I would love to but unfortunately not having any plan to travel to TX. Very nice work for someone so young - if your listed age is correct.

And very interesting. Questions:
1. You adjust individual corner height to achieve desired cross weights, and at the same time dialing in the preload?
2. I assume then preload of sway bar affects cross weight? When is too much too much?
3. What if you don't want preload on the sway bar, could you have done it by adjusting individual corner height in your car?

 

Thank you, I can assure you I have learned mostly the hard way LOL. Yes my age is correct.

1. Yes, all pre-load adjustments affect weight at a corner of the car.
2. Yes, the sway bar connects to each side of the car. A change at one end affects the diagonal load transfer. When it comes to the sway bar too much stiffness matters on a lot of factors. Generally it would be once the slip angle is increased significantly where the car understeers or oversteers excessively. OR when the inside tire lifts off the ground. You will always be faster around a corner with all 4 wheels on the ground.
3. Yes, there are a lot of options to move weight around in order to achieve a corner balance.

 

Thnx - I've learned a few things from this very interesting discussion. A couple questions please:

1. My other car is 2011 M3, which also has electronic damper control like our Turbo. In both M3 and our Turbo, the stock suspension has this annoying behavior that soft setting is very soft/ponderous with lots of body roll, and the stiff setting is completely overboard the other way, overly stiff and "jittery," and in the M3 case, still with a lot of body roll. In neither car there seems to be a happy medium. Why do you think this is so? Is the culprit too low spring rate and then trying to compensate with damper control? In trying to do too much (covering too wide of a range with damper settings), they have got nothing right?

2. Just curious if you happen to know how your H&R is different from Bilstein Damptronic? Did they just put a label on, or did they change spring rate and/or modify damper.

3. Are you still hooked up to PASM in your car? Or has it been bypassed? What spring rates are you using?

PS Just so happens my M3 is at the shop having Ohlins installed. I drive daily through mountainous roads and have become oversly sensitive to subjective road car feel in the curves. It drives me nuts when it doesn't feel "right."

 

There is a lot to unpack in your first question. Reading the below and the many other m3forum posts there will help.
http://www.m3forum.net/m3forum/showthread.php?t=601913

With that said I will try and give you general answers and we can go from there.

1. Depending on the BMW it can be a few things. The E92 might have flat ride with the springs? I am not sure. Typically cars don't with the exception of Porsche, GM cars, and the F30 BMW's (that I know of). Flat ride is a tuning strategy in which the front springs + shocks respond slower than the rear. This changes pitching motion (bad see-saw motion) into bounce where both ends of the car settle evenly when encountering bounce. You will hear a large number of people tell you that the manufacturers have put lots of R&D into their products ergo they must know what they are doing. For clarity I am not arguing this point, they have developed a durable mass produced product which needs to fulfill safety standards (example: built in understeer, which is considered safer than oversteer). So I would not exactly claim they got anything wrong per-say. I would claim they have not optimized the product for targeted performance out side of what a passenger car should be doing. With the electronic shocks whether it is Porsche or BMW, or Magnaride (Chevy) they are still passive... maybe you can call them semi active. But they are still passive as they are reactionary and you are at the mercy of the processing speed and performance algorithms of these systems. In your case the BMW's springs are very soft for comfort's sake and the shocks are going to provide "comfort" in their normal mode. The "Sport Mode" is just a massive change in damping forces so you "feel a difference". However that does not mean what you feel (harshness) equates to an increase in performance.

2. I have been trying to find the stock damptronic dyno graphs for a long time. No one has been able to provide that. I can send my stock PASM units to be dyno'd but when they are unplugged they default to the stiffest setting. So my results will be incomplete
H&R are a passive system. The H&R shocks use a bilstein piston which is made to H&R's design specifications.

3. I removed the PSAM controller and no longer PASM at all. The spring rates I am running are 284lbs front (1.9hz) and 514lbs rear (2.3hz)

Ohlins seem to run flat ride and while they have a lot of damping they do seem to have pretty decent damping curves and are digressive.

 

What about Pss10 and DSC unit ? Is this the way to fix the problem ?

 

It made a big difference for me, but you mileage may vary. I had the same complaint: too bouncy in regular mode and too harsh in Sport mode.

Ed

 

It's hard to say because what you and I find bouncy may be entirely different. In my opinion no they will not. If you want to address the "bounce" then get height adjustable coilovers, and choose a spring rate that we know will not be "bouncy". If you daily drive the car I would not recommend springs heavier than 350 front and 600 rear. If you want to track the car you can use stiffer springs. Really what would help us make recommendations is what your budget is, and what you wan to use the car for primarily.

 

I found this about Tyre pressure :

Road use
• Use the cold pressures recommended by the car manufacturer

• This information applies to the majority of cars regulalry used on circuits e.g: Audi R8, BMW M3 E90 / E46 / F80, Porsche GT3 / GT3 RS / 911 Carrera / Boxster/Cayman, Renault Megane RS, Subaru Impreza/WRX/BRZ

For all other cars and in particular for heavy cars or for any other specific information, please contact your local website

What Shall i do ?

 

You should start by following the recommendations on the sticker in the door jamb of the car. From there you can deviate, just remember that each move in either direction will impact how the tire performs, and since the tires are part of the suspension, any tire pressure change will have an effect. More pressure = stiffer tire, less pressure = softer tire. However I do not think there would be much impact on the "bounce" you describe, but more on road "feel" and cornering. I do not track, but from what I can recall, pressures are less on cars that track to allow the tire to grip better in the corners, however others who do track will be able to speak better about this.

I have run the suggested tire pressures or greater in most vehicles I have owned. I have not done a lot of less than suggested pressure, however I have not seen a great impact on how the car rides. The most impact tires have ever had is when I have switched to winter tires, where they give up much in terms of stability and cornering compared to performance tires.

While I do not know your specific situation in terms of wrenching abilities, if you were going to pay someone to switch out springs or otherwise modify suspension components, the $1200 or so for a DSC would be a more economical attempt to resolve your issues and only require you to reach up into the passenger foot well and disconnect/connect the module. Like I have said in previous posts, this one change has been the most significant impact on the suspension characteristics of any car I have owned, and I have modified the suspension on almost every car I have owned from my '84 16v Scirocco to this vehicle. What the DSC does is augment the PASM sensors to provide better instructions to the active shocks compared to the stock PASM unit. For me, it eliminated much of the "bounce" that I did not like, as well as make the Sport setting more compliant, but at the same time stiff enough to hold the corners at higher speeds. Others with a better technical understanding may be able to give a more complete explanation of how the DSC unit does what it does.

If you are prepared for a complete suspension overhaul, then you have a variety of options, starting with changing out the springs on the coilovers, to replacing many components, including but not limited to the coilovers themselves. No matter what, this is a stiff car with a performance suspension with a short wheelbase, so undulations in the road surface will have a pronounced effect. My progression has been/will be:

1. DSC
2. Sway Bars
3. Engine/Trans mounts
4. Tarret Drop Links
5. Tarrett Bump Steer Kit (future)
6. GT3 LCA's (future)
7. Tractive Coilovers (future)
8. Return to 19" wheels (future - currently running 20's)

Hope some of this information helps.

Ed