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Gosh …. There are a few comments above that I must respond to.
Foremost, I DID NOT HAVE A TRACTION PROBLEM so TIRES ARE NOT AN ISSUE !!
1. My problem with the '07 RX400h-AWD was not traction (static or dynamic friction) of the new factory tires to the snow surface. Remember that I could back up the driveway (all electric) but it just wouldn't go up frontward (multiple demonstrations each) in an inch of snow that became packed. My problem was that a combination of VSC, TRAC & VDIM was totally constricting the engine power to the front wheels (engine and MG2) and electric power to the MGR. It would not apply enough power to break the static friction of the tires to the snowy surface at a very low speed.
2. As stated in my initial writing, my new '07 RX350-AWD is awesome, as was my '02 RX300-AWD. These vehicles meet my entire expectation of AWD and will accept increasing ("feathered") engine power to all drive wheels until ALL FOUR tires break static friction on a snowy / icy surface. I couldn't ask for a better AWD performance … and if I needed more TRACTION, I know that I could (and would) move to a Snow Tire.
3. NET: The RX350 will climb my snowy driveway without any wheel spin but the RX400h just stopped due to an uncontrollable restriction of engine and electric to the drive wheels. I was, and am, really very disappointed that the RX400h-AWD cannot yet meet an AWD performance expectation easily demonstrated by the other RX models.
Ron Pierson