TRAILER TIRES Trailer Tire requirements differ greatly from automotive tires. Automotive tires must maintain traction during all driving conditions: pulling, stopping, turning, or swerving. Because of this they must have more flexible sidewalls to maintain tread to road contact. Since trailers have no driving torque applied to their axles, the only time trailer tires must have traction is during the application of trailer brakes.
Trailers with heavy loads, high vertical sideloads (like camper trailers), or trailers with inadequate tongue weight can be affected by trailer sway problems. Automotive bias or radial tires with their more flexible sidewalls can accentuate trailer sway problems, whereas the stiffer sidewalls of the ST (special trailer) bias ply tires help to control and reduce sway problems. For this reason it is not recommended that (P) Passenger or (LT) Light Truck tires be used on trailers. Best trailer control will be achieved with (ST) Special Trailer tires. TYPES OF TIRE CONSTRUCTION A.) Bias Ply Bias Ply - Poly or Nylon cords crisscross the tire from bead to bead with the same number of ply at both tread and sidewalls, providing stiffer sidewalls and more resistance to sway. B.) Bias Belted - Bias BeltedStandard Bias Ply crisscross, bead to bead construction, but with additional belts under the tread. C.) Radial - Radial Radial Plies run at right angles straight across the tire from bead to bead with belts (usually steel wire) under the tread. This provides excellent traction holding tread to road during swerving or turning. These are very important features for controlling a car or truck, but the flexible sidewalls of this type of tire may aggravate trailer sway problems when this type of tire is installed on a trailer. TIRE SIZE IDENTIFICATION A.) Originally American tires were provided with numeric sizing (480x12, 600x13, etc.) This gave the section width (the widest point of the tire) and the diameter of the rim. Some smaller trailer tires today still retain that numeric identification (480x8, 570x8, 480x12, 570x12, etc.) Table with 2 columns and 3 rows NUMERIC 570X8 570 8 SECTION WIDTH RIM DIAMETER table end B.)Then in the 1960's tire manufacturers and D.O.T. changed most tires to alpha numeric identification to provide more information (B7813C, F7814C, H7815D, etc.) Table with 4 columns and 3 rows ALPHA NUMERIC F7814C F 78 14 C Air Chamber Size Aspect Ratio = Section Height Section Width Rim Diameter: 13", 14", 15", etc. Load Range: A, B, C, D, and E, etc. table end C.) Finally in the late 1970's and early 1980's, D.O.T. and domestic tire manufacturers converted the majority of tire production to the metric system again providing more information about the tire. Table with 5 columns and 3 rows METRIC ST20575D14 ST 205 75 D 14 Application Type ST- Special Trailer LT-Lite Truck P-Passenger Section Width: 205 mm 215 mm 225 mm, etc. Aspect Ratio = Section Height Section Width (70, 75, 80, etc.) Construction Type: D - Bias Ply R - Radial B - Bias Belted Rim Diameter: 13 14 15, etc. table end Aspect Ratio ASPECT RATIO = SECTION HEIGHT SECTION WIDTH For trailer application, it is essential that you select the correct tires to match your application and capacity requirements. (ST) Special Trailer tires are normally more expensive than (P) Passenger car or (LT) Light Truck tires because they are built tougher with more material and are more bruise resistant. This is necessary because most trailer suspension systems are stiffer and less sophisticated than automotive suspension systems. Consequently the tires must be capable of withstanding more ABUSE. ********************************************************************** This message and its attachments may contain legally privileged or confidential information. If you are not the intended recipient, you must not disclose or use the information contained in it. If you have received this e-mail in error, please notify the sender immediately by return e-mail and delete the e-mail. Any content of this message and its attachments which does not relate to the official business of Eraring Energy must be taken not to have been sent or endorsed by Eraring Energy. No warranty is made that the e-mail or attachment(s) are free from computer virus or other defect. ********************************************************************** [Non-text portions of this message have been removed]
