Car feels a bit unstable at speed

[Luftwaffe1O1]

Hey Guys,

I recently replaced my front control arms, and lower steering U joint/coupling, car was taken to get aligned afterwards, but I have noticed it feels somewhat unstable now.

At lower speeds under hard cornering it seems more or less ok, but at 70 plus, I had the DSC come on a couple of times exiting the freeway on a long swooping curve. This was on my way to work, and I had taken this off ramp many times over the years, so DSC coming on at this speed was quite alarming.

I spoke to my Mechanic a bit about this (He is also a buddy of mine), he said everything seemed pretty solid when they checked before putting the wheels together and sending it for alignment.

The car currently is running:

Meyle HD front control arms with all new bushings
Bilstein Sports all around
H&R sport springs
IE Polyurethane subframe bushings
IE polyurethane trail arm bushings
Diff mound was replaced within the last 2 years with OEM rubber one
The one area I had not done much in the terms of upgrades has been the Sway bars. My initial hunch is that the sway bar bushings are gone and or in bad shape. I had noticed in the last year the rear end was not as planted or solid as it was previously. The Subframe bushings still seem to be in ok shape, they are about 5 years old now.

Alignment specs are as follows:

Front:

Caster:

Left - (+6.95)
right - (+7.29)

Camber:

left - (-1.92)
right - (-1.67)

Toe:

left - (+0.08)
right - (+0.08)


REAR:

Camber:
Left - (-3.13)
Right (-3.17)

Toe:

left - (0.07)
Right - (0.06)

I should point out one other thing, I am running the shocks + springs from an M roadie, also have front e36 M3 spindles + brakes etc.

But that has been on the car for sometime, just the front control arms and lower steering bits were replaced, as well as all new brakes (rotors + pads) all around and SS brake lines.

[BimmerBreaker]

Your tires ok? When I replaced my wheels/tires recently, I was shocked at how worn the insides were while the outside shoulder looked fine... lots of camber on these cars... you mention most other stuff but not tires, though I imagine mechanic would have noticed

LCA's torqued when car on level ground?

[Luftwaffe1O1]

Your tires ok? When I replaced my wheels/tires recently, I was shocked at how worn the insides were while the outside shoulder looked fine... lots of camber on these cars... you mention most other stuff but not tires, though I imagine mechanic would have noticed

LCA's torqued when car on level ground?

Hahaha man I was about to edit my post to update about the tires, as I realized I forgot to mention that.

So rears are about 1000 miles old, replaced them in late November. Bridgestone Potenza RE760. When I got the car back from mechanic/alignment shop, I figured maybe the fronts are a bit worn, and they were on the inside, so I JUST replaced them with brand spanking new Bridgestone Potenza RE760s on Thursday. Car still kept being squirly.

Tire setup is 235/40/18 front 255/35/18 rear, wheels are stock Z4 M wheels, which is 18x8 front 18x9 rear.

- - - Updated - - -

And LCAs were torqued down with car level on the ground.

[ZZZING]

Hahaha man I was about to edit my post to update about the tires, as I realized I forgot to mention that.

So rears are about 1000 miles old, replaced them in late November. Bridgestone Potenza RE760. When I got the car back from mechanic/alignment shop, I figured maybe the fronts are a bit worn, and they were on the inside, so I JUST replaced them with brand spanking new Bridgestone Potenza RE760s on Thursday. Car still kept being squirly.

Tire setup is 235/40/18 front 255/35/18 rear, wheels are stock Z4 M wheels, which is 18x8 front 18x9 rear.

- - - Updated - - -

And LCAs were torqued down with car level on the ground.

Brand new tires need a few hundred miles to break in, can feel "greasy" for a time.

[Luftwaffe1O1]

Brand new tires need a few hundred miles to break in, can feel "greasy" for a time.

Even on old tires it was doing the same thing, and its been about 300 miles now since Thursday, still doing the same thing~

[pine1000]

If those toe specs are in degrees your total toe in .16. That's just barely within the factory spec.

Total Toe should be 18 +/- 8 arc minutes.
According to Google this translates to .16 to .43 degrees of total toe in.

My understanding is that the rubber bushings compress at speed (due to the increased load) and this adds unwanted toe out. Toe out causes the car to feel more twitchy.

BTW, it's easy to do your own alignments on these cars with a set of toe plates because there is only one adjustment.

[Luftwaffe1O1]

If those toe specs are in degrees your total toe in .16. That's just barely within the factory spec.

Total Toe should be 18 +/- 8 arc minutes.
According to Google this translates to .16 to .43 degrees of total toe in.

My understanding is that the rubber bushings compress at speed (due to the increased load) and this adds unwanted toe out. Toe out causes the car to feel more twitchy.

BTW, it's easy to do your own alignments on these cars with a set of toe plates because there is only one adjustment.

Is that toe in? I was under impression positive values are out negative are in? I could be wrong, values prior to alignment were:

Front left (-0.20)
Front Right (-0.10)
Total (-0.30)

With new values as seen above.

[Luftwaffe1O1]

I was quite wrong, the negative values are out, positive in.

The high toe out was due to suspension having been replaced, I am not sure what it was prior to the work being done.

[pine1000]

I was quite wrong, the negative values are out, positive in.

The high toe out was due to suspension having been replaced, I am not sure what it was prior to the work being done.

My car had 0 toe in and felt quite nervous and twitchy over 60. I set it in the middle of the factory spec and the car feels much more stable at higher speeds.

My point is that since your car is set to the minimum spec for toe in, you may want to increase the toe in while staying within the factory spec range.

[325bob]

Mine is very susceptible to tramlining, scary in the rain, always at the same worn spot on highway(truck ruts)

[s8ilver]

What are your tire pressures set at? During our last cold snap in the single digits, I adjusted my tire pressures accordingly. When it heated up drastically, my tires were a bit overinflated and the car felt a little squirly at speed. I brought them back in range, and the feeling disappeared.

I use a TPMS system that continually monitors temperature and pressure of each tire, and it's crazy how different the ambient temp makes, especially in low profile tires.

[nevan]

Did you installed the control arms yourself?

I hope the toe alignment addresses the issue. But in case that wan't the issue, also verify the torque applied to nuts/bolt when you installed the new control arms. As strange as it may sound, a bit of under-torqued nuts can actually do that in higher speed also. - I know this because I've made that mistake before by skipping torque wrench once. And that wasn't fun.

[Luftwaffe1O1]

Did you installed the control arms yourself?

I hope the toe alignment addresses the issue. But in case that wan't the issue, also verify the torque applied to nuts/bolt when you installed the new control arms. As strange as it may sound, a bit of under-torqued nuts can actually do that in higher speed also. - I know this because I've made that mistake before by skipping torque wrench once. And that wasn't fun.

I did not do the work myself, was done at a shop. Oddly enough, today the car felt more stable, not sure what the deal is, still feels a bit more wobbly at turns, I am really leaning to worn out sway bar endlinks/bushings.

I also had a tire go flat on me at work today, so that was fun.

[Blacksheep]

I had that happen to me on a brand new set of tires.

The tire grooves love the rain grooves and it feels strange. My head is straight while the car shimmies.

I replaced the tire brand and the problem was gone.

[Luftwaffe1O1]

I had that happen to me on a brand new set of tires.

The tire grooves love the rain grooves and it feels strange. My head is straight while the car shimmies.

I replaced the tire brand and the problem was gone.

Pretty sure its not the tires, old set and new set same thing.

In any case, this is a bit of a necro, but a quick update, had it at the shop for a bit, intermittently the ABS/Wheelspeed sensor was apparently throwing codes. As a precaution I made sure all the sway bar endlinks/bushings are new as well.

Car went to alignment etc, everything checked out ok. Got it back recently, and again on not very aggressive turns, ABS/Traction gets triggered.

When this problem started, both front control arms, and had all brake pads and rotors also replaced, along with SS brake lines.

Not sure really what it can be now, checked all suspension components, everything seems solid, alignment specs were fine etc.

Could the battery going bad cause any of these issues?

Could improper brake bleeding/install cause ABS/DSC issues?

I will check brake fluid level when I get home, not sure if fluid being low or high might cause some issues.

[khammack]

Most likely the wheel speed sensors. Who ever pulled the code and found them throwing codes, should have been able to tell which wheel(s) is/are the problem. Cleaning or replacing the defective sensor(s) should fix the problem.

[rf900rkw]

Get the steering angle sensor calibrated.

[zellamay]

Hahaha man I was about to edit my post to update about the tires, as I realized I forgot to mention that.

So rears are about 1000 miles old, replaced them in late November. Bridgestone Potenza RE760. When I got the car back from mechanic/alignment shop, I figured maybe the fronts are a bit worn, and they were on the inside, so I JUST replaced them with brand spanking new Bridgestone Potenza RE760s on Thursday. Car still kept being squirly.

Tire setup is 235/40/18 front 255/35/18 rear, wheels are stock Z4 M wheels, which is 18x8 front 18x9 rear.

- - - Updated - - -

And LCAs were torqued down with car level on the ground.

I just gotta say I love those wheels! I had them on my silver Z3 and I think they are the best looking wheels for that car. Had they fit on my Z3M, I'd have kept them.

[Luftwaffe1O1]

Get the steering angle sensor calibrated.

These guys told me it was calibrated when they replaced the steering U joint and control arms.

Most likely the wheel speed sensors. Who ever pulled the code and found them throwing codes, should have been able to tell which wheel(s) is/are the problem. Cleaning or replacing the defective sensor(s) should fix the problem.

There were some warnings for the drivers front wheel speed sensor, it was replaced. They thought they fixed it, since they took the car out, were able to replicate it, replaced sensor they said it wasn't causing the traction control to come on easily anymore. But when I picked up the car, within 30min I got it to come on, during an pretty calm turn, that I take every day to work.

It does not appear to be anything mechanical here, as if I kill all traction control, the car is just fine, it doesn't feel unstable that way.

I took it in for the original problem while it was there also replaced sway bar endlinks, (actually did M roady sway bars). threw on GC coilover conversion kit as well, and new strut hats and rear shock mounts.

Other than the ABS/DSC intervening for no apparent reason the car behaves just fine now, steering is nice and tight, grips well, brakes well, etc.

[Bryson]

My car is exactly the same. DSC triggers on long sweeping corners, it's been the same through multiple sets of tires and drives great with DSC off. Curiously, I'm also running M suspension on a non-M. Perhaps it's related to tire scrub that's different than DSC expects due to the M geometry changes..

[Dakar Ole]

Don't forget there is a lateral acceleration sensor that is possibly the culprit. Right now I'm looking at a toasted one on my car that was uncharacteristically doing a long sweeping turn activation of DSC prior.

[Tim95M3]

Don't forget there is a lateral acceleration sensor that is possibly the culprit. Right now I'm looking at a toasted one on my car that was uncharacteristically doing a long sweeping turn activation of DSC prior.

I agree with this. Sounds like a faulty yaw/lateral acceleration sensor to me. My dad's 01 M roadster has the same symptoms, and followed by random ABS lights at times.

[Dakar Ole]

Yup- Inpa=electrical failure Tool32=no connection DSC light always on. Vendor just sent me the wrong part and I'm waiting for the replacement ($25.00).

[Luftwaffe1O1]

Don't forget there is a lateral acceleration sensor that is possibly the culprit. Right now I'm looking at a toasted one on my car that was uncharacteristically doing a long sweeping turn activation of DSC prior.

You know, I could give you a hug right now...

It sounds exactly like this might be the issue. From what I was reading, if you just press the DSC button, it only disables the YAW sensor, and I am not having any of the stability issues with it at this point. It only happens on longer sweeping turns, which is odd because sharp hard corners don't trigger it.

In any case for those of you who might experience this:

34526864094 (01/02/2013 - Present)
34526754289 (07/01/2000 - 06/13/2013)
34521166003 (02/01/1999 - 05/30/2000)
34521164457 (03/01/1998 - 12/15/1999)

This are the part numbers over the years. Brand new an OE part is north of $600 so yeah...

edit: I forgot to mention, I posted all the historic part numbers in case you wanted to go for a used part. I realize $640 and up is pretty expensive for a sensor, and all of the part numbers above are interchangeable parts, they will all work with our cars. the 1166003 and 6754289 are quite widely available from what I have seen. Which would make sense since the latter was produced for 13 years.