When you turn on to a street, or go around a real sharp curve, all you have to do is loosen up your grip on the steering wheel and the wheels return to straight by them selves. Well, I just put a new set of tires on my 190d and it won't do that any more. I have to turn the steering wheel to get it straight. I put 175 R14 back on, the same size as before, and they are the correct size the car requires. I'm just wondering - what in the world.

Hugh Sr.

1984 190d (W201) 138,432

Self centering is a consequence of caster being set correctly. Just changing tires shouldn't change that, so something else is going on. You're going to have to bring it to an alignment shop and let them figure it out.

Did not think that happened with power steering. Thought you always had to straighten out the wheels yourself if you have power steering.

Your older tires may have been pivoting on the center tread area more. With both outer sides worn. Just a thought probably wrong but if you notice a change.

You could try a little more air in the front tires. Really though the car should not be doing this in my opinion. Did you have a front end alignment when the tires where installed? People can mess things up.

Another cause is a part in the system like a ball joint or tie rod end has partially seized. Not likely to have occurred when changing tires especially other that the geometry of the parts are changed when the front wheels are clear of the ground.

Another culprit is nobody adjusted the play out of the steering box? This can bind thing and can be dangerous if not understood properly.


The way in a simple fashion the self centering occurs is. As you go either side of center on the steering the front end of the car lifts a bit. It wants to gravity fall back into its lowest position. This is aided by the wheels want to track straight ahead because the ball joints are not in a vertical line. The top ball joint is further back than the lower one.

I think it is the "Steering Angle Inclination" (SAI) which controls the wheels tending to self-center, but wikipedia and others can give more exact. The SAI can't be adjusted (much). That is how a line between the ball joints leans inward. I expect that where the tire patch contacts the road is involved, so changing tires could affect it, though seems unlikely if the same tire size. Different wheels, with different "back-spacing" would be more concern.

Caster is the tendancy of the wheel to follow the motion, like a shopping cart. It doesn't direct the motion unless you have negative caster which would be unstable like a backwards shopping cart wheel. That same "ball joint pivot" line should strike the road in front of the tire patch for positive caster.

I agree to first check the steering system. Support the car on the frame rails with the wheels hanging and insure you can easily turn the wheel stop-stop. The gear-box is tightest in the center position, so if someone adjusted the slop off-center it can be too tight on-center. Start the engine and verify the box doesn't want to self-steer. On my Mopars, you loosen the spool valve on the top of a rebuilt gearbox and tap it back or forth until it doesn't self-steer. I imagine M-B is similar, though never had cause to fool with mine.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

You need to tell us more about the replacement tires to see if there are factors to consider such as size, if they are directional, if they were inflated properly, if you replaced the wheels together with the tires, etc.

Also did returning the old tires also allowed the steering wheel to return to center as before?

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I replaced both ball joints (they were shot), and that solved the problem.

Hugh Sr.