How many tire and wheel spares should a fleet keep on hand?
This difficult question is compounded by the sheer complexity of axle specific tire designs, increased use of higher quality retreads and the introduction of super wide tires. One point to consider is the cost of not having a replacement piece immediately available, or what costs to a fleet will result from using a “will-fit” assembly. The latter is a key but well overlooked consideration.
Most fleets and their tire dealers would agree that minimizing downtime should receive the highest priority. However, this can vary. Since most operators have established a time-related downtime cost, this number is usually accessible. The cost of the replacement parts is a good second consideration.
Tire pricing is notoriously volume sensitive, so picking a tire out of a dealer’s inventory or a shop rack compared to a spot buy of a tire might result in costs that vary by a factor of two. To help a fleet customer, it’s often a good idea to negotiate a low volume pricing structure with several break points such as two, five or 10 tires and limited-use restrictions. This increases the likelihood that you remain the emergency tire supplier as well as the primary supplier.
Often ignored is the cost associated with using a component that is compatible or “will fit.” When it comes to a tire emergency, using a “will-fit” option might result in a non-compatible casing for retreads, a tire that is difficult to match in a dual set at rotation time, or introduce a performance problem such as a steering side pull on a front-axle application. If the end result is a tire that must be removed early or moved to another wheel position, the fleet may face additional costs or the dealer may face unrecoverable costs.
With the help of their dealers, all fleets should have established guidelines for mixing tire brands and tread types across axles and in tandem drive sets in addition to matching overall diameters in dual sets. These restrictions are designed to maximize service life, eliminate safety issues, assure casing durability and determine if the replacement tire or wheel is a temporary or permanent solution.
Fuel economy penalties also can add to fleet costs. Tread depth and tire brand are the main variables that should be considered here. The use of a standard or premium tread rib tire on a trailer, tag or dolly axle is the most common misapplication. While small in some respects, this result of higher rolling resistance continues to build as the miles add up.
Another factor is the use of a new tire when a retread would be preferred. Savvy, cost conscious fleets often require vendors, especially national account providers, to maintain agreed upon quantities of retreads vs. new tires, as well as a guaranteed mix of tread types and depths in over-the-road service locations.
Expense offsets, security issues and the potential need for just-in-time delivery are also things fleets will consider when working with tire dealers and other vendors.
From a fleet perspective, just-in-time supply, plus guaranteed availability with a penalty if violated, can be negotiated with some suppliers. Regardless of who maintains the inventory, fleets should assure that their tire stock turns regularly so that the first-in-still-here inventory system doesn’t add to costs. Tires are made from chemical composites that are age sensitive after manufacture. This is one reason for establishing time limits for purging older tires (casings), first from line haul service, and eventually from short haul duty.
Some other variables fleets consider include:
Breadth/density of a fleet’s traffic routes
Geographic coverage of preferred tire/wheel suppliers
Inventory security considerations
Complexity/different types of tire and wheel choices
Overall availability of preferred parts.
This is only a partial list and will vary by operation. However, by addressing the inventory issue up front and from a fleet perspective, commercial dealers can find effective and meaningful cost savings and process efficiency that will make a difference with any fleet.