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      02-01-2013, 12:57 PM   #170
BruceOmega
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Drives: 2013 335i xDrive Sportline
Join Date: Jun 2011
Location: Alexandria VA

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Quote:
Originally Posted by drob23 View Post
FWIW - the default CarSim D-Class sedan has the sprung center of mass .54 m above the ground. The wheel center is .335 m above ground, which should be *at least* lower than the driveshaft + xdrive hardware. Thus the difference is .205 m which is not enough to lower the CM of a 328ix as compared to sport suspension 328i using my calculation above.

The GT model in carsim (supposed to be a Porsche) has the CM .39m above ground and wheel center .325m above ground. So for a sports car with low CM the xdrive would do nothing to the CM.
Interesting. I appreciate an engineering approach, but am having trouble following the above example for the D-Class sedan.

From looking at the drawing of xDrive for the 335i sedan on the BMW website, the extra hardware of xDrive looks like it is roughly in the same plane as the driveshaft, which is roughly in the same plane as the wheel centers.

According to the example above, the sedan's wheel centers are .205m / 8" below the COM, so that would put the extra weight of xDrive lower than the COM. If so, that should have the effect of lowering the vehicle's COM with xDrive.

I'm also having trouble following the effect of the 10mm lowered ride height for RWD with sport suspension. In terms of meters as the unit of measurement used in the example, that 10mm is only 0.01m.

Am I missing something?

Thanks
Bruce
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