String sets have unequal tension in large part because 40-60-80-100 seems like it’s a nice progression, but….it isn’t. It gets even worse if you continue the progression to a 120 for a B.
For equal tension, you want a geometric progression (each string is 4/3rds the diameter of the previous one), not an arithmetic progression (add 20 to the previous one.
If the folks making strings took Acoustical Physics in college, this wouldn’t be an issue, but unfortunately they didn’t, so we have what we have. I play 5 string basses, and have literally never bought a 5 string set, as the B is never one that matches the rest of the set. Why do people talk a lot on here about floppy B strings? It isn’t the bass’s fault, it’s a string issue - if the B string was big enough, things would be OK.
I play very light strings - a 95 for the E string. The B string with the same tension is a 130. If your E is a 105, your B should be a 140. Find me either of those sets…..