I have a JD8400 with 710/70R38 rear duals.  Driving this thing is like riding a bucking bronco all day.  With the front end driving I get power hop under any heavy pull and without the front end on, it still is bouncy as can be.  I've tried all the suggestions to get rid of power hop.  I'm ready to trade it but I'm wondering if I would be happier with a different tire setup.  Is anyone else running these tires on an 8000 and are you happy with them?