My understanding is the larger the wheel, the less rubber, the more prone to feeling the ride (worse ride) and the more prone to tire and wheel damage from less rubber (ie smaller wheels with bigger tires can survive some things larger wheels with smaller tires can not, tire and rim damage). Also, worse mileage and breaking and other factors with larger wheels.

Are 19" wheels practical, especially if a smooth ride ( over typical in many areas....imperfect roads) is a priority, or what manufacturers think customers want?

Effects of Upsized Wheels and Tires Tested - Tech Dept. - Car and Driver

 

For the most part I think it is market demand. The larger wheel, thinner tire does permit sharper turn in as there is less tire volume to distort the grip (less squirm sensation). But Yes, all the other attributes you mention come along with that.

The style trend is larger. Many enthusiasts demand it. But the less vocal driving majority would prefer the smoother, quieter and less road impact feel of smaller wheels, thicker tire sizes. The overwhelming majority of consumers are put off with the characteristics of optimum performing attributes. Look at this from a wider perspective, Acura as a brand chased the BMW performance benchmarks and created stiff rides in even non sport trimmed models to appeal to the auto journalists and enthusiasts who expect every pedestrian sedan to have track performance capability. The consumer voice eventually was heard and now Acura has created more 'comfortable' tuning. Note the success of the RDX, MDX and TLX with capable, yet comfortable tuning. Even BMW in now yielding more comfortable rides over 'ultimate' driving.

One note on the RLX. It still used double wishbone suspension. That configuration offers great handling & stability and more road feel that competing cars. I always define it as Accord handling vs Camry comfort to family and novices. It is more personal choice.

I find the suspension in the SH RLX an excellent blend of creamy smooth roads, and compliant on choppy, poor roads. Although impact harshness is good to me where it is, it does permit slightly higher impact sound than some other brands. That is a result of the suspension tuning and large wheel, tire choice and thinner tire configuration.

I am done channeling 'Captain Slow' (James May) who bucks the enthusiast trend and desires a daily ride NOT tuned at Nurembugh.

 

Your question is loaded to get a particular response, perhaps indicative of your having already reached an answer, for yourself, personally.

The basic reason you go with larger wheels and lower profile tyres is that you have that much less rubber to flex, so the car will be more under control and inspire more confidence in adverse circumstances.

If this is what you are doing as a manufacturer, then you have to make sure you make the right compromise with wheel and tyre sizes, and suspension design.

:-)

On the track with both H1 and H2 cars, people stuck with 15" 50-series tyres for many years, but it was more in recognition of severe fiduciary penalty changing that, and the racers just generally accepted that they would not do that.

Now that different people are racing and the costs are different, you see much bigger wheels and lower profiles.

In 2015 as well, the main reason that a manufacturer would want to stay with smaller height wheels and more conventionally profiled tyres is because of cost, because it's no doubt that you are compromising absolute handling potential with smaller wheels and higher profiles.


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My personal opinion is that it has become largely a marketing/sales gimmick that manufacturers HAVE to adopt or fear losing sales. That is, manufacturer A bolts 19 inch wheels onto it's new sedan, so manufacturer B is forced to follow suit because they fear the general public will conclude that 19 inch wheels MUST be better than 18 inch wheels (simply because the number is bigger and without any regard to handling or ride quality issues) and buy a car from manufacturer A if they don't.

I personally am willing to sacrifice "at the limit" maximum handling for a smoother ride and thus would prefer the RLX came with 18 inch rims or 19 inch rims as a no-cost option for the buyer. Given that choice, I would have chosen the 18's.

That said, the RLX Sport Hybrid has done an amazing job of getting the best of both worlds out of the 19's...combining the smoothest, quietest ride I've ever experienced (when on mostly smooth roads) with some really amazing handling.

Side note: I'll be running 17 inch rims on my snow tires in a few months and I look forward to comparing the ride quality and handling offered by a substantially thicker sidewall.

Additional side note: After thinking about reasons for the larger rims, I also wonder if narrower sidewall tires offer less rolling resistance and thus improve fuel economy and that could be another reason that manufacturers are making 19's the trend?? Also, they love the $$$ they make from selling new rims to unfortunate drivers who dent their rims on potholes, so the trend is also profitable.

 

That is why when my tires are done, I will be getting the Continental DWS tires as they are supremely quiet, have enormous traction, are very good in the snow (just short of true snow tires), and have a softer side wall, thus a smoother ride.