My grader is small, 4whd, 14k lbs. @cuttin edge and I both run these oddball small machines. In Texas it's called a maintainer, but Texans have a different word for many things. See pic below. It's excellent for country gravel driveways built with commercial road base. I think they were mainly built to do asphalt. My old tires were a decade old at least, and I worried about breaking down on a job site. They were also worn about 75%, and two had been tubed by the PO, one by me. So I got 4 new ones. The are R4 pattern, just like the old ones, but the sidewalls seem to be considerably stiffer, 16 ply. They are Samson Skid Steer Premium L2D in side 15 x 19.5 $550 each, ouch. The tire shop had them all at 75 psi and right away I spotted that was too rough, let them down to 30 and 45 psi, staggered diagonally. It's remarkable how the sidewalls never flex while I'm working. I generally work this machine at very low speed, so bounce isn't a problem. But these tires chatter and bounce when they slip. I just tried letting the fronts down to 22 psi to see what that does because the only the front was slipping. I'll report back to let you know how that works. Is there anyone else out here with a Mauldin M413XT ? This pic is with the old tires when I bought the machine.
I was reading somewhere about some tires needing to be run in because they aren't perfectly round but after being used a little they improve. Look on the internet under tire and wheel run out. One of the forums said Michelin tells you to drive for 500 miles to break the tires in. I realize that's vehicle tires but maybe off road tires could be similar. Also check they are seated properly on the rims. Do the new tires have a thick rim protector sidewall? If so I wonder if it might not let the tires squat as much. Is it possible you could exchange them for lower ply tires because of the issue you're having? That's a lot of money for tires that don't perform properly. I just adapted foam filled tires on a full size grader. I got them at an auction and didn't realize they were foam filled. Maybe ??? I could have returned them because they weren't listed as foam filled but they were a good deal for what they are. Your tires coming from a tire dealer should have some kind of application warranty. If you bought tires for a truck and they bounced you'd certainly want to exchange them. The wheels/tires I bought seem OK the couple hours I used them at slow speed but I'm not sure how they'll behave at higher speeds. I think they have 62 psi when the manual calls for 35 psi. They do squat a little so hopefully they'll be OK if I have to road the grader.
We had a 1 ton sweeper with foam filled rear duals. Drove it on the road and one blew out. Found out they were not meant to be used on the road. Never got above 40 mph before it blew and maybe 10 miles.. Not sure about foam filled grader tires.
The old tires were only 8 ply. I think I'm on the right track by running lower psi. That particular job is done for now so I'll have to wait a few days to try again. Because I always work off road, no pavement, I'm happy with a higher ply tire. It will resist those sharp Central Texas rocks we see here. The soil here is generally poor.
The difference in sidewall rigidity between 8PR & 16PR tyres will be considerable. The tyre pressure might have to be reduced to ridiculously low values to get rid of the problem you have but then you might run into the fact that the pressure is not enough to hold the tire on the rim and they start indexing. Typically graders run around 20-30psi, but that is on wide-base rubber.
As far as the foam filled tires I put on the grader, looking online I found some encouraging info. Some things I don't know such as what durometer of foam/rubber was used or what type. Some is made to run at lower temperatures in higher speed applications. I'd guess they have the most common durometer. The good things I discovered are that the radial tires I bought are specifically designed for graders, G2. Standard OTR tires like for a loader are not designed for sustained high speed like a grader may run. The grader goes a little under 30 mph top speed. I think tandem tires save on tire wear and heat compared to single tires too because the load is spread out. Very rarely would I need to go that fast. Some tires have dual purpose designations like E2/G2. Radial tires typically run cooler too. The tires I got also have a special rubber compound to resist ozone deterioration. I think I lucked out and the good points far outweigh the bad points for what I need a grader for. If I was doing high speed road maintainance I think I might have some big issues like tire bounce and possibly too much heat build up unless I was clearing snow. I've only just got the tires mounted but in about 2 hours of using the grader they seem fine. They're also a traction tire which is good for dirt work.
Would it be possible to put some kind of bead locks on the wheels/tires like they do on off road trucks?
I reckon I could. But it would involve fabrication, turning that outer bead into a flat surface, drilling and tapping holes, then fabbing up a lock ring for the outside. Probably a couple grand of work and a week of downtime. So before I consider that I'd try a heavy dose of bead sealant on both. I have seen cruder methods such as a dozen or more big old lag screws thru the bead of the wheel and right into the tire. But doing that to new tires would hurt my head. And it's bound to leak air.
Tubes might be another option so they won't leak air but at lower than normal pressure the tires could still slip on the rims and/or the beads could come off. With the problems you're having, I'd see if you can return the tires and get lower ply ones. The fact is they are not working for your application and that's a lot of money for something that doesn't work.
We're having trouble getting tires these days. The companies are rationing them out, and giving priority to government such as PD, Fire. Even Discount Tire has low stock. I checked on some Michelins for a pickup and they have only one set in stock. They used to stock dozens. Plus higher ply means longer life around here in our hot dry climate with sharp rocks all over.
My experience with "Samson" tires is not good in both semi truck, and semi trailer use. Balance has been the issue in all cases and short lifespan is the result. I am needing the same size tire and style you have for my manlift in 12ply rating, but won't consider the brand citing past performance even though the application is different.
Some tubeless tires do not work with tubes because the inside is not smooth enough and as the tube squirms during normal use, holes will develop where the tube contacts the inside of the casing
Tubes can sometimes be an option for slow leaks but I think running at lower than normal pressure tubes wouldn't help. I think it was on here there was a discussion about special rims that prevent them from spinning inside the wheel. It was concerning larger loaders but I think could apply to any (drive) tire running lower than normal pressure. There was also some mention about foam filled tires not preventing the wheel from spinning inside the tire too. The proper wheel would still have to be used. I was a little concerned about this putting the foam filled tires and 1 piece rims on my grader but it hasn't been a problem so far and the tires have spun a few times. Tires can spin on a grader before you even know it. The tires are likely at higher than the recommended pressure though. If they were at lower than recommended pressure I think they would be more suseptable to the wheels spinning inside them. A skid steer typically isn't as fussy about tire flex and/or tire pressure than a grader is, especially a single rear wheel grader. Like I said earlier, maybe you could exchange the tires. Even if there's a 10% restocking fee or something similar it might be the best option to get your grader working properly. You don't want the bulk of your jobs to take longer than necessary or have all the frustration.
I'd have to look at the 415, but it has the Galaxy Beefy baby, Yokohama maybe. It came with 30 PSI, but it was squatting too bad, and put it up to 80 PSI. The 2 413s came with the same as your machine, but they started leaking between the plys, and were replaced after a couple summers. We have the best luck with the Galaxys. They are rough with the high pressure, but it works the best.