Time after time I have witnessed a customer say:  I want  XYZ  line and 150 yards of backing on the reel.

I then ask them:  How do you know it will fit?

Without experience, some fly fishers do not understand that a reel will only hold so much.

The next question I hear is: How much backing should I put?

My standard answer:  Fill up the reel.

The truth is that if a fish were to run off 50 yards of line on a typical NC creek or river, he is going to be gone or you had better be running on the water to catch up with him.  Of course the ocean is a different story.

A properly filled reel minimizes line curl due to being so close to the center of the spindle.   Likewise it can prevent the friction of line rubbing against frame parts.

I see reels come into the shop where another store has simply overfilled in order to get the sale out the door.  A number of times, I have had to take off a line, remove an amount of backing, then reattach and rewind the owner’s line.

Several points to remember:

A double taper line uses a lot more room on a reel than weight forward tapers.   Using a double taper line may mean you will need a much larger reel to get an adequate amount of backing, or have to do without.  Using a reasonable reel size and a weight forward line usually means you will have plenty of space for backing.

Backing serves several purposes:

1.  Extra line for when that fish of a lifetime runs the fly line off the reel.

2.  Fills the empty space left in the reel, keeping fly line from being wound in small circles. Small circles will develop memory over time and the line will be difficult to straighten, therefore harder to cast.

3.  Makes winding in line faster.

4.  Works hand and reel less.

5.  Makes start up inertia  less, line begins to flow off reel smoother when a big fish begins to take line off the reel.

6. Plays a part in making your line last longer by not having it in those smaller coils.