Do expressions typically cause double transformations?

[kronique]

i've encountered them before  but i wasn't sure if it was a result of an error. I recreated the rig several times. Apparently the tutorial worked for others. Creating an expression that tells groups (golding controllers bound to mesh) to follow geo vertices >>> bad idea?

Mainly i'd like to  why or why not.  

[pilou--2]

Depends on what you have on the group you're controlling by the vertices. If there is something bind to the geo in it, it's not surprising that you get double transformations. Do you get cycleCheck warning when you do it by the way ?

expressions don't create more double transformations than another technique would.

It's hard to say specifically without seeing your graph.