By Christopher Lyon
Director of Fleet Relations
Published March 23, 2018
P-, Euro- and LT-metric tires
As truck manufacturers continue to bring Euro-style vans into the North American market, it is important to understand subtle differences in components that can have significant influence on operations. As safety is an important mission within your organization, it’s your job as fleet manager to provide employees and customers with safe, compliant vehicles and equipment. This includes understanding many aspects of vehicle design and OEM specification replacement parts.
Tire replacement is one of the easiest issues to overlook. As a fleet manager, you’ve likely standardized many components within your operations as this reduces downtime and inventory overhead. Tires, however, can be misunderstood due to labeling differences between Euro-style and North American tires. Sidewall markings can look similar, and tire size may be equivalent. However, it’s important to note load rating is calculated differently on P-, Euro- and LT-metric tires. There are a few standards set by either Tire and Rim Association Inc. or European Tyre and Rim Technical Organization. These two organizations use different calculations to define a tire’s maximum load capacity, but they use similar sidewall identification that can easily be mistaken when replacing tires. Specifically, the nomenclature looks similar but has different meanings. Nominal width, aspect ratio and rim size are identical. The subtle difference is knowing the type of tire that came from the OEM. The three main classifications for on-road tires are P-, Euro- and LT-metric tires.
What tire do you have?
If you have a Euro-style van in your fleet 235/65R16 and stock a P235/65R16, for example, could they simply be considered equal? The answer could be yes or no. The key factor is load index. P- and Euro-metric tires use different calculations to determine load and inflation values. Generally speaking, P-metric tires have a lower load capacity reserve than Euro-metric tires, so it’s important to note the required capacity when replacing tires. Be aware these tires may or may not meet/exceed OEM requirements. Escalating this knowledge to your users and customers is imperative. Using an under-specified tire can be dangerous and carries unnecessary risk.
Vehicle certification is another important point. Replacing components that do not meet or exceed original vehicle manufacturer requirements may result in falling short of National Highway Traffic Safety Administration certification standards. Knowingly or unknowingly allowing this to happen reduces fleet safety and makes your organization vulnerable to serious liability. It’s important to reiterate the fleet manager is responsible for supplying their users with safe, compliant vehicles. Some fleet managers may be less concerned than original manufacturers about replacing tires that have a lower load index for ease of standardization. Their thought process is based on how they perceive actual use and application. They realize the tires they’re replacing have a lower load index and carrying capacity than the original tires. However, they may not find this concerning as they realize their vehicles are not fully loaded to maximum capacity. In addition to premature wear and tear and safety compromises, this is a huge liability for your organization. In the event of an accident, regardless of cargo and weight, the vehicle does not meet regulatory compliance simply due to the tires. A fleet manager may face legal consequences for knowingly or unknowingly allowing this to happen.
The figure above represents a Euro-metric tire. C indicates this is a commercial tire, not a load range of C (found on an LT-metric specification). At first glance, this can be confusing due to the similarities and subtle differences. Most seasoned fleet professionals that have used LT tires are familiar with load range letters, which range from B to F and simply indicate the number of plies constructing the sidewall and maximum load pressure. This designation is not to be confused with load index — the weight-carrying calculation based on a given tire pressure which varies between P, Euro and LT-metric tires. It is important to understand these differences and ensure the tires being replaced meet or exceed required OEM specifications.
Reading the sidewall
When replacing tires, the first priority is understanding what the sidewall markings mean. P-, Euro- and LT-metric specified tires have similar sidewall markings. Keep in mind, a P- or LT-metric specification may not be equivalent to a Euro-metric specified tire when it comes to load rating. Looking at tire size, if it is prefaced with P or LT, this indicates a P- or LT-metric tire. These are normally intended for passenger or light truck applications, respectively. If the tire size does not have letters at the beginning, this is an indication of a Euro-metric tire. This will have a different load capacity than its P- or LT-metric counterparts. Tire width is the three-digit number that covers the width of the tire in millimeters. Aspect ratio is the next two-digit number — defined as a percentage of a tire’s height to width. For example, 65 would be 65 percent of the tire’s width — the greater the aspect ratio, the larger the tire profile. Tire construction is represented by a letter — most commonly R for a radial tire. Wheel diameter is the last two-digit number. Measured in inches, it defines required wheel size.
Ensure the correct tires
With all the litigation and liability facing the fleet industry, the best rule of thumb is to have a plan to ensure the correct tires, and meet or exceed OEM specifications. To start, this can be accomplished by looking at the current processes you have in place. Connect the specification writer with the procurement team. Communication is imperative. Make sure the procurement team has the information to identify potential issues. Have written documentation explaining key differences and consequences related to improper tire replacement. Generally, when people understand the consequences, they are more sensitive to the key differences. Consider keeping a written notice in the vehicle glovebox that identifies tire requirements. As operators may utilize different vehicles, it’s essential to communicate and have training on available information. Beyond this, maintain communication with your vendors. Procurement may request a certain tire by size, but it is important for them to start asking application questions. Taking a few more minutes on the front end can ensure compliance and safety.
At the end of the day, running a fleet can become overwhelming. There are so many small details that can create a world of noise and distractions. Having proper procedures in place can eliminate unnecessary mistakes that could lead to catastrophic failures. Engaging multiple lines of communication and training reduces the risk of any single entity (i.e., procurement, end users, vendors or even fleet managers) letting some small detail slip through the cracks. Providing the correct components on all levels will reduce maintenance costs; lower risk and liability for your organization; increase safety; and avoid premature wear on components.
Trucks with GVWR under 10,000 pounds include placarding that identifies the original equipment tire sizes, inflation requirements and vehicle weight capacity. This is located on the driver’s side door jamb. Beyond premature wear, proper inflation is critical to maintaining the correct load capacity of vehicle tires. If tires are changed from the original manufacturer’s specification, it is critical to ensure that proper tire inflation is achieved.
Green Truck Association (GTA), an NTEA affiliate division, offers a variety of resources to educate its members on techniques and technology that can improve fleet efficiency, reduce emissions across time, and lower the risk of fuel price volatility driving up operating expenses. GTA fleet members can get involved in a data logger drive and duty cycle program that provides information on how vehicles operate in varying environments; find details at greentruckassociation.com.
NTEA offers fleet managers access to publications and reference materials on current regulations, safety standards and other technical issues at ntea.com. To learn more about the tools, resources and solutions available exclusively to members, visit ntea.com/memberbenefits.