Dwarves of the East and West
 

I've been thinking what is the relationship between the Dwarves of the West (from Eriador to Rhovanion) and the East (from Rhun to the East coast)?

They knew about each other. They communicated every once in awhile. They all got together to fight the War of Dwarves and Orcs.

Other than that, I'm afraid we really don't know too much about it. :(

But we know, that some Dwarves fought along the side of Sauron in the War of the Last Alliance. Parts of every people (save the Elves, of course) fought on both sides, consequently there must be some 'evil Dwarves' in that time. And I would guess, that these Dwarves live in the East. Otherwise we surely have heard some details of it.

Actually, Sauron must have bought them with some gold...... ;)