I don't know if spacers can or should be used. Does this weaken anything by using spacers?
I don't know if there are adjustment on the rear axle. I will ask the dealer later today.
Most tractors have adjustable rear wheels. The rim is bolted to the center section. The center section is dished. By mounting the rim to the center dish in vs dish out you change the distance between the wheels. The place where the rim mounts is also off centerline, so you can change there too. That gives 4 distinct widths.
If the standard rim/center does not allow for adjustment, DON'T BUY IT. Tell the dealer to either provide adjustable wheels or buy them from the tire store yourself.
A lot of the "can't be done" the sales people give out just means we don't want to as it might bit into our profit.
Are R4 rims adjustable? My R1s are, of course, but I don't know about R4s. CrazyQ, on my Kubota the rims are just as John outlined above, and it can get a little hard to visualize and in some cases you have to remove wheel center, flip it and bolt it back to a different set of tabs on the rim. This really isn't difficult, but, the way mine came from the dealer, you could just swap sides with the whole tire/wheel/rim assembly for a wider stance. This is very very easy, just move the right one to the left, keeping the 'arrows' in the tread pattern facing forward. This simple change could move the high point of the tire (the center) out from under the fender altogehter.
R-4s are good all around tires, but IMO, the only thing worse in the mud would be turfs. I speak from experience. http://i153.photobucket.com/albums/s...1977/stuck.jpg
That time I was able to push it out with the bucket, a few times though, I could not. The biggest drawback to the R-4s in the thick mud is that when the front end goes in to the axle, often the back does not have the traction to pull the front out, even in a couple inches of mud. If you do not stop and re evaluate things right away, you will bury it every time. My rears are loaded with calcium and I have a 500 or so pound box scraper on it, and still lack rear mud traction due to the tread clogging.
A better rear weight in that situation is a forward rotation rototiller. It acts just like a paddle wheel and can give you a big boost out of a booger hole. Or just push you in even farther. I've done both!
I have recently bought a complete set of 4 R-1's, I am now looking for a good used set of front wheels. In hindsight, I should have just bought a good used hydraulic winch, it would have been way cheaper than another set of tires, and close to 100% effective, as long as I have a tree close by to hook onto, and I have lots of trees.