E30 M3 strut compared to E28?

[ajs1]

OK, I've never looked at the E28 5 series strut, how does it differ from the E30 M3, being that the hubs and the brake calipers interchange.

Any one got some good pictures of both?

[conrod]

No pics sorry. But I have compared them both side by side, and at first glance they look the same. But the bolt on steering arms are different (E28 has steering box v. rack on M3 I think, ackerman angles all different) and the struts had a few subtle differences, length, ARB mounts etc.

[E30-323ti]

The E28 also has the hub flange sticking out alot further and the steering arm (that bolts on the bottom) has 2 ball joint holes for the weird 5'er control arms (2).

I have heard of them being used on the E30 but I'd imagine you'd get some funny geometry going on...

[ajs1]

Cool, thanks guys.

Thought it was worth knowing a little more. The dual ball joint design is used to control wheel movement forward/aft I think, during steering angle changes. The 'theoretical' lower pivot point would move as the steering angle changes.

I was wondering if it may be possible to use them with M3 lower bolt on steering arms. But seems like it's not. (wheel flange sticking out further, may explain the unique rotor for the E30 M3 perhaps?)

[E30-323ti]

Yeah, something like that.

From what I have gathered you only use one of the holes and swap the struts left to right.
I'll find one at pick-apart and have a play some day.

I guess that would explain the unique M3 rotors.

[ajs1]

Hmm, something keeps me thinking that there could be something quite similar between these struts.

Car makers always try to go to the parts bin when doing low volume productions. maybe the E30 M3 struts were originally based on the e28 5 series.

Perhaps the only difference is the stub axle length, (shorter on M3??),
Sway bar mountin brackets.
And possibly the tube length, (as mentioned by CONROD).

Kingpin(stub axle) angle must be the same, as both cars share front brake calipers.

Question is, do the lower M3 steering arms bolt to the E28 leg?

If it does, then the only thing left is the stub length that dictates ht difference in rotor between M3 and E28.

So E28 legs may be able to be modded/machined to replicate an M3.

Plenty of E28 legs here is OZ, so maybe all I'd have to do would be to get some M3 lower bolt on arms.

Can someone with access to both strut legs, do some checking?
check if the lower arm bolts on,
and measure the stub axles.

Brake rotor dimensions would also be helpfull.

[ajs1]

OK I dug a little.

on the EBC brakes website, the catalogue lists rotor dimensions as..
E28 Dia 282 height 76
E30 M3 dia 280 height 41

[E30-323ti]

The E30 M3 & E28 steering arms are not interchangeable.
M3's have 4 bolts holding them on where as the E28 has 3.

After looking at the ETK for a while the E28 steering arms would not work on E30 CA's as the ball joints are different sizes (12mm Vs14mm).
So I presume those who have the E28 front end in a E30 either have made their own steering arms (not a bad idea) or have put the lower E28 arms in as well (modifying the subframe & chassis mount to suit).

[ajs1]

Are the E28's 3 bolts in different locations? 3 out of 4 might be enough...hehe

[E30-323ti]

No. Completely different.

You could look into a custom steering arm!!