The Right Truck Tires
Selecting the proper steer, drive, trailer, and dolly tires for your fleets is not always intuitively obvious. Depending on the specific service vocation, there are plenty of tire options available in the market.
Fleet operators, maintenance managers and tire purchasers all need to understand the tire selection process and the thought process in selecting the specific tires, which will maximize tire removal mileages, maximize the number of retreads per casing, increase fuel economy and give the best traction possible.
Many fleets have vehicles that run in various service conditions. Some vehicles may run in pure line-haul operations from coast to coast in a straight line while others may see more regional line-haul service. There is city driving that is included the pickup and delivery category.
Vocational trucks typically see both on- and on-off road applications. The most important consideration when specifying tires is to clearly define the specific service vocation. Every tire manufacturer has tires that fall under these various vocational categories.
Tires designed to run in pure line-haul highway operations will have long lasting tread compounds to produce high tread mileage and great fuel economy (low rolling resistance). These tires are designed to resist irregular or uneven wear.
Tread depths can’t be too deep because tread squirm will lead to both irregular wear and high heat. There is an optimum tire tread depth for the various wheel positions.
Tires that run in pick-up-and-delivery-type service see a high incident of turning and road hazards. Special compounds are developed for this type of service along with the ability to resist punctures. Sidewalls are designed to minimize damage from curbing on city streets.
In some cases, vehicles may see a combination of service vocations for which you need a tire that is a compromise. These tires may not perform as well as tires specifically designed for a particular service vocation, but they will provide good overall performance.
Many vehicle considerations include tire space requirements. The appropriate tire size is specified based on the worst case vehicle load scenario; air is what carries the load. There are normally only two or three tire sizes that can do the job based on your worst case load scenario.
In order to select a new tire size for a given application, the dimensional clearance of the tire must be acceptable. When it comes to tire clearances, there are three measurements to keep in mind:
- Vertical clearance;
- Front tire clearances; and
- Overall width.
Vertical clearance is the distance between the top of the tire tread and the vehicle above it. Of course, the clearance varies as the axle operates. Steer tire clearances are the distances between the front tires and the vehicle. The clearance of the steer wheels is checked by the turning the wheels from full left lock to full right lock.
The overall width of dual tires or wide-base tires is also important to measure to ensure there is enough room. On dual drive tires, a minimum of two inches of additional clearance is required if using tire chains to ensure enough vehicle clearance.
Another vehicle consideration is choosing the appropriate rims or disc wheels. The Tire and Rim Association publishes a list of acceptable wheels for every tire size. It is important to select the wheel that can handle the load and inflation ratings of the tire selected.
Wide-base tires are becoming more and more popular for weight savings (increased payload) and fuel economy improvements. Some of the other advantages include:
- Reduced tire and rim inventory;
- Eliminating of mismatched dual tires; and
- Easy to maintain since only one tire for checking tire pressures.
Another factor is matching tires for speed and axle weights. Consideration must be given to selecting a tire size and load range that at least equals the vehicle placard requirement by axle position. Some tires are speed restricted at 55 MPH. Highway tires are normally rated at 65 to 75 MPH.
There are also a few fleet operation considerations when selecting tires, which can include:
- Availability of product;
- Tire cost per mile;
- Retreadability and repairablity costs and servicing;
- Warranty; and
- Financial inventory investment.
It is always a good idea to work with your tire professional when its time to spec’ing tires and retreads for your fleets.
An excellent source of additional information on the subject of tire selection process is RP 223D published by the Technical Maintenance Council of the American Trucking Associations.