchet Head Racing #93 BMW Z4
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2014 Glacier Silver Z4 28i M Sport - See the build thread: http://e89.zpost.com/forums/showthread.php?t=950367