Sub-frame reinforcement plate upgrade for Non-M

Originally Posted by Corvis

Looks thin compared to the M54 plate, but the foldings add rigidity and you have to figure the M engineers did their FME etc. analysis in order to come up with a lightweight reinforcing member. The fixing of the plate by the multiple bolts also reduces the need for thickness (mass). Would be interesting to compare weights of the M54 and S54 reinforcing plates. Also see earlier post by cyberkaa who installed this as part of S54 to 325i swap ca. 2011.

I could probably compare weights the next time I have the M3 plate off as I still have the 325i plate in the garage.

Yes, the M3 one uses 12 bolts vs. 8.

Two extra bolts brace the control arm bushings.
The other two bolts brace the control arm ball joints.

I don't see why you'd want to use it. the reinforcement is where the CA bushings mount.

It's amazing how much more reinforcement the M car gets. Balljoint and CAB. That is awesome. Shows you how much room there is for flex in the chassis. Maybe the Z4M doesn't need/use the extra stiffening points because that body is much stiffer to begin with? Just a theory.

Terra, what would you suggest we could possibly use from the Z4M? Control arm geometry is the same, as you say... we're thinking outside the box here!

Originally Posted by ImolaSix

M3 and Non M have different drain plug locations so this would require removal of the reinforcement plate for an oil change.

That's actually a deal killer right there. That and the fact that this requires different bushing housings.

Originally Posted by WDE46

That's actually a deal killer right there. That and the fact that this requires different bushing housings.

I don't know that it requires it. I think Terra said the Z4M uses this plate despite using ZHP control arms.

Originally Posted by Mango

I don't know that it requires it. I think Terra said the Z4M uses this plate despite using ZHP control arms.

It may but I'm talking about the bushing housings with that extra bolt hole. Does the Z4M have those?

Originally Posted by WDE46

It may but I'm talking about the bushing housings with that extra bolt hole. Does the Z4M have those?

Like I said, it uses ZHP control arms which means it can't use the M3 bushings unless the Z4M has its own brackets w/ holes that use non-M bushings (which would mean WE could use those brackets) but i doubt it. i think it uses standard non-M bushings. not sure?!

Originally Posted by Mango

It's amazing how much more reinforcement the M car gets. Balljoint and CAB. That is awesome. Shows you how much room there is for flex in the chassis. Maybe the Z4M doesn't need/use the extra stiffening points because that body is much stiffer to begin with? Just a theory.

Terra, what would you suggest we could possibly use from the Z4M? Control arm geometry is the same, as you say... we're thinking outside the box here!

I'm thinking the Z4M kingpins and front suspension. The shocks mount similarly to the E36 shocks (bolted right into the kingpin/spindle) -- I believe this is largely responsible for the improved steering feel between the e46 m and z4m (even with equivalent steering racks). E36 has better feel too for that matter. Z4M does have off-center control arm bushings, which do increase caster.

Originally Posted by WDE46

It may but I'm talking about the bushing housings with that extra bolt hole. Does the Z4M have those?

ZHP/Z4M arms do not have the extra bolt holes. Not do z4m control arm bushings. Front cross member is the same. E46 m3 sway bars fit the z4m. And while I cannot find many real specs, it seems that the front hub track is the same as the e46 m3.

Edit:

Okay here's what I found so far. z4 non-M front suspension = e46 non-m front suspension. Same control arms/bushings, same spindles, same tie rods, same subframe.

This tells me that you can likely swap the entire Z4M front suspension to an e46 and the geometry would likely be correct.

Originally Posted by TerraPhantm

I'm thinking the Z4M kingpins and front suspension. The shocks mount similarly to the E36 shocks (bolted right into the kingpin/spindle) -- I believe this is largely responsible for the improved steering feel between the e46 m and z4m (even with equivalent steering racks). E36 has better feel too for that matter. Z4M does have off-center control arm bushings, which do increase caster.



ZHP/Z4M arms do not have the extra bolt holes. Not do z4m control arm bushings. Front cross member is the same. E46 m3 sway bars fit the z4m. And while I cannot find many real specs, it seems that the front hub track is the same as the e46 m3.

I'm not sure I believe the strut mounting method affects steering feel. The car would still theoretically steer even without a strut attached. I think the strut mounting design at the kingpin was just done to save weight or space especially on the strut body itself. I think it really comes down to the bushing and the weight of the car itself. The E36 M uses a very small (relative to the e46) solid control arm bushing. so if the z4m bushing is similar, then maybe that's the reason?

Seems there may be something there...

part# 31107838575

http://www.zhpmafia.com/forums/showt...ffset-bushings!

http://www.ecstuning.com/BMW-Z4-M_Ro...hings/ES48907/

Thoughts, terra?

Seems like there might be something to that bushing. Would caster alone account for a steering feel difference?

And I'm not sure why the shock wouldn't impact steering feel at least a little bit. Doesn't the shock keep the lower suspension where it's supposed to be via the kingpin? I have a hard time believing BMW wouldn't have simply used the E46 m3 or CSL kingpin and control arms if the geometry was appropriate and the shock mounting style had no impact on feel or handling. Seems like a lot of R&D for no reason otherwise.

Originally Posted by TerraPhantm

Seems like there might be something to that bushing. Would caster alone account for a steering feel difference?

And I'm not sure why the shock wouldn't impact steering feel at least a little bit. Doesn't the shock keep the lower suspension where it's supposed to be via the kingpin? I have a hard time believing BMW wouldn't have simply used the E46 m3 or CSL kingpin and control arms if the geometry was appropriate and the shock mounting style had no impact on feel or handling. Seems like a lot of R&D for no reason otherwise.

Yes that's not what I meant. Sorry. The strut does of course help with the front suspension holding up the car (Because it houses the springs). I was saying theoretically if there was no strut, the steering action would be still of course be via the tierods. It's just a theory of course. I don't know. And I'm not sure a lot of R&D had to be done to go back to an old strut mounting style since the E36 M3 (and non-M E36) had that mounting style. In fact I think most passenger cars like Accord, Camry, etc use that same strut mounting style for mcpherson struts. the two bolt style. I know my WRX struts mounted this way too and that car cannot compare to an E46 in terms of steering feel.

anyways I am really curious about the Z4M bushings. I'm curious what the final caster results in

OK here's a peak at the E9X M3 front strut:

Well most Japanese cars have a lot more front overhang and front weight than BMWs. And most companies aren't as anal as BMW with getting the steering feel right. Most reviews of the z4m claim the "new" shock mounting style saves weight and sharpens steering response.

Originally Posted by TerraPhantm

Well most Japanese cars have a lot more front overhang and front weight than BMWs. And most companies aren't as anal as BMW with getting the steering feel right. Most reviews of the z4m claim the "new" shock mounting style saves weight and sharpens steering response.

Hm ok. I guess. I just don't see how the strut is in any way integral to steering feel unless its design alone allows a particular geometry setup not possible with the pinch bolt setup.

Oh well.

Wonder if Meyle makes a Z4M bushing replica. or i'll look into the OE bushings w/ brackets

The z4m bushing might fit in the non-m lollipop. Both are 66mm

Originally Posted by TerraPhantm

The z4m bushing might fit in the non-m lollipop. Both are 66mm

Yeah. I just don't feel like attempting to press them in/out you think the caster will be fine?

Hard to say. It is possible that the only reason the z4m has such an offset bushing is to correct the caster since the kingpin/spindle/whatever you want to call it is different. I doubt it will cause any interference either way, but maybe it would look off?

Were E36 M offset and non-M centered bushings interchangeable? If so, these are probably fine too.

One of these days I would like to see M control arms side by side with non-M arms. If they are interchangeable, then maybe ZHP arms plus z4m bushing would give similar improvements?

Originally Posted by TerraPhantm

Hard to say. It is possible that the only reason the z4m has such an offset bushing is to correct the caster since the kingpin/spindle/whatever you want to call it is different. I doubt it will cause any interference either way, but maybe it would look off?

Were E36 M offset and non-M centered bushings interchangeable? If so, these are probably fine too.

Yes on the E36 M common mod was to use 95 M3 offset bushings in swap of the 96+ M3 centered bushing to gain caster. Looks like this pair w/ brackets will cost me $120. Not sure why we've never thought of this before. interesting

http://www.turnermotorsport.com/p-19...r-m-coupe.aspx

Originally Posted by Mango

Hm ok. I guess. I just don't see how the strut is in any way integral to steering feel unless its design alone allows a particular geometry setup not possible with the pinch bolt setup.

Oh well.

Wonder if Meyle makes a Z4M bushing replica. or i'll look into the OE bushings w/ brackets

Caster is pretty important to steering feel. It effectively adjusts mechanical trail. That's what makes your wheels turn back to center. The strut influences both caster and camber.

http://en.wikipedia.org/wiki/Caster_angle