Car wanders on crowned road? - PeachParts Mercedes-Benz Forum

pwalsh53 · #1 02-06-2007, 10:23 PM

Hi all!

Well, the alignment on my '84 300D is fine and all the wheels are balanced and such, but when the road is crowned, the car wanders alot.

Let's say I'm in the left lane and the left side of the car is lower. I have to steer right to go in a striaght line. And vice versa.

Could this be the idler arm and/or tie rods?

Also, I have a wicked nasty vibration around 50-60...gets worse when slowing down from those speeds. Does it whether on or off gas, in D or N. Driveshaft bearing maybe?

Thanks!
Patrick

#2 02-06-2007, 10:43 PM

That's normal for road crown. Gravity is pulling the car to the lowest point so you correct it by turning steering the opposite direction.

vstech · #3 02-06-2007, 11:04 PM

I don't think it is normal. Mine does it, but my suburban and my astro van do not. I do have a worn idler arm. after I rebuild it, I will see if it fixes the pull on the crown.
the vibration could be literally anything. driveshaft is connected with rubber flex disks so you wouldn't likely feel a problem there, there is a bearing in there, that may be worn. also check the wheel bearings and the brake calipers. mine had a wicked vibration, and it turned out to be a frozen caliper.
good luck, try to isolate it better, rotate tires and see if the vibration moves. etc...
John

Hatterasguy · #4 02-07-2007, 10:00 AM

Every old MB I have driven does it, W126's do it bad. Its because they are a heavy car and an old design.

bodyart27 · #5 02-07-2007, 10:27 AM

I've almost everything on the front end replaced now (down to passenger side ball joint and passenger side lower control arm). Car is at 225K. I've replaced upper arms and sway bushings, idle arm rebuild kit, tie rods (ok, a year ago), brake thrust rod thingy bushings at the control arms and at the carrier (carrier bushings too!)..... and I've had the car aligned at NTB (different ones just to see if it was the tech / machine) and it consistantly pulls right!

ARGH!

So after the last ball joint and LC arm bushing I'll do one more quickly align at NTB (getting my $s worth out of my 5 year alignment - poor bastards), then I'll take it to the dealer and see if they can figure out what the heck is up.

That being said - the front end is tight! Steering box is rebuilt unit installed about two years ago so it doesn't take much to change direction now.

Ugh... so makes me wonder about the rear (if it is steering the car). I've rotated the tires (4 months old) every which way and the pull doesn't follow the tires.

Tymbrymi · #6 02-07-2007, 10:32 AM

Quote:

Originally Posted by bodyart27

I've almost everything on the front end replaced now (down to passenger side ball joint and passenger side lower control arm). Car is at 225K. I've replaced upper arms and sway bushings, idle arm rebuild kit, tie rods (ok, a year ago), brake thrust rod thingy bushings at the control arms and at the carrier (carrier bushings too!)..... and I've had the car aligned at NTB (different ones just to see if it was the tech / machine) and it consistantly pulls right!

Make sure NTB has the "spreader bar" when doing your alignment. MB requires it, and most shops don't have it....

Also, tires can cause the car to pull to one side or the other. Exchange your front two tires and see if the direction changes.

Good luck with it!!

sailor15015 · #7 02-07-2007, 10:57 AM

So you haven't touched anything on the rear suspension? You very well could have some worn rubber back there, subframe mounts, diff mount, rear sway bar links, etc. Do a search on "rear steering." I'm not sure what it is exactly but I've heard it mentioned here several times, something about the rear suspension parts being worn and causing the car to want to do interesting things.

bodyart27 · #8 02-07-2007, 11:18 AM

I have done rear diff mounts and sway bar links.... I have not touched the subframe mounts....

I'm hoping a dealer can get the thing to go straight... if they align it and it still pulls right.... well, I guess it's the rear?

rrgrassi · #9 02-07-2007, 11:39 AM

In my auto mechanic's training classes in HS, we learned that the alignment for American based cars were set up to pull slightly left to compensate for the crown in the road. On a flat raod that car would pull left, slightly. Some shops set it to be dead on, so on a flat road, no pulling, but you had to fight the crown. A pull to the right is not normal.

captainmonk · #10 02-07-2007, 06:20 PM

for me I vote with Hat been thru most everything underneath the car aligned twice at Dad's favorite shop where he stands beside them as they do it and it still pulls noticably

t walgamuth · #11 02-07-2007, 06:45 PM

not to be disagreeable but the mercedes suspension is set up with a lot of castor. this means the pivot point (like the pivot point on a bicycle) is angled away from vertical. the top is laid back like a bicycle. maybe about 7 degrees. this causes a lot of stability on roads like interstate. the car will want to go straight. on a crowned road it will pull and you will have to always steeer uphil.

american cars typically (especially suburbans) have almost no castor. they deal with the car going straight by putting mechanisms in the power steering system that pull the steering back to center. this works ok but you won't have any "feel" for what the road is doing. the drawback is if you get some wear or the tie rod ends are adjusted a little wrong the mechanism will pull the car to one side or the other without regard to exterior factors, such as the crown in the road.

for myself i like this mechanism because if you happen to wander to the wrong side of the road in a benz you can feel it in the pull of the steerng wheel.

race cars are set up this way too.

this casor also will make the steering come back to center on the other side of a curve if you just let go of the wheel.

sounds like yours is behaving normal for a benz.

tom w

Hatterasguy · #12 02-07-2007, 08:45 PM

Quote:

Originally Posted by captainmonk

for me I vote with Hat been thru most everything underneath the car aligned twice at Dad's favorite shop where he stands beside them as they do it and it still pulls noticably

Yep I think its just a W126 thing, both of mine do it. The SDL has mostly new suspension parts.

Ara T. · #13 02-07-2007, 08:54 PM

Quote:

Originally Posted by t walgamuth

not to be disagreeable but the mercedes suspension is set up with a lot of castor. this means the pivot point (like the pivot point on a bicycle) is angled away from vertical. the top is laid back like a bicycle. maybe about 7 degrees. this causes a lot of stability on roads like interstate. the car will want to go straight. on a crowned road it will pull and you will have to always steeer uphil.

american cars typically (especially suburbans) have almost no castor. they deal with the car going straight by putting mechanisms in the power steering system that pull the steering back to center. this works ok but you won't have any "feel" for what the road is doing. the drawback is if you get some wear or the tie rod ends are adjusted a little wrong the mechanism will pull the car to one side or the other without regard to exterior factors, such as the crown in the road.

for myself i like this mechanism because if you happen to wander to the wrong side of the road in a benz you can feel it in the pull of the steerng wheel.

race cars are set up this way too.

this casor also will make the steering come back to center on the other side of a curve if you just let go of the wheel.

sounds like yours is behaving normal for a benz.

tom w

The caster spec on a Mercedes is actually about 9-10 degrees! Sure gives it some good off center feel and steers very very true at its top crusing speed.

vstech · #14 02-07-2007, 10:01 PM

this only explains why the car pulls on a crown... on mine, it only pulls on the left lane crown, not the right lane crown. explain that.
also, I have 4 brand new michilen tires, but only the left tire is showing feathering wear. I do need the idler arm rebuilt, and the alignment done after this is done, I will report on weather or not the pull is gone.
John

Hatterasguy · #15 02-07-2007, 10:20 PM

I have given up, I have almost run out of stuff to change. Its not the wheels or tires, I have four sets between my two W126's and swapping doesn't make a difference.

The only thing I have noticed is the SDL does it a bit less, but has a lot less wear in the steering box to. I suspect that contributes to it a bit.

The SDL will track like its on rails to about 120mph, the suspension is fine. I say its just a W126 thing, they probably did it when they were new.