AptosRX

I bought a CPO AWD 2017 RX 450h in October 2019 (replacing a CPO AWD 2010 RX 450h I bought in Nov. 2013). I drove it in snow--in California's central Sierra, over Thanksgiving. Starting at about 3,800 feet, Caltrans was requiring chains on all vehicles except for true 4-wheel drive vehicles with real snow tires (and they were still required to carry chains). Our RX has all-season tires rated M+S, for mud and snow. But they are NOT snow tires. So I installed our chains on the RX's front wheels, which act as the lone drive wheels most of the time. The car handled great, but I'm glad I didn't try driving in the snow up in the mountains without chains. Curious as to what the car's computer was doing as we drove through the snow, I selected the screen display showing a graphic of the drivetrain. I noticed that the RX's rear electric motor (which powers the rear axle) engaged more frequently than it would have on dry pavement--which is hardly at all, except perhaps in situations involving hard acceleration. So I assume that the computer did its job figuring out when the RX needed a push as well as a pull in the snow. Would we have made it to our lodgings without chains? I didn't know and didn't want to find out. I hope this helps.

golferjack

I did not know that California had that sort of requirement. Here in Colorado, chains are only required on semis, and non 4wd/awd vehicles. I live in the mountains and just have all season tires and have never had an issue with either of our awd vehicles. I suppose that we only encounter 10 -12 inches at any one time on a non plowed road and they perform flawlessly.

AptosRX

Good to know.

calumin

California doesn't have a chain requirement level which excludes AWD vehicles or vehicles with M/S rated tires. There are three levels, of which only the first two are common:

R-1: Chains or snow tread tires required. Snow tires must have a tread depth of 6/32” with a “M & S” imprint on the tire’s sidewall.
R-2: Chains required on all vehicles except four-wheel drives or all-wheel drives with snow tread tires on all four wheels. Four wheel drives must carry chains. If you have four-wheel drive – engage it. Refer to vehicles operators manual for correct selection of 4 wheel drive or offroad functions.
R-3: Chains required on all vehicles – no exceptions. R-1 and R-2 are the most common chain controls.