Just an update on my
BX2660 with my two front R4's constantly going flat. At the advice of my local Kubota rep, he said to have the front's tubed. My local dealer couldnt do it but the tire place next door could, and they would pick up the cost.
Well thats what I did. Cost me $40 that I still havent been reimbursed for. The tubes lasted about 4 days when I noticed one was completely flat. Nothing I could do at home to fix it. I called the place that did the tube work and he said they had to put oversized tubes in it because they didnt have the correct tube size for my fronts. Im thinking to myself you goddamm idiot! Ofcourse it went flat, it probably pinched itself and blew up. That pissed me off, so I went to a friend of mines small engine repair shop. Brought the tires in, he ripped the crappy tubes out and remounted them the way they came from the factory. So far, after 2 weeks, still holding air fine. $20 bucks.
I would advise using against tubes simply because if and when it goes flat, your dead in the water. At least with out the tubes, you can makeshift something to get by.
Add me to the list of BX2660 owners. It was bought in May of 2009 and the right front QTR Grass Master Turf Type leaks slowly year around with and without using the FEL. The other three hold air properly. I increase the front psi when using the FEL per operator manual. So far I haven't done anything except monitor all the tires more closely. This is the pits on a brand new machine. No wonder there was 40psi in that tire when the BX was delivered from the dealer. The dealer guy probably got tired of filling it up on the lot. 
