Diagnosis of Poor Tracking

[Amskeptic]

BMWs are supposed to track somewhat better than an overloaded old Ford station wagon with low tire pressures.

'93 525i with 210,000 miles, has decent front and rear tire wear characteristics, no clunks in the steering, tire pressures are 35 all around on Michelin MXVs.

How do you determine if there are bad control arm bushings or ball joints
or bad rear suspension subframe mount bushings, or bad "pitmann links" or even bad differential mounts? I pry parts with a lever and everything seems attached. I'd like to hang out a rear passenger door and look underneath while accelerating and decelerating, but I have been advised against this.
Colin

[Blitzkrieg Bob]

Speed?

Shimmy?

Shake?

Vibration?

Loose feeling in the rear on turns?

Not going in the direction you point it?

[Felixdacat]

I think he is talking about the car staying straight when driving. My car seems to pull when I get into ruts in the pavement from the dump trucks. Mine does this because of the 18" rims, and my PZeros.

[Boom n Zoom]

I am thinking the same thing felix

I have that similar problem with the following wheel grooves in the road from trucks as well but I am running 8.5" X 17" with 235/45's up front and 10" X 17" with 255/40's out the back.

I just last week got the Front Koni's fitted along with new lower control arms (alloy) and upper strut mounts. (also with lowered Eibach springs that were already fitted)

Having had this done has pretty much negated the problem, it will only do it if the road is really bad and even then it is very minor, just a bit of a twitch from the wheel.

I also recently replaced the rear pitman arms, this reduced the squat problem and has helped to firm up the rear, but I am still waiting for Koni Australia to supply me with the rear Koni adjustables then I feel it will be pretty much sorted out as it is obvious to me that the rear struts have gone south as well and the rear is not as firm as it should be.

As I had three items replaced in the front suspension it is difficult to pick which was the culprit, but the total sum of the parts replaced has as I said negated the problem.

In your circumstance, I would look to the steering and check the tierod ends (inner and outer) Pitman arm, (this is opposite to the arm from the steering box), Drag link, (this is the arm that holds the steering arm, pitman arm and inner tierods together).

Also check that the steering box is adjusted correctly and that there is within specification freeplay.


If this all checks out I would be inclined to replace the lower control arms as the lower balljoints/inner bushes do take a great deal of load. I would also replace the Thrust bushes (Upper control arm) with either:

Stock bushes (you will have to change these again in about a year as they have proven to not be very good)

750iL bushes (much stronger than stock and a common fitment)

M5 Spec Bushes (Not sure on the availability of these but I have heard them mentioned a few times from people on the board)

Finally I would replace the front strut inserts along with the Upper Strut mounts as a very small amount of movement here can be amplified in the opposite direction due to the pivot point of the lower control arm.

A good place to start is to use the 'Search' on the forums under steering and suspension this will give you even more detailed information on things to look for and be aware of.

THE place for parts is here http://www.bmaparts.com/ These guys have the biggest range and the most competitive prices with quality all the way.

Could I also suggest that you fit Lemforder parts for suspension components, as these are the same as the OEM parts and they last (The extra money is worth it for the peace of mind, that and the fact that you won't have to worry about those parts for a few years.)


Like I mentioned, do a search. If you have any more questions feel free to ask and somebody will help you out.

Good luck :)

P.S. The reason the search is mentioned so may times is that if Qube catches you, your gonna be unhappy!! ;)

[Felixdacat]

Amskeptic,

This is a pretty good write up that Boom has provided, You will see that most of your questions have been answered. Replacing the front end parts isn't cheap, but is well worth the outcome. Alot of us have had the same problem with the front suspension, and will be able to answer your questions, BUT do yourself a favor and search the threads.

Just so you know Boom, on my end everything has been replaced with Lemforder parts. My complete front end is about 6 months old. I am +3 on the rims, and run front and rear 235/40/18 Pirelli PZero nero. Great tires, but have a soft sidewall, and love to track. I have BAV springs with Bilstein sport struts and shocks. This will all be replaced in the spring. Not sure with what next.