Stupid Single Tires
I initially sent this as a private message reply, but thought better of it, apparently I didn't send it to the OP anyway LOL. The info here would be beneficial to anyone considering this...
DON'T. For the love of God and all that is holy, DON'T.
As a trucker, I can tell you that these things are not all they're cracked up to be. Sehnsucht is right, but not just from a bearing wear standpoint. If not shimmed / spaced properly, they actually decrease stability, the whole reason for having duals in the first place. You actually need spacers or a wider axle in the first place, otherwise they give up a lot of stability, and you might tip it over before you have a chance to destroy the wheel bearings...
For example, I drove a 2016 Freightliner that had Stupid Singles when I got it at 4500 miles. But I can almost guarantee this was not a factory install. When hooked to a trailer, I could visibly see that the outer sidewalls were a good six inches in from where the outer dual's outer sidewall would have been -- PER SIDE.
Giving up a foot of width greatly decreases stability when the bulk of the vehicle's weight rides above the tires, and curved exit ramps at perfectly legal speeds that would have been no problem with duals, scared the hell out of me with the Stupid Singles. The narrower the wheel track, and the more top-heavy the vehicle is, the more easily the vehicle will roll over, and I can tell you from experience, switching from duals to Stupid Singles is not a good idea.
If you do, make sure that the proper size shims and spacers are used to maintain sufficient wheel track. Stupid Singles have less traction in certain situations as well. Reason being that a dual setup can simply push loose stuff out between them instead of spinning a single surface above it.
Another benefit of having duals is that if you blow one tire, you can limp on what's left to have it repaired. Can't do that with Stupid Singles, and every minute you wait for a road service to repair/replace your tire is a minute you're at risk for someone running off the road and crashing into you.
They have been said to increase fuel mileage, but I'm not seeing it. I managed 7.5-8.1 in a dual-wheel Peterbilt 386, that Stupid-Single Freightliner managed 6.6-7.0. Another Cascadia with dual-wheel managed 6.4-6.8.
To compare...
The 386 - 10L, 10-speed, 3.42 gearing, 7.5-8.1 with 46k loads
SS Cascadia - 15L, 10-speed 3.23 gearing, 6.6-7.0 with 38k loads
Dual Cascadia - 15L, 10-speed, 2.94 gearing, 6.4-6.8 with 44k loads
The first two were pulling 38k-46k on average, both had fairly level roads for the most part. The third one did far more mountain driving and had an average 44k load to boot. So as you can see, have not seen where Stupid Singles help fuel economy that much, if at all. New Stupid Singles cost anywhere from $550 to $1400 or more each, you can get duals for around $250 each.
As you can tell, not a fan, mostly from a safety standpoint. Wide singles are okay for heavy-haul trucks that need more weight distribution on the front tires, but I haven't seen where they're beneficial as drive or trailer tires.
