How wide is too wide to start hydro-planning on our CX-5s? I don't think going from 225 to 245, a difference of 0.39370079 inches is enough to all of a sudden cause our CX-5s to start hydro-planing. I think the tire tread design plays more of a factor when driving in the wet.
Of course that's enough to make a difference. Hell, I've hydroplaned my CX-5 with the OEM tires. It's all about speed, weight, tread width, tread diameter and of course tread depth and design and water depth. There is no magic width at which hydro-planning begins for any given vehicle. A wider tire hydroplanes at much slower speeds, all else being equal.
But to answer your question more specifically, all else being equal, a 245 is 8.9% wider than a 225, which is quite significant. It will hydroplane much easier than the 8.9% would appear to indicate because as a tire becomes wider the tread is progressively less able to evacuate water (and this happens at a much faster rate than the width increase would indicate). So not only is the ratio of vehicle weight per contact patch (lbs./sq. inch of contact patch) reduced by 8.9% but the water does not evacuate around the wider tread as easily (water builds up). It's a problem that compounds at an exponential rate to the increase in tire width.
Conversely, I need to be going quite fast (well over 100 mph) to get my 500 lb. Ducati to hydroplane. Simply because the tires have a rounded profile (180 rear, 120 front) while car tires have flat treads.
That young guy who lost control of his Accord while driving in the rain on the highway, must have been running really wide tires, otherwise the police officer shouldn't even notice how wide his tires were. Considering he was young and had a loud exhaust, maybe he was driving a car with significant negative camber too just to fit his wide wheels/tires? Based on the photo of how the 245 tires fit on our 19 inch wheels, I don't think a police officer can easily tell that it is running a slightly wider size.
I don't know about you but, for me, all it takes is one look at most "riced cars" to know the tires are wider than OEM. It doesn't take any special training to easily distinguish this in most cases. It's generally obvious. Plus, in an accident under rain conditions a competent LEO will check the tires tread depth to see if a "bald tire" ticket is appropriate. I'm guessing they had adequate tread because the only ticket was "too fast for conditions". Even a new tire with full tread depth will hydroplane at 50 mph if the tire is simply too wide for the weight of the vehicle and the amount of water on the road at that speed.
Living in Western Washington I drive in a fair amount of rain. The area is known more for all day drizzles than heavy rain but, like anywhere, we do get heavy rain. My observation when the Interstate has a good amount of standing water, most drivers will push their speed to within about 10 mph of dangerous hydroplaning. That typically means drivers might slow down from 70-60 mph but might not slow down at all in a 60 mph zone because they feel fine at 60 mph. If you are the odd one out with tires 8.9% wider (or maybe your tread depth is getting in the lower half, or a combination of factors) you might have to slow down to at least 55 but more likely 50 mph to achieve a similar margin of safety. But the margin of safety in such situations is often very thin indeed and the problem approaches suddenly with a blocked drainage drain that causes the water to be much deeper on one side of your lane than the other. That's when even a driver with good reflexes and driving skills can find themselves in a world of hurt. And, you can bet your life that 8.9% extra width can EASILY make all the difference in the world.
It looks better wider. Stock 19's are an oddball size clearly done for MPG reasons. I believe most of its similarly shaped competitors go with a wider profile.
