[ZHP]

Originally Posted by Volke

... I'd be willing to take some measurements and try to figure out the difference if I can get my hands on a 330 knuckle.

I'm not sure if you got my PM. I offered to buy a 330 steering knuckle and have it shipped to you to compare. Interested?

[Obioban]

Originally Posted by Volke

They do not increase track at all. I have a set waiting to go on my car. I measured all the relevant dimensions that would impact track and compared to the regular M3. There was no difference.

What I did find is that they add ~1 degree more negative camber without changing the SAI(steering axis inclination).

I didn't understand why they would do this instead of using camber plates at first, so I spoke to someone much more knowledgeable about suspension geometry. Here's what I found out...

Camber plates add negative camber by moving the top strut mount toward the center of the car. Unfortunately, on a MacPherson strut front like the E46, moving the top mount inward also increases SAI. Larger SAI results in more caster loss as the wheels are turned left or right, and in turn, less effective caster throughout the range of motion results in more positive camber gain.

Note this doesn't contradict the opening post. Caster is measured with the wheels turned to a certain angle, so you would see more caster with the CSL knuckles installed.

A car with CSL knuckles will maintain more caster and gain less positive camber throughout the full range of motion of the wheels. It should also have "better" steering feel, but that's subjective and hard to quantify. Theoretically, a track car with CSL knuckles can achieve the same side to side tire wear and temperature distribution with less static negative camber than a car with the regular M3 knuckles. This is especially nice for dual purpose cars because running a lot of static negative camber will cause the inner edge of the tire to wear faster than the outside when cruising on the highway or driving around town.

For a dual purpose or primarily street driven car like the stock CSL, it makes a lot of sense why they would go through the trouble of creating a new knuckle part number instead of just messing around with the strut top mount. I'm not sure if the CSL knuckles are worth it on an all-out racecar though unless you're having trouble getting enough negative camber since straight line tire wear is not that big of a concern, and the only other benefit is "better" steering feel.

... Damn it, now I want a set.

[M spec]

Originally Posted by Obioban

... Damn it, now I want a set.

Same, this is a substantial upgrade.

[idntknow2005]

Part numbers?

[M spec]

Originally Posted by idntknow2005

Part numbers?

https://www.ecstuning.com/b-genuine-...31212282855kt/

Now days you can literally google "e46 m3 (insert part name here)" and ECS Tuning will pop up as one of the first results, no part # needed to search! Love how well they've done their SEO

[Obioban]

This thread is going to make BMW run out of stock on these :P

... I wonder if they'll make more

[Volke]

Quick update: My 330 knuckle came in today. Took some quick measurements, and found that it appears to add ~1 degree of positive camber from the regular M3 knuckle. This means it has ~2 degrees more positive camber than the CSL knuckle. The non-M knuckle is a completely different casting from the M3 & CSL knuckles which only differ a little in the lower strut mount machining.

It also locates the steering tie rod ball joint a little closer to the LCA ball joint, so it quickens the steering ratio a bit.

[ZHP]

Volke, thank you again for sharing this info.
How about the roll center? Is the ball joint further from the axle, vertically, on the M3 than the 330?
I recently heard the ball joint taper was smaller on the 330 than the M3, can you confirm that.

[terraphantm]

I've always been a little curious about why BMW did things the way they did on the Z4M - wonder if you have any thoughts on the matter as a mechanical engineer.

Basically the Z4 non-M has the same steering knuckle as the E46 non-M. But the Z4M steering knuckle is fairly different from the E46 M3 knuckle. The shock bolts onto the knuckle (E36 style) rather than fitting through the ring like on the E46 / Z4 non-M (pictures below)





Any thoughts as to why they'd essentially go back to an earlier design? Is there an advantage of one method over the other?

[twentyseven]

Originally Posted by M spec

https://www.ecstuning.com/b-genuine-...31212282855kt/

Hmm... why does their description claim it adds 10mm track width when Volke says they don't?