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Old 07-15-2014, 05:55 AM   #11
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Join Date: Jan 2006
Location: Cyprus
Posts: 6,564
My Ride: ESS TS2 320ci
Originally Posted by SLO Town View Post

I am not starting this thread to stir up a conflict on this forum. Rather, I'm starting this thread to educate people on the risks associated with lowering springs.

Lowering springs have a very serious negative - that being the fact that they reduce suspension travel; specifically suspension travel from the resting height to that when the bumpstop is contacted under compression.

I have a series of pictures that lead me to believe that the H&R Sport springs on my bought new 2003 E46 330Ci ZSP reduce suspension travel too much. I think the reduction in suspension travel was a factor in the seizure of my right front Bilstein Sport strut. This strut had only 30K miles on it.

Those who are familiar with me know that I am obsessively meticulous, respectful of automotive capabilities and limits, and that I perform 100% of my own mechanical work - all of it to a very high standard. In other words, this thread is not the result of some kind of installation error or product misuse.

I will be the first to admit that H&R Sport springs provide a much more aggressive look than the Eibach Pro-Kit springs. See the comparative pictures and I'm sure you'll agree. Let me add this, the Eibach Pro-Kit springs raised the front of my ZSP optioned car to stock height in front, 1/4 inch lower in back. In other words, if you have a ZSP or ZHP 330Ci and want a slammed look, don't get the Pro-Kits springs.

I have fine tuned the chassis of my 330Ci to a very high level. With the H&R Sport springs I found that the best balance was achieved with my H&R F/R anti-roll bar set to full soft on front, the midpoint on the rear. After installing the Eibach Pro-Kit springs and testing the car on my favorite section of road (smooth and grippy), it felt like I had put all season tires on it. I was amazed how much the handling had degraded. To say I was disappointed would be an understatement.

Because of mechanical (softer spring rates) and non-mechanical (higher center of gravity) changes, I re-adjusted my anti-rolls bars to full stiff in front, full stiff in back. I also changed tire pressures from 32/32 to 34/34. This made a HUGE difference, my car regaining about 95% of the lateral grip it had with the H&R Sport springs. The car is still exceptionally quick and extremely well balanced.

Ride-wise, the Eibach Pro-Kit springs are much, much softer riding then the H&R Sport springs. I greatly value "transient response" and, in truth, I lost some of that with the softer Eibachs. However, I did regain most of it by setting the anti-rolls bars full stiff. With the chassis loaded up in corner, the stiffness of the H&R/Eibach setups feels very similar (because of the different anti-roll bar settings). In some ways, I am enjoying the softer ride. Not only is it less jarring, I'm sure it's easier on the chassis as well (e.g. strut towers).

The pictures say it all. Take a look. It would take a 3,000 word essay to fully describe all the nuances. I won't do that but feel free to ask questions. I have weekend guests so be patient.

With the strut fully extended (as per picture where you're measuring), is it acceptable to have a very small play between the shaft and the body? That is, having the bottom of strut and top of the shaft bolted in place, grabbing the shaft at the lowest point (where it meets the body) reveals some play
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