[TowerTalk] New Sheaves for Crank-Up

[N3AE]

Hello tower experts, 

I'm in the process of refurbishing an old EZ-Way crank-up and looking to replace some lift cable sheaves which have excessive wear in the ID of the groves. The current 3" OD metal sheaves are sized for 3/16" cable. The sheaves are rather narrow, measuring 0.38" at the rim and 0.45" at the hub where the ball bearing is pressed in. The tower sheave brackets will only accept a maximum sheave width of 0.50", and that's tight. 

While looking at McMaster-Carr's web site ( http://www.mcmaster.com/#wire-rope-sheaves/=o71onb ), I was surprised to see Nylon sheaves for wire rope applications. For the size I'm looking for, they have the same load rating as the metal sheaves shown near the top of the web catalog page. 

Does anyone have experience with using Nylon sheaves in the lift systems for crank-up towers? Somehow, this seems wimpy to me, but they do meet my max width requirements and have the same load ratings as similar sized metal sheaves. 

I've found another source that has what I need in stainless steel (with a bronze bushing rather than a ball bearing), but still curious about the Nylon. 

Thanks 

Shawn - N3AE