I remember reading in the past that rims from a later model 212 and possibly another model, will fit the 1R and allow a bit wider tire to be mounted. I've tried searching, but can't find the thread. Does anyone happen to have a part number for the proper rim? I think my machine has 3 of the correct rims now. It had a 13:00-24 mounted that didn't rub. Those rims are 3 piece with a flat lock ring. The 4th rim is also 3 piece, but the lock ring is round. I found a set of 4 NOS 12:00-24's cheap and want to use them. Thanks.

Have you measured your rims? The part where the clamps attach it to the center may be offset in the rim enough to allow the wider tires. Or if that part is offset, you may be able to mount the tires so the offset moves the rim away from the frame.

I think there were wider rims shown in the parts book for the front if mounting a Vee snow plow, but don’t remember anything about the back ones. Sorry, I no longer have either the grader or it’s parts book.

Have you checked the circumference of the larger tires won’t cause them to scrub each other on the tandems?

There is no provision to change the orientation of the rim to change the offset. Scrubbing shouldn't be a problem, it had some tall rock truck tires mounted on it. They had plenty of room. I only have the parts book for my machine. Not sure what other machine rims might fit. There is no info online and the places I've checked with have no idea. It's possible I already have the rims I need, but no way to know for sure.