Tech Bulletins

 

TIRE MIXING

When tires need to be replaced, do not guess what tire is right for the vehicle. You must consult the tire placard, which is normally located on the vehicle door edge, door post, glove box or fuel door. The placard tells you the size of the tires (including the spare) that were mounted on the vehicle as original equipment (OE). It also includes the recommended cold inflation pressures for the front/rear axles and the spare tire as well as the load capacity. If the vehicle does not have a placard, check the owner's manual or consult with the vehicle manufacturer or tire manufacturer.

IMPORTANT: Always check the vehicle manufacturer's recommendations for the OE tire size, load capacity, inflation pressure, and speed symbol information before replacing a tire with a different size and construction. It is not always possible - usually due to temporary emergency conditions - to select the same tire size for a replacement tire. Never choose a smaller size replacement tire and/or a tire with less load carrying capacity than the specified size on the vehicle placard.

The RMA provides the following insight for emergency/temporary nonstandard fitments:

The following is a passage from the RMA Replacement Guidelines for Passenger & Light Truck Tires manual.

TIRE MIXING

It is recommended that all four tires be of the same size, speed rating, and construction (radial, non-radial). In some cases the vehicle manufacturer may require different sized tires for either the front or rear axles. NEVER mix P-Metric or European Metric passenger tires with light truck sized tires on the same vehicle.

Match tire size designations in pairs on an axle, except for temporary use of a spare tire. (See Dick Cepek Truck and Offroad Tech Bulletin #5 "Replacing Less Than Four Tires").

If two radial tires and two non-radial tires must be used on a vehicle, put radials on the rear axle. If radial and non-radial tires are used on a vehicle equipped with dual rear tires, the radial tires may be used on either axle.

  • Speed rated tires - If the vehicle tire placard and/or owner's manual specify speed rated tires, the replacement tires must have the same or higher speed rating to maintain vehicle speed capability.
    1. If replacement tires have lower speed capability than specified by the vehicle manufacturer, the vehicle's speed must be restricted to that of the replacement tire. Also, vehicle handling could be affected. Consult vehicle manufacturer or tire manufacturer for recommendations - and consumers should know the speed must be restricted to the limits of the replacement tire.
    2. With the exception of winter/snow tires (see below), if tires with different speed ratings are used, it is recommended that the lower speed rated tires should always be placed on the front axle. This is to prevent a potential oversteer condition.
  • Four-wheel drive (4WD) and All-wheel drive (AWD) vehicles-
    If no instructions for tire mixing appear in the vehicle owner's manual, follow these guidelines:
    1. DO NOT mix tire sizes. All four tires must be marked with the same tire size, unless otherwise specified by the vehicle manufacturer. This also applies to winter/snow tires.
    2. DO NOT mix radial and non-radial tires. All four must be either radial or non-radial.
    3. DO NOT mix tread pattern types such as all-terrain and all-season.
  • Winter/Snow tires - It is always preferable to apply winter/snow tires to all wheel positions, including duals, to maintain vehicle mobility and control.

Should you wish to order copies of RMA Replacement Guidelines for Passenger & Light Truck Tires manual, you should contact RNA at the following address:

RUBBER MANUFACTURERE ASSOCIATION
PUBLICATIONS DEPARTMENT
1400 K STREET, N.W.
WASHINGTON, D.C. 20005
PHONE 800-325-5095

This is Dick Cepek Technical Bulletin #7 (Updated 08/26/2010)
For more information regarding Dick Cepek Products ph: 330.928.9092