Car wonders in lane when WOT

[brusk]

I haven't tested the power levels required to do this but it does it FBO 93 and maybe a little more with an E85 blend. At about 70MPH on the highway in 3rd when I floor it, about the point that sometimes tries to break the tires lose a little I get a case where the car will not track straight it wonders slowly I have to correct it. If I had a video it would look like this - Floor it, car goes to the left edge of the lane, I correct it and then it goes to the right edge of the lane etc. I've actually chased this wonder all the way up to 120+. If I do the same thing in 4th or 5th at that speed it tracks straight. I think I did once try this in 4th at a higher speed and it also wondered around.

Car 08 135i 6MT 32K miles
Suspension - mods are M3 front control arms, one set of the rear arms are M3 and another set is roque adjustable arm, M3 rear subframe bushings and E46 M3 Trans bushings.
Tires - Michelin PSS with about 30PSI in the tires, have tried with more and with less air same results.

[alexc93]

why do you not have matching rear arms..? that could be a key part of your problem.

[brusk]

Originally Posted by alexc93

why do you not have matching rear arms..? that could be a key part of your problem.

They are matching, One set of the arms are upgrades from an M3 and the other set the track bar or some bar is the adjustable Rogue ones.

Edit: Fixed OP to say set.

[Suds]

My rear end was wandering under hard third gear pulls and found the E93 M3 front bar seems to have reduced this, along with front body roll.

[jake1220]

I recently had this problem. Realized one of my rear tires was 4.5psi underinflated.

[Eyeman]

You have more power and suspension mods than me, but my car does this also. I thought it was just something related to the excessive HP for such a short wheel base and the traction issues in general. I had hoped the rear subframe bushings would help when i get around to that mod.

[Nugget]

It is the e-diff reacting to the loss of traction and tugging at the wheels.
This went away when I installed a LSD, now it tracks straight even when wheelspinning.

[dcaron9999]

Originally Posted by Nugget

It is the e-diff reacting to the loss of traction and tugging at the wheels.
This went away when I installed a LSD, now it tracks straight even when wheelspinning.

+1!!!

I had this problem and my Quaife LSD solved it. Exactly like you mentioned, with the original open diff, the car would kick sideways in hard second gear pulls with DTC mode on or DSC OFF.

I also spun the 135i a few times on the track before my LSD. I called it my one wheel drive wonder car.

[Nugget]

Yep, LSD made the car a hell of a lot less twitchy accelerating out of corners as well.
I also spun on track a few times pre LSD, haven't since.

[brusk]

I've already got an LSD. And the 1 series doesn't have that short of a wheelbase.

[dcaron9999]

Originally Posted by brusk

I've already got an LSD. And the 1 series doesn't have that short of a wheelbase.

What is your alignment set up (camber and toe, front and rear)?
What are your front and rear tire sizes?

[brusk]

I'm not sure I feel any better knowing that so many people have the same problem. If that's the case I might have to start looking into alignment specs to see if something can be done. I haven't seen any videos of 335i's having the same issues.

[dcaron9999]

Originally Posted by brusk

I'm not sure I feel any better knowing that so many people have the same problem. If that's the case I might have to start looking into alignment specs to see if something can be done. I haven't seen any videos of 335i's having the same issues.

If you had not done the rear subframe bushings, I would have called that out immediately. Im thinking that with all that torque, your rear toe arms may be bending or twisting. Some use solid steel toe arms such as Megan Racing, Ground Control, Rogue Engineering, etc to prevent this from happening.

It would also be wise to check whether your current alignment is not off. It's easy to throw it off with a few good potholes...

[MightyMouseTech]

It is amazing how fast the toe can go out of spec, and how big of a difference it makes. Just did an alignment on my car, last one was about 15k ago. My rear toe was at zero. Little toe in made a world of difference.

[dcaron9999]

Originally Posted by MightyMouseTech

It is amazing how fast the toe can go out of spec, and how big of a difference it makes. Just did an alignment on my car, last one was about 15k ago. My rear toe was at zero. Little toe in made a world of difference.

+1 here too.

I had my rear toe tucked in a little as well (negative toe), as I track the car and have a higher 3.46 LSD ratio. I think this is a must as the toe arms bend under hard acceleration and generate positive toe.

I still run stock toe arms and control arms in the back, and car is neutral with a very slight oversteer when pushed hard...

[brusk]

Originally Posted by dcaron9999

If you had not done the rear subframe bushings, I would have called that out immediately. Im thinking that with all that torque, your rear toe arms may be bending or twisting. Some use solid steel toe arms such as Megan Racing, Ground Control, Rogue Engineering, etc.

It would also be wise to check whether your current alignment is not off. It's easy to throw it off with a few good potholes...

LOL Toe Arms, that's what pieces are the Rogue Engineering. It's been so long I don't remember what pieces were what. Funny thing is before the Toe arms and a bad alignment the first time, it would pull one direction on WOT slightly but not back and forth back and forth.

[MightyMouseTech]

Maybe the rear toe is bad on both rear wheels now? Both my rear wheels were at 0.

[Nugget]

Originally Posted by brusk

LOL Toe Arms, that's what pieces are the Rogue Engineering. It's been so long I don't remember what pieces were what. Funny thing is before the Toe arms and a bad alignment the first time, it would pull one direction on WOT slightly but not back and forth back and forth.

I've heard the bushings in the Rogue Engineering arms wear out pretty quickly, maybe check that.
I went for the Megan Racing ones, but I think Mfactory are going to be making similar ones at a cheaper price.

[NORAGRETS]

e-diff for sure

[brusk]

So I decided I would jack up the car, loosen all the rear control arms and check everything out. When I got under the car I noticed the tires (both) were excessively worn just on the very inside. While highly pissed now that I need new tires I'm trying to figure out what on the alignment would cause this kinda of wear. I did loosen everything and lower the car before properly torquing all the control arms back up. Guess I'll order tires and try an alignment again.

BTW Tires were Michelin PSS with 12K miles on them, 8K of that highway from out of state trips. The rest were ran hard and pushed in corners when the gf would allow so I'm confused on this one.

[dcaron9999]

Looks like you got too much negative camber on your rear wheels, or too much toe out.

If you rear end wanders, this is a sign of soft stock rear subframe bushings, soft or damaged toe arms, or bad alignment and too much toe out.

I noticed that you have a few power bolt-ons, and possibly a custom tune or at least OTS Cobb tune, with a LSD.

Maybe you are due for new toe arms to tame that power and prevent bending of the toe ams under hard acceleration, which by the way, creates a tendency for toe out...

edit #1: I noticed you have rear M3 subframe bushings, so Im going to rule that out.

edit #2: I noticed you may have Rogue Engineering toe Arms, so cross that off the list too.

Please post your rear alignment specs if you have a print out of them from your shop, which I encourage everyone to keep as a reference point.
...

[brusk]

Here's the alignment last time it was done after doing the bushings, M Camber arm and toe link. Only put maybe 6K miles on it since then.