Tire Sizing - specifically, two things:
1.) metric sizing
OK, so you like the metric system better and I do too. That said, sizing tires by tread section and aspect ratio seems...well, obnoxiously complicated and ill suited to much of anything other than keeping the number in pretty multiples of 5. OK, an over simplification...but, every time I want a 33x10.5" tire and realize that 32.8x11.2 inches is all most people make because they run metric sizing, it makes me sad. For that matter, how did 285x70x17 become the standard not quite 33" tire when we could have had 275x75x17? Why do I need 32" tires in 245, 255, 265, and 275 widths? Why does selection suck above 32"? OK, so I can answer most of those...that's why this is a gripe.
2.) tires not running true to size
Self-explanatory - whether it's a 40 inch tire or a 33 inch tire, the dang thing ought to measure out to what you paid out for. It's not as if tire manufacturing were some immature process and we couldn't figure out how to do this...we just don't.
OK - gripe complete...