Information regarding F31 specific coilovers / suspension & what I know
Springs & Struts:
ACS springs $
320.00 - Bad reverse rake (Previously owned these) For those who aren't aware, they are rebranded Eibach springs -
Appear to have been discontinued
RS-R Ti2000 springs $
339.00 - No information
H&R springs $248.75 - Too low for stock dampers, it causes a bouncy ride as your strut is effectively too soft to dampen the spring movement. A possibility with Bilstien B8 or B6.
Eibach springs $239.00 - U.S. Website doesn't even list F31, European website lists two springs options (0.8"/0.6") with two variations, one has higher load front springs. I listed the eBay link where I purchased my set Part# E10-20-031-14-22.
Koni special active/ Koni sport struts $686.24,
$812.00 - Special active struts seem viable, sport struts good for drops exceeding 1"
Bilstein B4/B6/B8 struts $426.00,
$706.02,
$776.00 - Good option to use B6/B8 for lowering springs. B4 is an OEM replacement but is OK with ACS/Eibach
Affordable coilovers:
ST coilovers $892.49 - Same as KW V1 minus the coating
Bilstein B14 PSS coilovers $1044.00 - Have heard people who experienced coil binding/chaffing
BC racing coilovers $1050.00 - Not the best quality and poor customer service, is there even f31 x-drive coilovers from them? This is a possible option if you don't mind some drawbacks in quality
Ksport coilovers $935.00 - Never seen anyone try these, personally not a fan of the clamp style attachment for the brake line
CATuned coilovers $1250.00 - Also no info on anyone running these.
Pricier coilovers:
H&R coilovers $1414.95
(Currently running these) They are fairly stiff, not for those seeking comfort. But a solid build with a competitive price point.
Bilstein B16 coilovers $2034.00
Bilstein clubsport coilovers $4208.00
KW V1 coilovers $1444.99 - Coil bind/chaffing? adjusted through preload and not shock body, slammed in the rear (at max height)
KW V2/ KW V3 coilovers -
$1827.49 ,
$2294.99
KW Street comfort coilovers $1886.99
KW DDC coilovers $3459.99