Issue link: http://read.dmtmag.com/i/34501
TREAD DESIGN TREAD DESIGN Tread designs can be categorized in two basic groups. The proper selection of a tread design will enable the user to maximize tread life. Selection will vary according to various vehicle differences and/or operational conditions. Tire tread mileage can be maximized or shortened depending on the tread design chosen. RIB TREAD DESIGN: • Characterized by grooves placed parallel to the bead, thus forming ribs, ranging in tread depths from 11⁄32nds to 23⁄32nds. • Usually significantly better for fuel economy, although does not provide enhanced wet or snow traction. • Usually found on the steering axle of a truck/tractor and on other free rolling axles such as trailers, dollies, tag and pusher axles. • Also placed on torque axles when traction is not a high priority. DEFINITIONS DOT SIDEWALL MARKINGS All new tires sold in North America for use on Public Highways must have a DOT (Department of Transportation) number molded into the lower sidewall. This certifies compliance with Federal Regulations. All retreaded tires must also have an additional DOT number affixed to their sidewalls as well. It is recommended that this marking be placed in the lower sidewall near the original DOT code. Certain states may require labeling in addition to the Federal regulations certifying compliance with the Industry Standard for Retreading. The first 2 characters on an original tire code indicate the factory that manufactured the tire while the first 4 letters on a retread indicate the dealer who manufactured the retread. Production dates are indicated by the last 3 or 4 digits of this marking. Tires made or retreaded prior to the year 2000 used 3 digits, the first two numbers indicating the week and the last one indicating the year of production, followed by a solid triangle to indicate the 1990’s. Tires made or retreaded after the year 1999 will have a 4 digit code: the first 2 indicate the week and the last 2 indicate the year of manufacture. LOADS PER AXLE AND INFLATION PRESSURES The carrying capacity of each tire size is tabulated for various inflation pressures by individual tire load and by axle load for single applications (2 tires) and dual applications (4 tires). Due to the effects of load distribution and road inclination, the four tires in dual may not equally share the axle load. Therefore, to protect the tire carrying the largest share of the load, the capacity for duals is not twice the capacity for a single formation, but is usually between 5 and 13% less depending on tire size. Ensure that the air pressure between the dual tires and/or tires on the same axle does not differ by more than 5 psi. Also ensure tires run in dual are within 1⁄4 inch diameter to help achieve equal loading. All trucks should be weighed, fully loaded, on a scale (not to exceed the GAWR - Gross Axle Weight Rating). Each axle, front and rear, must be weighed separately. Actual gross axle weights should be compared with the load and inflation tables to determine the inflation pressure required. The load carried by each individual front axle tire should be noted. Due to uneven loading, motorhomes should be 52th Week of 2005 8 Section One: Tire Selection weighed by wheel end. The inflation pressure recommended must be capable of supporting the weighed values. Therefore, the maximum wheel end BLOCK OR LUG TREAD DESIGN: • Characterized by grooves placed laterally and perpendicular to the bead, ranging from 14⁄32nds to 32⁄32nds. • Selected primarily for traction and improved mileage. • Usually found on the drive or torque axle. • The increased tread depth is needed to offset the scrubbing and/or spinning that can occur when power is transmitted to the drive axle. Due to constant innovation and development, the types and sizes of MICHELIN ® tires are always changing. For the most current product offerings, please also refer to the product line brochures, the price lists, the applications data books, and the websites: www.michelintruck.com, www.michelinrvtires.com, www.michelinearthmover.com.