yeah, triplet diddle, not triplets with arms. we do it cause its hard to play triplet diddles at 170 with wrists only. our teacher noticed that the quad line isn't really good at lefts, so we played it slowly at about 75 to get comfortable and then we sped up about 10 bpm after some reps. its definitely helping, i can see it getting much better.

make yourself an excercise and break it down slowly to get the feel of "threes"...then eventually work it faster up to a higher tempo with maintaining the same grip that you had at the slower tempo and you will get better. PRACTICE

I think everything has already been said.
But if it hasn't already, make sure you don't get tense when you do threes.You have to be loose.

alright, thanks. i've practiced threes snugglebunny more and i am now able to play them much better. still not as good slow on the left, but it has definitely improved.