Americas Tire co ( www.tires.com) says that you can put up to 245/70/16 tires on the stock wheel. they say that there will be no rubbing and that there is enough room for snow cables. ive seen 1 rx300 with 245/70/16. the question is should you zero plus size the tires. what will you gain? personally, i like the look of the wider tire. however, when you increase the width without changing the aspect ratio, the tire will be a bit taller, and subject to more flexing from the side wall area.(actually 235/65/70 would be a good fit, but good luck finding a tire this size). this would translate to a more sloppy feel during turns. would this cancel out the improved traction from the wider footprint of the tire? I dont know. also you might expect to see a decrease in the fuel economy, though im not sure how much. also, if you plus size the tire on the stock rims, your odometer and speedometer will be off slightly. The larger tire may also put increase strain onthe breaks. so in the end, if you zero plus size your tires, from the 225 to a 235 or even 245, while the car might look better, overall performance may not be improved. i think that you are best off putting the best quality tire, size 225, that you can get. i would look at the michelin cross terrain or ltx m/s.
good luck