E34 Rack and Pinion conversion completed...

[Cacatfish]

Some people were curious for a report of the final product in my half-baked idea to have the reviled E34 steering box replaced with a close ratio rack and pinion unit. Well, the conversion is complete and my first impression is: Wow! The dead spot on center with accompanying play and the lack of road feedback as been replaced with tight linear precision trough the range and superb feedback through the steering wheel. (I also specified solid mounting and as little rubber as possible in the steering shaft linkages for maximum feedback).
Where I felt as if the steering was leaving me isolated from the actions of the front tires and weight transfer, now I feel much more involved in the all around driving experience and more confident driving the car in a sporting manner. If anyone has considered it, I would say give it a shot!
The rack itself is one specd for a mid 90s VW gti (about 14.7:1 ratio) and tie rods, and lower steering shaft were fabricated using replaceable tie rod ends and u-joints. If anyone is interested in any more details, let me know. This was done by Rick Haner at HanerHaus in Santa Rosa, Ca.
Colin

[JR'Z 525]

Awesome sounding project! Post some pics...tell us more..how is the steering shaft connected to the rack...costs etc. Sounds like a great alternative to a worn steering gear box!
JR
92 525

[George M]

to congratulate you on your effort to make the transistion to R&P steering. Completely agree with your assessment and motivation to make the change away from the dated recirculating ball type gearbox for the reasons you mentioned. The steering system in any car is pivotal ingredient to its personality and have no doubt making this change has transformed the way the car drives. I have always felt the steering on these car's was its achilles heel. The ratio you stated seems about right as well. One of the biggest challenges...there are a few...when adopting a generic R&P steering gear to a recirc. ball car is rack travel relative to max wheel angle which establishes max.turning radius. Do you have any issue with respect to rubbing of your tires at max lock? If not, your tuner did a good job. Manufactures go so far as to offer different rack stops on similar model cars with different wheel packages for that reason...tire clearance at full lock. Generally when a R&P gear is adopted to a recirc. steering box car, a tuner will err on the side of conservatism when setting up the rack to negate tire rubbing at full lock thereby compromising some turning circle. Colin, as these cars age and more steering boxes fail, believe many others would be interested in your installation. Do you have any pictures you could post of the conversion?... would love to see how the rack was packaged. Finally, how many turns lock- to-lock is your new set up?
Thanks for sharing your major accomplishment.
George
90 735iL/149k...original steering box

[MBXB]

Sounds like a great alternative for those of us with aging E34s, who wouldnt mind going non-stock with the steering system.

If you wouldn't mind sharing the whole procedure and posting photos or whatever, that would be great! Did you keep the power steering?

Thanks in advance.

MBXB




Some people were curious for a report of the final product in my half-baked idea to have the reviled E34 steering box replaced with a close ratio rack and pinion unit. Well, the conversion is complete and my first impression is: Wow! The dead spot on center with accompanying play and the lack of road feedback as been replaced with tight linear precision trough the range and superb feedback through the steering wheel. (I also specified solid mounting and as little rubber as possible in the steering shaft linkages for maximum feedback).
Where I felt as if the steering was leaving me isolated from the actions of the front tires and weight transfer, now I feel much more involved in the all around driving experience and more confident driving the car in a sporting manner. If anyone has considered it, I would say give it a shot!
The rack itself is one specd for a mid 90s VW gti (about 14.7:1 ratio) and tie rods, and lower steering shaft were fabricated using replaceable tie rod ends and u-joints. If anyone is interested in any more details, let me know. This was done by Rick Haner at HanerHaus in Santa Rosa, Ca.
Colin

[jplacson]

What are the advantages of the stock recirculating ball steering over rack & pinion?

[MBXB]

JP

RP is a simpler mechanism than RB.
Feel is very direct.




What are the advantages of the stock recirculating ball steering over rack & pinion?

[jplacson]

:P I know... that's why I was asking what the advantages of the stock box are over the simpler R&P. :P hehehe :D I enjoy reading all the stuff people do to their E34s... at the same time, I'd also like to know the advantages of the stock setup, over the mods... BMW engineers are far from stupid, so I just enjoy knowing the reasons for certain stock component choices over aftermarket upgrades.

[Tiger]

Mmm... isn't 525i R&P setup whereas 535, 530 & 540 Recirculating system?

[jplacson]

would that mean that my Euro 520i is an R&P? If it is R&P, does that mean I can't adjust the steering nut under the dash as well?

[Alan Y]

:P I know... that's why I was asking what the advantages of the stock box are over the simpler R&P. :P hehehe :D I enjoy reading all the stuff people do to their E34s... at the same time, I'd also like to know the advantages of the stock setup, over the mods... BMW engineers are far from stupid, so I just enjoy knowing the reasons for certain stock component choices over aftermarket upgrades.

I thought the reason for not having R&P was that the BMW engineers could not find enough room for it. I can't think of any advantage the stock box has. Of course, the engineers found enough room in all subsequent BMW models...

[winfred]

on the e39 the 6 cylinder has a rack but the v8 has a reculating ball including the mighty m5

[Cacatfish]

George,
You make an interesting point about the turning radius. I think you are correct in that my tuner was conservative in max wheel angle. No rubbing, but my turning circle is larger by a couple feet, I would say. Not horrendous, but noticeable. When I get an opportunity to get the car in the air, I will try to portray the layout. I havent checked turns lock to lock yet, but I will.
Thanks for the feedback, Colin



to congratulate you on your effort to make the transistion to R&P steering. Completely agree with your assessment and motivation to make the change away from the dated recirculating ball type gearbox for the reasons you mentioned. The steering system in any car is pivotal ingredient to its personality and have no doubt making this change has transformed the way the car drives. I have always felt the steering on these car's was its achilles heel. The ratio you stated seems about right as well. One of the biggest challenges...there are a few...when adopting a generic R&P steering gear to a recirc. ball car is rack travel relative to max wheel angle which establishes max.turning radius. Do you have any issue with respect to rubbing of your tires at max lock? If not, your tuner did a good job. Manufactures go so far as to offer different rack stops on similar model cars with different wheel packages for that reason...tire clearance at full lock. Generally when a R&P gear is adopted to a recirc. steering box car, a tuner will err on the side of conservatism when setting up the rack to negate tire rubbing at full lock thereby compromising some turning circle. Colin, as these cars age and more steering boxes fail, believe many others would be interested in your installation. Do you have any pictures you could post of the conversion?... would love to see how the rack was packaged. Finally, how many turns lock- to-lock is your new set up?
Thanks for sharing your major accomplishment.
George
90 735iL/149k...original steering box

[Cacatfish]

The only E34 with R&P from the factory was the AWD 525ix. I looked into swapping in that setup but too complex. All others are RB.


Mmm... isn't 525i R&P setup whereas 535, 530 & 540 Recirculating system?

[Cacatfish]

Thanks for all the feedback. I will fill you in on what I know.
The pump used was from an m50 e36, so it will fit directly on an m50 525i. The stock E34 RB pump operates at way too much pressure for any factory rack to handle (around 1700psi). The upper steering linkage was cut and the lower one custom made. As the angle from the shaft to the rack was too tight for standard u-joints, racing units (by Torgesen) were used which can accomodate a 70% angle.
I will try to get some photos in the by and by and post them up. Custom welding was needed for the subframe rack mounts and bearing support flange also.
Cost was about $2800, but my mechanic burried himself in hours, so the next job might cost a bit more (his first time on an e34). he charged me the price because that was what he quoted me. he is a good guy to work with.



Sounds like a great alternative for those of us with aging E34s, who wouldnt mind going non-stock with the steering system.

If you wouldn't mind sharing the whole procedure and posting photos or whatever, that would be great! Did you keep the power steering?

Thanks in advance.

MBXB

[George M]

Colin,
Increase in turning radius can be due to a couple of things. Most likely there aren't any rack travel restricters on that particular rack, but what you can do is pull up the bellows on each side and take a look. Removing the bellows isn't easy if you have Oetiker clamps, which many do...but since you may have custom outer tie rods to connect with your steering knuckles, you may have serviceable clamps on your bellows. If there is a wafer like part..generally made from a glass filled nylon, that looks like a poker chip with a hole in the middle where the rack end goes through between the undercut of the rack end adjacent to the thread where the tie rod ball joint threads on...you could try removing them, threading back on the tie rod (with loctite 242)...and seeing if you have restored your turning radius without rubbing. Again, possible that your tuner is savy to this...but maybe not. If no restrictors on the end of the rack, then you are internally limited to rack travel relative to knuckle arm length which not only affects overall steering ratio (over and above rack specific gear ratio) but turning radius relative to rack travel.
Do post up some pics Colin when you get a chance.
George

[Anthony (M5 in Calgary)]

One of the stated benefits of recirculating ball steering systems as originally advocated by BMW (and Mercedes for that matter) was the non-linear steering response possible in the RB unit. As the wheel is turned farther from center, the faster the ratio becomes.

Rack and pionion steering is great for on-center feel but is restricted to linear ratios.

My $0.02 (Canadian)

Anthony

[George M]

even if BMW and Mercedes espoused that particular benefit of a RB box over rack & pinion...it is an unworthy tradeoff as you spend very little time off center when you drive your car. Any give up to the RB box in this regard can easily be compensated for with a R&P gear by changing the pinion/rack ratio which is historically much faster than RB boxes anyway and also compensated by revising torsion bar spring rate which can more precisely calibrate pressure versus angle onset of assist. There is no comparison in terms of steering precision between a RB box and R&P....why virtually all cars have evolved to it..including BMW's foray into electric steering which is a motorized screw nut mounted on a steering rack in replacement of conventional hydraulic assist.
George

[Cacatfish]

Rack and pinion is not limited to linear ratios. For example, most years of the e36 M3 have a variable ratio rack (14.x to 19.x) that speeds the ratio up further from center.



One of the stated benefits of recirculating ball steering systems as originally advocated by BMW (and Mercedes for that matter) was the non-linear steering response possible in the RB unit. As the wheel is turned farther from center, the faster the ratio becomes.

Rack and pionion steering is great for on-center feel but is restricted to linear ratios.

My $0.02 (Canadian)

Anthony

[Cacatfish]

Thanks for the info George. Ill look into that and see how it looks.
Right now it is livable, but a tighter circle would be nice (though I dont think it will compare to the ole Volvo 740 :))
I emailed my mechanic for photos as I know he snapped a few. Ill get them up as soon as possible.
Colin



Colin,
Increase in turning radius can be due to a couple of things. Most likely there aren't any rack travel restricters on that particular rack, but what you can do is pull up the bellows on each side and take a look. Removing the bellows isn't easy if you have Oetiker clamps, which many do...but since you may have custom outer tie rods to connect with your steering knuckles, you may have serviceable clamps on your bellows. If there is a wafer like part..generally made from a glass filled nylon, that looks like a poker chip with a hole in the middle where the rack end goes through between the undercut of the rack end adjacent to the thread where the tie rod ball joint threads on...you could try removing them, threading back on the tie rod (with loctite 242)...and seeing if you have restored your turning radius without rubbing. Again, possible that your tuner is savy to this...but maybe not. If no restrictors on the end of the rack, then you are internally limited to rack travel relative to knuckle arm length which not only affects overall steering ratio (over and above rack specific gear ratio) but turning radius relative to rack travel.
Do post up some pics Colin when you get a chance.
George

[George M]

you are right Colin about variable ratio R&P as well...sounds like you know a bit about steering...explains why you went to the effort you did to transform your car. The book on variable ratio R&P is...on center you want a numerically higher ratio for good on center feel thereby reducing the car's nervousness, and conversely you want a quicker ratio off center for lively overall steering transient response, also helping for example in parking manevers. This is accomplished with a fixed involute/helix angle pinion with variable rack tooth/involute spacing. For those interested, the reason this will work...not unlike a variable ratio RB steering box, is on center where you spend most of your time, you have the highest rack forces/gear tooth stresses....therefore you want rack to pinion engagement to be its fullest...which is called optimizing the contact ratio and crunched by a computer program based upon twenty or so gear tooth geometry inputs. Off center the rack tooth spacing is increased which in effect compromises gear engagement and reduces contact ratio but is tolerated because maximum hydraulic assist off center diminishes rack stresses.
George

[MBXB]

What was your bottom line for the conversion? Parts cost, Man Hours etc.?

MBXB

[Cacatfish]

I was charGed $2800 because we areed upon that price ahead of time.
It ended up takin him a lot lonGer than he estimated, so the next one may
be sinificantly more.
hours: many, but it was a first for him on an e34
Parts: Im not sure. With fab work (some outsourced), at least $1500

[black_bird_blue]

:P I know... that's why I was asking what the advantages of the stock box are over the simpler R&P. :P hehehe :D I enjoy reading all the stuff people do to their E34s... at the same time, I'd also like to know the advantages of the stock setup, over the mods... BMW engineers are far from stupid, so I just enjoy knowing the reasons for certain stock component choices over aftermarket upgrades.
Steering boxes have some different characteristics that may be thought of as advantages or disadvantages depending on context. The big difference is that they have a very poor reverse efficiency, which translates as superb isolation from road disturbances. Or very poor steering feel, depending on how you view it. Personally, I've never found the feel on my E34 lacking; as soon as the back of the car moves the steering tells me where it is well enough. That's all I want, the rest is noise.

Steering boxes also have a great package flexibility, you can pop them more or less anywhere, whereas a rack has to be in just the right position, which is one of the reasons why BMW stayed away from it. However, as crash legislation has got more and more stringent, there is more and more space being forced under cars and so it's getting (comparatively) easier to fit a rack in.

The other difference a steering box has is an increasing ratio as you come off-centre, which naturally gives lighter parking efforts for a given level of assistance. To make a rack offer the same level of ratio compensation you end up needing Active Steering or some other fancy tomfoolery in the rack cutting, both of which are expensive - see, for example http://www.bishopsteering.com/steer_tec_rack.htm.

Another advantage is the ability to dial in different levels of friction in different parts of the travel - firm for on-centre disturbance rejection and looser for good feedback in corners, as our E34 boxes are.

Yet another advantage is the ability to get very large levels of rack bar travel without some of the rack-based difficulties associated with that - in particular the position of the valving has to move inboard the more rack travel you have, and inboard is exactly where you don't want to go - back to that package advantage again.

There is also some sort of detail design advantage inside the unit. The high precision components are balls, which are cheap because they are made in volume. Everything else is more or less "industrial", whereas a power rack is quite an expensive piece of machinery gram-for-gram. However, so much effort has been put into power racks now that this one is not really true any more.

If you look around at very maintainable vehicles with a tight turning circle - London Taxis and most delivery vehicles - then they almost all use recirculating ball. It used to be the norm until racks started to become cheap enough. Then for cars the level of feedback (the primary technical difference) was allegedly an advantage, and so racks started to take over. I say allegedly because there is a lot of friction and other stuff going on in the steering that significantly reduce levels of steering feel, and most people don't know what they're feeling anyway, so it's all a waste!

Damian

[Cacatfish]

Double post

[Cacatfish]

London Taxis are back in SFO again. Anyone seen em?

[black_bird_blue]

oops, sorry - finger trouble...

[jplacson]

Steering boxes have some different characteristics that may be thought of as advantages or disadvantages depending on context. The big difference is that they have a very poor reverse efficiency, which translates as superb isolation from road disturbances.

Damian

THAT'S what I was looking for. Thanks! :) I figured BMW engineers are far from stupid. Having been given the task to design an executive car, I'm sure they were told to make it as comfy as possible... I don't think they expected suits to do slalom turns home at break-neck speeds... or do a 180 driving their kids to school! ;) Although it would make the 'fetch the kids from school' a fun-drive everytime! hehehehe

It makes sense why they placed a RB instead of a RP in the 5. Thanks!!! Learn something new everyday!

[flash635]

I've been thinking of doing this conversion on my E28 based E24.
I'm in Australia so my car is right hand drive.
This conversion would free up a lot of space for a turbo installation.

My question is- can I use the same pump for the rack and pinion as is used for the brakes?
How do you get around this?

[grave77]

your project sounds awesome, I really wish to have that feeling on the steering, but one thing I tried was when I drove my dads car 735i it has a softer steering and it has no gap too, I asked about it and they told me that the hydrolic pump it uses is differant. but it seems to work on the 535i too.. this sounds like a cheep upgrade and easy one too.
I also like to ask about the popular vibration 5 series suffer from when anything fails in the steering system, any effects happenend with ur upgrade ?

[winfred]

one thing that most e32s have that i've yet to see on a e34 is servotronic, it varys the steering effort in relationship to speed


I tried was when I drove my dads car 735i it has a softer steering

[bahnstormer]

has anyone considered quickening the oem RB on the e34?
i'd like to have less turning to do whilst drifiting around....

[grave77]

well still that’s cool, will it fit in the e34? I would love to do that!! I mean one thing I really love in American cars is the steering wheel u can spin it with ur tiny finger and still got the grip.

[Incantation]

i've wanted to do this since i bought my e34...

[Mr Project]

The E34 M5 had Servotronic....not sure if it was all the versions or only certain models.

[infinity5]

I'm the 3rd owner, but per the dealers window sticker my 530 has servotronic.. i'd be interested to drive one without it so notice the difference.. although at high speeds you can definitly feel how tight the steering gets.