VAC toe and camber weld-in question

[Zoupe6]

Since my subframe is out, it seems like the right time to put these in. Is the general consensus that they should be welded in with max toe and camber adjustment since they are only needed when lowering, or should I leave a little room for stock height adjustment?

[Randy Forbes]

On the Z3, I always biased the camber installation set so that you would not get greater negative camber than stock, only less.

The toe set should be put in with them "centered" on the stock location (for plus & minus adjustability).

The exception would be if you're compensating for mildly bent components, but never biased so much that it would throw off a new stock trailing arm.

Follow?

I made up fixtures for the M version so I could test both trailing arms, and the carrier. The fixture for the carrier could be used for the Z3, but the camber points (inboard RTA mounts) were slightly off (YES, the factory put more negative camber on the Z3 than the M versions).

[Zoupe6]

Gotcha! I was going to pick points and triangulate for side-to-side comparison. It won't tell me which one is wrong if there are differences, but that's about the best I can do, I think.

[mikeshammer]

I have a jig set up to check the rear subrames and trailing arms. The problem with offsetting the bushings too much can be seen by running a straight rofd through al lfour mounting points o nthe subframe. you will see once one hole is not in alignment with the other three wear to that bushing will occur in a few hundred miles. I also repair the subframes to oem and if they are within a degree can weld In the adjusters to compensate

[rf900rkw]

Curious. Is this jig E30, Z3, or Z3M. We know the trailing arms are totally different. And we know the Z3M subframe is different. If nothing else, it's much heavier with internal reinforcing, The question I've never been able to answer with authority is if the geometry is the same. I had one source that claimed the Z3M ran 11 degree rather than the E30 14 degree trailing arm mount. Got any input to this age old preponderance?

[mikeshammer]

right now Ionly do the m subframe. I have not really gotten into the e30 and stock z3. I really have not gotten into how many degrees difference it is. I just bought a new subframe and sett he jig up off of it .I then installed 2 used from cars I had that I knew the alignment and they checked dead on. I will have to pick up a stock z3 and compare it . Right now I am doing more control arms than subframes.

[BimmerBreaker]

Curious. Is this jig E30, Z3, or Z3M. We know the trailing arms are totally different. And we know the Z3M subframe is different. If nothing else, it's much heavier with internal reinforcing, The question I've never been able to answer with authority is if the geometry is the same. I had one source that claimed the Z3M ran 11 degree rather than the E30 14 degree trailing arm mount. Got any input to this age old preponderance?

Ive never heard that before but thats interesting. It always seemed to me there had to be more in the difference in how the M feels than just the trailing arm width. I have an M subframe off a car, how would I even measure the mount angle accurately if I procure a non-M or E30 subframe?

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If thats the case, I wonder how an M subframe with non-M arms would feel

[rf900rkw]

Thanks. If you find anything interesting, I"d love to know. We can see the big differences between them, but how many subtle differences are there in the geometry, both front and rear. For example, we know the front knuckles have a difference in the steering arm/tie rod location relative to the hub. But what about the subframe. Where is the rack in relative 3D space compared to the stock subframe? 0.050" makes a difference in bumpsteer.


Graham, Project a line through the mount tabs. Project a line between the bushing centers. Block out a right triangle and toss some math at it. Or attempt to use a protractor between the lines. Or even lay it face down on a level surface, stick a rod through the tabs, and use an inclinometer app on your phone.

If there is a difference in the angle, mixing arms and subframes would net a large chunk of static toe, either in or out. Basicly 3 degrees worth in this case.

[BimmerBreaker]

I was thinking I could get a large thin dowel rod to stick through the slots on the mounts, to help visualize (and give something to measure angle against) the angle. I may also try the inclinometer app too. Ill source a non-M subframe and see how it compares.

This could be interesting... For years people have said they were the same. If not the same then the difference was the M reinforcement internally

I may also ask Garagistic. They powdercoat E30 rear subframes and have done Z3M too. They might know

[Randy Forbes]

Curious. Is this jig E30, Z3, or Z3M. We know the trailing arms are totally different. And we know the Z3M subframe is different. If nothing else, it's much heavier with internal reinforcing, The question I've never been able to answer with authority is if the geometry is the same. I had one source that claimed the Z3M ran 11 degree rather than the E30 14 degree trailing arm mount. Got any input to this age old preponderance?

When I put a Z3 suspension carrier on the fixture made from (a brand new, dealer sourced) M carrier only the inboard rta mounts differ; picture them "shorter" lowering the innermost bushing, yielding more negative camber.

Because my RTA fixtures index using the hubs, fitting the Z3 version is a non-starter. I had considered making them adaptable to both series, but making the fixtures was costing me time away from the car that the new pieces were intended for.

I was thinking I could get a large thin dowel rod to stick through the slots on the mounts, to help visualize (and give something to measure angle against) the angle. I may also try the inclinometer app too. Ill source a non-M subframe and see how it compares.

This could be interesting... For years people have said they were the same. If not the same then the difference was the M reinforcement internally

I may also ask Garagistic. They powdercoat E30 rear subframes and have done Z3M too. They might know

Not this people! I had been able to get a >>visual<< comparison as early as October/November 2001.

[BimmerBreaker]

Thats why we should all listen to the Randys!

Good to know about the difference. Im curious how the Ms and non-M stock alignment specs compare now. Ill do some digging