If you look at my math, the width of 225/55R19 is within half a millimeter of 245/50R19. Would your comments still apply if the total diameter is that similar? Seems like it would be imperceptible but I haven't ever tried something like this.

 

in your case, the diameter difference is minimal and the sidewall difference appears minimal between those 2 tires. Your still going to get a bulge/bubble effect from slipping 245 tires on 7 inch OEM rims. Double-check it on tiresize.com and make sure the diameter is within the 3% rule. Check tire manufacturer for narrowest rim that a 245 tire you want will fit on. Each manufacturer and model tire may be different. Also check the rub and remember that wider aftermarket wheel will prevent the bulge/bubble effect. And yes the bulge does affect handling, from slight decrease in handling to big decreases depending on the situation. One person went with black rhino 17 x 8 " rims with a 245 tire and had no complaints.

 

Your math is shaky at best. . A 225R55-19 tire has a width of 9.2”. A 245R50-19 tire has a section width of 10”. The 225 vs 245 is the nominal section width in mms. Where did you obtain your tire data?

Manufacturers list the rotations per mile because this is the value which matters when comparing tire sizes relative to functional diameters. I am still confused as to your tire data.

 

I put on 245/50 X 19 high performance all seasons. Car has a lot more grip on freeway entrance ramps. Diameter is essentially same as stock.

 

Lfungus - which tires did you go with? I was looking at the Michelin CrossClimate2 245/50R19

 

I have Michelin Pilot Sport 4S on my 2019 Signature, happy with them.

 

Those are good tires. I'm running them on my MX5. I'm running the Crossclimate 2's on my CX5.

 

I've had cross-climates on other vehicles. Very good all around tire that performed well, and it's especially available in the size you need.
Currently running my favorite Firestone destination AT2 in 16 inch on the CX-5 and 17 inch Nokian Hakka's in winter.
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Worst tires I've owned on any vehicle is a tie between Pep Boys Futura and the Mazda OEM Toyo tires. Both were slippy as hell.

 

I second your vote on the Toyos. I replaced them at about 20,000 miles because I disliked them so much. My worst tire was a Firestone (can't remember the name of the model) back in the 1960's which I had on my '65 Mustang. Had the tread separate while doing 70 mph on the expressway which had just opened around Cincinnati. Unneverving would be a polite way of describing it. I've never bought Firestones again.

 

The 19 inch wheels on the CX5 are only 7″ wide ,and you are best off sticking with 225/55R19 size tires . You will be far better off getting a better quality tire in 225/55/19 for the weather/environment, conditions where you drive . The engineers at Mazda have engineered the the suspension for that combination. Squeezing a wider tire on a 7 inch rim is not going to be as good as the stock size. If you think you want a wider tire ,get some 7.5 or 8 inch wide rims . This may open up a whole other set of problems with back spacing rubbing when turning, stone chipping on the body panels paint. This would also more than likely reduce your MPG slightly. A wider contact on the road should give you better grip ,providing the suspension, shocks, and spring rate can handle the extra weight and grip. Chances are pretty damn good that the Mazda engineers knew what they were doing .