Black & Tan 332iT

[heinzboehmer]

Huh, that's surprising. Static camber and caster (and toe?) look different too?

I would trust the geometry of the pickup points for the LCA, tie rod, strut and caliper brackets in the scan. Not sure I'd trust the relation between the hub and the aforementioned features, though. The heat shield was hard to wrap the scan around.

What happens if you line the scans up on the LCA/caliper bracket mounting points? I would think those are the same between the M and non-M knuckles. Almost looks like the non-M tie rod pickup point would end up higher than the M one, resulting in a slight change in effective LCA to tie rod distance.

[Flow]

The amount of knowledge in this thread is insane.
Thank you for doing all this and sharing it with the community !

[YoitsTmac]

Insanely interesting to see the two overlapped. Looks like the caliper bracket position is tied more to the strut than the LCA.

The BMW community can always depend on me to have the most random parts lying around🫡. Got home and immediately chucked that thing in the bin.

[Bry5on]

Thanks to YoitsTmac and heinzboehmer we've got an interesting finding. I've overlaid a non-m knuckle scan to an M3 knuckle scan, and the numbers do not match the BMW quoted steering ratios.

So here's what I've got for LCA to tie rod distance:
M3: 130mm
Non-m: 126mm
SuperKnuck: 122.9mm

That means that if M3 CSL/ZCP is 14.5:1, then
Non-M: 14.05:1
SuperKnuck: 13.7:1

And consequently, if the non-M is 13.7:1, then
M3 CSL/ZCP: 14.13:1
SuperKnuck: 13.36:1

Now I'm going to have to pull up the numbers in NCS expert to see what the DSC module says. Guess that knuckle I ordered is a bit of a tighter steering ratio than planned!

Blue is M3, brown is non-m:

[heinzboehmer]

I need to schedule time with him. I'll just bring that as an item and we can scan it for you!

Yep! Need to meet up with both you and Slideways in the not too distant future. The list of things to scan is growing longer every day

[Bry5on]

I need to schedule time with him. I'll just bring that as an item and we can scan it for you!

Love it. Thank you!

[YoitsTmac]

Yeah at some point here I'll make the trip up. Or Heinz can scan it

I need to schedule time with him. I'll just bring that as an item and we can scan it for you!

[Bry5on]

I have one rusting on my back patio. You making a trip back up? They're much easier to get ahold of though.

Yeah at some point here I’ll make the trip up. Or Heinz can scan it

[YoitsTmac]

I have one rusting on my back patio. You making a trip back up? They're much easier to get ahold of though.

[Bry5on]

For what it's worth when I was looking into those adjustable tie rod kits with some track nuts, someone said the E46 M3 knuckle retains good geometry and minimal to no bump steer when lowered and doesn't need nearly the correction a Non-M could.

As someone who daily drove a non-M for over a decade, most lowered (like my now M3), I can confirm I never even think about bump steer anymore. I'm also not an engineer and am unaware of other negative drawbacks when lowered.

That’s interesting, I wonder if this is what drove the steering ratio change? Would be interesting to scan a non-m knuckle and overlay them as I’d be surprised to see much of a difference.

[Obioban]

Center of the wheel to fender is the number I’m looking for, just in the vertical plane

13mm lower than nominal as measured purely in the Y.

[YoitsTmac]

For what it's worth when I was looking into those adjustable tie rod kits with some track nuts, someone said the E46 M3 knuckle retains good geometry and minimal to no bump steer when lowered and doesn't need nearly the correction a Non-M could.

As someone who daily drove a non-M for over a decade, most lowered (like my now M3), I can confirm I never even think about bump steer anymore. I'm also not an engineer and am unaware of other negative drawbacks when lowered.

[Bry5on]

Just went out and measured (never had before-- set height by bump/droop travel, and then corner balanced from there), and it appears my car is 13mm lower than nominal/spec e46 M3 ride height.

So, I guess for me, 13mm would be optimal...

... or is it less, since I'm measuring at the face of the wheel and there's some motion ratio effect? Maybe 12mm would be optimal...

Center of the wheel to fender is the number I’m looking for, just in the vertical plane

[Obioban]

I took a look at this last night in more detail. Cursory analysis limits it at about 15mm before you need to change Ackerman or kingpin inclination axis as the tie rod will impact the heat shield if you go any lower. At about 30-35mm lower the tie rod will actually impact the rotor. Now I see why Porsches run 50mm front offsets without such flat wheels, it’s a hell of a packaging challenge. One way to gain clearance is to move the rotor out a few millimeters, which would then necessitate higher offset front wheels to maintain reasonable scrub. It’s doable but you introduce tradeoffs, which in my opinion would be worth accommodating.

You’d also be able to run 18s in either scenario.

Just went out and measured (never had before-- set height by bump/droop travel, and then corner balanced from there), and it appears my car is 13mm lower than nominal/spec e46 M3 ride height.

So, I guess for me, 13mm would be optimal...

... or is it less, since I'm measuring at the face of the wheel and there's some motion ratio effect? Maybe 12mm would be optimal...

[Bry5on]

I wish my car wasn't lowered at all. Aftermarket shocks often just don't play nicely with that-- if you want any droop travel, often you must lower the car (especially in the front).

... let me ponder the optimal amount it would target. Certainly don't want to get into a situation where 18s are no longer viable (don't know if we'd be anywhere close to that).

Just release it as for fun online viewing of CAD files, not for use on cars, etc :P

I took a look at this last night in more detail. Cursory analysis limits it at about 15mm before you need to change Ackerman or kingpin inclination axis as the tie rod will impact the heat shield if you go any lower. At about 30-35mm lower the tie rod will actually impact the rotor. Now I see why Porsches run 50mm front offsets without such flat wheels, it’s a hell of a packaging challenge. One way to gain clearance is to move the rotor out a few millimeters, which would then necessitate higher offset front wheels to maintain reasonable scrub. It’s doable but you introduce tradeoffs, which in my opinion would be worth accommodating.

You’d also be able to run 18s in either scenario.