Suspension Upgrade

Post your E12 technical questions and comments here. Please, no off-topic posts.

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gmonsen
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Suspension Upgrade

Post by gmonsen »

Just to be sure I haven't screwed up, let me ask. I have Bilstein B6's all round. I ordered the Ireland Engineering sway bars and a set of H & R Sport springs (40mm lower). Sound reasonable? I didn't really know about the springs but read later that the springs from the factory on the US introduction were notably softer than their European equivalents. That, and being 45 years old might account for the soft front end I felt. Not really porpoising, but just some up and down movement that seemed soft. I figure the H & R springs should be just a bit harder than the late e12 or e28 springs?
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528i-1981
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Re: Suspension Upgrade

Post by 528i-1981 »

There was a thread in March started by EE-onetwo where I think he used the same combination you're thinking about here. Patinabeforepolish talked to Bilstein directly, who told him B6s were ok to use on lowering springs. I don't know if that application involved 40mm lowering.
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gmonsen
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Re: Suspension Upgrade

Post by gmonsen »

Thanks. Yes. Saw that thread and again seems like things should be fine. Couldn't find much here on what sway bars people like, but, since I am getting the sway bars from Ireland, they should work well.
HB528i
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Re: Suspension Upgrade

Post by HB528i »

I use the B6 HD on my coupe with lowering springs, no issues.
PatinaBeforePolish
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Re: Suspension Upgrade

Post by PatinaBeforePolish »

Yes, Bilstein said the B6’s are fine with lowering springs. The early ones use a different strut according to the part numbers. I think the porpoising effect is slightly magnified by the seat construction with springs vs. foam but I’ve never driven one with a more modern seat with all foam seat cushions. Maybe someone more knowledgeable about suspension design could offer insight about the ride.
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528i-1981
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Re: Suspension Upgrade

Post by 528i-1981 »

gmonsen wrote: Sat Apr 24, 2021 2:03 pm Couldn't find much here on what sway bars people like, but, since I am getting the sway bars from Ireland, they should work well.
I installed ST 52015 on mine (28mm front/22mm rear), which I think is the set IE sells. I think you'll be very pleased if you're still running the stock sway bars.
(oo=00=oo) Eric
1981 528i Manual
gmonsen
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Re: Suspension Upgrade

Post by gmonsen »

528i-1981 wrote: Sat Apr 24, 2021 8:38 pm
gmonsen wrote: Sat Apr 24, 2021 2:03 pm Couldn't find much here on what sway bars people like, but, since I am getting the sway bars from Ireland, they should work well.
I installed ST 52015 on mine (28mm front/22mm rear), which I think is the set IE sells. I think you'll be very pleased if you're still running the stock sway bars.
Thar's exactly what I ordered from them. Thanks.
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maybeillbuyit
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Re: Suspension Upgrade

Post by maybeillbuyit »

PatinaBeforePolish wrote: Sat Apr 24, 2021 5:20 pm Yes, Bilstein said the B6’s are fine with lowering springs. The early ones use a different strut according to the part numbers. I think the porpoising effect is slightly magnified by the seat construction with springs vs. foam but I’ve never driven one with a more modern seat with all foam seat cushions. Maybe someone more knowledgeable about suspension design could offer insight about the ride.
I have spoken to Bilstein in the past looking for information regarding shocks for HD B6s vs Sport B8 springs. I've found info online etc that indicates that B6 HDs should be used with stock or stock height springs and Sport B8 shocks ( NLA unfortunately) should be used with lowering springs.
This is what I've found online many times when looking for info:

"The longer B6 shaft on the HDs used with lowering springs will sometimes unseat the spring from its perch!!"

Now I'm not saying this is true, just repeating what I've read. I'm also looking for lowering springs and Sport shocks but of course I haven't had any luck finding Bilstein Sports.

Any comments would be welcome from anyone with experience with this issue. I'm getting close to redoing my suspension and would like to get parts soon.
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gmonsen
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Re: Suspension Upgrade

Post by gmonsen »

maybeillbuyit wrote: Mon Apr 26, 2021 10:22 am "The longer B6 shaft on the HDs used with lowering springs will sometimes unseat the spring from its perch!!"
I have seen that comment, but never in an authoritarian way. Nobody that had done it and experienced the spring coming off the perch. And, as importantly to me, I don't see how a shorter spring would ever unseat. The spring is really the primary mechanical join between the body and the wheels. The shock's rebound capability shouldn't be able to separate the spring from its perch.

Maybe PatinaBeforePolish or someone else can comment?
PatinaBeforePolish
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Re: Suspension Upgrade

Post by PatinaBeforePolish »

The spring is contained by upper and lower perches on both the rear shock and front strut. A very short spring could rotate and lose its orientation under full extension, but unless something breaks, the spring remains secure in the assembly. I have H&R springs front and back. They both require a small bit of compression to assemble and the spring does not rotate within the assembly in a fully relaxed position. Bilstein rear shocks have 3 height settings for the perch so I suppose the spring could rattle around with the perch on the setting allowing for the longest travel. I have mine set in the middle.

BMW OEM shock and strut assemblies use bump stops on the piston rod to prevent bottoming out at full compression which could damage the shock. Bilstein uses internal bump stops for the same purpose with lowered suspensions. Shock travel would be affected if external bump stops are used with a lowered suspension.. They won't fit on the front Bilstein struts anyway so that's easy.

I think using H&H springs with B6 struts will be fine for spirited street use. Track day or hard autocross is another conversation. I have front struts from Wallothnesch that are (allegedly) specific to the M535 and they work fine. I have no idea if they're B6's or B8's. It's my understanding from Bilstein that the rod length is the same and the valving is different but I've never had a B8 for comparison. Notably the reason B8 struts aren't available for the e12 is because it's a unique applications. The rears fit e3s and e9s so there's more demand and Bilstein keeps making them.

There, that's everything I know about e12 shocks and struts.
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gmonsen
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Re: Suspension Upgrade

Post by gmonsen »

Thanks, much, Patina. I put the car up on the lift and with the Bilsteins fully extended checked the H&R springs and the springs were still well-seated.
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