Which type of sidewall makes you feel bumps and cracks in the road more...a hard side wall or a softer one? My gut tells me a harder one will make you feel them more because there isnt as much flex in the tire to absorb the impacts. Am I right?

 

Low profile, hard = more bump/feeling, but a bit better response to steering. Can be "twitchy" and follow cracks/etc



High side, soft = less road feel, more cushioning, slightly less steering response, tends to be "smooth" feeling and not follow cracks



That's my synopsis, based on the summer 205/40ZR-17's and the winter 205/55R-16's for my current car, and the stock 195/55R-15's on my old car and my friends car.



Others feel free to chime in, since my data may be flawed.

 

With nothing else changed, stiffer sidewalls will probably transmit more bumps into the cabin.





What you are effectively doing is increasing the spring rate of the tyre, and it is hard to predict the effects of this. The tyre is both a spring and a damper, there is another mass (your steering knuckle and suspension arm), then the actual coil spring and damper inbetween the road surface and your ass. Fiddling with the spring rate of one spring will not always have a predictable effect on ride quality.





Using a cushier sidewall might result in the natural frequency of the tyre being poorly damped, or the natural frequency of the whole suspension could change to match a particular set of bumps in the road.





In any case, we are talking about tiny differences here, but if you make a drastic enough change, it can make a noticeable difference.