Radials: 180/70R-16 150/80R-17
Bias: 180/70B-16 150/80B-17
As far as the OEM Bridgestone Exedra's are concerned, radials are all is offered. Now that being said I have a Vulcan 1600 that weighs 25 lbs. more than my "dressed" standard and it comes from the factory with bias ply. Why? I don't know but a lot "heavys" use radial tires. I'd stay with what the factory used/design fot the Valk's ride/suspension setup. If this would be your 1st. tire change I'd stay with the radials to determine the difference in ride with new tires. That alone is a night and day difference in most case. The wear factor between bias and radials, I just can't say as I respect that the manufacture knows best but....
OEM were Dunflops. At least on the two I bought.
Also +1 on the Avons well over 100k. And still happy.