Why bubble levels are so important to setting level nock travel? Well, they allow you to ensure that your bow is both laterally and vertically level, hence why the use of these levels with a 90 degree reading on it is so important…
Also you want to make certain you know where to place your rest in relation the the berger button hole.. Every bow is different, the newer HOYT bows seem to be the happiest, when the arrow runs through the top half to 3/4’s of the hole.
The position of the D Loop in relation to the berger hole has a lot to do your bows cam sync… With the top cam hitting slightly faster than the bottom cam.
This is most important to achieving level and vertical nock travel when the arrow is released!
By placing a bubble on your arrow, while at the same time utilizing the above mentioned bubble level on your string, you can achieve a true levelled string and thereby a 90 degree angle for your D-Loop! At this point you can focus on your center shot placement!
In the above example, you can see that the newer CS TURBO likes the arrow to run through the berger hole quite a bit higher than you may be used to… These bows achieve much better nock travel in this manner!