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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > Steering rack swap?



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      05-21-2013, 04:05 PM   #1
ajsalida
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Steering rack swap?

In another thread in the non-Xi section, somebody mentioned that he was considering swapping a M3 steering rack for his 335i rack. Ratio for M3 is 12.5:1, 335i is 16:1. That got me thinking, what is the steering ratio for the Xi?

Well it is 18.2:1! No wonder the Xi feels a bit less crisp than the i. Has anyone happened to look at an Xi rack side by side with an i to see if it would fit? Better yet an M3 rack? Can you imagine...

Rebuilt racks are pretty cheap, under 600 for an M3 + 200 core charge.
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      05-21-2013, 09:18 PM   #2
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Hmmmm, interesting...
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      05-22-2013, 06:46 AM   #3
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Mounting the rack to the car is generally a direct swap for the E30 rack. You need to use a couple of spacers as the mounting points on the E36 rack are not really as tall as the E30 ones. The spacing of the bolt holes is the same though. You could either make up some spacers or pack it out with washers Possibly would work.
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      05-22-2013, 07:44 AM   #4
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Quote:
Originally Posted by ajsalida View Post
In another thread in the non-Xi section, somebody mentioned that he was considering swapping a M3 steering rack for his 335i rack. Ratio for M3 is 12.5:1, 335i is 16:1. That got me thinking, what is the steering ratio for the Xi?

Well it is 18.2:1! No wonder the Xi feels a bit less crisp than the i. Has anyone happened to look at an Xi rack side by side with an i to see if it would fit? Better yet an M3 rack? Can you imagine...

Rebuilt racks are pretty cheap, under 600 for an M3 + 200 core charge.
335i rack:

http://www.realoem.com/bmw/partgrp.d...50&hg=32&fg=10

335xi rack:

http://www.realoem.com/bmw/showparts...80&hg=32&fg=10

Looks like the mount to the subframe on different sides. The xi mounts on the front of the rack, while the i mounts on the rear. But how difficult would it be to fab up an adapter? Also, these are just diagrams.

On the other forum MisterEm said RackDoctor had experience with Bimmer rack swaps on earlier chassis. I would think welding on tabs pre-reman would be pretty simple.

That being said: super interested if the price isn't absurd.
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      05-22-2013, 08:11 AM   #5
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Quote:
Originally Posted by Doyle View Post
335i rack:

http://www.realoem.com/bmw/partgrp.d...50&hg=32&fg=10

335xi rack:

http://www.realoem.com/bmw/showparts...80&hg=32&fg=10

Looks like the mount to the subframe on different sides. The xi mounts on the front of the rack, while the i mounts on the rear. But how difficult would it be to fab up an adapter? Also, these are just diagrams.

On the other forum MisterEm said RackDoctor had experience with Bimmer rack swaps on earlier chassis. I would think welding on tabs pre-reman would be pretty simple.

That being said: super interested if the price isn't absurd.
I was staring at those diagrams for a long time the other day and couldn't see anything helpful. The 335i one you show is for active steering so I am not sure how it mounts. But I think you are right about the tabs. Here are some pics from reman vendors, they claim these are not generic but actual items:

335i


335xi


I need to get under my car for some other stuff soon and I will pay attention to how the rack is mounted. It looks from those pics like there may be other things going on with the hydraulic fluid lines and so forth that may interfere even if the tabs were swapped.

edit: I wonder if you could just take a 335i (or M3) rack apart and use the rack & pinion gears, swap out the Xi for the i (or M3) and leave the whole original housing intact, not mess with changing tabs etc.

Last edited by ajsalida; 05-22-2013 at 08:17 AM.
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      05-22-2013, 11:15 AM   #6
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Yeah, so those pictures corroborate the realoem diagrams.

Dunno about which option is easier. Rerouting hydraulic lines shouldn't be that difficult. I don't know what sort of witchcraft goes on with BMW's steering assistance, with regard to swapping internals. I'll defer to the pro's.
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      05-27-2013, 05:42 PM   #7
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Quote:
Originally Posted by Ant94 View Post
These wouldn't be a direct swap, the i and xi have two completely different front sub-frames. Check out the real oem front axel diagrams
*Sigh* does anyone bother to read threads anymore before commenting?
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      05-30-2013, 07:45 AM   #8
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Lol. welcome to bimmerpost...

Another option is a tie-rod relocation kit.

http://blog.perrinperformance.com/50/

alot of drift guys use something similar for roll center, bump steer, and Ackerman adjustment.

Basically changes the lever arm between the "Dave Point" and tie-rod ball joint.
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      05-30-2013, 09:50 PM   #9
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Quote:
Originally Posted by Doyle View Post
Lol. welcome to bimmerpost...

Another option is a tie-rod relocation kit.

http://blog.perrinperformance.com/50/

alot of drift guys use something similar for roll center, bump steer, and Ackerman adjustment.

Basically changes the lever arm between the "Dave Point" and tie-rod ball joint.
Would this kit work for us?

I am so fed up with the steering on my Xdrive coupe. Coming from an Evo VIII and an STI the xdrive steering is unresponsive and sloppily dull. I have done eibach springs, bilstein shocks, and M3 rear sway and subframe bushings. It is way better than stock but nowhere near the Evo. Some may say "then get an Evo" Well I am now 35 years old and drive to work in a business suit so my boyracer days are behind me. Speed, comfort, snow traction, and fit and finish are all light years ahead in the BMW. The steering response and handling not so much.
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      05-31-2013, 09:55 AM   #10
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Quote:
Originally Posted by SaviorXi View Post
Would this kit work for us?

I am so fed up with the steering on my Xdrive coupe. Coming from an Evo VIII and an STI the xdrive steering is unresponsive and sloppily dull. I have done eibach springs, bilstein shocks, and M3 rear sway and subframe bushings. It is way better than stock but nowhere near the Evo. Some may say "then get an Evo" Well I am now 35 years old and drive to work in a business suit so my boyracer days are behind me. Speed, comfort, snow traction, and fit and finish are all light years ahead in the BMW. The steering response and handling not so much.
This particular kit? No.

However, something similar shouldn't be too hard to fab up.

Also, I'm currently waiting on some control arm options to come through that should also tighten up the front end.

Right now, with 265's up front, -3d, 450# springs, and UUC f sway bar I'm not quite to the Evo's "sneeze and i'm 2 lanes over" steering, but close. I'm hoping new arms, better tie rods, and potentially this kit will get me there.
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      05-31-2013, 10:10 AM   #11
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interesting..
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      05-31-2013, 11:00 AM   #12
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Looks promising
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      06-01-2013, 03:03 PM   #13
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Pretty interested in this, initially driving around in a friends 335i is the whole reason I went for it. Seems like the xi, however, is a whole other animal when it comes to handling.
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      06-01-2013, 04:07 PM   #14
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Quote:
Originally Posted by BrokenMyWallet12 View Post
Pretty interested in this, initially driving around in a friends 335i is the whole reason I went for it. Seems like the xi, however, is a whole other animal when it comes to handling.
Better suspension helps a lot, but the steering is pretty slow.
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