Every winter, tire dealers in the Northern states recite a snow prayer for one simple reason: Vehicles with worn tires get stuck. If the white stuff stays around for extended periods of time, pavement on some surface streets and back roads will be completely covered. And if there's a continuous cycle of snowing and melting, non-paved surfaces become quagmires. In either case, marginal tires will get stuck.
Unfortunately, I can't reference a study on the percentage of traction increase in snow conditions with each 32nd of tread depth over federal minimums for drive axles. But I can say that it's been my experience that tires at the 2/32 minimum are more likely to get stuck than those with 6/32. I can also say that since tires in a snow environment are constantly “wet,” it's tougher to retread casings that are near the minimum tread depth.
Then there's the argument between open-shoulder and closed-shoulder tread designs. In theory, the open-shoulder tires should result in better traction because there are more tread blocks to displace the snow. But some fleets feel these tires tend to deliver fewer miles and consider them to be louder than their closed-shoulder counterparts.
While contemplating this theory, I remembered an old customer that manufactured industrial lubricants and cleaners. One driver in particular refused to run traction tires on the drive axles. John ran steer tires on all 10 tractor positions because he figured if conditions were so bad that he couldn't get traction with 80,000 pounds, he shouldn't be on the road. He also liked to drive with the window open and enjoyed the quieter ride. In addition, he made me rotate his tires every six months and replaced the drive tires at 4/32. And he never got stuck.
Maybe John was onto something. Highway tread designs run more smoothly-and it's unlikely that an OTR vehicle will face a packed snow or quagmire situation. We never compared the actual miles-per-32nd to standard drives, but John was happy and that was enough for the company. I would suggest contacting your tire supplier for their recommendations before issuing a memo to the maintenance department, but the concept is interesting.
And you can't have a discussion about snow tires without mentioning tire chains. Most states that allow or require chains say they must be on at least one drive axle; some have additional requirements for trailer axles. The general rules are to drive no faster than 30 mph and make sure chains fit snugly before they're needed. Just because the box says they fit 11R22.5's doesn't mean they'll fit all tread designs and retreads.
There's also a movement to eliminate the weight of carrying chains by switching to cables, which weigh approximately 60% less. Most states don't distinguish between the two, but one state specifically excludes cables in certain applications when chains are required. According to the Colorado DOT, “tire cables constructed with high-strength steel spring cross-member rollers that are at least 0.415-in. diameter or greater can be used instead of chains on commercial vehicles, with the exception of single drive axle combination vehicles. On a tandem power drive axle commercial vehicle, any type of cable can be used only if there are chains on the outside tires of one of the power drive axles and cables on two or more tires of the other power drive axle.”
Finally, keep in mind that road salt and other ice-melting compounds have an extremely negative effect on the lifespan of aluminum and steel wheels. Periodic fresh-water rinses will improve their appearance.