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?

Sweep_the_Leg Sweep, you don't tell us the year, mileage and past (suspension or other) repairs to your X5.

Even with a conventional suspension, after time & miles or km, your shocks and other suspension parts will need replacement. The X5 had some known bushing & other parts that need attention every 5 to 10 years based on your roads, driving style, wheels (wide 18, 19 or larger diameter wheels will accelerate this).

I have a 2002 3.0 diesel (I live in Europe) with conventional front and air rear. Rear bags showed signs of cracking, so I replaced them proactively with Arnott products. Two hours start to finish, easier than with springs as you don't have to use a spring compressor. Bilsteins (B6 the yellow ones) as well.

I would suggest that repairing your front air struts is not any different as replacing shocks on a spring / shock suspension and WITHOUT the hassle of compressing springs.

Buy Arnott front air struts, easy to replace (they have lots of videos to show you). Look at your rear air springs and if you see visible cracking, consider proactive replacement - it's really quite easy.

Mine is a 2005 with just under 79,000 miles. I don't know about any previous suspension work, as I've only had it for about six months and wasn't privy to prior service records when I bought it.

I ended up swapping out the factory front struts with Arnotts today. From the online research and calls I made, there is apparently not a single coil suspension kit that works on a 4.8is. Even KW told me that their coilover kit is not compatible.

The car obviously feels much better with the new Arnotts. I had slow leaks on both sides, which generally meant that car was having to pump itself up every time it sat for 8 hours or so. Steering is much more responsive and the ride feels both more stable and softer at the same time. Not surprising, I suppose, considering I was basically driving it around with both fronts at various stages of low to full inflation.

While I would rather have just put coils in and forgotten about the whole air system, the Arnotts weren't too bad. Once I get my core deposits back, and with the decent labor rates at my indy, the total damage will be a tad over $1300. I would have tried tackling the install myself in the driveway, but I've got too many other things going on right now.

I'm not saying they are the greatest as I was only able to dig up with one review. The BC Racing Coils for the X, and the review was from one of the forum members X5girl. They will run ya just around a G note.

You can read post #6 in this thread to see the why I think KW is pretty much the top of the heap (nothing worse then trying to save some $s on a labor intensive mod only to find dissatisfaction in the end result). I'm currently looking into a TOTAL Powerflex/heavy duty suspension bushing set to install with the KWs. With the ultra-stiff bushings there will be no excuses at alignment time to see a printout and hear "that's close enough" from the tech. I'm going for minimum camber/tow so the X is not a tire eater.

Having owned several coilover vehicles and setting corner balance/cross weights on my scales, I like the fact that the KWs have a low friction thread coating process that allows for adjusting without unloading the coilover (it sucks having to jack up, adjust, drop, re-settle the vehicle during the process).

I'd love some KW's but for 3 grand it costs a pretty penny. I'm also looking into eibach sway bar kit, but the front is rare to come by.

I've seen them as low as $2300. Currently $2600 on e-bay.

KW Suspension Variant 3 Three coilover Kit 01 06 BMW x5 E53 35220053 | eBay

How's the warranty on the K&W?

Original owner has a lifetime warranty on defects. These are not covered for bottoming out/abuse (crash a curb and it's not covered).

The Var 2s on my Viper were $4000 and don't even have that warranty. Galvanised steel and no warranty for 4k (V2s) vs INOX Stainless steel and warranty for 2.3k (V3s), go figure.

I would troll e-bay and buy when a set pops up for $2300 or less, that's what I did.

I wonder how many coilover owners actually set them up correctly.......

Adjusting The COMPRESSION (Bump) Damping Control (Very Important to do this FIRST!)
Bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward movement of the suspension as when hitting a bump in the track. It should not be used to control the downward movement of the vehicle when it encounters dips. Also, it should not be used to control roll or bottoming.

Depending on the vehicle, the ideal bump setting can occur at any point within the adjustment range. This setting will be reached when "side-hop" or "walking" in a bumpy turn is minimal and the ride is not uncomfortably harsh. At any point other than this ideal setting, the "side-hopping" condition will be more pronounced and the ride may be too harsh.

STEP 1: Set all four dampers on minimum bump and minimum rebound settings.

STEP 2: Drive a moderately bumpy road briskly to get the feel of the car. Note: When driving the car during the bump adjustment phase, disregard body lean or roll and concentrate solely on how the car feels over bumps. Also, try to notice if the car "walks" or "side-hops" on a rough turn.

STEP 3: Increase bump adjustment clockwise 3 clicks on all four dampers. Drive the car bumpy road again. Repeat Step 3 until a point is reached where the car starts to feel hard over bumpy surfaces.

STEP 4: Back off the bump adjustment two clicks. The bump control is now set. Note: The back off point will probably be reached sooner on one end of the vehicle than the other. If this occurs, keep increasing the bump on the soft end until it, too, feels hard. Then back it off 2 clicks. The bump control is now set.

Adjusting the REBOUND Damping Control
Once you have found what you feel to be the best bump setting on all four wheels, you are now ready to proceed with adjusting the rebound. The rebound damping controls the transitional roll (lean) as when entering a turn. It does *not* limit the total amount of roll; it *does* limit how *fast* this total roll angle is achieved. How much the vehicle actually leans is determined by other things such as spring rate, sway bars, roll center, ride heights, etc.

It should be noted that too much rebound on either end of the vehicle will cause an initial loss of lateral acceleration (cornering grip) a that end which will cause the vehicle to oversteer or understeer excessively when entering a turn. Too much rebound control in relation to spring rate will cause a condition known as "jacking down." This is a condition where, after hitting a bump and compressing the spring, the damper does not allow the spring to return to a neutral position before the next bump is encountered.

This repeats with each subsequent bump until the car is actually lowered onto the bump stops. Contact with the bump stops causes a drastic increase in roll stiffness. If this condition occurs on the front, the car will understeer; if it occurs on the rear, the car will oversteer.

STEP 1: With rebound set on full soft and the bump control set from your earlier testing, drive the bumpy road, paying particular attention to how the car rolls when entering a turn.

STEP 2: Increase rebound damping three sweeps (or 3/4 turn) on all four dampers and drive the road again. Repeat Step 2 until the car enters the turns smoothly (no drastic attitude changes) and without leaning excessively. An increase in the rebound stiffness beyond this point is unnecessary and may result in a loss of cornering power. Note: As with the bump settings, this point will probably be reached at one end of the car before the other.
However, individual drivers may find it desirable to have a car that assumes an oversteering or understeering attitude when entering a turn. This can be easily "dialed-in" using slightly excessive rebound settings at either end.

When I read posts that state "my car corners much flatter with my new coilovers", my thought is spring rates are too high or low rate damping is set WAY to stiff for street use, the vehicle is a wreck waiting to happen.

Stiffer sways reduce roll, and on roads with less then perfectly smooth paved curves, reduced unsprung weight helps increase control (this is where 315s on 20 or larger actually work AGAINST ideal control/handling.)


Some will argue this does not need to be done on a street vehicle, but undesireable handling is not something you want to experience during an emergency situation on public roads. Lives could be lost.

Just noticed something: you own a 4.4i. Yours does not count. It is not a self-leveling setup. Quiet!

Eibach front sway bar can be purchased through European vendors. You may have to pay a little more for it since its coming from so far and rear in the US.

???

I made that point clear in the 9th post of this thread..."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."

The rear air has yet to fail (over 200k miles).

Don't understand the "Quiet" comment, having researched/installed/set-up/corner balanced/tracked/street driven (over 150k miles) several coilover vehicles personally (sig pic show two of them, ZR-1 & Hennessy Viper, at Sebring track day).

Yes the rear air X5's can last quite some time. I have see 3 examples so far in excess of 220,000 miles on original rear air system.