Try lowering the tyre pressures a bit. This will ease the dual wheel "slap" which causes shock loading on rims and bolts.
I`m no tyre expert and I don`t operate a Combine. but 30 PSI or even 28 on Duals seems too high. I`d try lowering that to 25 and see how you go.I think 30 psi is recommended. I am at 28 psi
How low can you go with no tyre damage ?
Had the Cleve dealer mods done at the end of 2013 harvest Tony, it involved new higher grade studs 1000 ft/lb torque, and grinding paint off the rim contact areas. No cracking or broken studs this year (350hrs).The newer CNH duals have gone from 12mm to 14mm centres with different dishing which helps.
Upgrading to 12.9 grade studs from 8.8 also has been an improvement.
NH required as a warranty job to crank ours up to 1100 insanely tight but have been 1000h trouble free.
We have also dropped our 620 duals from recomended 35?psi to 28, prefer to split sidewalls at 4000+h than break rims and studs every 500.
Personally think one of the bigger flaws is that they should have a inside and outside rims. Inside rims (normally go first) dont require the large holes to clear the 5 inner nuts which is a huge weak point.
We have a rim with a 20mm welded centre if you want to have a look nobby
This makes sense.We make a 1/2" thick ring spacer that goes on the outer surface of each rim to prevent them from cracking out. The factory 1" thick bushing spacers cause localized pressure on the bolt holes that causes the cracking. A full ring plate provides distribution of the load throughout the entire mating surface. We've repaired a set of 4 rims by removing the centers, and replacing them with 1" thick rings welded in. But as a preventitive measure these ring spacer plates work well. The factory lug bolts work with these. The set of 4 spacers are available for $200.00 though Supreme Welding Inc. Home