Steering "darty" PLEASE HELP!
 

This is driving me nuts now... my W124 300D is darty as can be at highway speeds. It's scary to drive over 50mph! I have replaced sway bar bushings, rear subframe bushings, and drag links. Shocks and struts are relatively new. I need to get an alignment next, but eyeballing the front tires, the only this I notice is that camber is probably zero (or even slightly positive). Another thing I have noticed is that the steering will NOT center itself after a turn, which I am sure contributes to constant input being needed on the highway. I can't feel any slop in the front tires when the front is jacked up, and backing off the load adjustment in the steering box doesn't seem to help much; I thought maybe someone had over-adjusted it in the past.

Any ideas? I am going nuts here! I'd just spring for an alignment, but I want to make sure I have changed all the suspension items I can before I shell out the bucks for the alignment. FWIW, I bought this car in April and the steeirng wheel was off-center from the time I bought it. Botched alignment last time 'round?

Thanks all!

Anyone?

Sounds like you're on the right track.

I'd start by checking toe, simply measure to get an idea how close it is, and feel for feathering of the tread inward or outward. I'm guessing you have a lot of toe-in.

Also look at the rear suspension, the torque-arm there is a common bushing failure and can cause on/off throttle steering of the rear, plus other bushings back there can steer the car.

Thanks, Jeff. I need to install my new strut mounts and just bite the bullet & pay for an alignment. Guess there's no real way of knowing if it's something else w/o checking the alignment first. I do believe there's a bit of toe-in, but I couldn't say how much.

This is sure driving me batty, though. I've replaced a lot of parts and seen little/no improvement.

Castor affects the ability for the wheel to return to center after making a turn.

Overtightening the steering box adjustment will also bind up the return.

Sure you adjusted it the right way? It's not intuitive.

Jim

Hi Jim -- thank you for your reply; I appreciate it. As I read it, turning the steering box adjuster CW loosens it, and CCW tightens (opposite of what you'd expect). Is that correct? Either way, adjusting it doesn't seem to make a lick of difference. 8^(

Be sure to adjust it with the steering straight. The steering box is designed with some play off-center, if you adjust that out it will bind on-center.

Try this.....
 

I just had a similar experience with a 190D that I'm resurrecting for Fuel Mileage.......very squirrelly over 50 MPH......

I used a couple of jackstands.....got a couple of long and...straight 2x4's.....set 2x4 up on jackstand and lay it up against the center of both tires on each side 2x4 should contact both sides of the rear tires, and the rear side of the front tire, with the front sides of the front tires just a very, very little bit of gap (toe in).......this will tell you how your car is tracking and will also tell you how much toe in/ out you have.......

Hillbilly Engineerin' 101

SB

This assumes that the track is the same front and rear. Not often the case.

I use a lumber pencil to scribe a mark on the center of the tire, after jacking the front end up. Drop the car, then I roll the car back and forth a few times to make sure the suspension is settled.

Then, using a tape measure, check the distance between the lines at the same distance above the ground at the front and rear of the tire.

Simple geometry will reveal the toe in (or toe out) of the front wheels.
All you need is the horizontal distance between the front and rear measurements, and the difference between the two (front and rear) distances.

Jim

Torque struts rear
 

Courtesy GSXR

Toe out or too little negative castor will make it unstable.

Tom W

Toe out or too little castor will make it unstable.

Tom W

Tires can have that effect also. What tires are on the car? How many miles are on them? Are they the stock size? What are the air pressures?

You may want to switch them side to side, and back to front, and see if this has an effect. Tires are the cause of many weird handling problems. Are you using the stock MB wheels? If not, are the off-sets in spec?

Hope you find the culprit(s).

Another chapter in the Hilbilly Engineerin' Handbook.....
 

Had a friend follow me and watch the track......also you can drive on a dusty roadway and observe your track, if the tires don't follow in the same track when going straight....you've got a problem......

Also of note......Astorg MB of Parkersburg WV charges $39.35 for a 2 wheel alignment and 59.95 for a 4 wheel alignment.....I changed every bushing, ball joint,and tie rod on my 300D.....and then took it to Astorg for the full alignment treatment......I prefer to use the MB Dealership for alignment on these cars because the suspension is way different from the cars that the Tire Dealers usually see.....

SB

Is this the same as the drag link? I thought the forwardmost arm on the rear suspension was what really threw things off. Thanks!