K35's have been my "go to" on lower end flip bikesso I usually stocked up when I'd find a good sale. In the past couple years I have had 2 blackwalls with a VERY noticeable twist in the tread, almost like a broken belt in a radial. I got the first one replaced but by the time I discovered the second one I couldn't send it back. It never occured to me that there would be 2 in the batch and you couldn't see it until the tire was mounted and aired up. It was very annoying when riding. I tried using one on my trainer but it "thumped" on every revolution of the rear wheel. Never an issue with the gumwalls.