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  #1  
Old 11-06-2008, 09:13 AM
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What causes steering to self-center?

I know this isn't a diesel-specific question, but you guys are so much better about answering my questions than are the other forums!

(On a W124 specifically,) what causes the steering to self-center after a turn? Is that a function of suspension geometry (camber, caster, toe, etc...), the steering box, a combination thereof, or something else entirely? I am trying to wrap my mind around how centering works.

Thanks!

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  #2  
Old 11-06-2008, 09:17 AM
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Positive caster, with a little help from the idler arm bushing.

Last edited by tangofox007; 11-06-2008 at 11:06 AM.
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  #3  
Old 11-06-2008, 09:33 AM
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Quote:
Originally Posted by tangofox007 View Post
Negative caster, with a little help from the idler arm bushing.
Thanks; so when I look at the W124 alignment specs and see caster listed at just over 10 degrees, that's assumed to be negative? I think mine measured at just under 10 degrees (9.7 or so as I recall) after my last alignment, and I am having centering issues. I have tried loosening the steering box already, and while there is now more play, it still doesn't self-center.
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1998 Jetta TDI, 132K "Rudy"
1974 Triumph TR6
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Old 11-06-2008, 10:11 AM
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mine centered very well until I put wider wheels and tires on, do you have stock tires and wheels?
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Old 11-06-2008, 10:14 AM
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Originally Posted by lutzTD View Post
mine centered very well until I put wider wheels and tires on, do you have stock tires and wheels?
Mine are a bit wider, but it did the same thing with the previous (stock) size tires. Does yours not center at all now?
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  #6  
Old 11-06-2008, 10:43 AM
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toe in is critical.... follow all the rules... use search ... many good threads on subject...
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Old 11-06-2008, 10:49 AM
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Originally Posted by leathermang View Post
toe in is critical.... follow all the rules... use search ... many good threads on subject...
That's the off thing -- my toe adjustment is fine. I have searched and searched (for better than 2 months now), and while there are indeed many threads, the vast majority have to do with the steering box adjustments, which I don't THINK are my problem. That's why I asked whether self-centering was a function of the steering box itself; my assumption is that it's not, but that an overly-tight steering box can prevent self-centering. Am I wrong?
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  #8  
Old 11-06-2008, 10:52 AM
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Yes, an overly tight steering box can prevent self centering...
So, how are you sure your toe in is ' fine' ?
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Old 11-06-2008, 10:55 AM
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Quote:
Originally Posted by cscmc1 View Post
That's why I asked whether self-centering was a function of the steering box itself; my assumption is that it's not, but that an overly-tight steering box can prevent self-centering. Am I wrong?
Self centering is not a function of the steering box itself... but drastic out of bounds setting of it can affect self centering.
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  #10  
Old 11-06-2008, 10:56 AM
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Quote:
Originally Posted by leathermang View Post
Yes, an overly tight steering box can prevent self centering...
So, how are you sure your toe in is ' fine' ?
Good point -- I have had the front end aligned locally, and while the specs they adjusted to were for a W201, the "after" printout showed toe to be within W124 specs. Thanks for the input, by the way; this issue is driving me nuts as the cars performs very, very well aside from this issue.
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Old 11-06-2008, 11:05 AM
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I should add that I am more than an hour from my closest dealer, who also happens to charge $150 for an alignment, or I'd have just bit the bullet and gone to the experts in the first place. I felt comfortable that the local place I used could handle a rudimentary alignment because he knew of the spreader bar, admitted they didn't use one, but said he had done W124's before and that he'd never had a complaint. Of course, I could be wrong about their familiarity with W124's...
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  #12  
Old 11-06-2008, 11:07 AM
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Ok... search for this using my screen name... I know there are some threads which Larry Bible and I put up some good info...
Basically you need to understand that no matter what they print out... if everything in your steering and suspension system is not correct they are pretty much " getting it as close as they can " and sending you out the door with respect to the toe in....
During a summer break from college I worked in a front end shop.. first half as a mechanic and the second have as ' service writer/ parking the cars in the stalls'... LOL...
The guy that did the alignments was old and cranky... but for some reason liked me... I asked a lot of questions and watched him closely. It was also a tactile education being able to drive a whole lot of cars which needed work from the front around through some pot holes and then into the back of the shop... getting to ' feel ' that was very interesting.
If you can't find them hollar...
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  #13  
Old 11-06-2008, 11:08 AM
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Quote:
Originally Posted by cscmc1 View Post
Thanks; so when I look at the W124 alignment specs and see caster listed at just over 10 degrees, that's assumed to be negative?
I should have said "positive" caster in my original post, which has now been corrected.

It's the caster angle that is primarily responsible for steering wheel return. There is no other mechanism that causes it to happen, although there are plenty of opportunites for problems in the steering system that could interfere with the return to center.

Last edited by tangofox007; 11-06-2008 at 11:16 AM.
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  #14  
Old 11-06-2008, 11:11 AM
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OH, Geeez.... not use the measuring stick ?

Here is what I suggest... put everything on new...including springs ...set the toe in yourself... I did mine last time and it worked fine..... lots of crawling around....
Also, wheel bearing settings must be correct... and use the micrometer method ( in the FSM )... the only correct way for these cars...
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  #15  
Old 11-06-2008, 11:12 AM
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Quote:
Originally Posted by tangofox007 View Post
I should have said "positive" caster in my original post, which has now been corrected.
Makes sense -- thanks for the help, and for the follow-up!

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