Unstable steering at speed

[EZ$]

Haven't been taking the car on many longer trips, but this past Sunday I went to a C&C about 65 miles from home with a friend. I'm running PS with a stock Mustang PS pump that I modified the internal spring by cutting, I believe, 7/16" off to lessen the pressure and the amount of assist it provides. Anyhow, when on the freeway I noticed that the car wanted to dart back and forth in the lane, but what was concerning was that it didn't seem to be from input to the steering wheel, and when correcting it seemed to over-correct, thus making the movement worse. I don't think that it's the PS because during a previous long trip it did not manifest itself and was in fact quite stable. The car ran great otherwise so I need to correct this unstable issue to make the car more pleasurable to drive. I'm just not sure what could be causing the problem.

I could really use some help in determining the problem, so if you've had this issue and solved it, or you have some recommendations of things to check let me know.

As a note, I had the car aligned at Roger Krause Racing in June of last year. Here's the printout. 20240424_142909 by Rick Paul, on Flickr
Not sure if this will show anything that might be causing the issue.

Thanks for the help.

[65 Cobra Dude]

I would check tire pressures. You only want about 23lbs and it sounds to me like you’re running much higher pressures.

Henry

[Jeff Kleiner]

As Henry said, no more than 23 PSI. You could stand to have a little more positive caster, say 7 to 8 degrees positive but the ~6 that it shows isn't too far off. Ideally I like to see about 3/32" (0.10 degree) total toe in.

Jeff

[rich grsc]

Am I reading that incorrectly, or is that toe out?

[EZ$]

I'm only running 20-22 lbs pressure. I'm not sure if that is toe in or toe out. It seemed to be driving OK, but this trip it was like a squirrel!

[Jeff Kleiner]

I'm only running 20-22 lbs pressure. I'm not sure if that is toe in or toe out. It seemed to be driving OK, but this trip it was like a squirrel!

If it was good and now is not I'd be giving it a good going over to see what has changed, come loose, or???

Jeff

[Nigel Allen]

Could be a loose part of the steering/ suspension components. Worth going over front and rear components. As the handling of the car har recently changed, it could be a warning that something is coming loose.

[EZ$]

Thanks Nigel! That is on the agenda.

[BEAR-AvHistory]

Did you put a trace line on all your nuts & bolts to see if any moved? Part of my inspection routine is checking that all the lines are still perfectly aligned.

[EZ$]

It's been quite a while since I assembled that area, but I'm sure I did. I plan on getting it in the air tomorrow to check all that out.

[Alan_C]

I bought a Saturn Sky Redline Turbo late last year. The car exhibited the same darty behavior you describe. The alignment was off and all four tires were 14 lbs over inflated. Just goes to show how lame some dealership mechanics can be and the crappy driving manors two issues combined can generate.
In addition to a thorough mechanical check, take a look at the tires to see if you have a tread separation in progress. If the tires are 7 years old or more, time to replace them. Mechanical items rarely change when a car is simply not used. Maybe you hit a pot hole before putting the car away. Do you have a copy of your prior alignment specs for reference. Obviously changes were made to the alignment, but were they good changes, like it was said regarding toe in or out. Just changing the toe number does not mean it was changed enough.
When I had my MK4, I always did a beginning of the driving season mechanical check as it had been recommended by several members. On one trip, a rear caliper bolt came loose and fell out. I missed that one and made sure it was installed with Locktite after it was replaced. I suggest you consider you were experiencing bad driving manors and you did not return home, kind of dangerous no? Sometimes we need to be reminded that these cars are not our daily drivers. When they start talking back to us, we should listen because, as we all know, these cars can bite and bite hard if not respected. It will be interesting to hear what the cause turns out to be. I ordered a Gen 3 coupe a couple of weeks ago and I will do more to make sure the car is in good condition before getting out on the road. The comment about torque stripping the nuts is a good one as you can visually verify something is as it should be very quickly visually rather than have to retorque each and every fastener.

[ydousurf]

If you have ever experienced the speed wobbles or a.k.a. “the wobble-of-death,” you’ll sh!t your pants! Especially if you’re moving at a high rate of speed. On my jeep, I previously had Super Swamper’s and decided when I bought new tires I went with the BF Goodrich brand. The BFG’s were a much softer compound and worked great for wheel’n and snow, but they brought on the w-o-d and I had never experienced it prior on my other tires.

I agree with everyone saying validate anything that may have changed or has become loose on all steering components. Your tire pressures and factor the age of tires as well. However, two questions:
Does the “darting” occur all of the time or was it just sporadic?
And if so, do you recall what that section of highway or stretch of road was like. Meaning, was it asphalt or cement and the possible age too?

Why I mention the road is and you we all know this, but when semi trucks and just normal traffic especially on older asphalt together will create grooved impressions and that has to be factored-in. My BFG’s only tend to be affected by the grooved asphalt. I had been on this particular stretch of highway a couple times on my older tires and never experienced the death wobble.

Now, I’m not knocking the BFG’s. The other variable was my older tires, and they were definitely old and “hardened-up” over the years... So, that has to be factored into the equation.

Anyway, good luck, I hope you solve the issue and let us all know. Stay safe Rick!

Doug

[F500guy]

I would just add, jack up each corner and try to wobble the wheels like previous posters stated to look for loose suspension. Rear steer problems could cause the car to dart. I mention this because even though I am still in my build, A couple months ago (may Update my build thread about this) the driver side wheel seemed to have a clunk and moved a bit. Went through all the bolts and finally narrowed it down to the heim joint on the toe link, frame side. Took it apart and it was very poor quality and the inner race was loose with 0 miles on it. I upgraded both sides to a higher quality heim joint and also the bolt that is used in that spot.

[Al_C]

A little late to this party, but I can share my experience. Same issue on my roadster a couple of years ago. The car felt loose and wobbly at Interstate speeds. My issue was the tie rod/steering rack ends were not tight. They weren't really loose, but they weren't tight. IIRC the torque spec for those are 40 lb/ft. My steering rack is the stock FFR power steering unit. Once they were tight the problem went away.

[Rdone585]

I know you probably have different steering components than I have with a MK II, but I would start by checking the ball joint connections with the spindle. I've had issues and I know others here have as well with them being fully tight, but not fully seated. Then through some exercising of the steering it suddenly becomes loose when it magically seats into the proper place.

[Jeff Kleiner]

... I would start by checking the ball joint connections with the spindle...

Also check the screw in ball joint in the upper control arms. I had one come in for paint a few years ago and when I pulled the wheels I found that one of the upper ball joints had backed almost completely out of the control arm!

Jeff

[J R Jones]

EZ$ There is a potential problem that is most often experienced as darting side to side on pavement with longitudinal grooves cut in the pavement. It is also felt on bridges with steel mesh deck.
The problem is a bent wheel that wobbles enough to "search" on the grooves.
To a lesser extent you will feel the "search" on longitudinal slab edges in the pavement.
Spinning the unloaded tire will reveal a bent wheel.
jim

[MPTech]

Hey @Jeff Kleiner. would you mind sharing you alignment specs? I searched and couldn't find them.

[Jeff Kleiner]

Hey @Jeff Kleiner. would you mind sharing you alignment specs? I searched and couldn't find them.

Mark,

Power steering street car:
7 to 8 degrees positive caster
.5 to .75 degrees negative camber
3/32" total toe in

If manual steering back the caster down to 3 to 4 degrees.

Jeff

[GoDadGo]

Mark,

I'm running the specs Sir Jeffski outlined and have no stability issues.
4 degrees on the caster since I'm utilizing a manual rack.
My rear is a 3-Link and tire pressures are set at 23.

Steve

[EZ$]

Hey guys, a lot to digest here. I'm going to try to go through this over the next few days. Once I find something I will definitely post it here. Thanks for your concerns. As a note, Alan, you are spot on regarding my continuing on the trip. When I first noticed it, I thought I was overreacting and that the steering was just faster than I remembered, but it probably was not.

Thanks again everyone.

[MPTech]

Mark,

Power steering street car:
7 to 8 degrees positive caster
.5 to .75 degrees negative camber
3/32" total toe in

If manual steering back the caster down to 3 to 4 degrees.

Jeff

THANKS Jeff!

[CraigS]

Since you show negative camber in the rear I assume you have irs. If so, check the camber adjuster in the rear uca. The intermediate adjuster likes to work loose in the uca. FFR recommended red loctite there. I ran mine for several months until I was sure I had camber in a range I could use and welded the piece vs loctite. That meant I had only the rod end to make adjustments with and had to take the bolt out of the spindle but camber adjustment was so infrequent it wasn't a problem.

[EZ$]

Craig, I have the T-Bird IRS, and I don't remember any adjustability in the uca, but I'll check it out while I'm under there.

[Railroad]

Don't forget about the spindle and half shaft nuts. I have read, some did not get torqued properly and became loose.
good luck,

[EZ$]

I'll need to add that to my list!

[Its Bruce]

I had an inner tie rod go bad within 250 miles (cheap repo and probably not in the best shape when i installed it). Play in left/right of wheel is typically tie rod. Play in top/bottom is typically ball joint.

[EZ$]

Thanks Bruce. I can't do anything until tomorrow. When things go bad they go bad. My DD F150 decided that today was a good day for the battery to take a dump on me. It's parked close enough behind the cobra that I can't get a jack into the back of the car to jack it up. Hopefully the battery is charged back up in the AM so I can access it, and I will add that to my notes of things to check.

[Ford & Jeep Fan]

Could be a loose part of the steering/ suspension components. Worth going over front and rear components. As the handling of the car har recently changed, it could be a warning that something is coming loose.

I was just thinking this.