There are a few key lengths of a bell rope where we can assume the lengths of, there's a couple that are unique to your tower.
The length to tie off around the spokes, we tend to assume is between 10-15feet long. Longer works too if that's what you want, it just requires a little more time to tie it off around the spokes.
The key difference between all towers is the length between the top fo the sally and the garter hole. We can call this the working length. Where this exceeds 25-30feet, is when considering either UHMPP or Dyneema top ends is worthwhile, below this, there's very limited benefits.
Sallies are nominally 3ft. If you're measuring you'rs and it's 3ft 3 or 3ft 4, it started life as a 3ft sally and has bedded in it has got longer with use and time.
Untucked tail end lengths are nominally 9-12feet for a range of bells from about 3cwt up to 20cwt