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View Full Version : Rear end going squirrely... that's not normal, right?



Ghosty
09-15-2007, 07:32 PM
This has been going on for quite some time. Doesn't seem to be getting worse, but I've got a bad feeling about it.

It usually crops up on certain stretches of interstate that I travel on a weekly basis. I know it's related to the road conditions, how bumpy they may be, but it doesn't explain it entirely.

I'll be traveling 70 - 75 mph down these stretches of interstate, and all the while the rear end has an enormous wiggle, always swaying like left to right or right to left, bouncing back and forth.

Curiously, this is fierce enough to cause my keychain to sway with it, and bash over and over into the steering column.

It's more than just a nuisance, because it does take some energy to keep the car going in a straight line. I would imagine if you ran into an unfortunate series of events on the interstate while this was happening, you'd loose control. At 70 or 75. But I can always keep it on track in normal circumstances.

The thing is, I have no idea what suspension components I should look at. Here's some details, though.

1) This is a coupe we are talking about, my ST. I would think the rear end would be less susceptible to this on that fact alone.

2) Front and rear swaybar bushings were recently replaced from years of wear and upgraded to SuperPro polyurethane. The wiggle was there before the installation, and it seemed to stymie the wiggle temporarily. Some bolts had snapped in the process, but everything worked out in the end (just the front, not the rear), because it was in the hands of a mechanic of 30 years experience (my Dad). I trust the installation 100 percent. He's inspected the car on numerous occasions, as well. Could not find anything.

3) The struts aren't what they used to be. I have no idea how that would play into the wiggle, since this motion is left/right, but I thought it was worth mentioning.

4) This can't be replicated except on those portions of road, going at speed. This can't be replicated in-town. Also, having a load in the trunk, or having a passenger doesn't seem to have an impact on the wiggle. It doesn't lessen the wiggle, or increase it, it's just more load that gets thrown around.

5) The wiggle cannot be replicated in any car I have driven on that portion of road. Furthermore, I would imagine the wiggle is violent enough to be observed from passing cars. I have not seen this in other cars driving about on that road.

6) There is a moderate amount of rust underneath. This is a midwest car, and it has seen much road salt over the years. Much of the suspension seems caked in a layer of rust. We recently replaced the fuel neck because it had a pinhole leak from corrosion.

Any idea what this may be?

hobbie2k
09-17-2007, 04:09 AM
Does the wiggle seem to be timed with the up-down motion of the rear end? I remember having an old Buick that seemed to do it when the rear end was bouncing up and down. What type of rear suspension does the 5th gen have?

KoreanJoey
09-18-2007, 08:22 AM
um... how's your alignment?

Ghosty
09-30-2007, 09:44 PM
Does the wiggle seem to be timed with the up-down motion of the rear end? I remember having an old Buick that seemed to do it when the rear end was bouncing up and down. What type of rear suspension does the 5th gen have?


I don't always notice a correlation between up and down bumps, and the side to side motion.

I have also noticed that the swaying is sometimes induced under braking. That is to say, weight shifts to the front wheels, and that weight shift seems to make the end wiggle.

The suspension on the 5th gen ST (coupe) is independent front and rear, McPherson type suspension. Quite solid, really. I think it's the same as the GT and the GTS, although they use beefed up sway bars.

As I've said before, this car has much rust on the underbody. I suspect that bolts on the underside, ie, bolts that tie together the suspension, have been weakened by the rust, and therefore some play has been introduced, specifically compromising rear rigidity.

I'm starting to wonder if the bolts that hold the rear sway bar end links are toast. Or maybe even the end links themselves. Would this cause a wiggled rear end? Anyone have this problem?

Anyone have a squirrelly rear end?

(also I did not suspect this is an alignment issue, but that might be a good place to look... I'll have to check into that)

GT4SOM
09-30-2007, 11:36 PM
Do you have used tires? Check for impact bumps. You definitely shouldn't be getting squirrely on a FWD especially under normal driving conditions.

extremeskillz
10-01-2007, 01:04 AM
Check alignment and if any suspension parts are broken.

davmac
10-01-2007, 06:10 PM
+1 for 4 wheel alignment which couldn't hurt. Go to a full service shop with good reputation and ask they check tires, tire pressure, sway bar / stabilizer bar links, and bushings. Bad stabilizer bar links and bushings would normally also make some clunking or other noises. If your struts are really shot then replace them as they would be responsible for dampening the movement. Sometimes on grooved cement (for rain traction) type roads or ashphalt roads that have been worn into grooves certain cars with just the right (wrong?) width between wheels will slide into and out of the grooves. Slightly bigger or smaller is no problem. If you have the 4 wheel alignment and inspection and get a clean bill of health I would try changing lanes - or at least not worry about this when on those roads.

Playfortoday
10-01-2007, 08:07 PM
Just another quick input based on davmac above me... When I was running 17" Volks with 235/40/17's, my last 92 Alltrac would do what you are describing due to not fitting into the grooves, I would constantly fall into and out of the road groves on older roads. Same thing with my CRX with the same tire size as my celica. My motorcycle is even more apt to do this on any uneven surface due to the tiny contact patches. davmac could be onto something.

Now, I know what I input doesn't get you any closer to an answer, but it is something to consider. You mentioned having a midwest car... Keep in mind the condition of you tires too regarding the side walls. They tend to dry rot and in the process the side walls lose rigidity, and it feels like driving a car on innertubes. Again, still doesn't explain your inability to create it anywhere but that particular stretch. It could be something in the road that hits some weird harmonic balance with your car in its particular condition like a bridge and and earthquake.

Just spewing thoughts...

Ghosty
10-04-2007, 06:06 AM
Thanks everybody, for the advice!

I'll make a post when... er... if I find out what's going on back there. I hope it's just alignment.

{edit: The tyres are not that old, and I always check my air pressure... maybe the tyres are defective, don't know...**

Conrad_Turbo
10-04-2007, 04:57 PM
Grab your tire at 3 o'clock and 9 o'clock and see if there is any slop. Always helps to jack the car up so the tire is suspended, then see if there is any bushing wear in the rear suspension. I have 2 bushings I have to replace in the back of my Celi to get the slop out...my signs are not nearly as bad as yours, but my rear inside bushings are on their way out.

Ghosty
10-04-2007, 11:10 PM
Grab your tire at 3 o'clock and 9 o'clock and see if there is any slop. Always helps to jack the car up so the tire is suspended, then see if there is any bushing wear in the rear suspension. I have 2 bushings I have to replace in the back of my Celi to get the slop out...my signs are not nearly as bad as yours, but my rear inside bushings are on their way out.


I don't know to which bushings you are referring to, but I would like to know- so as to take a look at them myself.

I've replaced the swaybar bushings, however- to superpro polyurethane- I wouldn't know what other bushings to look at.

KoreanJoey
10-04-2007, 11:44 PM
I think he's talking about the control arm bushings. (the ones going from the inside of the car to the hub). Well it's spherical bearings/bushing... and yeah, they go bad. Actually my both forward control arms on my car were bent... (3-wheeling pwns the suspension).

Ghosty
10-05-2007, 06:50 AM
(3-wheeling pwns the suspension).

Oh, but is there any other way to drive? :)

Thanks for telling me where to look. I bet I'll have a nasty surprise when I get to it.

cs363
10-05-2007, 09:37 AM
control arm bushes would be my first suspect - the standard ones are very soft to start with so if they are worn or damaged I'd say these could be your culprit ..... or perhaps where the arms bolt to the chassis could be corrosion damaged.

Good luck with it :)

alltracman78
10-05-2007, 04:17 PM
The very first suspect is the alignment, plain and simple.
End of story.
Your dad has been a mechanic for 30 years and didn't mention this?
Or you just didn't tell him about this?
Classis case of wrong thrust angle.

Unless you know for a fact something is broken back there.
In which case fix it first.

When they do the alignment they SHOULD check all the suspension components.....
Depends on the shop though.

Ghosty
10-13-2007, 09:14 PM
Update: Possible culprit found...

While the mysterious swaying could have been (and was probably contributed to by) wearing control arm bushes, and perhaps suspension play from wear, it seems that the primary factor was a WORN TYRE.

As I said before, the tires are not that old, but apparently we didn't get around to rotating them quick enough before one of the tyres experienced excessive wear. The wear is located on the inside tread, on the edge of the tread.

This was noticed when the car was put up into the air as to diagnose a problem with a leaking gas tank. Will put up a new thread about the leaky gas tank soon.

With aggressive cornering on a FF car, where the tyres are not rotated frequently enough, it makes sense. These cars are so light in the rear as is, and that was a contributing factor. Funny thing is, now that we've diagnosed it, I think I've noticed a decrease in the swaying, maybe wear is catching up on the tire and evening things out.

extremeskillz
10-14-2007, 02:16 PM
well at least it was something simple :hehe: