iX 2 Door to 4 Door Swap?

[nando]

There was a discussion about it a long time ago, now lost, on E30tech.

I doubt the increase in bump steer would be significant from the caster changes. It's not very noticeable even on a very lowered ix with the maximum caster possible. It could be a problem if the ball joints don't have enough travel though due to the extra angle involved.

[The Dark Side of Will]

The caster angle wasn't a mistake. It was done to optimize traction on slick surfaces for both acceleration and braking - it's all about weight transfer.

Where'd you hear that?
I'm not sure I buy it... weight transfer doesn't care about geometry. Weight's going to transfer based on wheelbase/track, CG height and g forces.
The geometry just controls how much of the weight transferred goes into the springs vice the suspension pivots.

I wonder if it would actually work just fine to have the ix drivetrain with the RWD strut towers - it may in fact handle better, albeit on dry surfaces (the extra dynamic camber would be nice). The important part would be the ix subframe, which you'd definitely need to swap over. I think on later cars the frame rails are basically the same and you can bolt it on, on earlier cars you'd have to extend it.

Especially if the ostensible reason they built the AWD cars with no caster was traction on snow and ice, I think that an AWD powertrain in a RWD shell would handle much better than an original AWD car, at least as far as the items we've identified: contact patch feel & caster induced camber gain. However, such a beast would gain some bump steer because the extra caster would raise the outer tie rod end. The rack could be spaced up, but that would probably interfere with engine position. Might as well just make some bespoke hub carriers to fix the bump steer ;-)

It would make sense that once BMW started to build the AWD cars, they would have used the AWD frame rails across the lineup in order to simplify supply chain and manufacturing, but Germans are generally not good at simplifying things.

[nando]

The trans tunnel fab should not be difficult. Don't let that stop you.

The strut towers are, I think, very much open for debate.

My iX has power steering disabled (belt's been gone he entire time I've owned the car). It doesn't bug me, but what it does is give me *much* better contact patch feel at the limit of tire grip.

The iX, because of its very small caster angle has very poor feel for when a contact patch is about to break loose. There's essentially no change in load on the steering wheel between full grip and sliding.

That being said, the extra caster of the RWD body would *certainly* help contact patch feel.

However, would AWD with that caster angle induce torque steer? I don't know. I suspect not, but I haven't built such a car... yet. I'm also not sure why BMW built the car with so little caster. Did they make a mistake because of their lack of experience with front wheel drive?

Did they feel like the drive torque + caster would muddy steering feel? I can't see that as being their motive because what they did in response certainly muddies steering feel.

In your shoes, I'd do the swap. Please let us know how it turns out.

ETA: Another point: the AWD crossmember bolts to different locations on the body than the RWD crossmember. I've been told that the front bolt holes of the RWD crossmember are in the same location as the rear holes in the AWD crossmember. If that's the case, just bolt the AWD crossmember up to the front two locations in the RWD body and then weld steel in until you have the other two bolt holes. You may also need to notch the front frame rails a little bit for axle clearance.

There's no torque steer on an ix. That's mainly caused by unequal length halfshafts (from center of joint to center of joint), common on FWD cars.

The caster angle wasn't a mistake. It was done to optimize traction on slick surfaces for both acceleration and braking - it's all about weight transfer. They didn't do this on later AWD cars but they also came with crummy open center differentials and fake limited slip controlled by the brakes (E46 I'm looking at you). Cost comes before performance these days when it comes to BMW.

I wonder if it would actually work just fine to have the ix drivetrain with the RWD strut towers - it may in fact handle better, albeit on dry surfaces (the extra dynamic camber would be nice). The important part would be the ix subframe, which you'd definitely need to swap over. I think on later cars the frame rails are basically the same and you can bolt it on, on earlier cars you'd have to extend it.

Otherwise, if you want more caster angle get the M3 offset bushings and run the GC camber plates. It's good for a couple more degrees, which is a lot considering stock is about 1.0-1.5.

[JIM1inWisconsin]

swap

I might get an ear full but I've heard that these types of German cars were made with virgin steel and less prone to rust. What I am sure of is that back in the late 50's early 60's Ford made cars that rusted through in five years or so no matter what you did to them.

[jackjtr]

JIM1inWisconsin, you're right. I should have said:

"Let's face it, 28 year old cars love to rust out"

That being said, my W126 has been driven through Connecticut's salty winters for 32 years, and there's virtually no rust, save for a small hole by the trunk that was caused by a tiny accident. I'm also not worried about the subframe randomly dropping out from under me at high speed.

E30s are VERY VERY well built cars, but a $42k car in 1984 is going to be of higher quality than a $32k car in 1988. Hey, it's what you pay for.

This is not an insult to E30s at all. Why would I have one if I didn't like them?

[JIM1inWisconsin]

swap

Exactly! I would also probably make a somewhat detailed write-up on the swap to assist others that want to do the same.

Let's face it... E30s love to rust out, but they're drivetrains are virtually bulletproof. So why not give this rare AWD system a second chance in a nice body?

Love to rust out? Come on. Let us not forget that they are at least 25 years old. How many other cars that age do you see on the road that you can't see through?

[chuckdizzle]

FWIW there's a guy up in Windsor CT breaking a white 4 door iX auto, has a blown tranny (whatever that means). He was willing to part with the complete car for $1k a couple of weeks ago.

No idea how much rust it has but I can check if it's still available if you like.

Is there a listing anywhere for his part-out?

[Nisse Järnet]

You're using an original iX chassis, though, right?

Yep :)

[The Dark Side of Will]

You're using an original iX chassis, though, right?

[Nisse Järnet]

Speaking of torque steer, I don't have any of that in mine even with the turbo setup :)

[jackjtr]

Exactly! I would also probably make a somewhat detailed write-up on the swap to assist others that want to do the same.

Let's face it... E30s love to rust out, but they're drivetrains are virtually bulletproof. So why not give this rare AWD system a second chance in a nice body?

[Eskie]

I'm really curious to see how this all plays out as well. It would be really cool if it turns out that swapping an iX drivetrain to a RWD chassis made a better handling/feeling car. That and you could basically "make" an iX..which is cool because their numbers are limited. Exciting...


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[jackjtr]

This swap wouldn't happen for at least a year. I have finish building my Benz V8, and then I've got a VR6 and TDI swap. Oh wait, wrong forum haha.

Thank you guys VERY much for this wealth of information. I definitely want to go for this now. It'll be a decent amount of work, but well worth it in the end for a light, cheap, tossable AWD E30.

Seawolf, seems like a good deal, but I don't have that kind of money to drop on this. I paid $450 for mine. Thanks for the suggestion though!

Right now, all I can hope for is that my coupe doesn't fall apart on me, especially at high speed.

Again, thank you for the info guys. I feel obligated and motivated now lol.

[Seawolf]

FWIW there's a guy up in Windsor CT breaking a white 4 door iX auto, has a blown tranny (whatever that means). He was willing to part with the complete car for $1k a couple of weeks ago.

No idea how much rust it has but I can check if it's still available if you like.

[The Dark Side of Will]

If I found a rust-free 4 door rear drive E30 for cheap, and had my iX as a parts car, could I not (theoretically) swap the complete drivetrain and front end AWD components into the 4 door? And would this (again theoretically) be bolt in?

You will need an IX shell due to the bump out in the center tunnel to clear the transfer case and the vertical strut towers in engine bay (less castor for awd)

The trans tunnel fab should not be difficult. Don't let that stop you.

The strut towers are, I think, very much open for debate.

My iX has power steering disabled (belt's been gone he entire time I've owned the car). It doesn't bug me, but what it does is give me *much* better contact patch feel at the limit of tire grip.

The iX, because of its very small caster angle has very poor feel for when a contact patch is about to break loose. There's essentially no change in load on the steering wheel between full grip and sliding.

That being said, the extra caster of the RWD body would *certainly* help contact patch feel.

However, would AWD with that caster angle induce torque steer? I don't know. I suspect not, but I haven't built such a car... yet. I'm also not sure why BMW built the car with so little caster. Did they make a mistake because of their lack of experience with front wheel drive?

Did they feel like the drive torque + caster would muddy steering feel? I can't see that as being their motive because what they did in response certainly muddies steering feel.

In your shoes, I'd do the swap. Please let us know how it turns out.

ETA: Another point: the AWD crossmember bolts to different locations on the body than the RWD crossmember. I've been told that the front bolt holes of the RWD crossmember are in the same location as the rear holes in the AWD crossmember. If that's the case, just bolt the AWD crossmember up to the front two locations in the RWD body and then weld steel in until you have the other two bolt holes. You may also need to notch the front frame rails a little bit for axle clearance.