A friend of mine bought a used Cantare.' it has the same self centering rudder system.
Her rudder seemed to have a bit of play. Not much, but not solidly centered like mine.
You should be able to flick the rudder back and forth and it should center perfect and solid each time.
So, we opened it up to inspect the stop collar system.
Stop collar (white thing) was fine. In the early Ares days, some of those collars would crack where the screw holds it down.
They replaced that old plastic with newer, tougher plastic. If you have an older Ares, keep an eye on that collar.
I put a washer under my screws, because I'm fussy. I was concerned that the screw head might dent the plastic and make adjustment difficult - if it ever needed it....
Her problem was an easy fix.
The top of the rudder shaft has a square end that fits into the tiller wheel.
You can test the fit by inserting it and wiggling it without the screw.
If it feels sloppy, I'd get a new tiller wheel.
The wheel is plastic - if it gets smacked around or over tightened, the mortise may get sloppy.
We tightened up her screw and that eliminated the play.
She got a new tiller wheel today, it should fit better, with less torque required on the screw.
Mine sets tight without much torque at all. Probably just enough to smash the spring split washer.
Be sure to use the split washer in the tiller wheel and a small amount of blue locktite on the threads.
Size of the old and new line is very close. The new stuff is super strong.