Z4 vs Z4M (suspension)

[1979TransAm]

I'm just kind of curious and think this would be a good thread to have around with some good info. BTW browsing for suspension parts and seeing all the parts that fit the Z4M and not the regular sparked this these thoughts.

What are the suspension/chassis Differences between a Z4 vs a Z4M?

What parts could you swap between to two if any? Could you put an M suspension on a Non M car?

I did a search and turned up only one thread, but it wasn't as indepth as I had hoped. http://forums.bimmerforums.com/forum.../t-844305.html

It kind of brought up another question, Is the non M just based on the E46 non M suspension or are parts possibly interchangable?

Thanks guys
Zach

[caseysc1]

Good post Zach. I have wondered myself what compatibilities exist. Anxious to see the response

[Incompatible]

Good post Zach. I have wondered myself what compatibilities exist. Anxious to see the response

About a year or so back either Hack or Dammitt did an excellent detailed comparison of the suspension differences between the Z4, Z4 Sport, and Z4M IIRC. If I can find it, I'll put it up.

[vachss]

I don't know about springs/shocks (though the part numbers for aftermarket units for the M and non-M are certainly different), but I did look into swaybar compatibility about a year ago.

The rear bars are entirely incompatible due to the different shape of the M differential. The M front bar is not exactly compatible with the non-M, but supposedly can be made to fit with minor modification (not sure what is entailed, got the info from BMS). Rather than go this route I just chose an H&R front bar for my 3.0si - same 27mm diameter as the M bar, adjustable, and no mod required to make it fit.

[jragan]

You can also compare and cross-reference here: http://www.realoem.com/bmw/select.do

[1979TransAm]

Incompatible, the linked thread in my original post is yours. It seems to be a good start, but The Hack was the only one to reply. So I was hoping we could throw some more details out.

By that I mean maybe clear up on possible options to upgrade our cars suspensions that aren't M's.

[Leeman]

I had an 06 3.0SI with sport package that I liked very much. I now have an 08 M Roadster and I can tell you the differnce in handling and ride quality is astounding. The source for the article below is ZER Customs.

Extensive new engineering for BMW M

Starting with the Z4’s already excellent chassis engineering – Motor Trend commented in its May ‘05 issue that the Z4‘s “sport suspension and solid chassis make this car a thrill to drive on canyon roads“ – BMW M has endowed the Z4 M Roadster and Coupe with typical M modifications that further enhance handling and tailor the cars' road capabilities to M’s higher performance level.

Front suspension. While retaining the Z4’s basic concept – strut-type with forged-aluminum lower arms – the M engineers created an essentially new version with:
• A wider front track (by 0.5 in.)
• Newly configured lower arms, still of forged aluminum; more complex shape with open sections for lightness, similar to those of M3s
• New steering knuckles, bolted to the struts (saves weight, sharpens steering response)

Such changes, subtle yet deep-reaching, are – as good as the basic BMW model is – key to achieving the “beyond exceptional” reflexes of an M model.

Rear suspension. Though modifications to the Z4’s Central Link (multi-link) rear suspension are less extensive than at the front, they are significant. Among others, the following major M elements are shared with M3s:

• Rear subframe – larger and stronger; accommodates differential with M Variable Differential Lock
• Wheel bearings
• Central (longitudinal) Links
• Arrangement of anti-roll bar.

As at the front, these modifications sharpen handling capabilities.

Ride height and suspension calibration. Like the Z4’s sport suspension, that of the Z4 M Roadster and Coupe are set lower compared to the standard Z4’s setup. Unlike the Z4, however, the M versions get an all-around new calibration of springs, shock absorbers, anti-roll bars and bushings to BMW M parameters; this includes specific auxiliary springs at the front and rear.

A new steering system. BMW M has somewhat different priorities: a greater emphasis on absolutely accurate road feedback and ultra-spontaneous response to the driver’s commands at the steering wheel. In this context, higher parking and low-speed efforts are acceptable. Thus M gave the Roadster and Coupe a hydraulically-assisted rack and pinion with a power-steering pump calibrated with assist characteristics optimized for the Z4 M Roadster and Coupe. This system reduces parking efforts somewhat, but not to the degree that vehicle-speed-sensitive assist does. [/color][/size]

[1979TransAm]

Thank you leeman. Great find.

Could we use the stock M springs/shocks on our cars then?

Also what exactly are "Central (longitudinal) Links"? Their Function?

So the rear suspension on the M is a completely different animal from what is on any Z4 if I am reading that right, right?

Thanks for the info guys keep it coming this is looking good,
Zach

[GP20]

The Z4 uses E46 style struts. The Z4M uses E36 style struts. The ways the struts are bolted/connected are different and are not interchangeable.

To make it short, no you can't put Z4M suspensions on a non-M Z.

[1979TransAm]

OK, so you are saying the chassis itself is different, not just swapping out parts?

Would E46 struts be able to fit then?

Thanks
Zach

[KevinC]

You might be able to cobble together some kind of frankensuspension, swaping in SOME M parts. But it would be a huge hassle and expense, and the end result won't be a "real" M setup and could turn out to be a huge disappointment.

Better option would be to sell the non-M car and step up into an M. Methinks you'd be quite happy with that solution.

[The HACK]

OK, so you are saying the chassis itself is different, not just swapping out parts?

Would E46 struts be able to fit then?

Thanks
Zach

Not E46 M struts. The Z4 (non-M) suspension is similar enough to E46 (non-M) set-up that any suspension parts designed for an E46 will be a direct bolt-on.

The question is, why would you want to...Unless you're looking at aftermarket parts. Z4 springs and dampers are tuned to Z4 weight while E46 springs and dampers are tuned to E46 weight. Unless you go aftermarket and specify your own spring rate and damper rate, buying E46 OEM parts to fit the Z4 is a waste of money.

[Leeman]

Thank you leeman. Great find.

Could we use the stock M springs/shocks on our cars then?


Also what exactly are "Central (longitudinal) Links"? Their Function?



So the rear suspension on the M is a completely different animal from what is on any Z4 if I am reading that right, right?
Thanks for the info guys keep it coming this is looking good,
Zach

They mentioned an auxilary spring both front and back. I don't know if additional suspension components are required to support that. I have been trying to get a exploded view of the suspension but have not come across it yet.

Also what exactly are "Central (longitudinal) Links"? Their Function?
I am not sure.

So the rear suspension on the M is a completely different animal from what is on any Z4 if I am reading that right, right?

It sounds to me that the components such as control arms and subframe along with placement of cross members are different and also the ride height is lower. I parked mine next to a 3.0I and the M looked considerably lower. I say maybe an inch or so.


Click on the link to view the entire article. http://www.zercustoms.com/news/2008-...and-Coupe.html It is the most in depth review I've seen on the M. The multitiude of differences goes beyond the suspension to create a sensational driving experience. I would suggest you leave your car stock and buy the M when you're ready. One joy ride around town in the M and you'll know what I mean.

[1979TransAm]

The Hack, yes I would definately not be buying stock E46 parts to put on, that makes no sense. I would want to do a custom spec spring. I noticed while browsing for parts though that the Z4M is in a category on it's own and wanted to know why and how. I was mainly wanting to start this thread to look at options for our non M cars.

Remember guys I personally am not looking to turn my car into an M just wanted facts on the differences and possible upgrades for a non M car. So the response, "Sell your car and buy the M," is right if I wanted an M, but otherwise a null answer.

BTW, I have plans for my car down the road that are outside of the cookie cutter BMW M car performance, which while great I hope to improve. I wouldn't buy an M just to chop it up. I could use all the info I can get.

Thanks guys for the great replies. Leeman if you get those diagrams defineatly post those puppies. Keep the info coming guys

Zach

[gti20vturbo]

I think before I spent a dime on upgrading my 3.0i suspension I would look into replacing the rear end with something that drives both wheels a little better than the stock one. Does Quaife Engineering or someone make a decent differental setup for these cars?

[vachss]

I think before I spent a dime on upgrading my 3.0i suspension I would look into replacing the rear end with something that drives both wheels a little better than the stock one. Does Quaife Engineering or someone make a decent differental setup for these cars?

http://www.zpost.com/forums/showthre...ghlight=quaife

Or you can wait for another M to be totaled and transplant the differential, rear subframe, axles, and suspension (I think when all those are swapped together they'll fit nicely into a non-M)

[gti20vturbo]

Thank you, I sent them HP and email.

[The HACK]

The Hack, yes I would definately not be buying stock E46 parts to put on, that makes no sense. I would want to do a custom spec spring. I noticed while browsing for parts though that the Z4M is in a category on it's own and wanted to know why and how. I was mainly wanting to start this thread to look at options for our non M cars.

If your goal is to upgrade the suspension and you're wondering if the aftermarket stuff for the MZ4 will work on the Z4, then the simple answer is no. Just like all previous BMWs, no M suspension works on the non-M because of various reasons. For the Z4 it's because the front of the M uses E36 M suspension design. For the E46 it's because the rear subframe geometry and front end geometry is much different on the M. Same goes for the E36. Same goes for the Z3. So when you buy aftermarket parts for the Z4 you can not specify MZ4 parts since out of all the M models, this is by far and wide the most incompatible of all BMW ///Ms ever made.

However, if you goal is to get aftermarket suspension parts for your Z4 but Z4 specific applications do not exist, you CAN use aftermarket suspensions design to work on an E46 since they are interchangeable. The only thing you have to look out for, is you should get adjustable dampers since typical damper rate that works for an E46 will likely make the Z4 difficult to live with, and the ride height adjustment range may not be as wide since the Z4 springs are shorter (I believe). But a PSS-9 for a regular E46 will bolt right up, for example.

[1979TransAm]

Thank you The Hack.

[Jaredthejewler]

So i can put a z4 M subframe/links/diff etc into a non M?

[chickdr]

So i can put a z4 M subframe/links/diff etc into a non M?

Why would you? Just get an M if it is what you want.

[montaillou]

Why would you? Just get an M if it is what you want.

I suppose if you got the parts free or near free, and it was just all your own labor this might be one way to go. But yeah, generally, once you make a few mods towards an M, it's usually cheaper to just buy an M.

[Blackpony]

Hi All,
Our Z4 3.0i was hit on the right rear wheel by an Ambulance. The rear axle is bent and differential jammed in. The rear axle and sub-frame have to be replaced. Will the Z4M rear subframe and axle fit the Z4?
Z4 M wheels were too wide to clear the Z4 fenders, so the Z4M axles or differential are narrower?
Has anyone done the Z4M rear end to Z4 rear end swap?
Thanks,
Dan Conrad
810-794-9907

[Z4DanC]

Some great information on this thread - thanks to all contributors!

Does anyone know if the Z4 Coupe 3.0si sport model is the same suspension as the 3.0i? I.e. so all of the above thread applies.

I would like to upgrade/renew the suspension and wondered if anyone has any recommendations? I was thinking bilstein b12 package as it has B8 + matching eibach springs.

I do not want to lower the car as its low enough already. I've read somewhere that you can get spacers to help with this. I'm after better handling + but don't want to be scraping over speed humps :-) May be could get away with a 5mm drop at the most.