Help me understand suspension geometry.

[SLR]

details? I want. Looks like it'll add ride height too.

Price will be $188 for the set. In order to get the hardware to sit recessed we use a 19mm plate. Most camber plates are 10-13mm, and since the strut top slopes upward toward the outside, you save a few mm there if you're running at max width so it's not a huge issue. The bearing still sits higher up in the tower than OEM for sure though.

[SLR]

Hey NovaBlue (Justin right ?).

Just wanted to add that you might consider running E36 knuckles on your car. With a lot of coilovers you can just get the E36 lower piece and just swap.

The really nice thing on E36 knuckles is you can adjust the KPI. Basically you can use shims to decrease KPI so the wheel is closer to the actual steering axis angle, meaning flatter contact patch at full lock. This is actually one of the reasons we never switched to E46 knuckles on Chelsea's car.

http://www.bimmerworld.com/Suspensio...him-Kit_2.html

You can go cheapo-depot by just using washers and locktite. Make sure you get longer bolts though, and 10.9grade minimum,preferrably 12.9

[protomor]

To clarify. Sean means the picture below. E36 knuckles attach via a through bolt up top but two mounting bolts to the strut. You can shim where it sits to the strut to dial out camber (negative).
Capture.PNG

Here is the E46 one. It just sets into a socket from the strut (ew).
Capture1.PNG

Sean. What's the negative of swapping knuckles? Is the wheel position the same regardless? Or does this put the wheel farther forward/backward/higher/lower in the wheel well? Are all E36 knuckles the same or do we need M3 stuff? Can we just bolt back on the E46 hub/assembly or do we have to downgrade to E36 brake bits? So many questions >_<

[Novablue454]

Hmm. Good to know. I think at this point in time new knuckles/brakes/coilovers/etc is a bit too much work for a flatter contact patch, but it is def good info to have!

And yep, I'm Justin.

[protomor]

I'm having a hard time finding measurements but if the E36 shock is the same diameter as the E46 one (and a similar height I suppose), you could just pick up E36 M3 knuckles and struts to do the swap. Which is why I'm asking questions. The M3 front brakes are bigger than E36 M3 front brakes. IIRC M3 front brakes are the same size as E46 330s.

[Press22]

I think you would ideally run the Non-M E36 Knuckle, E46 330 Brakes (which are bigger than E36 M3)
And if you have say BC coils you can just order up the bottom of your strut for the change.

Here you can see Chelsea's with some flat spacers on there
chelsea.JPG
https://www.youtube.com/watch?v=EFXADBd0UEU - Link to video

[tptrsn]

So what changing KPI do differently than changing camber? Something to do with the steering offset distance I guess, but what is the effect? As in, what "feel" change is noticed from this?

[SLR]

So what changing KPI do differently than changing camber? Something to do with the steering offset distance I guess, but what is the effect? As in, what "feel" change is noticed from this?

This gets complicated, KPI and caster both affect how much the camber of the tire changes throughout the steering range.

Static camber wont increase the amount of dynamic camber relative to the road as much as the same adjustment to KPI. I would only add shims (reducing KPI) on non-M knuckles or 1993-1995 M3 knuckles. The 1996+ M3 knuckles are machined with less KPI from the factory.

[SLR]

Hmm. Good to know. I think at this point in time new knuckles/brakes/coilovers/etc is a bit too much work for a flatter contact patch, but it is def good info to have!

And yep, I'm Justin.

I'm 97.4% sure E36 non-M and E46 non-M brakes are interchangeable. the 330i brakes are the easy way to put E36M3 size brakes on a 325i/328i without the M3 knuckle (more caliper offset required).

So basically, if you have BC's all you need is a set of junkyard knuckles and these: https://store.bcracing-na.com/lower-...sm3-p4522.aspx


A lot of guys prefer the trail of the E36 non-M knuckles.

[tptrsn]

So for '97 non-M knuckles for example , you would add shims at the bottom, and push the top of the strut outward?

My surfing the net seems to tell me that the KPI is determined by the line from pivot point at the top of the strut and the lower ball joint... So to me it seems like you would tend to increase negative camber by adding shims more so than decreasing KPI? Or is it the idea of the relationship between negative camber and KPI that we're messing with by adding shims?

Said another way, I'm having a hard time envisioning how adding the shims is really changing the KPI as much as it is adding negative camber so you can then move the strut top outward which will give you reduced KPI when you get the wheel back to the same camber setting as you were at without the shims.... So confused.

[SLR]

So for '97 non-M knuckles for example , you would add shims at the bottom, and push the top of the strut outward?

My surfing the net seems to tell me that the KPI is determined by the line from pivot point at the top of the strut and the lower ball joint... So to me it seems like you would tend to increase negative camber by adding shims more so than decreasing KPI? Or is it the idea of the relationship between negative camber and KPI that we're messing with by adding shims?

Said another way, I'm having a hard time envisioning how adding the shims is really changing the KPI as much as it is adding negative camber so you can then move the strut top outward which will give you reduced KPI when you get the wheel back to the same camber setting as you were at without the shims.... So confused.

KPI is defined as the difference between the plane of the wheel/hub, and the line drawn through the two ball joints (steering axis) KPI is also called SAI (steering axis inclination).

Dont confuse it with how much it's actually inclined as installed on the car. Adding 10° of camber at the strut top will not change KPI/SAI at all, since KPI is determined by how the strut mounts to the knuckle/upright.

So let's say your car has a KPI of 9° (quite common on a strut car) and your front camber is set to zero, your steering axis will be leaning inward 9°, Now if you add 3° camber, your steering axis will physically now be at 12° from vertical, but the KPI hasn't changed since they are rigidly bolted together.

Lots of strut cars with 2bolt knuckles-strut attachments will use eccentric shims to adjust camber, and consequently alter KPI at the same time.

On a car with limited steering angle, adjusting camber like this is generally fine. LMP and F1 cars still use camber shims to this day between the upper steering arm, and the benefit to this also is that they can adjust camber without affecting alignment at all. Scrub radius will be slightly affected though since the contact patch is moving relative to the steering axis.

[tptrsn]

AH!!! Makes sense now, thank you!

[Novablue454]

http://www.super7thheaven.co.uk/glos...s-inclination/

So doing the E36 knuckle swap with shims would also reduce weight jacking as well? Do we want the weight jacking effect? Sorry, this is all pretty new to me, haha

[protomor]

So non M E36 stuff is good for something? Nice! So can you use E46 shocks in E36 strut housings?

[Press22]

So can you use E46 shocks in E36 strut housings?

With a lot of coilover brands yes. BC, Broadway. Not all brands though.

[SLR]

http://www.super7thheaven.co.uk/glos...s-inclination/

So doing the E36 knuckle swap with shims would also reduce weight jacking as well? Do we want the weight jacking effect? Sorry, this is all pretty new to me, haha

Both the increase in trail and the KPI decrease will reduce jacking. With low offset wheels the scrub will big the biggest contributor to jacking force though. Jacking isn't something I would want to completely eliminate though. Some other companies believe in removing it as much as possible, but in counter-steer it helps with weight transfer and quick transitions. Scrub and jacking both also contribute to self-aligning torque.


This is why suspension is such a black art; everything you touch will screw up everything else you already got working well, so ultimately you're constantly searching for a sweet spot in compromise. Drift cars make it even more impossible because of the huge dynamic range the steering contributes.

The ultimate suspension on a drift car would incorporate an axial steering system. I have conceptual designs for it already, but it basically requires redesigning the whole front of the car.

- - - Updated - - -

So non M E36 stuff is good for something? Nice! So can you use E46 shocks in E36 strut housings?

Just check with your manufacturer. BC mostly uses M53x2.0 A lot of others use M52x2.0

[tptrsn]

The ultimate suspension on a drift car would incorporate an axial steering system. I have conceptual designs for it already, but it basically requires redesigning the whole front of the car.

Theoretically speaking, if you developed a setup like that and it worked great on Chelsea's car, it would probably be illegal for the next event, right? Lol