Hydraulic steering conversion - how much better is it?

[DaveD]

Hi guys

I’m making good progress on my coupe with the aim of making it the best B road car it can be. Upgrades to date are:
- new oem lollipop bushings
- B6 dampers on sport springs
- eccentric ring on electric steering motor moved c5mm.
- forged 405M 18” alloys (9.2kg/wheel) running square 225/45/18 pilot super sports
- full geometry alignment with camber pins pulled.

I am pretty happy with it now. It can take some rough roads at decent speed (when appropriate) and body control is tight. The square set up makes the rear so much more involving and doesn’t really want for grip, although a Quaife lsd is on the list when funds allow

With the higher profile 45 section tyres and lightweight rims plus the tweak on the eccentric ring, steering is good and only rarely deflected by bumps/cambers. It doesn’t try to throw you off the road. However, I do wonder how much better it could be with a hydraulic rack from the 3 series?

Has anyone got any direct experience, and even better, is there anyone who has done this near Warwickshire so I could have a look? Don’t think I’ve seen one done on an Si yet, but looks possible. If this drives a big improvement to the steering, I may look at this as a winter project...!

Thanks in advance

 

[abar121]

How close would it be to an M?

There is a vast difference in feel between the M hydraulic rack and the normal Z4 unit.

 

[kis]

Not sure I’ve heard of the 3 series one. A few people have done the conversion with the M steering rack tho?

 

[Warming]

Also keen to know the difference and in Warwickshire. Btw have you weighed the 405m wheels yourself or is that quoted on the internet?

Hi guys

I’m making good progress on my coupe with the aim of making it the best B road car it can be. Upgrades to date are:
- new oem lollipop bushings
- B6 dampers on sport springs
- eccentric ring on electric steering motor moved c5mm.
- forged 405M 18” alloys (7.2kg/wheel) running square 225/45/18 pilot super sports
- full geometry alignment with camber pins pulled.

I am pretty happy with it now. It can take some rough roads at decent speed (when appropriate) and body control is tight. The square set up makes the rear so much more involving and doesn’t really want for grip, although a Quaife lsd is on the list when funds allow

With the higher profile 45 section tyres and lightweight rims plus the tweak on the eccentric ring, steering is good and only rarely deflected by bumps/cambers. It doesn’t try to throw you off the road. However, I do wonder how much better it could be with a hydraulic rack from the 3 series?

Has anyone got any direct experience, and even better, is there anyone who has done this near Warwickshire so I could have a look? Don’t think I’ve seen one done on an Si yet, but looks possible. If this drives a big improvement to the steering, I may look at this as a winter project...!

Thanks in advance

 

[DaveD]

Also keen to know the difference and in Warwickshire. Btw have you weighed the 405m wheels yourself or is that quoted on the internet?

This is from t’internet (edit, just seen typo as should be 9.2kg. Amended). Haven’t managed to find much detail to be honest but they are noticeably lighter - you notice that the car feels flatter and the body more controlled over bumpy roads - guess the wheels can move up and down faster so suspension is doing more. It is noticeable. Some people say you can feel faster acceleration but I’m not sure on that - but having upped the sidewalk to 45 from standard 40, I’ll have lost a bit of acceleration. Speedo now reads bang on accurate at 70mph

 

[buzyg]

Sounds like an interesting project.

 

[Mr Tidy]

I don't know if it helps, but my daily is an E90 330i so has the same engine as my E86.

But it has hydraulic PAS - which is just worlds better in terms of feel. I just wish I had enough spannering ability to try a retro-fit for my E86. :roll:

 

[QUIKSTER]

If someone figures out how to do this, I'd be up paying for parts and labour.

As long as its not dealer labour rates. :wink:

 

[Mr Tidy]

If someone figures out how to do this, I'd be up paying for parts and labour.

As long as its not dealer labour rates.

Yes, I would be too! I can't help thinking the EPAS also contributes to the tendency Z4s have to tramline.

 

[QUIKSTER]

This is taken from a buyers guide I came across before I bought my car.

Used columns require extreme caution because it needs to be removed carefully in the locked position. Like the N52 cam bearing problem, there is a market here for a fluid PAS conversion using an E46 rack (£50 tops), PAS pump from an E60, some custom pipework and a modified column as well as a remap to restore lost throttle response – the Sport button is activated by the electric steering motor but all that does is alter the speed at which the throttle reaches wide open status so it’s not essential.

https://drive-my.com/en/blogs/entry/buying-guide-the-sublime-bmw-z4-3-0si-coupe-e86.html

 

[QUIKSTER]

Yep, the tram-lining is something I have started to notice more and more since my purchase in Feb, was actually going to respond on the "Steering Issue" thread to see if anyone can tackle mine before the hot summer temps kick in.

 

[Capa]

This is a thing and I've been considering it on & off for a while. There is something akin to a guide on the forums here:
https://z4-forum.com/forum/viewtopic.php?t=92858

Ergen Motorsport in Fareham will do a drive in/drive out swap, but I believe you're looking at the business end of £2,000.

Given the costs and/or effort involved, it strikes me as only worth doing if you plan on keeping the car forever. Bear in mind that the Z4M isn't generally thought of as having the last word in driver/steering feedback anyway, so you're not going to overnight give it the steering feel of a Porsche...

Edit: another thread here:
https://z4-forum.com/forum/viewtopic.php?f=2&t=106739

 

[ph001]

Maybe it's just me but I don't really find the electric steering in the 3.0Si bad at all. I regularly drive it back to back with the E46 M3 (hydraulic) and I'm pretty hard pressed to tell much of a difference to be honest. On that basis I would say it's definitely not worth it.

 

[MrPT]

Bear in mind that the Z4M isn't generally thought of as having the last word in driver/steering feedback anyway, so you're not going to overnight give it the steering feel of a Porsche...

Great point. It's been a while since I drove 911 but I don't think it's crazy to say that there's as much difference between a non-M and M as there is between an M and something like a Porsche 997.1. An Elise would be another step up again (unless you're parking it...).

That said, it's a worthwhile upgrade if you can do it yourself (i.e. cheaply). I found the biggest improvement was getting rid of the artificial feeling of weight when in Sport mode and not so much a sudden abundance of feedback when driving the M. In terms of accuracy and being able to place the car on the road there isn't much difference. The Z4MC rack, in particular, is also pretty quick and can be a bit of a shock when you drive one on the motorway for the first time. The non-M steering in non-Sport mode is very relaxing.

The front end of the Z4 is pretty keen anyway. Sorting the rear makes a much bigger difference to handling.

 

[Ruofdez]

If someone figures out how to do this, I'd be up paying for parts and labour.

As long as its not dealer labour rates. :wink:

As would I! Couldn’t justify spending thousands on it but not a big fan of the electric steering so if a forum member cracks this and wants to make a bit of money from labour doing another please send me a pm

 

[MACK]

Electric steering wise I actually prefer the E85/86 steering to some of the later Bmws such as the pre facelift F21 1 series, although it does seem a bit better on the face-lift cars

 

[MACK]

Also keen to know the difference and in Warwickshire. Btw have you weighed the 405m wheels yourself or is that quoted on the internet?

This is from t’internet (edit, just seen typo as should be 9.2kg. Amended). Haven’t managed to find much detail to be honest but they are noticeably lighter - you notice that the car feels flatter and the body more controlled over bumpy roads - guess the wheels can move up and down faster so suspension is doing more. It is noticeable. Some people say you can feel faster acceleration but I’m not sure on that - but having upped the sidewalk to 45 from standard 40, I’ll have lost a bit of acceleration. Speedo now reads bang on accurate at 70mph

I used a 3.64 diff to compensate for the M tyre sizes as it effectively gives you the 3.46 of a e86 coupe. Made a big difference to my pre facelift 3.0i which comes with a 3.07 as standard, certainly livened things up. One other thing to consider is the M tyre sizes are a bit heavier than the standard profile tyres. It was circa half a kilo per tyre with my goodyears

 

[Felix79]

Would it not make sense to get an E46 M3 front end and do a full swap?

I don't know how true this is (I would like to know if you can teach me pls) but isn't the subframes from the E46 M3 what they used for the Z4M? With the sheer number of people who are buying cheap E46 M3's and the writing them off, there must be a way you could get most of the parts you need to upgrade to a type of M's spec, without spending mega bucks? IMO, it's the S54 that dominates the Z4M and is what really makes the car what it is, rather than how precise the steering is.

While the steering with my E85 is kinda nice, I would love to try an E86 M's rack which I've read is the CSL rack, as I think it would make it feel more sharp on the front end.

 

[Mr Tidy]

Electric steering wise I actually prefer the E85/86 steering to some of the later Bmws such as the pre facelift F21 1 series, although it does seem a bit better on the face-lift cars

Funny you say that, as I had a facelift E87 (so EPAS) before I got an E86 and the steering in that didn't bother me - but then it was a different sort of car!

The only thing they had in common was a tendency to tramline.

It's hard to describe, but the HPAS on my E90 just has so much more "feel".

But if an M isn't that much different maybe it's more to do with the Z4 geometry, etc.

Looks like I need to try an M one day!

 

[Felix79]

Electric steering wise I actually prefer the E85/86 steering to some of the later Bmws such as the pre facelift F21 1 series, although it does seem a bit better on the face-lift cars

Funny you say that, as I had a facelift E87 (so EPAS) before I got an E86 and the steering in that didn't bother me - but then it was a different sort of car!

The only thing they had in common was a tendency to tramline.

It's hard to describe, but the HPAS on my E90 just has so much more "feel".

But if an M isn't that much different maybe it's more to do with the Z4 geometry, etc.

Looks like I need to try an M one day!

I'm only over in Oxford, would be happy for you to try my E85M out if you want? I'm free pretty much all the time, so can pop over to Berks as soon as "today" if you'd like?