Ok, thinking that I had arrows figured out based on knowing that the first two digits denoted diameter and then understanding the last two for wall thickness I was set. Also spent time testing how the 2018 that I was shooting acted, as well as reading all the info here for those of us that are slow learners LOL. When you look at the spine values that Easton puts out the confusion comes back! The 2018 that I shoot has a 0.464 spine factor, so I was going to go down, making the assumption of being somewhat over spined; but if I go down to a 2016 it has a 0.531 spine and a 2114 has a 0.510 spine. Is not the Higher the number the heavier spine?

0.464 is stiffer than 0.531 those numbers are the deflection in thousand's of an inch. Hope that clears it up for you  

QuoteOriginally posted by hormoan:
0.464 is stiffer than 0.531 those numbers are the deflection in thousand's of an inch. Hope that clears it up for you      

Oh, thats it, now it does make sense, thnak you.

Jamie, if a shaft had 0.000" deflection it would be 100% stiff. Just a way I keep it straight  

Jamie,
The higher the spine deflection number the weaker the arrow.  Has nothing to do with arrow size marked on the aluminum.

Easton uses their own standard --1.94 pound and 28inch spacing on the supports. But the old standard is easy. 26 inch spacing of shaft supports, 2 pound weight. Divide 26  by deflection = spine rating  in pounds  for a 28 (YES 28!) inch arrow.

Yes it's a 1.94# weight between 28" centers.It is measured in thousandths of an inch.The higher the number the weaker the shaft.A .400 will be 10# stiffer than a .500 shaft.

Sorry R.H. that doesn't correlate with the charts. .10 (the difference from .400 to .500) does not equal 10#
A 2020 spine tests at 77 lbs. .426 deflection.
A 2016 spine tests at 61 lbs. .531 deflection.
I guess you could round it up to that but in my experience a 5# spine difference does make a difference. Gary

There are some charts you can see at Easton Archery and Foxfire archery that will show you the different spines and deflections of aluminums. Gary