Front thrust arm differences

[blanz]

Have replaced both front thrust arms on my '94 840 and notice that the front wheels seem to be closer to the rear of the wheel wells than before. These units were lemforter (sp?) that were pre-loaded with the infamous bushings. Was there some design change at some point where there could be two different length arms available? The shorter arms are causing a toe out condition and I'm now looking at a wheel alignment (if I can find someone that can do it).
Any insight would be greatly appreciated.

[jcs1966]

Not sure about the length of the thrust arms, but you will need to have an alignment done anytime you change any of the control arms or ball joints.

[IJustDrive]

I think I read somewhere that the arms for cars with x-brace were slightly different length. I think that is most cars from from 4/92 on. RealOEM shows the same part, but I think the mount point on the two brace types were slightly different.

[peezen]

Not true. I added an X-brace to my 91 car and used my original arms.

[affa]

Same here. Upgraded to x-brace. No diff.

[BMSman]

My 91 does not have an X-Brace. Does it make much difference?

[affa]

The arms are the same pre and post '92 x-brace.

Edit:

If you meant performance diff - do you think bmw would make a production change and spend $$ if they didn't think it was needed?

IMO the actual diff is minor and will only be apparent in more 'spirited' driving. My guess is that they found out after a couple of years the early cars were losing their front wheel alignments due to chassis flex.

There's a designed-in 'weak point' ( forgot the technical name) on the frame rails between the engine carrier that the lower arms mounts to and the rear crossmember that the thrust arms goes. The weak point is there so the frame rails will bent down in a head-on collision and will try to take the engine under the survival cell. Constant flexing from suspension load might be causing unwanted movement or stress there. I believe the x-brace helps distributes this load away except in a frontal collision situation.

It is for the same reason that the full x-brace extends all the way to the torque boxes just under the footwells. If the frame was strong enough they wouldn't have needed to extend the brace all the way there.

[m6bigdog]

There are 2 upper control arm lengths that look very similar.
E31 & E32 is the longer arm with E34 being the shorter version and if installed will move the suspension back and reduce the wheels caster value.
So you should not have the toe set/aligned with the wrong arms as the steering return to straight will be greatly affected.

I suggest checking the part numbers cast into the arms to make sure the installed thrust are the ones for the E31 p/n 31121139999 & 31121140000, I suspect they are the E34 arms.

[Fatandre]

My wheel on the driver side is close to the door and when I have my wide wheels it rubs against the fender.
Could it be the case I have the e34 upper control arm and that could be the case?
This has been making my sleeping a problem as I had the car aligned and still nothing changed.

You can see how it is rubbing and the other side is all good.

[clockwork]

Odd. I finally got around to installing my Wokke UCA and habe noticed the exact same issue now!
Why do they look like the wheels sit further rear in wheel wells?

[wokke]

My 91 does not have an X-Brace. Does it make much difference?

It makes a hell of a difference. One of the best suspension upgrades you can get for a pre '92 E31.

- - - Updated - - -

Have replaced both front thrust arms on my '94 840 and notice that the front wheels seem to be closer to the rear of the wheel wells than before. These units were lemforter (sp?) that were pre-loaded with the infamous bushings. Was there some design change at some point where there could be two different length arms available? The shorter arms are causing a toe out condition and I'm now looking at a wheel alignment (if I can find someone that can do it).
Any insight would be greatly appreciated.

that's how it should be.

[Fatandre]

So its possible o have the wrong arm?

[dragon850]

So its possible o have the wrong arm?

Well not quite, what do you have for a bushing up there?
I had used poly bushings on my earlier 850 and the wheels were in fact too far back, for what ever reason.
Installed M5 bushing,alignment, fixed everything. Not sure how any of this made a difference on an original arm..

[m6bigdog]

Well not quite, what do you have for a bushing up there?
I had used poly bushings on my earlier 850 and the wheels were in fact too far back, for what ever reason.
Installed M5 bushing,alignment, fixed everything. Not sure how any of this made a difference on an original arm..

The arms are a fix length, so replacing the bushing shouldn't matter unless the bushing is totally gone.
The E34 arm (image attached) is 17-5/8" overall length. The number on this new arm is 1133667.1 which is weird because the order part numbers are 1141097 & 1141098.
If someone has an E31/E32 arm are laying around please measure it and post the overall length and the casting part numbers for the record.
011.jpg

[Fatandre]

So you M6 say its possible that if I have on one side an arm from the e34 and on the other side from a e31 the arm from the e34 will put my wheel back, right?

[shogun]

I have a used old E32 thrust arm here, overall length as mesured by you is (roughly) 47cm = 18.5", no name product, that was a cheapo one I replaced on an E32 of wrenching buddy

[dragon850]

Measured new BMW control arm I had laying around , 18.5"

[AUS840]

This is interesting. I have the arms with the bushings that Wokke sells in my '97 840 and the wheels are too far back in the well. In fact, with the camber plates installed the alignment shop was not able to get the correct caster with a negative camber.

[IJustDrive]

So, from what it sounds, we have arms between 7 5/8 and 8 1/2. That sounds like it may cause the problem described by OP.

[toomanyparts]

So are Wokke's arms the correct length?

[blanz]

Have replaced both front thrust arms on my '94 840 and notice that the front wheels seem to be closer to the rear of the wheel wells than before. These units were lemforter (sp?) that were pre-loaded with the infamous bushings. Was there some design change at some point where there could be two different length arms available? The shorter arms are causing a toe out condition and I'm now looking at a wheel alignment (if I can find someone that can do it).
Any insight would be greatly appreciated.

Had a four wheel alignment done yesterday and as I suspected, the toe was way out from replacing the thrust arms. The shop did a fair job trying to get all the settings within spec, but caster is still out. I'm still convinced that there are differences in the lengths of the thrust arms. Caster s/b 3.5° to 4.5° according to their machine, my front end came in at 7.0° and 7.4°. Caster can only be a function of the length of the thrust arms, and from the attached image, the front wheels on my 840 favor the rear of the wheel wells. They dialed in toe just fine. Camber, being what it is, was just on the edge of being out, being a tad on the negative side.
2015-10-24 10.58.51.jpg
I checked the part numbers on the thrust arms that I installed some time ago, and they are the correct part numbers.
And the mystery continues...

[shogun]

Found another upper arm made by Meyle, HD version, for E32, right side, also 18.5"

I posted this a while ago, copied from the E34 forum: That is what happens when the parts from E32/E31 are used for the E34. Just got done at the alignment shop hoping to fix my problem but they said there was nothing wrong with my front end.
https://images.tapatalk-cdn.com/15/05...10723e098c.jpg
The PO said something about putting e39 control arms or maybe 7 series? Could this be the issue? The alignment shop said that the thrust rods may be to long causing it to push out?
-------
I'm going to go out on a limb and wager that some dope installed e32/e31 thrust arms on your E34 car, part #31121139999,31121140000 . Replace them with part #31121141097, 31121141098 with bushings #31121136605
You can shop around and find them with bushings already installed, but this ought to give you a very good idea of why your wheels are mislocated.
--------------
I got the wrong 7 series control arms once and they did the same thing.
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what was in there, but they where wrong https://images.tapatalk-cdn.com/15/05...5241b6f530.jpg Correct ones in then I was off to the alignment shop for the second time today. And we are all fixed

[m6bigdog]

So you M6 say its possible that if I have on one side an arm from the e34 and on the other side from a e31 the arm from the e34 will put my wheel back, right?

It is very possible to install the incorrect parts on one side and end up with a goofy front end (turning and tracking performance is unbalanced).
The difference in caster between the front wheels will make the suspension and steering wheel react differently as the wheels returns to straight.
The front wheel caster makes the front suspension want to steer straight ahead. The caster needs to be very close on both wheels so the suspension will not tramline or pull excessively and when one front wheel has a substantially less caster then that wheel will not return to straight as forcefully when that wheel is on the outside of the turn, i.e. reduced camber on right front with car turning left.

[wokke]

So are Wokke's arms the correct length?

I sure hope so. I run them in my E31s and have no issue (see above picture). Same on my black 850i.

- - - Updated - - -

So, from what it sounds, we have arms between 7 5/8 and 8 1/2. That sounds like it may cause the problem described by OP.

7 5/8 is the E34 version which is shorter than the E31/E32 version.

[m6bigdog]

There is no magic about the front suspension geometry. Of you measure the arms installed the 1 inch difference between shouldn't be to hard to conform.
I have uses a wire coat hanger bent to make the ends contact the desired measurement points (free form caliper); when a tape measure is not useful to measure the ends of an object.

The shops 3.5 to 4.0 deg. caster spec. is wrong and the caster gets smaller if the wheels move back not larger to 7.0 & 7.4 deg.
The caster for the E31 should be 8 deg. +/- 1/2deg., so 7 and 7.4 deg. is too little for an E31.
However I would have anticipated a 1" shorter UCA would have reduced caster more than that 1 deg. but the arms are at an angle and the actual geometry will cause less than 1" wheel displacement. Most likely 1/2" displacement with 24" to top mount so 1 deg. reduction in caster is about what to expect.

If a short upper control arms was installed the front wheel will move back in the wheel well (reduced caster) and it will have excessive toe-in then you take it in for alignment.

Also, don't just rely in the parts order numbers as the BMW warehouse can mix-up the parts bins and the physical parts so you will want to confirm the part numbers cast in the parts and length measurement for extra measure if the solution seems allusive.