in the market for a new e3 tire so I'm lookin through the jpcycles book and see both kinds of tire.. any advantages or disadvantages to either of them

 

Conventional wisdom is to use radials on both wheels, or on the rear only (not front only). I have a bias front and radial rear on my Glide (not Dunlop). If you use the JP guide for tyres for your model of bike, they should show you the correct spec of E3, which when I did it for an '05 come up as Bias both ends.

 

Harleys do best running bias ply.