How 'bout sticking to the articulable facts of the matter with respect to SRW vs. DRW applications without getting emotional?
The issue of 'stablility' was brought up -
Just the facts:
Basic physics -
The three factors affecting stability:
1) Increasing the mass increases stability
2) Lowering the center of gravity (CG) increases stability
3) Increasiing the area of the base increases stability
With DRW, does having two additional wheel/tire assemblies:
1) increase the mass? YES
2) lower the CG (due to increased mass in the rear of the truck at the lowest possible point)? YES
3) Increase the area of the base? YES
So clearly, and personal opinions aside, DRW configuration is inherently more stable than SRW. That is purely fact.
Now, regarding tire ratings and such:
As an example, the tires I have on my dually are LT235/85R16 rated 'Load Range E', which translates to 3042# max. wt. per tire in a SRW application and 2778# max. wt. per tire in a DRW application (load ratings are at max. inflation). There is a difference in the weight rating due to the fact that in a DRW configuration, if the sidewalls of the tires are rubbing on the load bearing side (i. e. the six o'clock position) there is a heat buildup that could likely cause failure of the tire(s) (i. e. blow-out). Therefore there is more tolerance for the bulging effect due to a heavy load in the SRW application, thus the higher weight rating in the SRW application. Generally, heat is what causes tires to fail before the end of their service life (faulty workmanship and/or material notwithstanding).
A little simple math:
Let's say the empty weight on the rear axle is roughly one metric ton, i. e. 2,200# (less the weight of the tires themselves). Please feel free to correct my assumption on the weight on the rear axle.
SRW w/ Load Range E tires: 3,042# x 2 = 6,084# max. wt. capacity on rear tire combination; 6,084# minus 2,200# =
3,884# max. load on SRW truck equipped with load range E tires
DRW w/ Load Range E tires: 2,778# x 4 = 11,112# max. wt. capacity on rear tire combination; 11,112# minus 2,200# =
8,912# max. load on DRW truck equipped with load range E tires
8,912# minus 3,884# = 5,028# (roughly, as an example)
A substantial difference.
Ok, let's give the SRW an advantage, e. g. Rickson 19. 5" tires w/ a load range G rating (3,970# per tire) -
3,970# x 2 = 7,940# max. wt. capacity on rear tire combination; 7,940# minus 2,200# =
5,740# max. load on SRW truck equipped with load range E tires
Now suppose one is towing heavy and the pin weight is 3,500# on a Ram 3500:
SRW: two load range E tires will be loaded approximately 90% of their wt. rating
SRW: two load range G tires will be loaded approximately 60% of their wt. rating
DRW: four load range E tires will be loaded approximately 40% of their wt. rating
Being that a heavier load generates more heat in a tire (again, heat is the #1 cause of blowouts), it would only follow that a tire that is loaded less than half of its wt. rating would be far less likely to blow out than one that is approaching 'redline'.
Generally, electrical cirucuits are designed and installed to run a load of no more than 85% of the rating for the wire and breaker or fuse for safety reasons. JMO, but I am convinced that tires should be kept within the same safety factor.
Is it possible one tire blowing out in a DRW application could result in the consequential blow-out of the one next to it? Certainly. But again, a tire being run at less than 50% of its rated capacity would be much less prone to blowing out than one being run at 90%, therefore, all other things being equal, the DRW application is still far safer for that one reason alone.
BTW, I grew up in the tire biz (3rd gen. ). Those 'super singles' have been around at least 35 years. We ran them (Goodyear Super Singles in 16. 5") on our one ton fleet body service trucks, we even had a truck or two with these in Goodyear military tread. Guess what - if these super singles haven't caught on in 35 years, they probably won't.
Attention: TDR Forum Junkies 
