We have traveled to Europe, UK and Ireland for the past two summers and learned how much stricter the airlines are for carry-on size and weight is, than in the U.S. We traveled with Delta, BMI and Iceland Air. We have older carry on bags from Rick Steves. They have a total linear measurement of 46 inches. I included the wheels. However, on paper, Delta and Iceland Air state 45 inches is maximum. When did Rick Steves reduce the carry on size. Think we bought the bags about 3+ years ago? Should we be buying smaller carry on to accommodate the extra inch?
As long as I remember, the total linear measurement for most airlines has always been 45 inches. I don't think Rick reduced it from 46". However, I see on the Iceland Air website that the max weight in 2nd class is 13 lb. The current rolling bag weighs "just over 7 lb." If all you can carry on is less than 6 lb, you might as well use a grocery sack. Might I suggest that you look at the Essential Carryon. It only weighs 1¾ lb and is only 43 in. If you put into it the less than 6 lb you can carry onto Icelandic Air in a 7 lb roll-on, you'll only have 8 lb - no need for a wheels. And it only cost $30!
Normally people consider a 21" bag the max for carry-on. Unfortunately when you add fixed wheels and a handle , your 21" bag becomes a 22" bag and doesn't quite fit. You can either get a 20" roll-on or do as Lee suggests. My wife prefers a roll-on, I prefer a convertible. As long as her bag fits within the carry-on requirements, it's her choice.