Non-MB tech question (struts) - PeachParts Mercedes-Benz Forum

cscmc1 · #1 05-16-2010, 08:34 PM

Our 99 Saab 2.3lpt wagon continues to confound me. The car has always had a bit of a shimmy/shake (esp. evident in the steering wheel) that I chalked up to improperly balanced tires. It would go away a bit after any given balancing, but some back over time. I have checked subframe bolts (OK), replaced sway bar links, and replaced two of the motor mounts. Nothing FEELS loose in the front end when I jack the car up and move the wheels.

That said, it is a little shaky over 65 mph or so. When we hit grooves in the highway, it feels and sounds like the tires are over-inflated; sort of a hollow sound like when you kick a tire's sidewall. It lasts just long enough to feel it resonate a tiny bit though the whole car, and the shake/shimmy can come and go. It's more pronounced in high speed turns, but the car doesn't really porpoise or bounce like you'd expect a car with blown struts to do (or as they have behaved in my experience, anyway).

Still, I'm to the point that I think maybe the struts are blown so the whole car feels more "springy" and any wheel shake at all feels amplified since the struts are not dampening it much if at all. What do you guys (and gals) think? Am I off my rocker, or on to something? Car has only 80K miles, and has had a recent alignment.

This is my wife's car, and she is pregnant. I want to get any and all mechanical/suspension issues ironed out ASAP, as I am leaving for a brief deployment to the middle east soon (courtesy of Uncle Sam).

Thanks in advance!

JohnM. · #2 05-16-2010, 08:59 PM

I think bad struts would cause more of a suspension bounciness than a speed related shimmy.

Are the wheels stock or aftermarket? You might have a bent rim, more likely since its the wifeys car too! I had a pretty good inner lip bend on one of my rims. Tire techs will never tell you you've got a bend, just balance it close enough and call it good! If all four rims are true, try finding a place that does a dynamic balance....I think its called. They actually balance the wheel with road force applied.

cscmc1 · #3 05-16-2010, 09:02 PM

Thanks, John. No bent rims (not visibly bent, anyway). They are all stock Saab 16" wheels. It's sure got me perplexed!

Of note, there is also a metallic clank sound sometimes when we hit irregularities with the left (driver's side) front wheel. Sounds like a loose sway bar end link or caliper,but those things don't appear to be loose.

JohnM. · #4 05-16-2010, 09:08 PM

You really need to spin each wheel off the ground to see if it wobbles or does it spin perfectly straight. Inner lip bends are generally not all that visible. They can be tricky bastards to spot until you watch the wheel spin.

I have had a wheel that was so tweaked on the inner lip that the car couldn't go above 55mph without feeling like you were going to die. Discount Tire balanced that wheel 3 times and told me it was good to go!? That threw me for a loop on diagnosis like a MF'er!!!

Chris W. · #5 05-17-2010, 09:32 PM

I'm not familiar with a Saab front suspension, but on BMW's the front control arm bushings are notorious for developing slop as the miles accumulate, leading to shimmy and shake which can not be balanced out with a wheel balance or new brake rotors, etc.

The bushings can be replaced.

Rgds,
Chris W.
'95 E300D, 314K

JohnM. · #6 05-17-2010, 10:21 PM

God I hate the thrust arms on BMWs. The front suspension on those cars seems very weak compared to the Benz!!!!

cscmc1 · #7 05-18-2010, 08:46 AM

It's clear, after some poking around, that the rear shocks are blown. I have a set on order and will pop those in and see where they get me. Thanks for the tips, everyone!

cscmc1 · #8 05-19-2010, 09:21 AM

Got the Monroe shocks in the mail yesterday (day after I ordered them!), and swapped them in last night. My brief test drive points to a marked improvement; I need to run the car further to confirm this, but I may have tracked down the source of my "shimmy!"