Need Advice - E46 Touring suspension

In December I picked up a 2004 325i auto wagon in decent shape. The original/pre-previous owner seemed to have taken good care of it, but the PO to me also seemed to have picked it up as a cheap DD to pile the miles on and only did more minimal maintenance. I'm catching up on that now.

It'll need brakes at minimum sometime this spring. I'm thinking I'd like to just do the whole refresh of brakes/bushings and new performance suspension at once.

The good news seems to be there are lots of options, but I'm also a little lost at having so many.

To define goals for the vehicle: Primarily an enjoyable DD that I can also take to the track for HPDE. Not terribly interested in autox since i'd rather rallyx :D This could also evolve into a non-competitive one-lap car in a few years so my best friend and I can check it off our bucket lists.

specific advice requested (remember, starting from a non-sport option wagon):

• I'd rather not lower too much, and go with a well matched stiffer suspension setup. I'm OK spending some money here for good dampers (dampeners? I can never remember) to get that and keep decent street manners.
• bushings. softest poly available? other thoughts?
• I have a feeling I'd be happier long term if I swapped to some better calipers up front, but haven't really researched at all yet.

Basically, I trust GRM to give me the straightest poop and save a bunch of time and effort over digging through the other BMW Forums.

Meet "Greta". While doing driveshaft maintenance, this is test fitting the new shoes (17" w/ hankook ventus v12 evo2) she'll be getting once I've installed the above . 

Everyone has their own tolerances for NVH but for being primarily a street car I'd try to keep as much rubber in the suspension as possible. Maybe upgrade to M3 bushings where possible as those are usually a little bit stiffer (but also more expensive).

I'd stay with rubber except maybe in the sway bar mounts and the rear subframe bushings. I think the easiest upgrade will probably be the ZHP or M-Sport parts, which seem to be readily available, at least for the front. Don't know how much different the rear suspension is on the wagon, which may affect the interchange option out back.

As far as I can tell, the wagon rear is the same as sedan other than beefier springs and maybe thicker ARB.

If you want to stiffen up the rear, I'd suggest poly subframe bushings over a bigger bar. The stock bushings are pretty soft to begin with (though not as bad as the E9x), and 15 years will not have done them any favors. Probably adds a little NVH, but really unslops the rear end. That, new poly sway bushings and end links, upgraded ZHP front control arm bushings (and maybe the arms), struts and shocks, and roll. Brakes should be plenty for street use with new rotors and good pads.

The nice thing about the older 3-series stuff is the front really only has 2 bushings to consider, the FCAB  (front control arm bushing) is almost certainly wasted by now. On a street car I like the Meyle HD bushings, they're fairly cheap but stiffer than stock so you don't get wandering toe during hard cornering.  The fancier stuff works even better and won't add any NVH in my experience but if lap times don't matter it's just extra money.  The rest of the control arm joints are balljoints so no real upgrade to be had there from OEM or similar. If any of the boots are torn, I like to replace them at the same time as the FCAB's because pressing FCAB's on and off is far easier outside the car. 

The other front bushing to consider is the upper strut mount, OEM works here or any of the usual German replacement brands, Febi, Meyle, Lemforder etc. or Camber plates of your choice but both the Ground Control and Vorshlag options I've experienced clunk over bumps so keep that in mind for a daily.

Moving into the rear the most important in my mind are the subframe bushings. The more worn out they are the more likely it is that the unibody has cracks. As these get older it's starting to seem more and more like 100% of e46's have either had subframe reinforcements welded in or they're cracked and awaiting repair. I'd go stiff here. Poly or solid aluminum both work, the goal is really just to securely lock the subframe in place rather than letting it have any opportunity to flex and fatigue the metal. The trick is to replace the differential mounting bushings with oem or similar. With factory rubber holding the diff you really don't gain any NVH from the stiffer subframe bushings. but pairing solid diff bushings with solid subframe mounts will give you a bit of whine inside the cabin. with a full interior and softer poly it's not too bad, with aluminum and gutted interior it sounds like straight cut gears at cruising speeds.

Moving outward from the diff/subframe check the lower control arms, the salad tongs can be bent by curb hopping or a big pothole, they're relatively cheap to replace and prevent alignment issues. The upper control arm bushings seem pretty stout, we're at 160k miles on the factory ones with plenty of hard track miles and they still show no discernable play.

The last bushing to consider replacing are the RTAB's (rear trailing arm bushings) Vorshlag has a boat load of info about why the Z4M bushing is the best performance minded option on a daily driver. https://vorshlag-store.com/products/oem-z4-m-rear-trailing-arm-bushings-pair

This is not a bushing where you want to go poly due to it's multi axis pivot requirements. Either OEM rubber or something like the bimmerworld spherical bearing I think the z4m bushings will work just fine for your use, I'd also suggest adding the RTAB limiters to help extend the life of the bushings and give a bit more performance.

Cliffs notes: upgraded rubber FCAB and RCAB, new rubber diff mounts and Poly rear subframe bushings.

Just FYI, a lot of current Febi production seems to be from China. Lemforder is still mostly European, and I had one too many bad experiences with Meyle, so I'm not sure where they're currently getting stuff.

I haven't heard much good about the regular Meyle parts, but some of their HD bushings are said to be good (and beefier than stock).  I've got their HD thrust arms on the front of the E38 with the solid rubber bushings (compared to the stock fluid filled ones). 

thanks, guys, especially Klodkrawler!

KK, that sort of insight on the various bushings is exactly what I was hoping for.

02Pilot, you don't think I should consider upgrading to different calipers/rotors (sport/Zhp/m3)?  I'm not even sure what all the options would be actually, but I would think it'd be a good time to do so if use of the vehicles includes HPDE's. Is that not the case?

I've been very happy with the ride of bilstein HD's on vehicles in the past. I'll probably go for some flavor of them here once I sort out the various current part numbers/flavors of bilstein options between the various e46 model trims. With that as a yardstick, are there other dampener options I should consider?

Seems like all the spring options include lowering. I may need to go with some sort of 2.5" coil seat setup with my own spec rate in order to get a higher rate at a close-ish to stock ride height. Based on my experience with trying to tune the rear height/rates on my rallyx e30, I think i'll need to figure out whatever beehive works best. I wonder if the early x3/x5's use them..

I was trying to think of a way to describe the balance of ride/handling I'm going for, and I think it's this: I want it to be crisp and enjoyable enough, but supple enough, that I'll WANT to get in it and drive it across the country hitting all the best roads/tracks on the way.

I'll give the Bilstein HDs a thumbs up in the E38 application.  With one exception.  I gained a good 1/3 - 1/2" of ride height in the front (no change in the rear).  So my front end is jacked up to almost non-sport ride height despite having the sport springs.  

bluej said:

02Pilot, you don't think I should consider upgrading to different calipers/rotors (sport/Zhp/m3)?  I'm not even sure what all the options would be actually, but I would think it'd be a good time to do so if use of the vehicles includes HPDE's. Is that not the case?

It's fine if you want to do it, and I'm sure you'll be able to improve braking performance, but how much do you really need? I'd get new rotors and good pads in there and get a baseline. If you're getting fade on lap 3, then upgrade; if not, leave it stock. Note that bigger brakes may require wheel upgrades as well. For HPDE use, ducting may be useful as well.

Love the wagons!

If you want a cheap upgrade, the 330 front calipers and rotors are an easy way to increase swept area, but it’s not a huge difference. I’m not sure whether you’d need the 330 caliper bracket. Your 17” new wheels should fit, but 16” will not. I’m pretty certain that e46 m3 rotors/calipers won’t fit under anything smaller than an 18” wheel. 

Thanks, guys. I want to keep the 16's as winter wheels, so sounds like stock calipers are in order.

Definitely stock brakes if you need clearance for 16s.  An old roommate had a 330 sport and the stock 17s barely cleared the brakes on it.  Which I find funny considering the front rotors are almost exactly the same size as the ones on my 740 (and smaller than a 750) and the 740 and 750 both fit 16s just fine.  Must just be a difference in caliper design. 

Looks like the h&r sport springs for an x3 wouod be about 35% stiffer than stock, assuming both mine and an x3's original relative stiffness is the same. Might be worth risking @ $200.

H&R also makes an "OE Sport" spring that even milder in drop than the standard sport.  Might look into those.

If I'm using x3 springs, I want the drop so I don't jack up the wagon, just stiffen the rate.