Question on Balljoints for a 99 E46

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Carver - 28 May 2005 12:31 GMT

All,

There is a procedure using a huge pliers for checking balljoints. This
procedure checks the movement in the joint in the vertical direction,
however the outer ball joint is supposed to control movement
horizontally (affecting caster and camber). Hence the test with the big
pliers does not check the direction in which control matters. Further,
the rear mount of the control arm is in a rubber bushing which does
allow some motion in the horizintal plane which affects caster and
camber (just think of the inner balljoint as the pivot point). So we
have some slop in the control of the caster and camber, and in my
opinion this is by design. For me the real question is what is the real
tolerance for the balljoint play, and how is it measured, given the play
in the system? How do you know that the balljoints need replacing?
Using the huge-pliers-test both joints are showing some motion after
only 25000 miles, yet the dealer feels only one joint has slight play. I
have two new control arms to install so I plan to wait a bit. If I
recall right, Bentley manual says when you get vibration, but does not
say much else, and does not mention the test with the big pliers. I am
getting vibration above 80 mph, but not on all road surfaces. The
wheels are well balanced. None of my rims are perfectly round, and I am
thinking about replacing them, it seems to me that some of the washboard
roads around Baltimore Maryland may have contributed. In genenral do
these 17inch alloy wheels need periodic straightening or replacing. If
a rin is sufficiently out of round, why is the vibration not on all road
surfaces? Maybe the vertical play in the joint, and wear on the
bushing, when combined is what is contributing to the vibration
depending on the smoothness of the road surface.

If anyone knows the story on these balljoints, I am very interested in
finding out.

I suspect it was BMW's intent for some fuzziness on the alignment,
otherwise why use that rubber bushing?

At 110,000 miles the car continues to be a sweet handler at all speeds
except for the vibration.

Any help will be appreciated.

Carver

Reply to this Message

Malt_Hound - 28 May 2005 13:30 GMT

> All,
>
[quoted text clipped - 3 lines]
> horizontally (affecting caster and camber). Hence the test with the big
> pliers does not check the direction in which control matters.

Well, sort of... The outer balljoint is the one that wears out.

The inner one is not prone to wear because, as you noted, the only force
on this joint is the relatively small lateral force caused by the drag
of the wheels against forward motion. The motion within the joint is
limited to the angular changes that the control arm makes when the
suspension flexes.

OTOH, the outer balljoint must both flex and pivot as the steering wheel
is turned. So checking the outer joint is the key. On older 3 series
cars you could replace the outer joint (press in and out) but I believe
that on the E46'es you must replace the entire control arm, so you'll
probably never see an E46 with a worn inner joint.

> Further,
> the rear mount of the control arm is in a rubber bushing which does
> allow some motion in the horizintal plane which affects caster and
> camber (just think of the inner balljoint as the pivot point). So we
> have some slop in the control of the caster and camber, and in my
> opinion this is by design.

Correct on both counts. There is "slop" or more accurately "flex", and
it is entirely intentional. But the design of the bushing is such that
it primarily allows motion in the horizontal direction. This translates
to allowing the wheel to move fore and aft on the car. Because the
inner and outer balljoints are lateral to each other, and their
dimension does not change, the camber will not vary with this flexing.
The Caster is what will vary with this bushing;s flex, as the wheel
moves forward and backward underneath the fixed strut top.

> For me the real question is what is the real
> tolerance for the balljoint play, and how is it measured, given the play
> in the system? How do you know that the balljoints need replacing?
> Using the huge-pliers-test both joints are showing some motion after
> only 25000 miles, yet the dealer feels only one joint has slight play.

This is a tough one. The design of some BMW outer balljoints is such
that the joint is encapsulated in a hard rubber surround that is
supposed to reduce the transmission of vibration through the chassis.
The will be some "normal" motion on these joints when using the "huge
pliers" test. I do not know if this is true of the '99 E46es. I find
it makes it difficult to diagnose.

> I
> have two new control arms to install so I plan to wait a bit. If I
[quoted text clipped - 9 lines]
> bushing, when combined is what is contributing to the vibration
> depending on the smoothness of the road surface.

I think your assessment of the vibration is right. I would suspect
wheels and especially tires before the suspension itself. In fact, I
would not suspect vibration when the joints are worn at all. I would
expect some clunking on bumps when they are really bad, but otherwise it
is primarily an alignment and safety issue. I have no idea where this
vibration story came from.

-Fred W

Reply to this Message