Comprehensive Steering Information Thread

[Obioban]

Wish I could read through the old m3f thread... Planning to do reduce my power steering pressure, how many shims is everyone doing? I have a ZHP rack and underdrive pulleys, I want heavier steering but don't want a workout while parking my car. Suggestions?

I did 2 shims/25% on both cars and have no regrets.... and my wife hasn't complained

[Obioban]

I do find it funny that pretty much all of the rack upgrades ended up being 50mm/rev and linear. and in fact to date there's nothing confirmed to be faster. You'd always hear about people calling the 330 rack a modest upgrade which had a progressive feel while others would say the Z3 rack is so twitchy that it's hard to drive on the highway. Shows how much of our perception is susceptible to suggestion.

Might have more to do with the cars they're installed in stock-- e.g. the Z3 has a short wheelbase, so it likely does feel twitchier on the highway with the same rack.

[dl.m3]

Wish I could read through the old m3f thread... Planning to do reduce my power steering pressure, how many shims is everyone doing? I have a ZHP rack and underdrive pulleys, I want heavier steering but don't want a workout while parking my car. Suggestions?

[duracellttu]

It does not. That's a myth due to the CSL having 10 mm wider track width up front. 6mm comes from the wheels being 3mm lower offset. The other 4mm is from the change in control arm angle at the lower ride height.

The CSL king pins either add 1 degree static negative camber without increasing SAI by 1 degree like you get using camber plates to make the same adjustment, or they decrease SAI while keeping static camber the same. Just depends how you align your car. Either way, the result is your car loses slightly less caster when you turn the wheels off center compared to a regular M3 with the same camber specs, and that means you gain a little less positive camber when the wheels are turned. I've heard it makes turn in feel a little better, but I cannot confirm.

I'll add more about the king pins and the effects on suspension geometry to the original posts when I get a chance. Promised some guys on FB I would do that too.
.

Thanks Volke! I was one of those guys on FB

[bigjae46]

I have the shims...it’s fantastic. I recommend it for any track car.

[Johnvu]

_{Just got the shims installed! I should have the car up and running this week! Can't wait!}

[terra]

The nice thing is all the 50mm/rev racks should play well with MK60 DSC set to ZCP steering.

Yep, makes things a lot easier

[Volke]

I've read that the CSL king pin gives a wider stance by 10mm. Can you confirm that?

It does not. That's a myth due to the CSL having 10 mm wider track width up front. 6mm comes from the wheels being 3mm lower offset. The other 4mm is from the change in control arm angle at the lower ride height.

The CSL king pins either add 1 degree static negative camber without increasing SAI by 1 degree like you get using camber plates to make the same adjustment, or they decrease SAI while keeping static camber the same. Just depends how you align your car. Either way, the result is your car loses slightly less caster when you turn the wheels off center compared to a regular M3 with the same camber specs, and that means you gain a little less positive camber when the wheels are turned. I've heard it makes turn in feel a little better, but I cannot confirm.

I'll add more about the king pins and the effects on suspension geometry to the original posts when I get a chance. Promised some guys on FB I would do that too.

Good to see this thread back. I was the one who measured the Z4MC racks on the old thread, I measured a reman one direct from BMW and one that came factory from a car. Both were 50mm\rev linear. I also measured a variety of z3 racks, 1.9 and 2.5s. Again all 50mm\rev linear. I think it's safe to say that until proof of the contrary 1.9l z3s don't have a quicker ratio (read a couple times that some are actually slower, but I've never seen one myself).

Interestingly I also measured a rack that supposedly came from a prototype Z4MC in germany, but it had a Z4M roadster original part#. It also measured 50mm\rev linear.

Sorry can't remember all the part#s off the top of my head. I'll try to update later with them.

I'll update the Z3 rack. I'm not really surprised all the Z3 racks are the same. IIRC, the last time I tried looking, realOEM listed the same steering rack part number for both 1.9L and 2.5L.

I do find it funny that pretty much all of the rack upgrades ended up being 50mm/rev and linear. and in fact to date there's nothing confirmed to be faster. You'd always hear about people calling the 330 rack a modest upgrade which had a progressive feel while others would say the Z3 rack is so twitchy that it's hard to drive on the highway. Shows how much of our perception is susceptible to suggestion.

The nice thing is all the 50mm/rev racks should play well with MK60 DSC set to ZCP steering.

[terra]

I do find it funny that pretty much all of the rack upgrades ended up being 50mm/rev and linear. and in fact to date there's nothing confirmed to be faster. You'd always hear about people calling the 330 rack a modest upgrade which had a progressive feel while others would say the Z3 rack is so twitchy that it's hard to drive on the highway. Shows how much of our perception is susceptible to suggestion.

[lapoune]

Do we have a Z4MR rack measurement? It's quoted as being a slower rack. If it's proportional to linear displacement, I guess it'd be ~47mm/rev

Yeah that's why I was surprised. Mine had non-reman part# from a Z4MR but BMW might have messed with it. Would be interesting as I don't see how the two cars can have different ratios with the same racks.

[terra]

Do we have a Z4MR rack measurement? It's quoted as being a slower rack. If it's proportional to linear displacement, I guess it'd be ~47mm/rev

[lapoune]

Good to see this thread back. I was the one who measured the Z4MC racks on the old thread, I measured a reman one direct from BMW and one that came factory from a car. Both were 50mm\rev linear. I also measured a variety of z3 racks, 1.9 and 2.5s. Again all 50mm\rev linear. I think it's safe to say that until proof of the contrary 1.9l z3s don't have a quicker ratio (read a couple times that some are actually slower, but I've never seen one myself).

Interestingly I also measured a rack that supposedly came from a prototype Z4MC in germany, but it had a Z4M roadster original part#. It also measured 50mm\rev linear.

Sorry can't remember all the part#s off the top of my head. I'll try to update later with them.

[duracellttu]

I've read that the CSL king pin gives a wider stance by 10mm. Can you confirm that?

[Volke]

The Z4MC rack was measured by another member at 50mm/turn.
He also posted the part nb which confirms it’s a Z4MC rack. Unfortunately that is now lost on the old forum.

Thanks, I will update it!

[silaciM3]

The Z4MC rack was measured by another member at 50mm/turn.
He also posted the part nb which confirms it’s a Z4MC rack. Unfortunately that is now lost on the old forum.