New Struts and Shocks for my 2006 Z4C - OE differences ?

[Z4Mariner]

I'm trying get the best (most appropriate) suspension refresh for my 2006 Z4 3.0Si Coupe for the way I drive and the roads I drive on. There are hundreds of threads out there, but I have a question or two that I haven't seen addressed.

Question 1: How different are the OE BMW struts & shocks for my 3.0Si Coupe with M-Sport (M-Tech, S704A) suspension from the Standard struts & shocks ? On RealOEM they have different part numbers and different prices - and for that matter, the part numbers for the corresponding E85 models are different still. So if I lump both suspension options for both E85 and E86, I have four sets of part numbers for struts and shocks. The prices are same / similar for E85/E86 with S704A and both are higher than prices for the standard suspension E85/E86 units. In light of this, I see my major vendors describing their Sachs and Bilstein B4 struts & shocks as "OE Replacement" for both standard and M-Sport suspensions - and I wonder whether this means they are closer to Standard, M-Sport, or in between.

Question 2: How different are Sachs from Bilstein B4 struts & shocks ? I would like to have the car closer to original M-Sport.

The M-Sport (S704A) ride height is just fine, and I don't want to lower it. I drive my car daily 7 to 8 months a year, but not in winter here with snow, ice, and salt. Though I like to drive spiritedly, local roads are a bit rough, and when I venture into the city there are plenty of potholes and broken pavement. At 89K miles with the current (original?) suspension, the ride is about as firm as I'd ever want it - especially with my wife along as passenger (she enjoys riding in the car, and I want to keep it that way). The suspension almost certainly needs a refresh, and I hope that the right new struts & shocks may actually reduce "crash" a little and produce a smoother ride with at least as good handling.

I lean toward the Sachs or B4's, since those are the two choices a BMW Master Tech says he used to put on most of his customer cars. The BMW OE prices for the M-Sport struts and shocks are about 3X prices for Sachs or B4 struts, and almost 2X prices for B6 or B8 struts from my most usual vendors. I'm considering installing new Lesjofors springs at all corners, since I can order in a set for about $200 US.

I would appreciate any insight on my two questions - thanks in advance !

 

[Zedebee]

Not answering your questions explicitly, but:
- if you are running the OEM Bridgestone Potenza runflat tyres, nothing will do more to reduce crashiness than replacing these with a good quality alternative. You will also get less tramlining.
- the original dampers were made by Sachs, so buying Sachs to the same specification is like-for-like, whereas a Bilstein B4 is marketed as an OEM replacement. Both seem to have their fans on here; personally I prefer my car to look OEM hence I always go with Sachs
- the ride height is determined by the spring length, so there probably isn’t a lot of difference between SE and Sport dampers. In fact it seems to be quite difficult to find replacement dampers which claim to be for “vehicles with M-Sport technology”.
- I have used Lesjofors springs in the past, including to replace rears on my coupe with no discernible difference in performance. Suplex seems to be a popular, if more expensive, choice. So are Eibach lowering springs in connection with Bilstein B4s.

In reality, there is probably little difference between brands unless you start spending money on “upgrades” and there is no benefit to paying the extra for original equipment for BMW.

 

[Z4Mariner]

Thanks for your input, Zedebee.
- Current tires are Goodyear Eagle Sports (came on car when I bought it). I'll be evaluating new tires by end of this coming Summer; most likely choices would be Michelin, Bridgestone, Goodyear.
- Leaning toward Sachs (even though the vendors say "not for cars with M-Tech"), they're at the less expensive end of brands I trust. If I like the ride / handling mix, fine - at least I will have explored at lower initial cost.

 

[Birr97]

I went for the Bilstein B4s and the M-Sport equivalent Suplex springs with mine and they've been great, highly recommend the combination.

Nice compliant ride (for a sports car) over bumpy Welsh roads without excess roll and body movement. My shock absorbers were knackered at 103,000 miles, so the refresh improved cornering and ride comfort.

I really don't understand how people go for a stiffer set up on the road.