Ways to improve comfort without voiding warranty

[vogz]

Don't agree at all - I also have the 20s and the 18s. I find the 18s to be much more comfortable but I suspect it is down to the tire brands chosen. Different models will have different characteristics. Otherwise it sounds like you are saying all tires ride the same regardless of size or seasonal intent. Which again, has not at all been my experience. The larger, higher performance stuff is usually less comfortable. You have to find the blend of performance vs comfort that works for you.

I'm not saying that tire choice won't impact ride, I'm saying the small sidewall height difference won't do much. Especially not enough to help someone that is having back pain due possibly to how the car rides. Different tire brands/models of the same exact size can have noticeable (but still not significant) ride differences. They still aren't going to provide a major difference like changing suspension components will. "Much more comfortable" is also subjective. How much experience do you have swapping suspensions on cars? That might change your perspective on the wide range of comfort available on a specific chassis.

My experience is mostly going from Michelin Pilot summer tires of different models on large wheels to performance winter tires on smaller wheels (Michelin, Dunlop and Pirelli). I do notice a small difference, but is doesn't significantly, fundamentally change how the car rides, which is the point here.

I have a sneaking suspicion that people that change to smaller diameter expecting a SIGNIFICANTLY softer ride (mostly due to that being the general narrative on car forums) are experiencing a bit of a placebo effect. When I change my setup, it's for the winter, not for a smoother ride so I'm not "expecting" to experience anything (and I don't) except fantastic winter performance.