Alignment Z4M Vs M3 CSL

[daz05]

I thought it would be interesting to post the differences between the CSL and Z4Ms standard alignment figures, data taken from TIS, figures in the are degrees and minutes. I'm not sure if these are for the Coupe or the Roadster, but there didn't seem to be a difference.

Front total Toe (in) – 0 deg 4' vs 0 deg 10' - Zed has less responsive turn but more straight line stability.

Front Camber – 1.45 vs 1.00 - self explanatory

Caster (non adjustable) – 7.3 vs approx 5.7 – CSL steering as a result will be harder to turn, i.e. stiffer.

Rear total toe (in) – 0 deg 4' vs 0 deg 28' – significant difference here, the Zed is set up to be much safer at the back, which results in more understeer.

Rear Camber – 1.50 vs 1.50

I think the alignment set up is one of the main reasons the CSL gets such a good write up for road use. Key differences for me are that the CSL is far more neutral between front and rear, with both the camber and toe being similar, the Z4M in comparison has significantly more camber and toe in at the rear than it does up front, resulting in a safer but less entertaining driving experience. Some of the motoring journos said at launch that there was almost a disconnect between the front and the rear, I think this goes part of the way to explain why.

Anyway, using this data and some advice from Exdos I went for an alignment slightly closer to the CSL settings and am gutted that I waited so long to do it!

 

[wantanM]

That's interresting. Have noticed the improvement on a good mix of roads?

Mine is due an alignment soon and tempted to experiment a bit. Do mind me asking what settings you went for? I've tried to read exdos' posts but I don't understand most of them.

 

[exdos]

I've tried to read exdos' posts but I don't understand most of them.

Why's that? I always try to write about technical stuff in simple straight-forward language with the least use of jargon as possible?

 

[wantanM]

No offence intended exdos, I'm not from an engineering background. Your posts are always very detailed, but I just don't have the fundamental knowledge to follow a lot of it.

 

[exdos]

Anyway, using this data and some advice from Exdos I went for an alignment slightly closer to the CSL settings and am gutted that I waited so long to do it!

Daz,

I can see that you're getting a taste for this. Once you know how to do the adjustments and keep proper notes of what you've done, it's so easy to reset the geometry to OEM (or any other "safe" baseline settings) if you've tried some settings that you find you don't like. By experimenting with different geometry you get to understand how your driving technique and geometry settings are inter-linked and after a while, you instinctively can feel how the car is set up and adapt to it.

It amazes me that so few Z4MC owners on this forum except Beedub and a couple of others have done any significant performance/suspension mods

 

[exdos]

No offence intended exdos, I'm not from an engineering background. Your posts are always very detailed, but I just don't have the fundamental knowledge to follow a lot of it.

I didn't take any offence. I was just curious to find out why.

If you are interested in the subject but don't know where to start, just do a google for some of the technical terms (i.e. camber, caster, toe etc.) and read a few different explanations and it'll soon sink in.

 

[wantanM]

No offence intended exdos, I'm not from an engineering background. Your posts are always very detailed, but I just don't have the fundamental knowledge to follow a lot of it.

I didn't take any offence. I was just curious to find out why.

If you are interested in the subject but don't know where to start, just do a google for some of the technical terms (i.e. camber, caster, toe etc.) and read a few different explanations and it'll soon sink in.

Ha ha. . . 'Time, the most precious thing we seek to control...'

 

[exdos]

Caster (non adjustable) – 7.3 vs approx 5.7 – CSL steering as a result will be harder to turn, i.e. stiffer.

That's wrong. More caster makes turning easier because it sets up more negative camber on the outer front wheel when the car is turned. I've got front caster/camber plates on my Z3MC and the OEM caster setting is around 9 degrees, but if you increase negative camber only, the steering becomes far too reactive. So if you increase negative camber on that car, you need to reduce caster to compensate.

 

[daz05]

Could well be wrong I took that from Tire Rack's website.

I read more positive caster = more steering effort http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4

"Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tire lean when cornering (almost like having more negative camber) as the steering angle is increased".

"What's the downside to positive caster? If thevehicle doesn't have power steering, a noticeable increase in steering effort will be felt as positive caster is increased. Other than that, the effects of positive caster are pretty much "positive," especially increasing the lean of the tire when the vehicle is cornering while returning it to a more upright position when driving straight ahead."

 

[exdos]

Could well be wrong I took that from Tire Rack's website.

I read more positive caster = more steering effort http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4

"Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tire lean when cornering (almost like having more negative camber) as the steering angle is increased".

"What's the downside to positive caster? If the vehicle doesn't have power steering, a noticeable increase in steering effort will be felt as positive caster is increased. Other than that, the effects of positive caster are pretty much "positive," especially increasing the lean of the tire when the vehicle is cornering while returning it to a more upright position when driving straight ahead."

The quote actually points out that this only really affects a car without PAS. I don't really notice any difference in steering effort in the Z4MC with 5.7 degs of caster and the Z3MC with 9 degs of caster.

 

[daz05]

Fair enough John I won't be arguing with the alignment Jedi anyway

And in answer to the previous question, yes I have done lots of testing and am very happy with the outcome, far better drive on the local a and b roads.

 

[exdos]

And in answer to the previous question, yes I have done lots of testing and am very happy with the outcome, far better drive on the local a and b roads.

Daz,

The information in your initial posting in this thread shows that the handling of the Z4MC is "strangled" by all that toe-in, particularly at the rear end. It seems to me that BMW didn't want to produce another car with the very tricky handling of the Z3MC. :wink:

 

[RedUn]

FWIW From messing with previous cars more caster = more effort required.

It's interesting to see the comparison between the two, it's worth noting that less caster is actually better on track so don't feel robbed by the CSL settings.

exdos, I wouldn't say the car is strangled by the toe at the rear, I actually like that theres a lot of grip at the back?!

 

[Lower]

Increasing castor does increase the steering weight as increasing the castor means that you are tipping the tyre further onto it's edge when you turn the wheel. You are actually lifting the front of the car slightly as you wind on the lock.

Whether its actually noticeable or not depends on the car and how good the power steering is.

 

[RedUn]

Lower, good to see you around again, seems we've both gone to the dark side!

 

[daz05]

And in answer to the previous question, yes I have done lots of testing and am very happy with the outcome, far better drive on the local a and b roads.

Daz,

The information in your initial posting in this thread shows that the handling of the Z4MC is "strangled" by all that toe-in, particularly at the rear end. It seems to me that BMW didn't want to produce another car with the very tricky handling of the Z3MC. :wink:

Looks that way doesn't it, the car deliberately strangled, possibly because they thought it was too twitchy. It's like they half wanted to make the Coupe hardcore, stiffer damping, faster steering and then backed out at the last minute supplying crap tyres, overactive DSC system and a wimpy geo. :headbang:

I would also add that I think all that toe in actually makes it harder to catch when it does go.

Nevertheless the point stands that this is a very capable car and with the right tweaking, suspension and alignment it can be a great car.

exdos, I wouldn't say the car is strangled by the toe at the rear, I actually like that theres a lot of grip at the back?!

Yes you like the security but that hurts the front end, you drive the CSL for example, and you feel the rear end helping to push you into the turn under braking whereas the Zed is trying to push you straight on.

We have more tow in at the rear than the E46 and the E92 M3s.

 

[daz05]

Something controversial to add, the roadster has a slightly more aggressive geo than the coupe

Less toe in up front and less toe in at the rear, total figures are 0 deg 04 and 0 deg 22. Camber unchanged.

Very strange!

 

[ChawenHalo]

Daz 05 and Exdos. Sorry if I've missed a post or 2 what geo allignment setting are you now running of the Z4MC?

Are you getting a better feel through the streering wheel? (one thing I don not like on the car is that numb feeling in you hands).

nteresting ton read the comment on that slightly disjointed feeling. I'm coming top the end of my rear tyres and as I was canning it this morning on the twisties it did feel like the back was fighting the front... not quite following through. At least that's how I read the car but this subject is well outside my competence :roll:

 

[exdos]

Daz 05 and Exdos. Sorry if I've missed a post or 2 what geo allignment setting are you now running of the Z4MC?

I'm now running with almost zero toe-in at the front and rear, and -1.3 degree camber at the front and < -1 degree camber at the rear. My suspension is now far from OEM and so I can use this geometry because my car now remains flatter at all times.

 

[daz05]

Mine is fairly close to the above also, but slightly less aggressive with similar settings front and rear to make things more neutral.

Steering feel is 'maybe' slightly better but not a significant improvement, now the car isn't pushing me left and right on bumpy British roads, the steering is more relaxed and less busy than before.

As I said the biggest improvement for me is at the rear where I can feel it helping me to turn.