Black & Tan 332iT

[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.

[Obioban]

Well, my car isn't lowered, so...

I may give it a shot after the first prototype shows up - got an ideal target for lowering? 30mm? One nice thing is that the loads will be lower on that version because the ball joint will be closer to the ground.

I'm still pretty hesitant to let this out into the wild given the liability/risk of a failed part though honestly.

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

[Bry5on]

Given any thought to moving the lower mount points downward, to restore geometry for lowered cars?

Well, my car isn't lowered, so...

I may give it a shot after the first prototype shows up - got an ideal target for lowering? 30mm? One nice thing is that the loads will be lower on that version because the ball joint will be closer to the ground.

I'm still pretty hesitant to let this out into the wild given the liability/risk of a failed part though honestly.

[Obioban]

Given any thought to moving the lower mount points downward, to restore geometry for lowered cars?

[Obioban]

I can feel the weight savings in my wallet, looking at these pictures 🤣

[George Hill]

I didn't want to steal @Bryson thunder, but I have been man handling the latest design for a couple days now and its really impressive.

The part is 255mm "tall" and my printer max dimension is 256mm so pretty tight, but we got it fitted. After a couple fails I got a mostly "perfect" print.










The ball joint inserts printed in a different color and press nicely into the knuckle (and yes, I realize I could have picked a better color lol)




I really thought this was cool to see the evolution of his design and idea. The red one is the very "first" design compared to now. Bryson will correct me if I am wrong but if I recall the green one is stronger but still the same weight as the red one.

[Bry5on]

Ran a quick analysis on the stock parts assuming they're a similar enough material to 4340 and here we go - large deformations leading to camber loss. 11.5mm of displacement at the strut tower ~= 1 degree of camber. So at 1.6G, the factory parts are losing 7.2/11.5 = 0.63 degrees of camber, compare this with 2.0/11.5 = 0.174 degrees of camber in the latest knuckle version. Excellent.

[Bry5on]

Thanks guys, I’m enjoying this project as it’s giving me a chance to really test out Fusion 360 and generative design.


Tonight I worked on some lightweighting and managed to get this down to a .09kg weight penalty over the single clamp version. So we’re pretty much maintaining the 1lb (.92lb) unsprung mass reduction. Pretty good I’ll say!

And thanks to a member on e46fanatics we now have a visual and measurement of heatshield clearance - 3.25mm to the rotor - snug.

The latest:


Off to the printer(s) we go! (George is printing one too)

[D-O]

Wow. Just wow...

[enjoy_m3]

Very cool, so many cool parts comming between you and the carbon doors. Excited about building my wagon, funding not so much, lol. I have a set of f80 brakes sitting if you need to test fit.

[Bry5on]

That thing is spooky! Nothing like anything I've seen. Is your 1.6G load testing peak or average load test? What happens when you hit a hard bump at full load?

What is the issue re clearance to ZCP rotor? Isn't your rotor mounting surface distance to the tie rod equal to stock when looking down on the Z axis? If geometry is staying the same, then those parameters should all be equal, including clearance, no? I'll have to give you my stock clearance of my BBK, which Heinz notably pointed out the PO cut the shield or else I'd give you the measurements you're looking for

Yeah the output is pretty wild. I used some conservative numbers in there (full half car weight on the strut), extra loads for dynamic steering inputs at the limit, and also chose 1.6G as a pretty conservative limit case. The rest is taken up by the safety factor.

Clearance to the ZCP rotor is really just for verification purpose as I never scanned a rotor, even though it's the same as stock (plus those heat shields were a little bent . Trying to make sure I validate all possible mistakes here before I place any expensive orders. I got a STEP file of the ZCP rotors so I'll print a section and do a digital and physical test fit shortly!

[YoitsTmac]

That thing is spooky! Nothing like anything I've seen. Is your 1.6G load testing peak or average load test? What happens when you hit a hard bump at full load?

What is the issue re clearance to ZCP rotor? Isn't your rotor mounting surface distance to the tie rod equal to stock when looking down on the Z axis? If geometry is staying the same, then those parameters should all be equal, including clearance, no? I'll have to give you my stock clearance of my BBK, which Heinz notably pointed out the PO cut the shield or else I'd give you the measurements you're looking for