Post Z3-Rack Install Problems by JinormusJ

By diyauto
( 1 )

8 minute read

Post Z3-Rack Install Problems 

Compliments of JinormusJ @



I love my new Z3 Rack. Its amazing, steering radius is decreased (Meaning, your rack travels further and thus you have tighter steering; U-turns and u-turn clutch dumps/whips are easy as 1-2-3), and steering response is immense. I love it!......

Except for the fact I need an alignment BAD, I have a decent-to-huge amount of bump-steer, and my auto-return on my steering isn't returning my steering wheel to center after a turn (If I turn to full lock going 2mph, it stays stuck in full lock). My steering also has a flat spot taking any kind of tighter turn.

I have ruled out to the following factors:
1st: Alignment
My wheels are off bad. This will be the first thing I do at a hopefully reputable shop. I would normally just go to Ryan GMW, but they are 20 miles+ and require freeway travel; both of which are unsafe to do so as the car sits. The car does not "re-center" the wheel after a turn, meaning I have to manual turn the wheel back; however, when reversing, the auto-leveling steering works.

2nd: Binding
Possible binding of my knuckle is causing a flat spot. There is no audible metal grinding or sounds from the steering system while turning, just the hum of the power-steering pump under heavy load (full lock). I did not inspect the linkage knuckle while steering with the car on the lift to check for binding. (It was late and my buddy needed to leave and my e30 was the only car there). I probably should have, but I will have free time next week to work it out.

3rd: Bleeding
My fluid is brown in the reservoir. It was regular Red ATF before the swap, and my power-steering was working perfectly fine, but now it does not seem to return my wheel back to center after a turn. Maybe a kink in pressure lines causing uneven pressure (there is stuttering from the power-steering pump like its struggling to push fluid at a certain point in the turn, but not all the time.). Could this be a possible cause of my flat spot or lack of auto-correction as well? I will be checking my hoses as well as my knuckle when I have it up on the lift.

As of now, Car is rendered unsafe and inoperable, so I'd like to get all these sorted out ASAP. I was scared with all the bump-steer/twitchy memory-steer from just traveling 30MPH.


Well, the front definitely needs an alignment bad; with the steering wheel centered, the left wheel will track straight while the right wheel is toed in

Just think of it resembling this from above:

I have no doubt that a lot if not most of my auto-correct and memory steer issues are coming from an improper alignment; I did not align the the tie rods after installing the rack (although, I tried my best when I replaced the drivers side rod). This shows, as the passenger side tie rod is still on "Z3 Toe-Spec" while the other one is eye-ball aligned if that makes sense. Right wheel is toed in about 10*

Due to the nature of physics, a balanced system will return to lock regardless of the ratio or nature of how the gears are set (linear vs progressive) as the force behind the front wheels (the entire car), will shift the wheels the direction the force is traveling (ei, if you turn and let go of the wheel, the force of the car is no longer in a turn, and is traveling straight, and thus will center the wheels. In an unbalanced system, the force of the wheels in a turn can be greater than the force of the shell, thus the rack will not center.

I can hear tire screech from the wheels going straight as slow as 10mph. Also, my left wheel is wearing in little quarter side patches near the outside of the wheel

My power steering studdering has seemed to go away for the most part; I uncapped the reservoir, and spun the wheel lock to lock to bleed the system, during which I found out the rack was off-center when installed; my left lock was 1.1 turns, and my right lock was 1.6 turns. I ended up just taking the wheel off and adjusting, moving it a spline closer to the left, until I was a perfect 1.35 from center-to-lock.

I also think I have binding causing a flat spot (or better described as a stiff spot) in my power steering as off the car, the rack spun freely; once back on the lift, I will spin the wheel to check for any binding spots on my knuckle, as I expecting some in theory

So glad that these issues are at least easily diagnosable.



So I finally got back from my trip and was able to tackle the rest of this beast. Upon getting my car on jacks I noticed a few things:

1. Alignment and Auto-Centering

Yes, it came as to no surprise, my alignment was VERY toe-in /-----\. What I noticed before of just one wheel being off ended up being both wheels off with one way worse than the other. After some 20+ hours of researching steering geometry, castor, toe, and self-leveling; I've learned these key things.

Toe-in causes the wheels to be in a perpetual gridlock for grip and causes the wheels not to be able to self level, as the wheel opposite the turn (left turn/right wheel or right turn/left wheel) will be continually applying force into a steer. This in turn causes "memory-steer" which is often confused with bump-steer. Memory steer is the aspect that, if you steer to one side, the wheels will steer themselves back to that side because the opposite wheel will lock into more grip and continue the steer, even after the steering wheel is let go (and presumably, in a balanced system, will auto-level). Ultimately, this causes the car not to auto-level while traveling forward.

Toe-out, \-----/ on the other hand, will place the wheels in a position to where the castor will cause the wheels to be in a perpetual state of correction as both wheels are struggling to steer inward because of the nature of forward travel vs. grip of the wheel, leading to more stability, especially at higher speeds. After I aligned the wheels to correct specs as stated in the e30 Bentley manual: 1/32" toe-out (or close enough to that), my auto-correction worked perfectly fine.

I also noted that when I was toe-in, auto-leveling worked while I was traveling reverse, but now it work vice-versa (toe-out; auto-leveling while going forward).

2. Binding Knuckle. Bad.

I noticed the u-joint closest to the firewall (the top one; connected to the steering column spline, not the rack spline) was binging on itself from the increased angle of the rack; I ended up grinding the squared-off joints with a dremel to round them out, and a little inside the "U" and it freed up enough clearance. Applied some WD-40 afterward for safe measure and I'm free to enjoy my rack.

3. Bump-steer

After the barnyard string alignment and knuckle-binding issues were fixed, I took it out for a test drive and noticed NO BUMPSTEER WHATSOEVER with the spacer on top of the rack. It was better than even my stock e30 rack which had loads of bump steer. I made sure to drive over plenty of speed bumps and took an uneven back-road at higher speeds (60-70MPH): no drama to report.

As stated before, my "bump-steer" was actually memory-steer caused by my toe-in condition, and was confused as bump-steer. I also used the e36 tie-rods (which I highly recommend) because they are beefier, and have better tie-rod joints; these are probably the cause of my decreased bump -steer as my e30 rods were shot

4. Power steering stuttering.

I still have slight stuttering from my power-steering going lock-to-lock; not a full "OMG, it feels like power steering is gone" kind of stuttering, but just slight... Difficulty if that makes sense. As I had my car on jacks, I was spinning the wheel lock-to-lock and noticed my air bubbles coming out, so I put my money on air in my system; either it will most likely bleed itself out due to the nature of how BMW designed their power-steering system, or I just have to do a flush. No big deal as it hardly effects driving


My problems were:

1. Alignment was toe-in causing auto-centering not to work; aligning my wheels properly to slightly toe-out (1/32" toe-put) fixed my centering issue

2. Knuckle was binding; grinded down u-joint with dremel; no more binding.

3. No bumpsteer at stock height with spacers underneath rack. Stability better than even my e30 rack

4. Still have some air in system