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      01-14-2019, 11:38 PM   #1
taranfx
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Understeer with H&R swaybar?

I've 35is with with H&R swaybars with rear set to max stiffness. The car runs Michelin PS4S 235 & 265 19" tires.

When I push the car hard across the corners going downhill, the front tires scream and its a noticeable amount of understeer.

Is it because H&R front swaybar too stiff? Stiffer than rear causing this understeer?
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      01-15-2019, 11:16 AM   #2
Tangent
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It's because the swaybars alone aren't enough to get rid of the inherent understeer it has. The rest of the suspension tuning, the staggered tire sizes, and the minimal front camber all add up to understeer; especially in slower speed tighter corners.
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      01-20-2019, 10:51 AM   #3
Vetracr
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Quote:
Originally Posted by Tangent View Post
It's because the swaybars alone aren't enough to get rid of the inherent understeer it has. The rest of the suspension tuning, the staggered tire sizes, and the minimal front camber all add up to understeer; especially in slower speed tighter corners.
I also found from autox experience in order to minimize understeer you have to turn off DTC. DSC will cause Z4 to understeer in all modes when on. I have H&R bars with rear set a stiffest position and also run larger staggered tires and Koni FSD shocks. I have also added Ground control camber plates and run 2.5 degrees negative camber up front. Makes all the difference in the world. Car now handles neutral on track.
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      02-05-2019, 09:35 AM   #4
Asbjorn
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Quote:
Originally Posted by Vetracr View Post
I also found from autox experience in order to minimize understeer you have to turn off DTC. DSC will cause Z4 to understeer in all modes when on. I have H&R bars with rear set a stiffest position and also run larger staggered tires and Koni FSD shocks. I have also added Ground control camber plates and run 2.5 degrees negative camber up front. Makes all the difference in the world. Car now handles neutral on track.
Totally agree with Vetracr - a stock E89 Z4 has a lot of rear camber compared to front. Maxing out front camber with Ground Control camber plates helps massively. To get even more camber, you need smaller springs = coilovers.

With camber plates (no rubber) and more camber you get increased tire wear and NVH though.

I tried putting the stock sway bar back in, while keeping the H&R rear sway bar on its stiffest settings. Yes it decreased under steer, and made the front feel lighter and softer, but it makes the car less responsive and more wobbly. I personally did not like it, and went back after one track session.

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