Sway Bars - Who has installed them? Please come inside.

[Alpine M]

Hi everyone,

I am starting to modify the coupe finally (got 2,500 miles on her already). Anyhow, with my old 350z the single-most impressive modification that I did to that car was the addition of a set of Hotchkis sway bars (bang for the buck).

I am wondering if the M coupe will see the same benefit. I see the advertised stiffness increase vs. 3.0si sport, but not vs. M. So I am not sure how stiff the existing M bars are.

If any owners have installed these on any of their coupes, please share your thoughts on the results.

Thanks,
Jim

[MMMazing07]

http://www.zpost.com/forums/showthread.php?t=93894

[BimmerZealot]

Uh, he said Sway Bars not Strut Bar. The link you sent him to is for a strut bar. I've never seen a thread for sway bar install didn't know anyone made one either.

[vachss]

I know H&R and Hotchkis make bars for the Z. Stock diameters on the 3.0si are 25/19mm F/R (24/18mm for non-Sport) and the aftermarket bars are something like 27/21mm. I believe the torsional stiffness of a bar varies with diameter squared so if the end link geometry is the same I'd say the stiffness of the aftermarket bars is something like 15-20% greater than stock. Aftermarket bars are usually adjustable though, so this is just a first cut.

Update: A couple of things. First the M bars are significantly thicker than those on the 3.0si - realOEM says 27/22.5mm F/R. Also while 27/21mm is correct for the H&R bars, the Hotchkis are quite a bit bigger. Here's specs I downloaded...

Specifications:

- Front 28.5mm Tubular 3 Position Adjustable
- Stiffness: +19%,+38%+61% (Compared to stock Z4 Sport)

- Rear 24mm Tubular 2 Position Adjustable
- Stiffness +59%, +86% (Compared to stock Z4 Sport with 24mm front and 19mm rear)

It looks like the aftermarket bars I'm seeing are for the non-M Z4s. I don't know if the M and non-M bars are interchangeable. Regardless, it looks like the H&R bars are roughly the stiffness of the stock M bars, while the Hotchkis set up is subtantially stiffer than either. It would be nice to find out if the M and non-M bars are swappable as lots of us 3.0si drivers would probably just as soon install stock M bars as an aftermarket kit.

Update 2: A careful reading of realOEM shows that the part numbers for the end links the sway bars fit into are the same for the M and non-M Z4 coupes. I suspect this means that they are interchangeable (but somebody should definitely verify this before ordering anything).

[mister_roger]

I have the hotchkis sway bars myself and absolutely love them. They really did a job on stiffening up the ride and reducing body roll. But in comparison to the ///M factory bars, it appearss to be a very small upgrade. Maybe the difference won't be as noticable. And then there is the question of fitment as well. I thought that the ///MZ4 shared most of its rear suspension from the M3?

[MMMazing07]

sorry . control arms ftw

[Alpine M]

vachss,

Thank you for the very detailed reply!

I'll pick up a set and report back soon.

Jim

[nlink720]

Bringing this post back a little bit.

For those who have added sway bars, I just want to confirm something: It should be a noticable reduction in body roll, right??

I upgraded my front only, since SCCA permits fooling with the front only in stock classes. My goal was to reduce body roll and a host of other things that should be beneficial despite the potential for increased understeer.

I have the H&R bar at the stiffest setting and noticed zero difference.

I cannot see any damaged end links or other problems, but felt there should be at least some noticeable difference. The difference between 3.0i sport and H&R is still a few mm in thickness... something seems strange, and the body roll still exists.

[xg3]

in my last car, mazda 3.. sway bar was more effective than springs in reducing bodyroll...

only reason i havn't done it to the Z4, is i was "hoping" for the same result, but you just gave me doubt..

can someone please confirm?

[nlink720]

To clarify my previous post: there IS a very noticable difference with the front sway only. My observations were skewed because I had a bad sway bar link.

After replacing that, the front is way tighter. It understeers like hell, but for daily driving it is way better. I am referring to H&R at the stiffest setting.

Another unintended benefit is that the steering wheel feels heavier and more precise.

I want now to get the rear as well, but first have to review the scca categories that I could compete in should I do the rear.

[Incompatible]

Originally Posted by vachss

..... It would be nice to find out if the M and non-M bars are swappable as lots of us 3.0si drivers would probably just as soon install stock M bars as an aftermarket kit.

Update 2: A careful reading of realOEM shows that the part numbers for the end links the sway bars fit into are the same for the M and non-M Z4 coupes. I suspect this means that they are interchangeable (but somebody should definitely verify this before ordering anything).

Did anyone ever determine if the M / nonM (3.0Si) bars are interchangeable?

[Haretakis]

Talk to Palantirion about his Ground Control sways...he knows his stuff.

[Incompatible]

Originally Posted by Haretakis

Talk to Palantirion about his Ground Control sways...he knows his stuff.

Good advice, should have talked to Earl first thing. Thanks.

[chinkwan]

What about the M Coupe bars?? THis is for the M roadster crowd..

I think I read somewhere that the M Coupe Bars are thicker then the M Roadster?? Is that true??

Also, can somebody find out about the Ground Control Sways? I read from the OTHER forum that it needs to be modified to fit our cars???

[vachss]

Originally Posted by Incompatible

Did anyone ever determine if the M / nonM (3.0Si) bars are interchangeable?

The rear bars are not at all interchangeable (shaped to fit around different differentials). The fronts aren't exactly the same, but the M bars are said the be usable on the non-M "with minor modification". I haven't physically examined an M and non-M front bar together, but this info comes from the folks at BMS who have.