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      01-02-2013, 06:08 AM   #23
exdos
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Quote:
Originally Posted by tikamak View Post
What's this? "my handling taste and requirements"
So are you suggesting that you don't have preferred "handling tastes"?

If you've ever spent any time adjusting various things on a car, such as damper settings, geometry and ARBs etc., you car can be made to handle in a host of different ways, some of which make the car easier to handle and others which make it worse. If you're sufficiently perceptive, skilled and experienced as a driver and mechanic, you can diagnose the handling configuration and hone the set up, so that you can make the car behave in a predictable manner with your driver inputs. If you understand the physics and vehicle dynamics of cars in motion, then it's a logical process of making the necessary adjustments to make the car behave predictably to your driver inputs.
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      01-02-2013, 06:15 AM   #24
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Quote:
Originally Posted by GuidoK View Post
That's a very clear explanation, thx
So the dynamic camber created is sufficient to produce the grip for turning in.
Exactly. An increase in negative camber only when it's required (i.e on the outside front wheel when turning).

Quote:
Originally Posted by GuidoK View Post
What's ACS? A brand or so?
AC Schnitzer see: http://www.ac-schnitzer.de/ I'm sure you know of them.
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      01-02-2013, 06:24 AM   #25
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Quote:
Originally Posted by exdos View Post
So are you suggesting that you don't have preferred "handling tastes"?

If you've ever spent any time adjusting various things on a car, such as damper settings, geometry and ARBs etc., you car can be made to handle in a host of different ways, some of which make the car easier to handle and others which make it worse. If you're sufficiently perceptive, skilled and experienced as a driver and mechanic, you can diagnose the handling configuration and hone the set up, so that you can make the car behave in a predictable manner with your driver inputs. If you understand the physics and vehicle dynamics of cars in motion, then it's a logical process of making the necessary adjustments to make the car behave predictably to your driver inputs.
No i'm asking you what's your handling taste and i was hoping that your answer will include on which track you were having problems but never mind, i'm not interested to know. Sorry to bother.
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      01-02-2013, 06:36 AM   #26
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Quote:
Originally Posted by Beedub View Post
Tika ,exdos, is soooooo far from a stance idiot, he other end of the scale he's a proper engineer. He added rake angle to his car for nothing other than performance I can assure you :-)
My answer was specifically to the redbull F1 raked car and HACK's post, not attacking exdos or his knowledge.

I don't like the term "rake", or "adjusting rake", i like "corner balancing".
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      01-02-2013, 06:43 AM   #27
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Quote:
Originally Posted by exdos View Post
AC Schnitzer see: http://www.ac-schnitzer.de/ I'm sure you know of them.
Yes I know

Still, cars that are known to steer very directly tend to use very small caster angles. An elise for example has a caster angle smaller than 4 deg.
Do you know the stock caster angle from a Z4?
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      01-02-2013, 06:47 AM   #28
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Quote:
Originally Posted by tikamak View Post
No i'm asking you what's your handling taste and i was hoping that your answer will include on which track you were having problems but never mind, i'm not interested to know. Sorry to bother.
I'm quite happy to hustle any car and drive it as it comes. I don't have any trouble driving the Z4MC hard in its OEM format, but I knew before I bought my Z4MC that I could make it handle so much better as well as improve the bloody awful uncomfortable ride, and make my driving experience more enjoyable by modifying the suspension and set up to give the car predictable neutral handling. I've already got a heavily modified Z3MC which I've had for 10 years, of which I transformed the handling, and I wanted to do the same to my relatively newly acquired Z4MC.
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      01-02-2013, 06:50 AM   #29
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Quote:
Originally Posted by GuidoK View Post
Yes I know

Still, cars that are known to steer very directly tend to use very small caster angles. An elise for example has a caster angle smaller than 4 deg.
Do you know the stock caster angle from a Z4?
IIRC, the Z4MC has a caster angle of 5 degrees. In comparison, the Z3 MC has a caster angle of around 9 degrees. As always, there's many different ways of achieving a result, but by experimentation, it's sometimes possible to find tweaks which makes things even better.
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      01-02-2013, 07:08 AM   #30
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Quote:
Originally Posted by tikamak View Post
My answer was specifically to the redbull F1 raked car and HACK's post, not attacking exdos or his knowledge.
I don't like the term "rake", or "adjusting rake", i like "corner balancing".
Tikamak,

Likewise, I'm not attacking you in answering your replies.

I'm afraid that we have to use the conventional terminology between ourselves so that we can exchange information and discuss our opinions. The term "rake" simply expresses the angle that the plane of the underside of the car makes with the road. It is highly relevant to the aerodynamic configuration of vehicles. If by "corner balancing" a vehicle you end up lowering the rear end of the car so that the plane of the underside of the car makes a "negative rake angle" (i.e. you can see the underside of the car when looking from the front of the car) you will increase drag and consequently increase aerodynamic lift. This will both slow the car down and reduce grip. Therefore, why would anyone wanting to improve the performance of a car wish to prefer to think solely in terms of corner balancing whilst at the same time choosing to ignore the importance of rake? I'm not wishing to be argumentative, just trying to be objective and logical.
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      01-02-2013, 09:35 AM   #31
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Quote:
Originally Posted by exdos View Post
Tikamak,

Likewise, I'm not attacking you in answering your replies.

I'm afraid that we have to use the conventional terminology between ourselves so that we can exchange information and discuss our opinions. The term "rake" simply expresses the angle that the plane of the underside of the car makes with the road. It is highly relevant to the aerodynamic configuration of vehicles. If by "corner balancing" a vehicle you end up lowering the rear end of the car so that the plane of the underside of the car makes a "negative rake angle" (i.e. you can see the underside of the car when looking from the front of the car) you will increase drag and consequently increase aerodynamic lift. This will both slow the car down and reduce grip. Therefore, why would anyone wanting to improve the performance of a car wish to prefer to think solely in terms of corner balancing whilst at the same time choosing to ignore the importance of rake? I'm not wishing to be argumentative, just trying to be objective and logical.
Having this cleared away, I can join the discussion again

Can you please send me your alignment, front and rear height in mm taken from the bottom end of the wheels to the gap of the fender.

To make it easier for both us please fill it in here so that i compare it to mine:

Front:
Height =
Caster =
Toe (total toe) =
Camber =

Rear:
Height =
Caster =
Toe (total toe) =
Camber =
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      01-02-2013, 11:01 AM   #32
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Quote:
Originally Posted by tikamak View Post
Having this cleared away, I can join the discussion again

Can you please send me your alignment, front and rear height in mm taken from the bottom end of the wheels to the gap of the fender.

To make it easier for both us please fill it in here so that i compare it to mine:

Front:
Height =
Caster =
Toe (total toe) =
Camber =

Rear:
Height =
Caster =
Toe (total toe) =
Camber =
Not a problem.

Here's the information you want.
Front:
Height = 592mm (OEM = 607mm 10mm)
Caster = OEM
Toe (total toe) = 0 degs
Camber = -1.6 degs (pins removed and OEM top mounts at maximum negative camber)

Rear:
Height = 605mm (OEM = 594mm 10mm)
Toe (total toe) = 0 degs
Camber = -1.15 degs
Caster doesn't apply at the rear.

Additionally, I've measured the height of the cill on a level floor immediately behind the front wheel (=138mm) and immediately in front of the rear wheel (= 158mm). Although the Z4MC doesn't have a flat floor or undertray, the bottom edge of the cill, being straight, gives an indication of a rake angle, and with my figures, this produces a positive rake angle of 0.66 degrees (OEM = +0.55 degrees). Whilst my rake angle has only been increased slightly, in degrees, the real effect of this change is that the gap between the bumper and the road has been reduced by about 25mm, which reduces the volume of air passing under the car, which according to the laws of Physics (Bernoulli), creates a zone of low pressure beneath the front of the car, which is also encouraged by the aerofoil shape in the OEM plastic undertray beneath the engine. In turn there is a zone of high pressure on top of the hood, with the net effect of reducing the tendency to lift.

By ensuring that there is a positive rake angle beneath the car, this additionally helps to increase the speed of air passing under the front of the car, which contributes to the increase in low pressure beneath the front of the car.

As I've said in an earlier post, the OEM springs at the front are made of 11mm wire, which permits excessive lift under acceleration, which opens the gap at the front of the car between the bumper and the road, probably by as much as 40mm or more, whereas with stiffer springs of aftermarket suspension, there is considerably less lift. Therefore, with an OEM set up, under acceleration there will be a dynamic reduction in rake angle, which might open the gap between the bumper and the road by a further 50mm, and by a total of some 75mm more than might occur with my car with an increased static rake angle and with stiffer aftermarket front springs which prevent lifting under acceleration. I can only see this as an advantage and not irrelevant as suggested by those claiming that attention to rake angle is unimportant.
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      01-02-2013, 04:41 PM   #33
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sorry about the rear caster, it was copy paste thing.

Mine is a Roadster and alignment is as follows:
Front:
Height = 10 mm lower = 598mm
Toe (total toe) = 1/16th
Camber = -2.3 degs

Rear:
Height = 10 mm lower = 585mmm
Toe (total toe) = 1/32nd
Camber = -1.8 degs

The car cuts corners like a samurai katana on speeds above 120+ mph.
Understeer is reduced.

It drives like it's guessing where you want to steer, it's very telepathical.
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      01-02-2013, 09:25 PM   #34
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I appreciate the responses everyone! I think I am just going to tell the shop to corner balance the car as first priority and if it makes sense to add rake while corner balancing it then to go ahead and do so.
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      01-03-2013, 04:37 AM   #35
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Quote:
Originally Posted by tikamak View Post

Mine is a Roadster and alignment is as follows:
Front:
Height = 10 mm lower = 598mm
Toe (total toe) = 1/16th
Camber = -2.3 degs

Rear:
Height = 10 mm lower = 585mmm
Toe (total toe) = 1/32nd
Camber = -1.8 degs
From what you've written before, am I correct to assume that the ride heights that you've got have been produced purely as a result of adjustment for corner weighting?

What are your cornerweights? What suspension do you have?

Here's a parts diagram for the front bumper. Part 23 (part number 51 11 3 442 832) which is described as "front spoiler". I wonder why BMW put this part on the car if rake and reducing the space under the front bumper is unimportant?

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      01-04-2013, 01:36 AM   #36
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I have found that raising the height in the rear will make the car squat a little too much on hard acceleration and induce understeer on high speeds.

I have prefered to keep the car rake stock then I used camber shim kit instead of camber plates in order to keep the scrub angle negative and closer to 0.

I lowered the car 9 mm front and 12 mm in the back:
1- To get closer to 50/50 (stock is 53/47)
2- I removed some weight in the rear more than the front
3- To gain the extra negative camber instead of using more shims and to keep an ideal scrub angle
4- Lower center of gravity.

I put some toe in front and rear about 1.2mm front and 1mm rear.

The cars handling is unbelievable, the grip is just too impressive, and i find myself struggling hard to break loose in second gear on a car that is pushing nearly 390hp with evolve.
Understeer is really up there on the limits of the car.

We don't have corner balancing in my country, only alignment, so I had to do the calculations by hand and based on OEM alignment figures as a reference i created the delta (delta = measurements of changes in variables).

I don't know if someone has an alignment similar to mine that can shine in.
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      01-04-2013, 09:03 AM   #37
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Tikamak,

This might help. I've searched this forum and found some actual corner balancing figures. They are in Post #27 found here: http://www.zpost.com/forums/showthre...=516581&page=2 and here's the information of the Z4MC after it's been corner balanced.





As the information shows, the car has been balanced at 50:50 with the weight of the driver in the car. Since the results are using Imperial measurements and we've been using metric, I've converted those ride heights into metric as follows.

FL = 590.5mm (23 1/4") FR = 593.7mm (23 3/8") Front Average = 592.7mm
RL = 587.3mm (23 1/8") RR =590.5mm (23 1/4") Rear Average = 588.9mm

Tikamak's Ride Heights =
Front = 598mm
Rear = 585mm

Therefore your car is 6.3mm higher at the front and 3.9mm lower at the rear than a car which has been corner-balanced. I realise that your car is a Roadster but is there really a 10.2mm difference in ride heights between a Z4MC and a Z4MR?
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      01-04-2013, 03:47 PM   #38
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What can I say, I wish suspension shops over here understand the need for a corner balancing run before starting to blindly do an alignment.

I repeat that I did my calculations by hand and logic and I am satisfied with results. I might pay you and beedub a visit someday when I'm in Europe, to check your cars and have some beers.
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      01-04-2013, 07:10 PM   #39
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Quote:
Originally Posted by exdos View Post
Tikamak,

This might help. I've searched this forum and found some actual corner balancing figures. They are in Post #27 found here: http://www.zpost.com/forums/showthre...=516581&page=2 and here's the information of the Z4MC after it's been corner balanced.





As the information shows, the car has been balanced at 50:50 with the weight of the driver in the car. Since the results are using Imperial measurements and we've been using metric, I've converted those ride heights into metric as follows.

FL = 590.5mm (23 1/4") FR = 593.7mm (23 3/8") Front Average = 592.7mm
RL = 587.3mm (23 1/8") RR =590.5mm (23 1/4") Rear Average = 588.9mm

Tikamak's Ride Heights =
Front = 598mm
Rear = 585mm

Therefore your car is 6.3mm higher at the front and 3.9mm lower at the rear than a car which has been corner-balanced. I realise that your car is a Roadster but is there really a 10.2mm difference in ride heights between a Z4MC and a Z4MR?

I recognize that data
I have my own scales.
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      01-09-2013, 01:45 AM   #40
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Is there a place where i can buy scales that are not very expensive in order to properly balance my car 50/50 ?
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      01-10-2013, 02:31 PM   #41
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Quote:
Originally Posted by tikamak View Post
Is there a place where i can buy scales that are not very expensive in order to properly balance my car 50/50 ?
I think they can be had for $1000-$1500. Not too expensive, but a little more that I would swallow just to corner balance the car.

Long Acre makes some good scales.
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      01-10-2013, 03:54 PM   #42
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Quote:
Originally Posted by seank View Post
I think they can be had for $1000-$1500. Not too expensive, but a little more that I would swallow just to corner balance the car.

Long Acre makes some good scales.
Considering I couldn't find a place around here that would do a corner balance for less than $300, it's not terrible.
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      01-10-2013, 04:09 PM   #43
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Quote:
Originally Posted by tikamak View Post
Is there a place where i can buy scales that are not very expensive in order to properly balance my car 50/50 ?
I bought a used set for $550
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      03-28-2013, 05:00 PM   #44
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Quote:
Originally Posted by exdos View Post




As the information shows, the car has been balanced at 50:50 with the weight of the driver in the car. Since the results are using Imperial measurements and we've been using metric, I've converted those ride heights into metric as follows.

FL = 590.5mm (23 1/4") FR = 593.7mm (23 3/8") Front Average = 592.7mm
RL = 587.3mm (23 1/8") RR =590.5mm (23 1/4") Rear Average = 588.9mm

Tikamak's Ride Heights =
Front = 598mm
Rear = 585mm
I run Front average of 23 5/8" and Rear average of 23 1/4".
With front spring rate of 400lb and 245/40/18 tire diameter, at high speed compression, it will rub the fender liner. I'd love to lower the front ride height but don't want to chew up the liner.
Stiffer spring rate may help but not sure whether it will add more understeer during midcorner than what it is.
The weight distribution with me on the car (no ballast or passenger, half tank) is:
LF 853, RF 835
LR 862, RR 852
Total 3402

With your front 23 1/4" ride, what are front spring rate and front tire size you have ? Thanks

Last edited by S2000; 03-28-2013 at 05:10 PM..
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