I have the R-1 tires and wheels which I purchased a year later after buying the tractor,I originally had the R-4 tires but the traction was not what I needed.I used the R-1 tires from June 2001 and neve started having my loose wheel bolt problems until I started using my backblade to pull dirt,I was in a big landscape project and was using my tractor to cut down a bank about 500' long.The only thing I can figure is when I was using the blade to cut this dirt with the blade is,the back wheels were under load constantly and the bolt/axle hub design was not up to the job,John Deere replaced my wheel centers and axles saying they were damaged at the holes,I personnally could not see any damage to the holes,nothing a machinist could easily fixed .So I have a tractor with new wheel centers and axles/hubs after 12 hours of backblading moving and rolling dirt,this time dirt that had already been moved once prior but still a good amount of torque was required to move the dirt with my John Deere 4400 and JD 45 blade,the new wheel bolts started coming loose at 12 hours of operation,so my theory is it is the constant torque I was demanding of my tractor may be the culprit and the way the bolts are installed would not stay tight compared to using the tractor mowing or tilling etc..............I might add I never had this problem with the R-4 tires and last year with the R-4 tires I had put the tractor under the same load as I have under the R-1 tires which are bolted up the same way with the same bolts,but the R-4 tires allow more slippage than the R-1 tires,I had previously landscaped about 300' of road bank which was in excess of 50 hours of heavy backblade use using the R-4 tires which allows more slippage.