Z3 to E30 rear sway bar swap

[Secniv 182]

Help/advice please. Has anyone attempted to fit a bmw oe non-e30 ie Ti or Z3 rear sway bar to an E30?

I’m in the process of replacing subframe and trailing arm bushes and discovered there is no sway bar (strangely given a PO went to the expense/trouble of upgrading to bilstein springs and shocks). Anyhow I was after a bar a stiffer than 12mm and more M3esk 14.5mm (going to aftermarket 16mm I expect will mean reinforcing the trailing arm tabs and stiffening up the front to compensate as well as a lot more cost).

Issue 1 - So I’ve got on trial a z3 1.9 14mm bar. Brackets fit no problems but the kink in the back of the bar doesn’t line up with the diff hanger and bar fouls the pressed crease in the hanger. Have tried fitting both ways but fouling is only worse. I could ‘modify’ the hanger  (hammer/grinder) but I expect this may compromise the stiffness/integrity of the hanger.

Issue 2 - note also that the arms of the z3 bar are longer than an e30 but the links are shorter which compensates? Until I have the car back on it’s wheels I won’t really know if this will be a problem.

Thanks  in advance 

 

Edited April 6, 2018 by Secniv
Spelling

[aja540i 1906]

Changing to a thicker bar will be pointless if the 'arms' are longer, the bar may end up feeling 'softer' as it is not working as hard because of the longer arms. Surely Whiteline or someone does an uprated bar to fit? That would be your best bet.

[Jacko 2156]

When I bought whitelines for mine, they were like $300 for front and rear from BNT at trade (cheap as chips)

[Secniv 182]

8 hours ago, aja540i said:

Changing to a thicker bar will be pointless if the 'arms' are longer, the bar may end up feeling 'softer' as it is not working as hard because of the longer arms. Surely Whiteline or someone does an uprated bar to fit? That would be your best bet.

Thanks for the reply Andrew.

I assume it works for the Z3 (I've never driven a Z3 to be fair)? And would the shorter Z3 links offset the longer arms? Plus the sway bar links for the E30 are a lot longer and thinner than the shorter thicker ones for the Z3.

[Secniv 182]

2 hours ago, Jacko said:

When I bought whitelines for mine, they were like $300 for front and rear from BNT at trade (cheap as chips)

Unfortunately it is more like AUD$600+ now checking through BNT and the Whiteline website

http://www.whiteline.com.au/do_segue4.php?make=BMW&model=3+SERIES&model_final=3+SERIES+E30&vehicle=5%2F1983-3%2F1991

Edited April 6, 2018 by Secniv
update

[Jacko 2156]

From memory there was only the one size (was a few years ago), but the rear has adjustable blades. Just bolted it on. 

[aja540i 1906]

11 minutes ago, Secniv said:

Thanks for the reply Andrew.

I assume it works for the Z3 (I've never driven a Z3 to be fair)? And would the shorter Z3 links offset the longer arms? Plus the sway bar links for the E30 are a lot longer and thinner than the shorter thicker ones for the Z3.

the links have no effect on the swaybar stiffness at all, what matters is the strength of the bar (basically the diameter) and the distance between the pivot point (the mounts on the car) and the attachment point for the links, the longer that distance the less torsion on the bar for the same amount of wheel travel. You will see adjustable sway bars have 3 or more sets of holes to bolt the links to which changes their distance from the pivot point and therefore the effectiveness of the bar.

The Z3 bar will be designed to work with the Z3 suspension geometry, i think it will be a waste of time fitting it to the E30, which probably has quite different geometry.

[Secniv 182]

1 minute ago, Jacko said:

From memory there was only the one size (was a few years ago), but the rear has adjustable blades. Just bolted it on. 

That looks like a great setup Jacko and the trailing arm tab appears to be in good shape too. I expect is 16mm? The length looks similar to the Z3. But AUD$330 for just the rear these days

[Jacko 2156]

Hit up BNT (and ask for trade) the prices RRP from whiteline etc were way more than what I paid at the time as well.

 

[_ethrty-Andy_ 2132]

can't be done. just use OE E30. stiffer than OE will only make an already tail happy car become more so.

In the E30 I throw about, I run OE in the back, and down rated to the 318i unit in the front.

 

[Jacko 2156]

3 hours ago, 3pedals said:

Correct alignment of the links is critical to the operation of the sway bar

Those shown at an angle fore/ aft and the others shown with that nasty wire link will be totally crap functionally. 

 

 

The figure 8 hoop "wire" ones are whitelines. Fugly, but they are solid. 

[Secniv 182]

1 hour ago, 3pedals said:

It doesn't matter whos they are,  the design is crap and the installation is equally crap reasons:

• the wire concentrates load in a narrow band round the bush causing more deflection,
• the angle means a lot of the action is lost just due to the angle and then even more is lost in lateral deflection. 

Net result is a very ineffective anti roll bar as most of the wheel force just goes into distorting the links and bushed and does not translate into spring (roll bar) action

That’s a very interesting point re the rounded whiteline link concentrating the load narrowly as opposed to the OEM part enclosing the bush.

Point 2: Would positioning the link on the other side of the bar so it was vertical equal improved functioning of the bar?

[Eagle 1662]

Had a rear 20mm Whiteline bar in my old E34 with the same issue. Replaced them with some other links that i cant recall.

[Secniv 182]

8 hours ago, Eagle said:

Had a rear 20mm Whiteline bar in my old E34 with the same issue. Replaced them with some other links that i cant recall.

According to the whiteline website the link is 100mm in length the same length as the E30 link.

Did you just bolt up or something else eg. washer (steel or nylon) in order for the bush to bar connection to function in the manner it is designed to?

[Jacko 2156]

I dont remember them being on the piss in reality, I think most of the angle is simply from the photo. It may have not even been hooked up on the other side yet! 

I remember the front whiteline sway bar was a pig to fit, the bushes rode into the radiuses of the bend in the bar, dont recall the back being a goofy fit though. 

 

[Eagle 1662]

2 hours ago, Secniv said:

Did you just bolt up or something else eg. washer (steel or nylon) in order for the bush to bar connection to function in the manner it is designed to?

Yeah think I used washers etc to match it up. May have been stock end links

[Secniv 182]

This discussion has been very helpful thanks guys.

With a slightly larger diameter than stock rear sway bar turning attention to the front my thinking is to keep the stock 20mm ARB and use some stiffer new links ie. from a Mondeo wagon 2001-07, a E30 Zone upgrade recommendation "These units are rose-jointed, giving a firmer, stronger hold over your anti-roll bar". they are Lemforder  manufactured so I don't feel so bad about putting them on lol.

Thoughts? 

[Secniv 182]

Update 

i purchased a 16mm whiteline rear arb and installed it with a pair of E30 OEM links with the whiteline polyurethane hanger bushes. Took it for a spin on some of our great Waikato roads this afternoon. Along with the other improvements I made ie. new OEM trailing arms bushes and AKG polyurethane subframe mount bushes what was good handling just got great with nice flat handling through the corner and with stiffer links up front turn in feels better as well. Still a track day would be the best place to really test it.