Wandering diesel

[IslandGrün]

Hello,

I'm new to this forum. My name is Edwin and i own a '92 525tds Touring.
I live in the Netherlands where the diesel is probably much more common.
My car is fairly standard except that the front is lowered by approx. 45mm to get rid of the enormous gap between the fender and the front wheel. It has the self levelling suspension at the rear axle.

Since I own the car -two years now- it has been great to drive. Although it has always been wandering a little when driving in a straight line. I allready replaced quite some suspension parts with no real improvement. Actually it is getting worse and on some roads I need to constantly correct to keep on track.
I really hope you guys have some suggestions

What i've allready done is:
-thrust arms with bushings
-control arms
-front shocks
-tie rods
-New 205-65-15 michelin tyres on original 15" wheels
-rear pitman arms (dogbones)
-rear subframe bushings
-steering box adjustment (almost no play)

The steering gear that has not been replaced whas checked several times. Several allignments done, last time with all the prescribed weights.

The only thing is there is a cluck noise coming from the back shock dome when driving over bumps. And the steering wheel is not returning very smoothly for the last 15degrees, I adjusted the box back by 1/8 turn to no avail. Also the back end is reacting a little slow on a steering action.

The rear shocks where tested and seemed ok, could this behaviour have something to do with a rear shock mount or shock itself?

Groeten uit Nederland,
Edwin.

[George Davis]

The suspension gurus here probably know tons more than I do, but I'd guess the problem is related to the car being lower in the front than the rear. Normally, front struts are angled forward, like this: < / the arrow indicates the front of the car, the slash shows which way the struts are angled. This angle is important. If you draw a line through the strut to the ground, you'll find that this line intersects the ground forward of the center of the tire contact patch; this gives a stable and self-correcting steering system.

With the nose angled down, your struts will be more nearly vertical. This moves the center of the contact patch under or in front of the point where the line through the strut intersects the ground. This destabilizes the steering system and could be the cause of the car's wandering.

Another possibility is related to the rear suspension. Semi-trailing arms change toe as they move up and down. Being angled all the time, their toe changes may have more effect and cause the rear to wander around a bit.

Either way, the answer may be to make the car level again.

Or I could be full of **it!

[632 Regal]

Have you checked and tightened the steering wheel shaft that passes under the dash? Just about everyone that checks it finds that the nut can be tightened substantialy. I dont know if your car has this but worth checking into.
god luck

[IslandGrün]

The suspension gurus here probably know tons more than I do, but I'd guess the problem is related to the car being lower in the front than the rear. Normally, front struts are angled forward, like this: < / the arrow indicates the front of the car, the slash shows which way the struts are angled. This angle is important. If you draw a line through the strut to the ground, you'll find that this line intersects the ground forward of the center of the tire contact patch; this gives a stable and self-correcting steering system.

With the nose angled down, your struts will be more nearly vertical. This moves the center of the contact patch under or in front of the point where the line through the strut intersects the ground. This destabilizes the steering system and could be the cause of the car's wandering.

Another possibility is related to the rear suspension. Semi-trailing arms change toe as they move up and down. Being angled all the time, their toe changes may have more effect and cause the rear to wander around a bit.

Either way, the answer may be to make the car level again.

Or I could be full of **it!

George,
I understand what you mean, your referring to the castor angle. I never thougth of it changing that way but this angle was also checked with the allignment, about an month ago, and was within spec. The influence on the castor angle of the front lowering is probably very small.
I did a rough calculation and I get a difference of castor after lowering of 0.6°. Which seems quite small. I agree that it isn't going to make it better.
Thanks Edwin.

[IslandGrün]

Have you checked and tightened the steering wheel shaft that passes under the dash? Just about everyone that checks it finds that the nut can be tightened substantialy. I dont know if your car has this but worth checking into.
god luck

Hi,
Yes I did tighten the 32mm nut under the dash until the axial column adjustment went heavy, it wasn't that loose, maybe half a turn. I also checked the rubber coupling that is more up in the direction of the steering wheel, which seemed fine.

I think I allready replaced and tested the most common causes for this problem and I'm afraid i'm getting to the real expensive stuff now, like the LAD struts and steering box.

Thanks,
Edwin

[philbyil]

Hi Edwin,
Seems like you did most of it but.....

[IslandGrün]

Hi Edwin,
Seems like you did most of it but.....

Hi,
Well, I didn't replace the idler arm or bushing because I can't find any play. I have tried to wiggle it up en down with a steel bar. Also had my girlfriend behind the steering wheel turning it from one side to the other, while I was under the car with one hand on de right ball joint of the drag link and the other on de idler arm. Pinch bolt of the pitman arm was also tight.

Would it be possible that the rear shocks or shock mount have anything to do with it?

Thanks,
Edwin.