Coilover Pros/Cons
 

Debating replacing my stock suspension on my 2000 4.4i (rear air ride) with a coilover type due to ongoing issues with it. Couple questions:

1) What is the typical height range adjustability?
2) Will lowering adversely affect towing capabilities
3) Will lowering adversely affect snow driving
4) What all else should I replace and refresh while i'm "in there"? What bushings are recommended? OE? Energy/Prothane poly? Powerflex?

I have a Thule roof rack that is low-profile but still does not clearance some garages. For this reason I would like to drop the ride height a little. Also should improve handling a bit in addition to what I assume will be a firmer ride (especially with Swift springs).

I'm assuming just the airbags need to be removed and the new coilover assembles mounted in their place in the rear. Do I need any other hardware if I go with something like the BC Racing kit?

I've heard you can then either live with the "Self Level Susp. Inact" dash cluster warning or code it out with diag software.

I found a local BMW independent shop that would do the install for $400 + $100 alignment. Seems reasonable to me. I do have a garage but this vehicle is too big to work on in it.

THANKS!

Coilovers can be found and I'm quite sure there are a few options out there. You will however want to either find an OEM equivalent (or OEM) in height and firmness/rebound/compression or you'll badly mess up the car's handling.

If you want to lower the rear, you need four corner coilovers and if you want to keep it drivable you will need high end coilovers and stay reasonable with lowering.
Some aftermarket brands (but I can't remember the name) offer some form of EAS setup for the four corners that would allow you to keep standard height for driving, and lower it when parking.

While you're doing that, if you use anything but stock height, you'll need to change all silent blocs linked to the front and rear axles since you'll be changing their resting position, you'll get dual wear and get lots of squeaking and some play that will get quickly worse over time.

You will also need to find adjusting options in order to aligne the wheels correctly and not get excessif wear on the inside of the tires and worse road holding ability.

On the plus side, high end coilovers correctly set up (by the factory, with axle weight and distribution info) wil give you a great ride, precise steering and a road hugging ride (barring stupid lowering and insanely firm spring) as they'll keep the wheel in contact more of the time.
Downside, this is not cheap at all and frankly, if your issue is just with parking, it seems excessive. Every coilover kit I've fitted to cars (from the 1970's to 2005 MFG date) has come from KW, they've all been great but I've always kept the ride height standard or very close.

On a side note, I used to race a WR250R and I'm thinking of getting another one for non racing off roading, how do you like the 2015?

Awesome. I'm going to see if I can buy a little time with the air ride by trying to reset it. It could be as simple as a blown fuse, and the compressor rebuild kits are cheap so thats worth a shot. The height sensors are easy to change too.

Long term I think I will be going the coilover route. If the above fails I may just buy the standard BC Racing coilover kit and try to match the spring rates as close to stock as possible and run it on the highest height (.5"-1" lower). I may just install the rears for now and do the fronts later so I can get rolling down the road again.

Do you know what the equivalent spring rate would be in the rear for the non-sport bags I am running?

I know it's not ideal but if it can get my by for a year or so it's not a bad option and gets me closer to my end goal cost effectively.

I'm sorry I have no data regarding the spring rates, maybe in the bentley manual but I'll have to check later, I don't have it with me.

It's worth trying to get the system working in your car, there's nothing magical about it and INPA or maybr PA Soft (I'd have to check) will tell you what's wrong and yes, resetting the error might bring it back to life.

One thing I forgot to ask, do you use the X off road? if so, keep in mind by lowering it, you'll losse ground clearance of course but also articulation.

Right. I think I've got INPA working properly now or at least I am on the right track. I am going to try to resuscitate the air ride for now. Things to try:

1) Check EHS module for error codes (I know at least one level sensor is bad)
2) Attempt to clear EHS module codes and reset air-ride
3) Test compressor by supplying +12V (should pump bags back up)

If none of the above works then I'll look at replacing the level sensor(s) and the EHS module itself.

I will still be going with coilovers long-term as I have a slow leak in my system anyway and I want to lower the vehicle.

I don't off-road.

Let us know what errors you find.

A slow leak is not a good enough reason to switch to coil overs, soapy water in a spray and you'll filnd the leak(s)

I think I'm almost there had to solder the pins on my OBD diag cable and I'm using the right INPA program now. Quite the song and dance but at the same time a great learning experience.

I agree I should give it the old college try with the soapy spray bottle and if that turns up nothing maybe I should blindly zip tie the F out of every darn air hose connection :)

I do want to lower the X tho... sigh

Do not zip tie anything before checking the connections, you'd probably make it worse. If they are as usual EAS connections are, there's not much to zip tie and most connections are "slip in".