[TowerTalk] Guy wire strength question

[hanslg at aol.com]

 Can anyone help me out? I am in the process of putting up a 85' tower. I am presently looking into guy wires. The calculated maximum force on the  guy wires is 2990 lb. I decided that 5/16" EHS 1x7 wire should be fine. Now when I receive quotes I find various grades (if the quoter even knows what grade it is). Can somebody explain what the difference is? I see that EHS is recommended by most tower manufacturer but why?

The strength of the different grades are mind boggling:

For 5/16" galvanized steel wire I have break force for:

Common Grade                       3200
Siemens Martin Grade             5350
High strength Grade                 8000
Extra High Strength Grade      11200
Utilities/Specification Grade    18000

 
(Obviously you need to know the grade. See "Common" compared to "Utility").

One of my questions is:" Can I use 9/32" Utilities Grade (11500 lb) instead of 5/16" EHS (11200 lb)? 11500 lb seems OK for a maximum expected force of 2990 lb (120 mph wind)? What would happen if I use 5/8" Common Grade (11600 lb)? 

Could I possible use 1/4" Utilities Grade (6000 lb) or is that to be too close to the maximum force (2990 lb)?

Hans - N2JFS