How long does it take for a horse to adjust to new bit? and the problems with old bit
14years old mare, well broke, was a showjumper before, now just trail riding (for 3 years). Her teeth are floated, was ridden with 21mm (0,83inches) single joint snaffle for 2 years (when I had her), then one year with 16mm (0,63inches). Her previous owner sometimes rode her with bit with no joints, 21mm, but mostly with single joint. Don't know with what she was ridden before... The last owner had huge problems with her, mare was throwing her head up on shows and ran away from the bit, owner couldn't control her and they never did good. She also used other things that helped her to hold mare's head down...
She is always opening her mouth when I'm bridling her, she doesn't close her mouth until I go out of the stable. I ride on loose reins, she is very good, when I gave her a signal on loose reins she starts to chew on the bit (I was told that's good though), but if I don't have loose reins she opens her mouth widely and moves her head on a side. She also does this if she is nervous, scared, or bored (doesn't matter if I have completly loose reins). If she is bored I start doing something with her and she stops, but if she is nervous it's impossible to make her stop.
She always had both nose bands (I don't know how are they called in english), to prevent her from opening her mouth, they didn't help. I took them both down last month, no changes in her behaviour.
I came to the conclusion the bit I have is too big for her, that she has a small mouth and maybe low palate (?) and the single joint bit isn't the right choice for her. I bought a french link bit yesterday, 12mm (0,47inches). She was a bit better when I rode her, she deffinitly didn't open her mouth so much, but if I took a hold of reins she did it like always. Maybe it's a reflex, a trauma of all the years she wasn't ridden with a right bit?
Is it possible to re-train her, so she wouldn't open mouth so much?
Will it go away by itself if this bit is ok for her and how long do you think it will take?
Should I be doing something else too?
What else do you think could be causing this problem?
How should I ride her?
Do you think it would be good to ride her with non-loose reins, so that she will find out it doesn't hurt (if my guess is right, then single joint bit was making contact with her palate and that caused her pain, so she opened mouth. With french link this won't happen. But if my guess isn't right, than holding reins will cause her pain and I don't want that)
Any advice or your story will help. Tell me your opinions please :)