95 M3 rear ball joint question

[Green95M3]

I am upgrading the lower outer control arm bushing to a ball joint, like the '96 and later M3's.

The factory bushing is offset somewhat:

HubBushing.jpg

It looks like if I install the ball joint and center it, the geometry will be off.

HubBallJoint.jpg

I'm concerned I'll have difficulty re-attaching the control arm or that the control arm will be at an unusual angle. Are there any tricks here? Should I just press it in and all will be well?

Any input would be appreciated.

[bluptgm3]

This image from a rear upright from a 1998M3 Sedan appears centered.
edit: sorry this is an upper 1996+m3


Lower lug 1996+M3 RTA lower lug w/uniform protrusion fed/aft.

[aeronaut]

I remember the same question/issue on my 95.
I can get pics tomorrow. Can't remember what I did, but I haven't had any problems.

[ScotcH]

Center it ... the old bushing likely moved (or maybe not, I don't remember, been a while since I saw a stock 95 ... but we've always just centered them).

[Green95M3]

Thanks everyone. This is very helpful!

Aeronaut, if you have some pics, I would really like to see them.

Thanks again!

[aeronaut]

I've had no issues with this. Basically, when one side is flush, the bearing is actually offset a bit, obviously not as much as the OE bushing.
For the record, the 95 trailing arm is a different part # than the 96+ trailing arm. Not sure of differences, but the angle/placement of this bearing location may be one.

IMG_20201022_105214.jpg

IMG_20201022_105229.jpg

IMG_20201022_105236.jpg

[bluptgm3]

I've had no issues with this. Basically, when one side is flush, the bearing is actually offset a bit, obviously not as much as the OE bushing.
For the record, the 95 trailing arm is a different part # than the 96+ trailing arm. Not sure of differences, but the angle/placement of this bearing location may be one.

IMG_20201022_105214.jpg

So for clarification, the ‘as installed’ position of the lower control arm bushing in the RTA lower lug, the outer bushing sleeve/race is flush with the forward face of the lug?
How about the upper bushing ‘as installed’ position? Centered?
Good to finally know the difference (at least one) between the 1995M3 RTA and the 1996+M3 RTA.

https://www.bimmerforums.com/forum/s...ion-difference

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[Green95M3]

I've had no issues with this. Basically, when one side is flush, the bearing is actually offset a bit, obviously not as much as the OE bushing.
For the record, the 95 trailing arm is a different part # than the 96+ trailing arm. Not sure of differences, but the angle/placement of this bearing location may be one.

Thanks for the pics. I noticed the same thing on realoem that 95 & 96 have different trailing arms. I'm willing to bet one difference is the geometry of the ball joint holder.

So for clarification, the ‘as installed’ position of the lower control arm bushing in the RTA lower lug, the outer bushing sleeve/race is flush with the forward face of the lug?
How about the upper bushing ‘as installed’ position? Centered?
Good to finally know the difference (at least one) between the 1995M3 RTA and the 1996+M3 RTA.

I'll post some pics of the original positions today or tomorrow.

[blckstrm]

Thanks for the pics. I noticed the same thing on realoem that 95 & 96 have different trailing arms. I'm willing to bet one difference is the geometry of the ball joint holder.

Check that link he referred to.

We had a long discussion about this earlier this year, and never quite got to the bottom of it. But bluptgm3 finally figured it out. Not geometry per se, but the 96+ change to ball joints top and bottom required a thicker bearing mounting point on the bottom.

Again, you can follow the conversation in that link to understand - we had the same question, and when this post resurfaced that issue bluptgm3 got to the bottom of it and posted it there...

[Green95M3]

Check that link he referred to.

Thanks, I just read the thread. Wow, tons of great info there. It appears that the final analysis of the 96+ RTA's shows that the lug for the lower ball joint is thicker than the lug for the lower bushing on the 95.

So for clarification, the ‘as installed’ position of the lower control arm bushing in the RTA lower lug, the outer bushing sleeve/race is flush with the forward face of the lug?
How about the upper bushing ‘as installed’ position? Centered?

From the above mentioned thread, you appear to be the ultimate authority on this topic. But since you asked...

Yes, the outer bushing sleeve/race is flush with the forward face of the lug.

Also, for clarity, the upper position comes with a ball joint from the factory and it is centered.

The pics below are of the left/drivers side RTA on my 95 M3.

TrailingArmJoints1.jpg

TrailingArmJoints2.jpg

TrailingArmJoints3.jpg

[cashmancab]

Not trying to beat a dead horse here but I mentally agonized over this ball joint when I did it this spring. I ended up centering it thinking the additional swivel of the ball joint would compensate for any offset and the OEM LCA is kind of flimsy anyway and would flex to fit. I have tracked the car several times and have not noticed any ill effects.

However, if I read this correctly. It should be mounted offset like the OEM Bushing was. This will drive me nuts and I will go correct it.

So a simple yes or no question. Should this balljoint be mounted offset in the 95?

[aeronaut]

I mounted my slightly offset, maybe, 3-4mm? Others have mounted centered.
IMO, it doesn't matter. It might change the camber curve through the full range of motion by small small irrelevant amount.
As long as it's not binding, drive it.

[bluptgm3]

However, if I read this correctly. It should be mounted offset like the OEM Bushing was. This will drive me nuts and I will go correct it.

So a simple yes or no question. Should this balljoint be mounted offset in the 95?

The fore-aft rotation-arm length is fairly set by the RTA. The slight shift in the position of either the upper or lower rose joint has little impact on the overall geometry. The (very) slight angle change of the lower lateral control arm, I believe is insignificant. The exception might be with those that use solid bushings in these inner lateral control arm joints....and thinking about it, I don’t see how those positions can be solid...though with ‘Race’ suspension there is little motion in these joints.


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[ScotcH]

Yeah ... I guarantee you will NOT notice any difference on a street car of 3-6 mm either way. All of these joints are meant to be multi axis. It's not a problem. If they affected anything to a significant degree, there would be stops for the bearings to bottom out on.

[cashmancab]

The fore-aft rotation arm length is fairly set by the RTA. The slight shift in the position of either the upper or lower rose joint has little impact on the overall geometry. The (very) slight angle change of the lower lateral control arm, I believe is insignificant. The exception might be with those that use solid bushings in these inner lateral control arm joints....and thinking about it, I don’t see how those positions can be solid...though with ‘Race’ suspension there is little motion in these lk

I take that as your version of a simple Yes. 😁