I tried unsuccessfully to have Walmart mount and balance 4 new 195-65-15" Hankook 727 tires (2000 Chrysler Cirrus rims) on my 2005 Vibe. They were a little concerned about mounting 15" tires on a vehicle which only lists 16" rims available, but THAT wasn't the deal-breaker.
The Hankook 727's are "H" speed rated, not the higher "T" rated tires required by the Vibes door panel specification. For liability reasons Walmart wouldn't mount a lower speed rated tire on my Vibe!
Actually, one of the Managers tried to help me out but I missed his line of reasoning at the time. This Manager asked me if these Hankooks were my "Winter" tires. I answered "no, just normal use All-season tires". Had I said: "These are my Winter-only tires", I think they would probably have mounted them for me.
I'm having a small independent shop mount and balance the tires later today, I don't anticipate any speed rating discussion.