rack and pinion 101

E28 technical advice asked and given! Troubleshooting, modifications and more.
Bill in MN
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rack and pinion 101

Post by Bill in MN »

OK, after numerous requests for info. on my RP conversion I decided to do a half assed attempt at a write up. I want to preface this by stating that I am NO engineer or fabrication whiz. I can't do math, have no geometry skills and am, in general, not the engineering type other than the backyard variety. Having said that, my approach to this mess was simple logic and a lot of trial and error. There's no doubt in my mind that things could have been done differently but this was an effort by your average "Joe" and if I can do it, anyone can. I did some research on this topic and didn't come up with much. I spoke with a few guys in CA that had "heard" of this having been done but was not able to make any connections. Given this, I went at it blind.

Searching for the rack to use was pretty easy. I had several e21 racks on the shelf so that was the logical choice. I despise the 4 turns lock to lock in my 323 and from the outset knew this would be an issue. I'd heard of the roundy round guys using steering quickeners and immediatly knew this would be the answer to the problem. The other problem with the e21 unit is that the e28 pump will more than likely blow the seals in the rack. With an e21 power rack being a pretty rare item, I chose to convert the e21 pump to fit the M30 and avoid any issues.

Frist off, modifiying the sub frame.

This was actually quite easy with an e21 rack. All I did was to weld some tabs to the backside of the subframe and the rack mouted right up.

Here's the only reference I had before I set out on this project. If it's your car I hope you don't mind the posting.
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The idea was sound but I chose to do the mounts a bit sturdier. This is what I came up with.
Image

Since this car is primarily for the track and the old steering shaft location was no longer useable, I moved the firewall opening a fair amount lower in the firewall. This allowed for a better angle of the steering shaft. Also, I mounted the rack at a downward angle so as to make the output shaft more in line with the steering shaft (if that makes any sense!)
Image

I cannot say that this method will work with the steering shaft in its OEM position (as it exits the firewall) with an e21 rack. I've since learned the 944 , e36, Pinto (yeah, Pinto) and several others might have more optimal angles. Regardless, it works fine for my application.

OK, this was all well and good until the car started going back together. It was then that I realized it was more than a little flawed and I needed to start over. With the suspension back in the car and having a look at where things were lining up, it became blatantly obvious that bump steer was going to be an issue.......and a big one at that.

Here's a pic with everything where it should be (approx). Note the extreme angle of the tie rod in relation to the lower control arm.
Image

Here's approx where things would have been under full compression. This ain't gonna work!!

Image

Several years ago on RF (prior to the exodus) I'd seen a writeup on bump steer issues with severly lowered cars. I recalled someone putting a spacer between the bottom of the strut tube and the steering arm plate. After a search I was not able to find anything like that on the market (since have found them) so I made some 1" thick alum. spacers. The results speak for themselves.


Here's at "rest", then under full compression. Better, but still not great.
Image
Image

This left me scratching my head. I bounced these pics off a few guys, most who said it might not be that big of a deal and to live with it. Something told me I could figure this out so I did something else for a few weeks and got back to it.

What I came up with was a complet re-think of the whole thing. Unfortunatly I got in the "groove" and didn't take any photos of this process but in short, I pulled the motor and remounted the rack as high as possible in the chassis. It now clears the oil pan by less than 1/4 inch. I also moved the rack back an inch further so as to lessen the fore/aft angle of the tie rods as they went from the rack to the steering arm. Given the rack is back a bit further I rotated the rack so the output shaft/steering shaft would still line up. This actually worked out better than before since the U joint takes a much less severe angle.

This was lot better but still not what it could be so I got creative. I came up with the plan to get rid of the ball joints, install some HD heim joints and attach them to the bottom of the steering arm. Bingo.
Excuse the poor pic, but you get the idea. The camera angle is poor but the tie rod/LCA is now parallel.
Image

How I did that was pretty easy. I removed the tie rods from the steering rack and cut them off. I then took some 3/4" steel bars, hollowed them out and threaded each end.
Image.

This setup comes with a price. Given the heim joints are located where they are, a 17" rim must be used. 16's rub and I can't see any way a 15 will work. I'm using 17"'ers so it was no big deal. Since the car is lowered quite a bit, this might not be an issue if the 1" spacers are not used.

There are still questions to be answered. One is that the e21 323 is a much lighter car up front and this setup might not work. This is quite true but there is nothing on this car that doesn't need to be there. I'm guessing the weight to be similar to that of the 323 and am crossing my fingers there are no issues. The trial and error approach once again!

Secondly, the way it's set up now it's 2 turns lock to lock. This may be great for AutoX but cruising down the highway might be a problem. If so I'll install the other quickener. If that's still an issue it'll be back to the OEM e21 ratio. Thankfully it's easy to install/remove the quickener!

Well, I'm sure there's plenty left out but that's it in a nutshell. This is by no means the definative way of doing it and I'm sure a more talented person can come up with a better way. I've gone so far as to hire a master welder and fabricator to come over and go over everything with a critical eye. It's got his thumbs up so I'm pleased from that standpoint.

I hope this helps those who are thinking about doing it.
Last edited by Bill in MN on Dec 24, 2008 4:58 PM, edited 1 time in total.
Shawn D.
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Post by Shawn D. »

Nice writeup, Bill!

The Pinto racks are plentiful, even in aftermarket form, where one can get different ratios, mounts, etc.
Bill in MN
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Post by Bill in MN »

Thanks to Bimmerguy: a link to the spacers.

http://www.teamdfl.com/bmw/e28/steering ... acers.html
Mark 88/M5 Houston
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Post by Mark 88/M5 Houston »

Very nice write-up Bill.
Bill in MN
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Post by Bill in MN »

I might add:

The mounts support both top and bottom of the rack. It's hard to tell in the pics but the rack slides between the two. It also now sports urethane bushings top and bottom to help with any vibration.

I was asked about the quickeners. I have a 2:1 (in it now) and a 1.5:1. Here's a pic of how it's mounted. This was quite early on in the fabrication phase and while it's changed a goodly amount, in principle it's pretty close to the final result.
Image

Note: Seinfeld had Superman, I've got Spongebob.
SpongeBob
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OK - My turn

Post by SpongeBob »

Does not work....will follow up with new solution in a few months.

SBSP
Last edited by SpongeBob on Jan 09, 2009 11:01 AM, edited 2 times in total.
Bill in MN
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Post by Bill in MN »

Flaming River makes a double U joint capable of doing 70 degrees. Any chance you can make one work so you don't have to chop up your firewall?

I too used a lower section (splined) from the e21, probably the same used by the e30. Our installs are not that far from each other, right down to the Koni's. :D
SpongeBob
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Post by SpongeBob »

Does not work....will follow up with new solution in a few months.

SBSP
Last edited by SpongeBob on Jan 09, 2009 11:01 AM, edited 2 times in total.
stuartinmn
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Post by stuartinmn »

There was a guy on the Minneapolis Craigslist recently who was parting out an e39 528i. He was selling the front and rear suspension/subframes as compete units; looking at the pictures, I wondered how hard it would be to adapt the whole thing to an e28.
SpongeBob
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Post by SpongeBob »

Does not work....will follow up with new solution in a few months.

SBSP
Last edited by SpongeBob on Jan 09, 2009 11:02 AM, edited 1 time in total.
Bill in MN
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Post by Bill in MN »

Since my car is now of tube frame construction I'd thought of adapting a different rear suspension. That's about as far as it got, though. There are some things best left alone :laugh:
vance
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Post by vance »

Thanks guys for taking the time to share your trials with us.

Vance
bdigel
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Post by bdigel »

What are the pro's and cons of doing this? I race an e12 with bmwcca and nasa gts and have often thought about getting a rack to get rid of the weight on the driver front cornor ,.
love your write ups, thanks
BD #112 black and blue
bmw4aaron
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Post by bmw4aaron »

Nice work Bill and SpongeBob,

I have been mocking up a rack and pinion conversion for the V8. I found that an e30 steering rack works great. I would have to offset it so that the neck/input shaft is as close to the frame rail as possible. Mostly because of the V8 engine. Using a double cardon shaft for the steering column/rack input. I found the lower half of two e30 steering u-joints, separated from the rubber donut and bolted together, provides the right length. An e30 complete tierod would work for the left side, while using an e30 inner tie rod for the right side, and an e28 outer tie rod with adjusting sleeve.
ElGuappo
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Post by ElGuappo »

2 FAQ's in 1 thread?! How much WIN can 1 thread contain?

Awesome.

Gives me hope there are still things left to be done to these old pigs.
Bill in MN
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Post by Bill in MN »

The e21 rack weighs 18lbs for the power rack, 13 for the manual. I'd suspect that most racks are within that range. The e28 steering box comes in at around 35lb and the rest of the assy (pitmans, tie rods etc.) is 13. I figure a good 30+ lb savings for my situation since I also got rid of power brakes and the heavy e28 MC assy.. All of that related gear is gone.

I think there's still plenty that can be done to these old boxes. Funny, I recall a few threads several years ago regarding R and P in our cars and the idea was generally thought of as virtually impossible. HA!
SpongeBob
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The next FAQ

Post by SpongeBob »

The next FAQ will be -

"how to install a m50-S52 based six in an e28".

anyone game?

SBSP
Bimmerguy2002
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Post by Bimmerguy2002 »

the m30b35 makes same power but a lot more torque than the m50, it would be a downgrade.
ElGuappo
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Post by ElGuappo »

Uh, YEAH!.....Not just yeah, but Oh HELLS YEAH!

Considering these are popping up with increasing frequency (out here at any rate) its an intriguing alternative.
vance
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Re: The next FAQ

Post by vance »

SpongeBob wrote:The next FAQ will be -

"how to install a m50-S52 based six in an e28".

anyone game?

SBSP
I didn't want to sound greedy, but since you brought it up...

Vance
bdigel
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Post by bdigel »

Thanks for the wieght info, any cons on this other than difficultly installing?

As far as M50 based motors goes ,I know a few guys working on putting them into an e28, right now, You might loose some torque but you also loose a lot of weight and the engine wont be as far out over the front axel causing reverse 911 handling! Also an m50 is easier to get more power out of and there is lot more stuff available for thoose engines.Wish I didn't have a ton of money in my M30 ! s54 would be a great way to fly!
bm0p700f
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Post by bm0p700f »

An M50 is an idea I thought about before doing the e to i conversion on the eta. I think it would be a interesting car. I know someone over here who is embarking on this. I'll have to find out how he's getting on.

Nothing is impossible (even teleporation has been achieved now) and this thread is giving me inspiration on some future upgrades.
Bill in MN
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Post by Bill in MN »

Pro
Cut some weight
clean up the engine bay
more precise steering

Con
Wasn't exactly cheap by the time it was done
No real benefit for a street car/DD.
Questionable benefits for a track car unless you're Skeen :laugh:
Major surgery if your car isn't already pulled apart
17" wheels and their associated pro/con
bump steer hurdles

As you can see, the Con outweights the Pro. I did the project simply because it sounded like something fun to try. Was it worth it? Definately. It was a great learning experience.
bdigel
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Post by bdigel »

Funny you mention Mike skeen.com, He co drove the sled with me just a couple of week ago, Turned 2 seconds a lap faster than me! That kid is something else!
so you think about 30 pound less than a steering box?
I have gone to further extreemes to reduce weight!
Bill in MN
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Post by Bill in MN »

bdigel

I weighed everything again and a 30lb reduction is pretty darned close. With as much as the front has been lightened on this car it's entirely possible I could get away with manual steering. If this is the case another 12-15lb can come off by deleting the pump and related gear. Add to that the (roughly) 30lb savings gained by the glass hood and there's the better part of 75lb pulled out. That's huge.

That being said, e28's are still heavy sows :)
winfred
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Post by winfred »

hmmm gives me some ideas for da shark, it has some bump steer issues having been dropped and going to a manual rack (i have a euro e30 unit stashed) would allow the elimination of the steering pump (e12 based with vacuum brakes) i could drop the alt to the pump location and have room for a blower 8) now if i can only get off my ass and get the blower i already have, installed on my hotrod stroker e30 and debugged
sucks up a bit of room but i have seen a couple of them installed and working on other e30s
Image
bdigel
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Post by bdigel »

30 lbs is worth the effort and $$$!! gonna have to look in to it more, don't feel like pulling the engine out again , just had it out!!
I think I will keep the power steering, I think it just works better with it and having large tires ! I did get rid of the cast iron pump that an e12 comes with, and also got rid of the stock large brake booster replaced with e28 528e car and put an e 32/34gear reduction starter which will save you aprox. 10 lbs from e28/12 style starter. Also got rid of factory chasis harness and fuse box and put new fuse panel on the passenger side where the glovebox use to be! My car with 17piont cage wet with driver is 2740ish . with coil overs can get cross wieghts real close to 50/50
Bill in MN
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Post by Bill in MN »

17 pt. cage?

I put in a b35 starter as well and it seems to me you're spot on with the 10lb figure. It's also a lot easier to R and R than the original beast.

I think the e21 and e12 use the same pump casing. Oddly enough the e21 pump was not much (if at all) heavier than the e28 unit. Keeping it was a lot easier than reworking the e28 pump. I did get rid of the OEM alternator and rigged up a 5.5lb single wire GM mini alternator, 65 amp. That's 8lb of un needed weight gone. Somewhat of a PITA to mount up, but worth it.
bdigel
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Post by bdigel »

yeah 17 piont cage, its a e 12 so started off with a flexy flier, we tied in all suspension pionts diff mount , subframe, etc
love the Alt idea, what did you do about brackets??
bornagain
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Post by bornagain »

wait wait wait lets go back to this teleportation thing......
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