In general, the same model tire with a larger wheel and equal outside total diameter will ride and handle better. This is because the air in the larger profile tire acts as a spring without the benefit of a shock dampening this motion. I have proven this fact on a previous Mazda and Prius. That being said, don't expect MAJOR improvements in ride quality. Although the difference in ride is better, you will really enjoy a major improvement in handling through less tire squirm. Tire construction has a lot to do with overall ride quality, and often lower profile tires are firmer. Select a tire that has better ride quality properties. There are ratings available. Also, lowering air pressure is a poor way to improve ride, for your MPG will drop substantially and tire life will decline. Good luck, and the factory 225/45/18 are a great choice for ride and MPG. Tire life is so-so.
Remember that there are many factors that effect ride quality, mostly designed into the suspension and car weight. Making a car softer riding will compromise handling. The Mazda 3 is an excellent handling sportish car, not a cushy boat.
I agree with everything you said. I could have written it myself. Almost. Except the part about low profile tires riding better. If undamped travel in high profile tire causes ride deterioration, then shouldn't lower inflation pressures in a given tire size also ride worse? That increases undamped travel as well. Isn't this why tires are pneumatic and not solid in the first place? If undamped travel causes a worse ride, wouldn't solid tires with no give provide the best ride.? Don't think so.
Are low-profile tires ruining your ride?
, In my Particular case I did not notice any deterioration in handling with slightly lower rear tire pressures. Had I a skid pad handy or even some nice tight curvy roads to push hard on around here to make comparisons , I might have been able to to discern a difference.
Also, using less air at the lightly loaded rear is an old autocrosser's trick to reduce understeer in front heavy cars, though in that case pressure is added at both ends, just a lot more at the front.
That's why I did not reduce air at the front much.
Yes. it will increase wear at the back but likely still nowhere near the wear rate of the heavily loaded front end. Tires need rotated less often?
Fuel economy will be worse. I need to make real world comparisons there, to see if I can live with the difference. I could except 1mpg less but probably not 2.
I should have done a better job of evaluating the car before purchase. Based on reviews and my short test rides on relatively smooth roads, I expected it to ride and handle in a similar manner to my 2016 Golf or 2014 3. I was smitten by its good looks and quiet, attractive cabin.
It rides a little worse than the old 3. A lot worse than the Golf. It handles slower than either.
By the way, stock tire is a 215/45/18, not a 225.
