Best Coil Suspension Conversion Kit?
 

I have received the dreaded diagnosis that both front air struts need to be replaced. Rather than continue to throw money (and time and annoyance) at a "feature" that I will never use and could not care less about, I am taking the plunge on a coil conversion.

In looking through all the various threads on this issue, I've seen reference to certain kits or combinations, but I never found a thread dedicated to just reviews of the various options that people have chosen. To my knowledge, for a four-corner conversion these are my choices:

1. Strutmasters kit (with warning light module) - They advertise Eibach springs, but no indication on the brand of shocks. This kit apparently gives you a stock (normal air level) ride height. I also see at the bottom of the description that their four-corner kit only works on 3.0 and 4.4 models, not 4.6is, 4.8is, or 4.4 sport models. Does this have to do with spring height? Or is it something different?

2. American Air Suspension - Looks like the same exact kit as offered by Strutmasters (even the same picture).

3. Suncore Industries - This kit looks different, and there is no indication what brand of springs or struts it includes. Looks like they have just put some Suncore stickers on whatever brand of shocks they are.

4. H&R + Bilstein shocks - H&R's site is showing a sport spring kit for rear suspension only. Anyone used H&R's on a four-corner conversion?

5. B&G springs - Looks like they have a four-corner kit. Any experience in lowering effect and ride quality with these?

Any experience, advice, recommendations related to any of these is appreciated. Are there any other possibilities I haven't listed? I know KW makes the coilover kit, but I don't really care about the adjustability or ability to lower the car to that level. Mainly, I just want to be sure that I won't have to worry about any suspension issues for at least the next 5-6 years. Factory ride quality or slightly harsher, with perhaps some slight lowering, is all I really want.

Mine has the H&R springs in front, rear airbags, and Bilstein shocks all around.

Overall a great setup but rides just a touch stiff. If I were doing it again, I would do the H&R springs with OEM or equivalent shocks/struts.

Best? KW Variant 3s.

Do you say that because of the ride quality? The flexibility? Or something else?

I just got an email from a Strutmasters customer service rep confirming that their four-corner kit DOES NOT work with a 4.8is. No explanation as to why. I still can't understand why that would be the case. Is there something particular to the 4.8is frame or the rest of the factory suspension components (i.e. mounting points?) that would prevent a kit for a non-sport E53 from working?

I also had an interesting and very uninformative phone conversation with a Suncore customer service rep. They would not confirm (or deny) that their four-corner kit works with a 4.8is, but did point out that it doesn't say it WON'T work on their website (yes, I see that, thank you very much). She also said that the only people who know what brand of springs and shocks they use is their purchasing department. Apparently they are very protective of that information. So, they won't commit to me that their kit will definitely work with a 4.8is, or tell me what it is exactly that I'm buying, but I should just go ahead and spend $1,699 on their product. Ummmm...ok. Probably not. Thanks anyway, guys.

Ride quality, German built, TUV cert, materials used, attention to details in the mauufacturing process. KWs are used exclusivly in DTM (German Touring Car) racing series.

KW automotive North America, Inc. /// Be successful with KW suspension - made for Winners!

Even vehicle manufacturers know they can do no better, BMW uses KW on the M3 GTS, SRT uses KW on the Viper ACR that holds the class lap record at the 'ring, Gumpert uses them on their Apollo 'ring class record holder.

I don't doubt their quality...just seems like it may be a bit of overkill on a DD baby-hauler (as mine is). I guess it would be nice to have it ready to go whenever I decide to put it on the DTM circuit.

Did your X have four-corner air? If not, then I'm wondering if there are any compatibility issues with the KWs and a 4.8is (or other sport model with four-corner air).

Physically speaking the kits made for the other models will bolt up to yours as well. You'll still have to work out all the electronics on your own though.

Most kits on the market have spring/damping rates that are too high for DD duty, this results in a harsh/uncontrollable ride. The spring rate of the KWs are only slightly higher then the OE setup on the X, the shock are fully adjustable.

For a set of coilovers to work properly on the street it has to have some bulletproof dampers to handle the bumps ($$$), many cheap sets have high spring rates (stiff springs are a lot cheaper to manufacture then good dampers), the high spring rates prevent damper failure but destroy ride quality/control.

Spring rates near OE, soft high speed damper settings to absorb bumps, high low speed damping settings to control dive/squat/roll, drop gradually and drive the worst roads you normally travel until you contact bump stops, raise 1/2", put it on scales and adjust corner weight, get alignment. This is the only way to get coilovers to work on a DD.

I personally run a set of staggered ultralight 19"s (255-285 aspect ratio, under 50 lbs per rear with full tread), to reduce unsprung weight, this will allow more drop then with the heavy OE 20"s.

I have rear air on a sport pkg '03, at first sign of airride failure the KW Var 3s will be installed, will re-code to remove airride function.

Far too many think "I am not tracking/racing my vehicle and can therefore cheap out on coilovers" when, in fact, the opposite is true.

Has anyone come up with any answers as to what fits 4.8is?