xDrive: Moment of Truth

The BMW 535i provides a smooth, stable ride that spoils the driver with a feeling of exceptional control. But its xDrive? In the past I’ve questioned the need for all-wheel drive in the city. It adds weight, creating a need for more power, fuel and hence expense.

However, this weekend I wasn’t in the city. And I got to experience the raison d’etre for the hours of research behind BMW’s xDrive system.

On regular dry surfaces it delivers a 40:60 power split between the front and rear wheels. But on less stable surfaces, say snow and ice on a rural Canadian highway near a ski hill, one or more tire may slip, causing over- or under-steer by a nervous driver.

Many weekend mechanics complain, these days, that cars are no longer any fun to tinker with because they’re ostensibly computers on wheels. Lift the hood and they look more like your motherboard than your dad’s 2-beer project.

Anyway, the BMW 535i xDrive is one of these rolling computers. Move it across a patch of ice in a tight s-turn and it senses any slippage, reassigning power to those wheels which aren’t slipping, countering your over- or under-steering. This response happens in milliseconds. So fast you may not sense it.

However there was a moment of truth during this one tight turn when I swore I sensed something. It slipped – yes, perhaps for a few milliseconds – then felt like the stable, efficient ride it was back in the city. This turn is very close to the chalet we stay at, atop a long hill with no one around for miles. I got out to examine the icy road conditions up close. I immediately slipped on a patch of ice and fell on my tailbone.

I was right. It had slipped and corrected itself, reestablishing a smooth and stable ride. Thankfully, the 535i has seat warmers too.

Next week: The rest of the 535i experience.

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