A few things:

 You may go through bearing seals, though I never have
You should probably size your outside 1 size smaller (do to caster causing binding) such as using a 14.9 instaed of a 16.9 or significantly deflate the outer.
You will burn through the outer dual quickly
You should consider not making this a true 30" spacing, mine is about 20".


http://talk.newagtalk.com/forums/thread-view.asp?tid=73191&mid=520903#M520903

I will never run this tractor without them again.