Ball Tracks

After each delivery, you will notice that your ball will come back with a line of oil round it.

This is known as your ball track and can give you useful information as to what kind of bowler you are.

Semi-Roller	Notice how the track is just to the side of the fingers and thumb. This shows that the ball is tilted a little as it rolls down the lane and then impacts with the pins. This tilt creates mix as it sends the pins in a more horizontal direction. This style is used by strokers.
Flare	Modern balls (since the mid-1990's) have introduced the concept of "dynamic imbalance" which means the ball moves off it's initial track and creates a new track with each rotation. This is called flare, and it means that more of the clean surface of the ball is in contact with the lane, potentially meaning more hook.
Full-Roller	This style was successful in the past, but is not that common in today's game, due to modern lanes and equipment. The track of the ball runs between the fingers and the thumb. If you measure the length of a full-rollers track, you will find it is equal or very close to the circumference of the ball (27").
Spinner	This is the sort of track you would find on a helicopter bowler's ball. The spinners release creates more axis-tilt, which reduces the size of the track. The end result is a ball that travels further down the lane with little lateral movement and deflects as it hits the pins. This style makes it easier to score on almost any condition.