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Old 05-09-2014, 06:55 PM   #1
SLO Town
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Join Date: Oct 2003
Location: The Wine Country
Posts: 580
My Ride: 2003 330Ci
Educational: H&R Sport vs Eibach Pro-Kit on E46 330Ci and the downsides of lowering


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.

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Original Owner 2003 330Ci ZSP, 3145 lbs, 5-spd, leather, Alcantara wheel, 19x8.5" BBS, RE-11s, ZHP FCAs/diff cover/weighted knob, M3 eng + trans mounts/outer RCABs/RCABs with Turner limiters, Group N inner RCABs, Bilstein Sports (E36 M3 rears), Eibach P-K, H&R bars, BMW Performance Rotors, Turner caliper bushings, StopTech lines, Borla, RE pullies/RSM, Stewart WP, M-Technic Trunk Spoiler, Mason pedal/strut bar/end links, B&M shifter, UUC DSSR

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