Elite III vs D251

[Idaho]

Can anyone tell me what the difference is between the Dunlop Elite III and the Dunlop D251 rear radial tire? Apparently the D251 was designed specifically for the Valkyrie. Beyond that I don't know the diff. Tread pattern? Number of bias and/or radial plies? Rubber compound?

Only reason why I ask is because when my ME880 recently wore out the only tire within reach here in East Idaho was a D251 so I bought it. The dealer who mounted it for me said that they had a h*ll of a time getting the bead to seat on the rim. I assume that means it is a lot stiffer tire but don't know for sure. Maybe I will get lucky and it will last longer than the Metzler did.