Comprehensive Steering Information Thread

[Michael9218]

Measurements on a Z4MC green tag rack.

Rack Rate = 50 mm/turn

Turns Lock to Lock = 2.8

Total Rack Travel = 140 mm

Linear

Also, the pinion shaft is taller than the gold tag E46 rack. Approximately 70 mm. The gold tag rack is 40 mm.

I also noted that the rack has built in limiters, so while the rack shaft length is the same (575 mm) the Z4MC has 10 mm less travel. Which also makes the lock to lock look better than it is.



Rack Rate = 50 mm/turn

Turns Lock to Lock = 3.0

Total Rack Travel = 150 mm

Linear


Steering knuckle on Z4MC:

Tie Rod Distance from Steering Axis = 130 mm

[Volke]

Measurements on a Z4MC green tag rack.

Rack Rate = 50 mm/turn

Turns Lock to Lock = 2.8

Total Rack Travel = 140 mm

Linear

Also, the pinion shaft is taller than the gold tag E46 rack. Approximately 70 mm. The gold tag rack is 40 mm.

I also noted that the rack has built in limiters, so while the rack shaft length is the same (575 mm) the Z4MC has 10 mm less travel. Which also makes the lock to lock look better than it is.



Rack Rate = 50 mm/turn

Turns Lock to Lock = 3.0

Total Rack Travel = 150 mm

Linear


Steering knuckle on Z4MC:

Tie Rod Distance from Steering Axis = 130 mm

Post #3 updated. Thank you so much for helping out!

[Volke]

Thanks for putting together it is good to have all this info in one place again! I have an 01 which has an MK20 ABS module (which is the abs in the earlier modules). I have seen on the M3 cutters that there have been some work arounds with changing parameters but the reviews have been mixed some people say you should stay away (if you have MK20 specifically) and some say you should do it. I know build journal has an update for the MK20 module which converts it to something similar to an "MK 60 M Track Mode". I was going to rebuild/replace or change out the steering rack anyways because there is play right now in mine.

1. I wanted to bring this up for anyone that needs to factor this in since it is comprehensive steering thread and I had not factored the difference between MK20 and MK60 ABS Modules.
2. I didn't know if there was anyone that has a work around for this if it becomes a problem during normal driving (other than turning DSC off)?

The DSC unit uses the output of the steering column rotation sensor to calculate which direction the wheels are pointed. Changing to a quicker rack will cause the DSC unit to assume less steering angle than is actually applied, and will not match the lateral G measured by the yaw sensor, so the car may think something is wrong and cut power / apply brakes as it thinks necessary.

The MK60 can be toggled to the ZCP steering settings when 50 mm/rev rack is installed and everything will work perfectly. I'm not aware of any such setting on the MK20.

There was someone on the old M3 Forum working on a dualCAN gateway that could be plugged in between the steering column sensor and DSC unit, to intercept the column sensor signal and scale it as necessary to maintain proper DSC function. Unfortunately, I don't remember his username. If anyone else has the skills to do it, the trick is to scale the column sensor output as follows:

[column sensor output] * [new rack mm/rev] / [stock rack mm/rev] * [stock knuckle steering arm length] / [new knuckle steering arm length]

[injekciona]

I'm considering to buy a yellow tag rack from rackdoctor. As far as I can see, the inner rods are included in the price and the outer rods could be additionally purchased. Is there any difference between the inner/outer rods of the ZHP and the M3 ones?

[Radekxpl]

I'm considering to buy a yellow tag rack from rackdoctor. As far as I can see, the inner rods are included in the price and the outer rods could be additionally purchased. Is there any difference between the inner/outer rods of the ZHP and the M3 ones?

Yes there is a difference can’t use Zhp putter tie rods on M3 only the inner are the same.


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[injekciona]

Yes there is a difference can’t use Zhp putter tie rods on M3 only the inner are the same.


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Thanks a lot. So I'll purchase just the rack with the inner rods included and I'll buy the outer ones separately. I also know that there is a difference but when I've contacted the rackdoctor and ask them if they can sell the rack with outer rods for m3, they answered that the outer rods are interchangeable among the e46 platform. Thanks for the confirmation.

[Radekxpl]

It turns out that there is alternative to ZHP Yellow tag rack, The 7852 974 678 Purple Tag has the same exact spec as ZHP 712 Yellow tag, check out comparison video between the two.

Purple Tag



Rack Rate = 50 mm/turn

Turns Lock to Lock = 3

Total Rack Travel = 150 mm

Linear

[terra]

Yeah, purple tag is from the 325i, yellow tag from the 330i. Both are 50mm/rev. So is the ZCP blue tag rack for that matter. Presumably the differences come down to steering feel / boost.

[PRIM3]

Terra, I’ve been eyeing a blue tag rack for sale locally. Can I be sure it’s from an E46 M3 ZCP? Haven’t found anything online to confirm. What spec number should I look for on the tag?

Thx


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[old///MFanatic]

It turns out that there is alternative to ZHP Yellow tag rack, The 7852 974 678 Purple Tag has the same exact spec as ZHP 712 Yellow tag, check out comparison video between the two.
Purple Tag

Rack Rate = 50 mm/turn
Turns Lock to Lock = 3
Total Rack Travel = 150 mm

The ZF .678 "purple tag" was also installed on the 325/330s. It's not "exactly the same specs" of .712 "yellow tag". True it does though have same ratio (as other 325/330s). But does not have the same valving/boost feel, just like Terra stated.
Since '01 the non-M E46s been getting this 13.7:1 ratio standard.

[old///MFanatic]

I’ve been eyeing a blue tag rack for sale locally. Can I be sure it’s from an E46 M3 ZCP? Haven’t found anything online to confirm. What spec number should I look for on the tag?

I was lucky to be a limited few who had two out of car in my possession back in 2013. Here are the numbers. It'll be a ZF and top row numbers end in .924 and bottom row ends in .640
Naturally if some how the internals have been swapped that another story. But doubt anyone would mess with the valving. You can measure and confirm the travel if needed.

[Radekxpl]

The ZF .678 "purple tag" was also installed on the 325/330s. It's not "exactly the same specs" of .712 "yellow tag". True it does though have same ratio (as other 325/330s). But does not have the same valving/boost feel, just like Terra stated.
Since '01 the non-M E46s been getting this 13.7:1 ratio standard.

That’s interesting, would definitely like see comparison between both installed and operating on actual car, highly doubt though that’s going to happen as it’s not 5 minute swap to change racks just to do comparison. But that could very well the case. Also I’m not sure what trim dictated this purple tag rack to be installed in particular car by bmw as not all 325/330 had 13:7:1 ratio.


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[terra]

That’s interesting, would definitely like see comparison between both installed and operating on actual car, highly doubt though that’s going to happen as it’s not 5 minute swap to change racks just to do comparison. But that could very well the case. Also I’m not sure what trim dictated this purple tag rack to be installed in particular car by bmw as not all 325/330 had 13:7:1 ratio.


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All 330s from April 2001 onward and all 325s from September 2001 onward had the 13.7:1 ratio, no exceptions

330s from 04/2001 to 09/2001 got the purple tag rack.
330s from 09/2001 onward got the yellow tag rack
325s from 09/2001 onward for the purple tag rack

This is for LHD markets. In RHD markets there was only a purple tag and 325/330s got the same rack. The tag being purple doesn’t necessarily mean it’s valved comparably to the purple LHD rack, but that would be my assumption since both purple tags came to be around the same time and the LHD-only yellow tag came later.

[old///MFanatic]

That’s interesting, would definitely like see comparison between both installed and operating on actual car, highly doubt though that’s going to happen as it’s not 5 minute swap to change racks just to do comparison. But that could very well the case. Also I’m not sure what trim dictated this purple tag rack to be installed in particular car by bmw as not all 325/330 had 13:7:1 ratio.

Hmm it's been a while since I researched all this but kinda remember all 330s moved to 13.7:1 around 04/'01. But who knows anymore. I will add that the late 2000-2001 had a bunch of mixed changes in the racks from BMW and retrofits by BMW for overboost feel.
But the one pictured was built in later '04 model run. July of 2004 it appears

[Volke]

It turns out that there is alternative to ZHP Yellow tag rack, The 7852 974 678 Purple Tag has the same exact spec as ZHP 712 Yellow tag, check out comparison video between the two.

Purple Tag



Rack Rate = 50 mm/turn

Turns Lock to Lock = 3

Total Rack Travel = 150 mm

Linear

Thank you for confirming. I added the picture to post #3.

Thanks a lot. So I'll purchase just the rack with the inner rods included and I'll buy the outer ones separately. I also know that there is a difference but when I've contacted the rackdoctor and ask them if they can sell the rack with outer rods for m3, they answered that the outer rods are interchangeable among the e46 platform. Thanks for the confirmation.

You can reuse the outer tie rods on you car unless you're looking to refresh them in which case I'd pick up a set of outer tie rods from FCP Euro and have a lifetime replacement warranty on them in case you ever fail a tie rod ball joint or bend one somehow.