sg530

I want ot get back to roll discussion. <_<

How can anyone (in any BMW model) corner with inside wheel(s) off the ground? Having near-zero roll is not an indicator of handling by itself. The body is not stiff enough nor light enough to lift even one wheel.
On a hard corner or turn on a flat, non-banked road, the tires let go and I drift. The tires scrub off rubber dust. This happens before any wheels could lift off the ground. I have sport w runflats. The DSC lights never came on.

Yes?

BetterMakeWay

Agree! As i said it's almost impossible to lift a tire in a bmw e60! If i picture this corectly DD doesn't help too much in terms of pure performance (times), mostly in confort, because eventually what happens when u take a hard left (eg) the car has the tendancy to lean to the right so if u have DD the supension helps by force reduce the body roll but that doesn't mean the tires are less stressed. They take the exact punishment as without DD. That force that keeps the car from rollin has to be taken somewhere, and that's at the end of the tire/wheel.
Anyway still wondering and i haven't got a response at my question: why DD is not allowed with M sport suspension?

pennetta

D.D. is a compromise between a smoother ride while going straight and reduced body lean while going around a corner. The M spec suspension is designed specifically for handling with less compromise for comfort, so you don't need D.D. with the M spec suspension.
Also you'll notice that the new M5 does not have active steering. The same principle applies. A.S. is a compromise with quicker steering while going slow to medium speeds and slower steering at highway speeds. The M5 has quicker steering overall as it compromises less to comfort and less nervous/twitchy steering.

BetterMakeWay

I got it! Ok...so if the DD would really make a car handle much better that with a tuned M sport supension than it would be on the M5 so as the AS. Or do i miss smth?

pennetta

I did not say DD handles better than the M suspension, I said DD makes a softer suspensioned car handle "more like" the M in the turns while keeping it smoother in the straights.
DD pumps up the shocks on the outside side of the car while in a turn to keep the lean angle to a minimum and then releases the pressure while going straight for a softer ride. If you are only concerned about extreme handling go for the M suspension and skip the DD.

UUronL

There's even more to it than that if you read the .pdf file I posted on page 2 of this thread. The self-steering characteristics of a car with a fixed roll stabilization bar are unchanging while an active system can provide benefits in many areas. I'm not even goint to try to paraphrase - here's the quote:

"In vehicles with passive stabilizer bars, the self-steering characteristics are fixed by the car's mechanical parameters for all driving speeds and driving situations; relevant parameters include the spring stiffnesses of the stabilizer bars in the front and rear axles. In contrast, Dynamic Drive dynamically adjusts the self-steering characteristics as a function of vehicle speed and driving conditions, resulting in improved handling, agility, and steering precision."


There are two graphs showing that Dynamic Drive requires less steering angle to achieve the same amount of lateral acceleration, which I suppose is a measure of self-steering. There is also a relative roll angle chart from 7 series testing that shows DD vs. non-DD roll. There's an astounding difference, and the 5 and 6 series are tuned to mitigate more roll than the 7 series (up to 5 m/s squared vs. up to 3 m/s squared).


For me, I picked the car based on this - I hate cars that lean and roll too much. I drove my car into one turn that caused DSC to kick in briefly while powering through the corner, and the car gripped ferociously. I love it.

BetterMakeWay

I did that! Thank you...

KrisD

I can attest to the fact that my 545i/Sport can corner significantly faster than the 2000 M Roadster I traded in. In fact, it was one of the first great tests of the 5'er on my way home from the dealer.