As a former emergency road service technician, I can personally attest to the frustration and aggravation that accompanies a flat or destroyed tire on the side of a road. It costs the fleet extra money all the way around and with time-sensitive delivery, the penalty for being late can be severe. While some might say the only winner is the company who gets paid to repair or replace the tire, I would ask them to crawl under a trailer on the shoulder of an Interstate highway in freezing cold temperatures before they give Regis their final answer. I never felt like a winner until I safely made it back to the shop.
Emergency road service for a failed tire will always be the cost of doing business for any company or organization that operates vehicles with rubber tires. Between the weight of the vehicle, debris on the road and the condition of the road itself, there are going to be times when an inflated tire doesn't have a chance. An unavoidable service call is exactly that, unavoidable. The driver cannot see everything on the road, and the surfaces tend to collect an incredible array of objects that can destroy a tire in a split second, so it's going to happen.
During the coldest months of the year, one component of the inflated tire assembly becomes extremely vulnerable. If the valve core inside the valve stem is exposed to rain, snow or ice and then parked in below freezing conditions, it can cause the tire to gradually deflate. I can remember days when the temperature dipped to below zero and there would be a rash of flats first thing in the morning, and almost every tire would check out in the dunk tank and on the spreader. None of them had a valve cap when we arrived, but they were all completely flat and off the rim.
Before I go any further, I have to define the word “valve cap.” In my view, a valve cap must be metal and contain a sealing ring on the inside to create an air-tight seal with the valve stem. Plastic varieties are basically dust covers and if the brake heat doesn't melt them in the summer, the cold may break them in the winter. A plastic valve cap gives the fleet a false sense of security because it won't prevent a valve core leak from deflating a tire. While it may seem absurd that a part costing pennies could cripple a vehicle, it's also a fact that failing to protect that part with a proper valve cap increases the chances for another avoidable emergency road service situation.
There are two types of acceptable metal valve caps capable of stopping a valve core leak: standard and inflate-through. Both have the sealing ring and both create an air-tight seal. While standard metal caps are effective and can be seen as the best approach, they require disciplined drivers, mechanics and service providers to make sure they are replaced after the inflation pressure is checked or adjusted. Inflate-through valve caps are the most practical if everyone is expected to check each tire with a gauge, but they are also more expensive and prone to disappear. Like most components, the level of quality is typically linked to price, so less expensive inflate-through caps may not have the same lifespan and performance as name brands.
Finally, if a fleet is going to spend the money on aluminum wheels, the inside tire will rarely be gauged unless it has an inflate-through valve cap, especially during winter.