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.
