911sc steers when road uneven

[enjefriy]

Hi all.

This problem suddenly has appeared.
On oscillating roads at highway speeds (100km/hr above), the front of the car seems to steer itself when faced with undulating road surface.
In other words, if the road was flat, no problem, but if any dips or lift was present on the road, and whilst at high speeds, the car would steer slightly from straight.

So with a series of undulating surfaces, i can see the nose of the car weaving or snaking, esp at high speeds.

Also because of this, i tested the car by steering left and right quickly and now noticed that the my inputs gives an amplifying output in terms or the cars change in direction. In other words, when i quickly steer left and right, the cars steering responce is to turn quite agressive, and recovery is lagging.

Overall, it takes alot of effort or concentration to drive the car fast on our imperfect roads here.

My actions taken so far was superficial to check the steering. By making inputs to the steering, i saw that output to the wheels were immediate and direct.
I still have the old type of tie rods on this car (i.e. not the turbo tie rods).

Front absorbers were replaced 5 years back (though needlessly, due to poor trouble shooting).

No recent changes were carried out on this cars geometry, so i suspect a failure of some sort.

My suspicion so far is the rubber bushing in the front suspension arms. The rears have already been replaced with poly graphite from PP. The fronts I have never touched. My theory is that checking for steering play with the car at stand still will not show this as the arms would not be moved about.

So with suspension travel caused by occilation road conditions, and worn rubber bushings within the suspension arms, changes in the geometry could be the cause of my wondering drive.

Does my theory make sence?, or am I also going in the wrong direction.

Cheers All.

[stlrj]

Try an alignment first.

[DanielDudley]

I wouldn't be screwing around at high speeds until I knew my ball joints weren't about to pop out, or some other failure. Check your front end, your tires, your pressure, your balance, your lug nuts and then your alignment. It could be something simple, but the word suddenly means be careful.

[T77911S]

a slight toe (out) change can make the car very unstable. make sure nothing is broken or lose then go have the alignment checked.
check tierods, the steering connection to the rack, make sure the bolts on the rear trailing arms are tight. grab the wheels and try to move them. have someone hold the sterring wheel when you do the front. shake the top and the front of the wheel.
put the car on stands, then put the jack under the wheel and jack it up, looking for movement in the ball joint.

you could even "string" the car yourself to check the toe, front and rear.

i would not drive it fast.
my car was very "twitchy" too. a little toe on the rear (my right rear was wearing on the inside anyway) fixed it.

[enjefriy]

Eureka,

I am a dweeb. Got my 4 year old son to wiggle the steering whilst looking for excess play in the steering system, and couldn't fault it.

Decided to jack a side up for visual inspection, and what i found was excessive play on the rear wheels.

On both side i might add. Removal of the rear wheels showed that the axle nuts were loosened.
Luckily the split pins stopped the nuts.

I had in the past removed the axles for replacement of the CV boots.
Obviously my cock up.

So all good now. Question now is, what is the correct torque for these nuts if anyone can recall.
Cant seem to find my bentley.

Thanks all

[slodave]

Torque should be around 220#.

[enjefriy]

thanks slodave.