My review/thoughts on recently-installed Koni/H&R setup:
Car: 1999 540 6-speed (Sport), 126,800 miles, mostly stock
H&R Sport Springs: #50464 (for 540 Sport suspension)
Existing Suspension mods: M5 sway/stabilizer bars front & rear
Suspension other: New Front wheel bearings, rear ball joints, rear stabilizer links last year.
Along with Koni/H&R install: replaced both front lower control arms/bushings/ball joints, tie rods ends, and both rear upper control arms/bushings/balljoints. New OEM fasteners, new bumpstops, new strut bearings, etc, were also installed.
Tires: Moderately worn Dunlop 2000E’s on stock staggered 17” Style 32 rims.
Driver Needs (me): 43 years old, seeking MINIMAL decrease in ride quality. Desire improved handling & controlled feel for my 80+% highway daily commute. Seeking lowered stance, hence the H&R Sport springs.
Rear Koni spring perch setting: lowest of the 3 possible settings
Rear Koni stiffness (not adjustable on-car): 1/4 turn from minimum
Overall impression of rear:
It is stiffer than stock (but better than some Koni’s I’ve tried), and very slightly jiggly (momentarily) on some surfaces, but not at all unpleasant except over rough/undulating road surfaces. Not optimal for my hind-end’s tastes, but very tolerable, except for increase in irritating squeaks from rear fold-down seats (was already an irritant). It feels like any tire imbalance vibration would be amplified, however.
Front set at 1/2 turn from Minimum:
This setting closely emulates stock Sport suspension, and actually feels a little more cushioned than stock Sport over small imperfections. Does not provide enough damping for the H&Rs springs - the front feels like it’s “pitching” sometimes. Less coherent front-to-rear than stock. NOT a recommended setting!
Front set at 1 full turn:
This setting feels a little flatter and more controlled than the ½-turn. Good damping match to the H&Rs. Decent handling – feels just a “little” better than stock; harshness is more pronounced than stock, but well within tolerability (to me). This would satisfy most enthusiast drivers, and is smooth as glass on most good highway surfaces.
Front set at 1-1/2 turns:
My preferred setting for everyday street use. Definitely harder ride than stock, but not much more than at one turn. Significant improvement in handling – now corners flatter than Gwen Stefani’s chest
– and front-to-rear coherence. Handling improvement well worth it, given the mostly smooth roads I ride every day. Bicuspids stay attached, minimal kidney shock.
Front set at 1-3/4 turns:
This setting might please younger drivers. Still very composed over bumps, and even flatter handling, but now the penalty in ride feel is just too much to take. Cuspids could start working loose. This is the outer limit of my tolerance, and only for short jaunts or autocrosses!
Front set 2 turns and beyond:
This would have to be a track setting only. Start looking for a kidney donor, and get fitted for false teeth. Forget about quieting squeaks and rattles; they will multiply like teenage rabbits. Car begins “hopping” on bumpy turns. Vision gets blurry…
Cosmetic Aspect:
See my “after” photos, posted/sent earlier; the photos don’t do the drop justice! The car looks absolutely menacing in person and on the street, even with the stock rims. I am also ECSTATIC at finally seeing a slight bit of negative camber in the front, thanks to the drop!
Overall/Summary:
There is a decrease in ride comfort, but if I had to do it again, I would probably do the same thing because I love the cosmetic aspect. The H&Rs, with their progressive rate, probably offer the best compromise available (short of Dinan) in handling with the drop provided. In everyday practical use, the drop doesn’t cause any problems, ground-clearance-wise. The handling is significantly better than stock. I don’t think this setup is for everyone, and certainly not for anyone who either (a) cannot tolerate ANY increase in ride harshness, and/or (b) rides over rough, ill-maintained roads. If the rear Konis were adjustable on-car, I’d like to try a 1/2 turn setting and see if it helps the very slight “jiggle” factor, but it’s really no biggie as-is.
I hope this helps someone considering a Koni/H&R install. Feel free to e-mail me with any questions/comments/suggestions!
Driving Impressions, Koni/H&R Install: E39 540 Sport 
urple'>Eric S.</span>
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