Fitting M Roadster Shocks/Struts to a Non-M car - a couple clarifying questions!

[Corellian Corve]

Well those MOOG's are a no-go. After some research, Moog does not make a specific control arm for M cars although the catalog lists as such. So ECS has these listed mistakenly. I was going to swap those but so far the only current source for M LCA's is OE BMW. Looks like I'm going to stick the plan of just swapping the upper mounts and leave it be.

[mpire]

I would be switching over the entire Strut/Spring assembly from the M car.

If you are not using the M sway bars & links then you will need M drop links, but that's about it.

You should be using NEW strut mounts, NEW Shock inserts, and NEW drop links (unless you get the GC rubber free ones)

Also, while you're at it, you can have Ed @ Bimmerbum rebuild some M control arms with new ball joints and save a bundle.

Come to think of it, do the steering tie rod ends while your in there, its maybe another 10 minutes of work once the control arms are out.

NEVER re-use old rubber bits, they cost so little compared to the labor and time to install them that its just not worth trying to save a couple bucks on wear items.

Its like bolting up second hand used warped brake rotors with new pads.

[BimmerBreaker]

OK OK Hold up.

So I just looked and you can get the MOOG M roadster LCA for $110 each side. I'm not 100% sure, but I think you can get them for about $60 each on Rock Auto . That's not much more than new upper strut mounts.

At that point, I could swap the entire assembly over and replace the LCA, and then just buy the endlinks to connect the swaybar to the strut.

I know that the normal Z3 sway bar is 1mm larger than the M sway bar, but should otherwise connect just fine, yes?

Swapping LCA's looks pretty straightforward.

At that price I have to suspect that it is not actually an M arm. Very often, parts are sold as "M" parts because they may physically fit an M, but they aren't real M geometry parts.

It is also not a good idea to mix and match M and non-M suspension parts anyways. The suspension is a system and the components work together.

[mpire]

At that price I have to suspect that it is not actually an M arm. Very often, parts are sold as "M" parts because they may physically fit an M, but they aren't real M geometry parts.

There are no "M" control arms sold aftermarket, that's the reality. Just have Ed rebuild them.

It is also not a good idea to mix and match M and non-M suspension parts anyways. The suspension is a system and the components work together.

This guy obviously doesn't care about handling because he is going to put Bilstein's on his car. Bilstein's are for people who hate their cars but are afraid of spending 30 minutes prepping the stock housings for Koni inserts with a drill and a sawzall.

One thing I'm going to change is my M Roadster has a set of aftermarket Bilstein Struts and *maybe* aftermarket springs. My plan is to get a set of original OE Struts and Springs, and replace them when I do my brake job since it's a pretty easy to do while you're there.

H&R sport springs are $220 and well worth the investment IMHO. I have every suspension for these cars and the only one that makes me angry is the Bilstein setup.

...I will have an extra set of good Bilstein units for M cars. I would like to put that set on my 2001 3.0 car.

These will fit just fine, he will just regret doing it.

My understanding is that other than the Top Hat and front sway bar mounting on the M Roadster, the strut is physically the same as the standard Z3. The Rear Shocks are a direct fit but the hub mounting bolt is different on the M cars. Pretty straightforward. This should also lower the car, correct?

No, it won't lower the car. Just get the M offset strut hats, why even consider the stock Z3 ones? Its the same price. The M hats add caster to the suspension, that pushes the wheels forward and is a big part of the handling upgrade over a regular BMW.

So when fitting the M struts to the Z3, I *assume* that I purchase the top hat for a normal Z3 and not the offset hat for the M? And also, I don't change the sway bar mounting in the front, I just keep the standard Z3 mount points?

You can, sure. It makes installing M struts on your car a complete waste of time and effort, but whatever.

I don't want to go through all the hassle of changing the lower control arms, etc. I was planning to get a B12 set to lower the 3.0 anyway, but if I can re-use the parts I have that's about a $1G savings!

Reusing parts is pretty stupid, especially considering your car is 20 years old and the ball joints and bushings were shot a decade ago. Penny wise and pound foolish in the extreme. You can get Ed @ Bimmerbum to install new ball joints into used M control arms for a fraction of the price of new non-m control arms. If they haven't been changed at least twice in the car's lifetime, then they are complete shit anyway and you should throw them away.

If your rubber bits are 2 decades old and haven't been replaced you should replace them. Its all worn out. The ONLY thing worth keeping are the springs, and I'd wager the $220 H&R springs are well worth the investment in happiness they will bring you. Also, installing them is a million times easier than putting the extremely tall and tapered Z3 springs on without losing a finger. Seriously, that's probably the most dangerous thing you could do with a Z3 is mess with the stock springs. Nightmare fuel. I paid a shop to install them on a spring machine the size of me because I like having functioning hands.

For everyone who is trying to save a buck on a service that apparently happens once every 20 years, I think you are all idiots. It makes so much difference to the way the car drives and if you think about it, a couple grand at most spread out over 20 years is pretty damned cheap.

[s8ilver]

Guys, did you even read his post? His M came with Bilstein struts and aftermarket springs. He's swapping them to his Z3 and bringing the M back to stock. There are no mysterious OEM housings sitting around for inserts. The swap to the Z3 will certainly lower the Z3, unless some moron lifted his M.

I sourced housings, Koni inserts, H&R springs and all the other bits and it came out to around $1200 all in. If someone likes the Bilsteins, there's no harm in saving $1k by refreshing the rubber and mounts. They're also certainly not two decades old, since they're aftermarket.

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