what is the power distribution on the BMW's xDrive ?

Is it rear bias ? or like Audi Quattro's 50/50 ?

 

Audi's Torsen (torque sensing differential) is not fixed 50/50 - it varies torque delivery depending on the amount of grip - but it doesn't have a rear bias as such.

Audi vehicles that use the Haldex differential (e.g. TT, S3) can ONLY deliver a maximum of 50% of the drive to the rear.

 

Car and Driver has this data in the 2006 5-Series AWD article it just published. Look here:

http://www.caranddriver.com/article.asp?se...1&page_number=1



"So, rear-drive old-schoolers, you're probably wondering how xDrive affects the 5's heralded handling. Is it possible to hang out the rear end under power? Since the engine is still directly connected to the rear wheels (there is always at least 50 percent of the power going to the rears), completely switching off the stability control will allow for power oversteer if you're so inclined. Keep the stability control engaged, and even the most ham-fisted driver will have trouble losing control of the vehicle. If you're in the mood for sliding the car around but still want to be saved if things get too hairy, the stability-control system has the dynamic traction control (DTC) setting. Compared with the fully deployed stability control, DTC doesn't dial back the throttle and allows the driver to slide the vehicle more before the brakes intervene to bring the car back into line."

It's hard to tell from this just how much of the torque will drive the rear wheels in normal conditions, but having at least 50% all the time seems promising. Also, being able to hang the rear out seems to indicate that it is done "right".

 

This article is also useful on the 2006 model 3 and 5 series xi: http://www.germancarfans.com/news.cf...id/2041221.002

I'm pretty sure these guys make the xDrive: http://www.magnadrivetrain.com/drive...ish/index.html