Help me before I crash...
 

Ok, here's the situation. I have an '89 coupe with 125k. A few months ago it started to feel like it was really following any imperfections in the road. It started kind of slowly but gradually got more and more noticeable. Since the tires were getting kind of old I got new tires all around then took it to have a four wheel alignment done. At the same time I told the mechanic about the issue and he checked the tie rods and ball joints. He said everything looked fine and that he took the car out and it tracked straight. It does track straight if the road is perfectly smooth, and I do mean perfectly smooth. If there are any imperfections at all the car will change course without any movement at the steering wheel. When driving I have to constantly correct my course or I'll drive off the road. It is very challenging to drive - in a bad way. Not the fun way. My wife often drives my car and she has noticed the same thing and feels unsafe driving it now. So my question is, what the hell is going on? What else could it be? Thanks for your help,
-David

Did your wrench check the steering rack?

Ummm, although you've had the alignment done, I still think it's an alignment issue. My wheel aligment guy said he does it with weight put in the front of the hood, or alternatively a little tow in. And the SC I drive is easy to drive, relaxing even.

David-its either a bad front tire(s) or excessive toe out, I'd bet.

My guess would be the tires??????? I have had new tires do weird things, like hard to steer, take them back and get different brands and my problem went away :confused:

I have been told that tires sometimes in the building stage gets a guy that is kinda tired that day and is not paying attention, wrong direction of the layers in the making process can make a tire be totally crap.

my 81 did the same thing since i bought it 6 yrs ago. FYI, when you bring one of these cars to joe blow alignment, they dont have a clue on the rear adjustments.

check your rear toe settings.
you have toe OUT in the rear, ill bet.

you need toe IN.

i did a ray scruggs home alignment, and followed some specs that the elephant racing dude put up, although i think its a little more than whats necessary.

i went with 1/8" toe-in each rear wheel.
1/16" total toe-in for the front. 1/32 per wheel

drives straight as a pin.

if you decide to do a home alignment, be prepared for the learning process involved, especially figuring out the puzzle that is trailing arm to swing arm adjustment

Re: Help me before I crash...
 

Have the tie rods and ball joints ever been replaced? 125K is alot of miles on OE. My car followed imperfections until I replaced both. (I also put on new tires, rebushed the rear suspension, new shocks and struts, lowered and aligned the car at the same time.)

You might want to get a second opinion. A ball joint failing can be very dangerous.

I took my car to a very a good and respected local shop for the alignment. They have also done the alignment before and it was great. Also, this problem was happening with my old tires as well as with my new tires. Could the ball joint or tie rods just be coming to the end of their life and it's not something that would show up just by checking them at the shop? Should I just have them do the ball joints and tie rods anyway? I was just wondering if there was some other component that could contribute to this problem.
-David

did you at any point changed the suspension , lowered, stiffened... and switched to wider , and/or low profile tires, with tough sidewalls.. then that could explain the phenomenon...

any of the above can result in more of what you described.

At that age, the entire suspension probably needs a refreshing. Worn rear spring plate bushings can make these cars feel unpredictable. Worn shocks also help these cars feel unsettled. New suspension bushings, new shocks, new tie rods and ball joints and an alignment done by 911 guys.....and you shouldn't have any difficulties tracking.

put me in the tire camp.
The garage that does my mounting now includes results from a dyno run with the wheel & tire combo run under 1,500 lbs of load. I was amazed at the "run-out' or "lateral pull" on new tires. My last pair of Potenza's had one register 14 lbs of pull when under load.
Since he knows most of my applications, he now marks them for the right & left to try to equalize the pull. (The dyno spits out the numbers in lbs of pull to left or right. )
damm it works.
also if you read the reviews in TireRack closely you might be able to pick up certain undesirable charactistics inherent in some tires. one such trait is what you are describing regarding the tendency to follow road imperfections.

Fun to guess but do you have the numbers from the alignment?

I had an similar issue with a Boxster following the imperfections in the road. It was at its worst when there were those rain grooves in the freeway, almost felt like the car was out of control. I did some research and the condition is called tramlining and is characteristic of certain tire patterns. I had a set of 17" Pirelli PZero Asymetrical tires. Good luck tracking this one down, there is nothing worse than the feeling of being out of control.
David

If alignment and steering is o.k. how about a tired/damaged front shock absorber ?

everyone is overlooking the rear wheel bearing, my 911 did just as david described.......didn't make any funny noise and the car showed true on the alignment rack, but it was a bad rear wheel bearing, replaced it and the car tracks perfectly.
go jack up the rear and give your rear wheels a good wiggle.

Bell could be right. I had the same condition and turned out to be a bad rear wheel bearing. It didn't take long (like a few days) to score the shaft the bearing rides on and require replacement.

Many have suggested alignment. What camber settings? My car does the same thing, but I run track camber settings. Once, again, like you, when on smooth surfaces (like the track) I can almost let the car drive itself. On the way home, I have a hard time keeping it the lane.

Alignment
 

Get a corner balance with the next alignment when all other things check out such as, tie rods, wheel bearings front & rear, ball joints, inner and outer trailing arm pivot points, Front struts, lower strut ball joints, steering rack bushings and rack gear backlash. These items are easily checked, most if not all can be checked at home in the garage.

For a quick test, try swapping the right and left side tires and see if the car drives any better. Just had a non-P car alligned by a good shop with a new Hunter allignment rig, drove the car and it still pulled to the right. We swapped the tires and the car drove straight as an arrow. I will swap them back in about two weeks because they are directional tires. It seems the tires and belts develop a memory in the direction of the pull.

can't swap the wheels , has to swap the tires,

if you swap front wheels, and not swap the tires, they will be mounted in the wrong direction... you better not hit any rain in that configuration...