ZHP Steering Rack Mod

Would you look at that it's the same part, the almighty zhp doesnt have magical parts?!?!?!?!?!

Sent from my DROID RAZR using Bimmer App

Originally Posted by sedanpowersc

Would you look at that it's the same part, the almighty zhp doesnt have magical parts?!?!?!?!?!

Sent from my DROID RAZR using Bimmer App

We already knew it had the same part number. Even at the beginning of this thread

Originally Posted by peytonracer4

maybe i misremembered that part. but i know the m3 rack is dynamic.

I finally checked - m3 requires 3.2 turns LTL. I really should swap in that 330/ZHP rack I have...

Originally Posted by TerraPhantm

I finally checked - m3 requires 3.2 turns LTL. I really should swap in that 330/ZHP rack I have...

Ahhh the ZHP bug is getting you.. and you drive an M3! it was a 330 rack first, y'know

330 rack 330 rack. the ZHP uses a 330 rack!

Originally Posted by TerraPhantm

I finally checked - m3 requires 3.2 turns LTL. I really should swap in that 330/ZHP rack I have...

i've driven on my new rack for one day and autocross with it.
it's a weird transition. i replaced the coupler and tie rods too and its very very touchy. it is nice though.

Originally Posted by E46Mango

Ahhh the ZHP bug is getting you.. and you drive an M3! it was a 330 rack first, y'know

330 rack 330 rack. the ZHP uses a 330 rack!

Haha, I just say 330/ZHP to emphasize that they're the same (the one I have actually did come out of a ZHP, but that's only because that's the only one I was able to find at the time)

Originally Posted by peytonracer4

i've driven on my new rack for one day and autocross with it.
it's a weird transition. i replaced the coupler and tie rods too and its very very touchy. it is nice though.

Well I did have a ZHP before this car so I think I'll be okay with the ratio itself. What I'm somewhat concerned about is the weight of the steering - M3 already feels stiffer because of its geometry... I fear going to a 13.7 would make it unreasonably stiff (there must be a reason BMW only put a 14.5 on the csl, right?)

Originally Posted by TerraPhantm

Haha, I just say 330/ZHP to emphasize that they're the same (the one I have actually did come out of a ZHP, but that's only because that's the only one I was able to find at the time)




Well I did have a ZHP before this car so I think I'll be okay with the ratio itself. What I'm somewhat concerned about is the weight of the steering - M3 already feels stiffer because of its geometry... I fear going to a 13.7 would make it unreasonably stiff (there must be a reason BMW only put a 14.5 on the csl, right?)

i really can't comment on why bmw put what rack in what car. the csl was for the euro market. they have some weird tastes sometimes.
i think the major change was the steering coupler though. there's absolutely no give in the steering now so on the highway it's touchy.
i think the feel would be good on the m3. i don't really notice any added effort needed to steer coming from my other rack.

i'd swap it if i were you. it's doesn't take crazy long assuming no issues. so you could always swap back

Originally Posted by TerraPhantm

Haha, I just say 330/ZHP to emphasize that they're the same (the one I have actually did come out of a ZHP, but that's only because that's the only one I was able to find at the time)




Well I did have a ZHP before this car so I think I'll be okay with the ratio itself. What I'm somewhat concerned about is the weight of the steering - M3 already feels stiffer because of its geometry... I fear going to a 13.7 would make it unreasonably stiff (there must be a reason BMW only put a 14.5 on the csl, right?)

Yeah I was just messing with you.

Hmm maybe it's as you said.. shorter ratio would be too twitchy on the autobahn or high speed maneuvering where a longer ratio would allow the driver to more easily control the vehicle at high speeds? ?

Originally Posted by E46Mango

Yeah I was just messing with you.

Hmm maybe it's as you said.. shorter ratio would be too twitchy on the autobahn or high speed maneuvering where a longer ratio would allow the driver to more easily control the vehicle at high speeds? ?

But it's not like the 13.7:1 rack on the non-Ms was exclusive to the US - if it's not too twitchy for a 330d, why would it be too twitchy for an M3?

And I wonder if hte realized ratio will be any different. I'm pretty sure the M3 has different length tie rods than the non-M... so that will probably effect the realized steering ratio when a non-M rack is installed in an M3.

i hate to get in the middle of this but i have had some recent experience with this issue and i found out some information that could be helpful.
i wrecked my 04' ZHP. drove over some train tracks, and didn't use the crossing
anyway after replacing all the broken parts, i had no power steering. traced it down to a bad rack. (this turned out not to be true i'll get to that later) wanted to replace with original. did research, read this forum, found lots of controversy. ended up calling rich, the man who actually rebuilds the units and a BMW collector, at the rackdoctor http://rackdoctor.net/Home_Page.html.
after telling him the number on the rack, the last three numbers, 712, on a yellow tag, he immediately knew what i had. he went on to say that this rack IS different than any other rack, even the ones on different cars that had the same ratio. something about the cut and design of the teeth in conjunction with the quick raito. he also went on to say that he had found this rack on a few non zhp cars, but was very rare and no continuity for his findings.
BTW his racks are very reasonable, $150 with his own rebuilt tie rod ends.
side note: my original rack was fine. turned out to be a stuck check valve in the pressure side banjo bolt. never would have thought to look there, found it by accident.
hope this helps....

Originally Posted by commandtoad

i hate to get in the middle of this but i have had some recent experience with this issue and i found out some information that could be helpful.
i wrecked my 04' ZHP. drove over some train tracks, and didn't use the crossing
anyway after replacing all the broken parts, i had no power steering. traced it down to a bad rack. (this turned out not to be true i'll get to that later) wanted to replace with original. did research, read this forum, found lots of controversy. ended up calling rich, the man who actually rebuilds the units and a BMW collector, at the rackdoctor http://rackdoctor.net/Home_Page.html.
after telling him the number on the rack, the last three numbers, 712, on a yellow tag, he immediately knew what i had. he went on to say that this rack IS different than any other rack, even the ones on different cars that had the same ratio. something about the cut and design of the teeth in conjunction with the quick raito. he also went on to say that he had found this rack on a few non zhp cars, but was very rare and no continuity for his findings.
BTW his racks are very reasonable, $150 with his own rebuilt tie rod ends.
side note: my original rack was fine. turned out to be the check valve in the pressure side banjo bolt. never would have thought to look there, found it by accident.
hope this helps....

thanks for the info and pix.

poor car. what are you going to do with that rack? are you going to sell it?

^Drove over train tracks?! Didn't use crossing?!


U WOT M8

He was street racing an M3 (self-admitted in another thread). Not sure i'd buy into anything he says. Also his info sounds... retarded at best

BTW, anyone with an 02+ 330 has a rack ending with "712"--he'd also immediately know "what you have"

turned the old rack in for a core.
also, before i found the rackdoctor, i had gone to the junk yard and got a rack from a 05' 330ci. it was not the same. it did not have the same last 3 numbers and the tag was purple
as i stated, it is found on other cars, not just the 330, and at the same time, not all 330's have the 712 rack.
why would i lie??? i'm passing on info that was told to me by a guy that does this for a living....
maby if i wrote in crayon and drew some pictures you could understand. i posted a link, call the place yourself, moron.

Hello I am reluctantly chiming in here in hopes that I may lend a point of view from a technical standpoint. I have had several PM's, e-mails, and phone calls asking me to explain this dilemma over the ZHP Rack. If I may say ahead of time I have no desire to argue fight debate or anything else about the subject I am simply going to try to explain this as it was explained to me By ZF engineers at the AAPEX Expo. as I too (after 26 years of building the rack and pinions) don't claim to know "EVERYTHING" and at times have questions that I need answered. If anyone would like to debate the information please contact ZF.

I am not here to make anyone right or wrong simply offer tech help when I can this is what I always thought that the forums were for a community of enthusiasts trying to help one another.

I took a little time to break down a few pinions to let you see what's on the inside and how they work.

YES the 330 and the ZHP rack share the same turn ratio (3.0 turns let's keep it simple) the racks function differently by the strength of the torsion bar that runs through the center of the pinion (or in simple terms the spool valve ..... I have heard 1000's of names for the pinion)

I am adding a few pictures to try and explain how the units are different I am aware the pinions are not BMW pinions as they are only for the purpose of illustration .

The easiest way to put it is the torsion bar is different in the ZHP rack. As torque is put on the pinion the the more fluid is passed through the pinion. The stronger the torsion bar the more the sport feel. (this is also where the famous over boosted steering comes from a weak torsion bar)

Below is a simple illustration of how a rack works. The torsion bar runs through the center of the pinion (in simple terms the pinion is the brain of the rack it tells the pump when it is turning (torque) give me more pressure to turn the wheels)



The next picture shows the pinions as they would have been removed from a steering rack



The next picture shows the barrel of the pinion taken off with teflon rings still attached



The next picture shows the barrel close up I wanted to show how small the fluid holes are in the pinion so I used a ball point pen for illistration. I wanted to show this so installers will have a better understanding of the importance of flushing the system out prior to installing a rack and pinion. It takes very little to clog these small holes



Ok Moving on the next picture shows the pinion broken down by components the thin bar that runs through the pinion is the torsion bar. This is where the units differ.



The next picture is just a closer look at the torsion bar. Side by side again with a ball point pen so you can get an idea of the size of the torsion bar in the pinion



The last picture is the assembled pinion with a down view so you can see where the torsion bar is in the pinion while it is assembled



I would like to take a moment to thank the forum members for your valued business. I Hope you find the information helpful and we can agree that simply because a rack and pinion has the same turn ratio does not mean that they all perform the same, much the same as on the E36 models the standard E36 and the 96-99 M3 racks have the same turn ratio the racks perform differently. I have a good friend that works for a BMW salvage yard and he tells me that he sells the M power engine covers all the time for people to slap them on their 2.8 L engines we all know that what happens internally is what makes the difference. Adding a ZHP shift Knob to your car does not make your car a ZHP.

We at Rack Doctor go to great lengths to separate these units rather than lump them all together so that when you order a rack you will get the specific rack you are looking for.

Thank you for taking the time to read through this, and again I hope you find it informative. I hope I have explained it well enough, feel free to shoot me an e-mail if you have any questions, or give me a call I will try to help whenever I can.

Be well

Rich (aka the Rack Doctor)

This thread just got epic.

Now that we know they are in fact different, how did BMW differentiate them at the factory?? There has to be some sort of way to tell externally, otherwise that would be a quality control/inventory nightmare.

Rich, Thanks for taking the time to share your wisdom, and experience on this subject.

:o wow. So... This is interesting.
Yes it would be nice to know how bmw told them apart. If the zhp rack is one ending in 712 it would seem that other 330s received the same rack other than the zhp cars