Comprehensive Steering Information Thread

[ChipperM3]

Us MK20 guys need to pool some money together to throw at whoever can figure this out. This NEEDS to happen.

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]

[Obioban]

Been reading through this and don’t have a definitive answer on what a viable steering upgrade would be for a 2002/MK20 car. Anyone provide insight?

If you drive with DSC on, stay with the stock rack. You could bump up feel and heft a bit by shimming the regulator.

[Thoglan]

S3diment 2002 mk20 car here, if you have a rhd car a solid steering coupler could be nice. Installed on mine but yet to drive with it. I also have a purple tag rack, no issues with it but yet to take it on track with the new rack nor do I run an aggressive wheel set up (yet).

[S3diment]

Been reading through this and don’t have a definitive answer on what a viable steering upgrade would be for a 2002/MK20 car. Anyone provide insight?

[Radekxpl]

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



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.

Glad to contribute to this awesome informational thread 👍😊


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[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.

[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

[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.

[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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[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.

[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.

[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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[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.

[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

[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.