R170 SLK230 Steering Geometry Challenge

[TJJ]

Morning All.
Would anyone happen to know where I can find dimension details for the Pitman arm and idler for an R170 please?
Symptoms.
When in a straight line the car drives fine. When turning to the right everything also seems fine. When turning to the left the left front wheel scrubs badly. The harder you turn it to the left the worse the scrubbing gets. My suspicion is that someone has previously fitted the wrong idler causing the Pitman and idler arms to be different lengths. I suspect that the tracking has been adjusted such that in a straight line everything is in the right place, but as soon as you turn the wheel the geometry goes wrong. The problem is, it's obviously happened a long time ago so everything is equally weathered. I can't tell whether it's the Pitman arm, the idler or both that's wrong.

Open to suggestions of anything else it might be but above are my thoughts. Any help gratefully received!

Forgot to say, it's gone through the last 3 MOT's like this as well....

 

[TJJ]

I'm guessing this information isn't easily available. My next plan will be to buy a replacement idler / intermediate arm and compare it to the one that's on the car. I guess if they're the same then it will be the Pitman arm that's at fault. In the meantime I need to get the roof working. The fluid level is low in the reservoir due to the hydraulic ram that operates the front locks leaking. Hopefully I'll get time to replace the seals today and top the oil level up.

 

[wheels-inmotion]

The Ackerman angle is wrong?... I think the pitman has a keyway so i doubt if that's fitted wrong. I would be inclined to count the threads on the idler and toe adjuster arms. It's possible the fitter screwed one side in and off-set the lock angles.

 

[TJJ]

Thanks for the reply. Yes the Ackerman angle seems to be wrong when on full left lock. In a straight line both the idler and Pitman arms are straight. There aren't any adjuster threads on the idler so I'm not sure what you're referring to there. I can't remember without checking, but I didn't think the inboard end of the track rod was adjustable either, but I really can't remember now. The diagram doesn't really show it. Interestingly, the tyres are also wearing evenly so I suspect everything is about right in a straight line. I'll try and get under it again this weekend. Appreciate your input to this, it's a strange one for me.

 

[wheels-inmotion]

Can you count the visible threads on the track-rod ends and post the results.

 

[TJJ]

Can you count the visible threads on the track-rod ends and post the results.

Counting the threads wasn't really an option as everything is covered in crud and rust. I can say with certainty that both track rod ends look to be pretty even in adjustment. I've just replaced the steering damper which has improved the driving experience exponentially, the old one having no damping effect left in it at all. MOT is due in May so I might see how it gets on then.