rbcsaver,
The chains I ordered for my B2910 did not fit when they arrived either.
Turned out that the place I got mine from sent the next size larger, and I had to remove a couple cross chains and some of the side chain to make them work. I think there is an old thread where I posted a question and some photos.
So if the chains are real loose, this may be your situation too. If they are too small, that is a different story... /forums/images/graemlins/smile.gif
Would not hurt to call the vendor and ask and see what they say...some sales literature I have says the B7510DT/HSD rear tire size is 9.5-16.