Problems with Bias Ply Tires on Specific Off-Highway Trucks{4203} Caterpillar

Off-Highway Truck:

773F (S/N: EED1-UP)

777D (S/N: AGC1-UP; FKR1-UP; 3PR1-UP; 2YW1-UP; AGY1-UP)

777F (S/N: JRP1-UP)

785C (S/N: 1HW1-UP; APX1-UP; 5AZ1-UP)

789C (S/N: 2BW1-UP)

793C (S/N: CBR1-UP; 4AR1-UP; ATY1-UP; 4GZ1-UP)

793D (S/N: FDB1-UP)

Introduction

The problem that is identified in the technical information bulletin that follows does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.

Problem

The current use of bias ply tires on off-highway trucks is the result of an exceptional circumstance. When you use bias ply tires, special care must be taken in order to ensure that use of the bias ply tire is successful.

Caterpillar has tested specific bias ply tires and approved specific bias ply tires in specific applications. Caterpillar cannot advise the use of other bias ply tires.

The installation of bias ply tires on Caterpillar Off-Highway Truck can cause the failure of the rims and rim components. Specific problems have been reported.

• Cracking of the bead seat band at the butt weld on the demountable rim

• Cracking in the rim base in the groove for the lock ring

Illustration 1	g01389544

The cracking of the bead seat band (1) has been associated with the use of bias ply tires when the load rating of the tire has been exceeded. The construction of a bias ply tire is stiffer than construction of a radial tire. The bias ply tire and the radial tire load the rim differently. When you exceed the load rating of the tire manufacturer, the inflation pressure or the travel speed, you will amplify the effects of the differences between the loads that are placed on the rims by the two types of tires. This can lead to the cracking of the bead seat band at the butt weld. The cracks eventually propagate across the bead seat band. Eventually, the cracks will cause the tire to gradually loose tire inflation pressure.

Illustration 2	g01389547

Limited reports have been received of cracking in the rim base in the groove for the lock ring (2). The data is insufficient to correlate these failures to the use of bias ply tires. The possibility of the correlation exist.

Solution

When you use bias ply tires, you must closely monitor the payload, the travel speed and the tire pressure. You will greatly increase the chance of success for the bias ply tires, the rim and the rim components by combining the monitoring with preventive maintenance programs for the proper maintenance of haul roads, the proper maintenance of the loading area and the dump area.

When you consider changing from radial tires to bias ply tires, consult with a representative from your local tire dealer for information on the load rating, the travel speed and the tire pressure in order to optimize the installation of the bias ply tire. The recommendations should closely reflect the industry standards.

The following table lists the industry standards for bias ply tires for load ratings, inflation pressure and machine speed.

When you use a bias ply tire within the industry standards, precise inspection of the rim and rim components is advised. Thoroughly clean the parts. Carefully inspect the parts for the initiation of cracks when you change the tires. Perform a visual inspection of the tire and rim and check the tire pressure daily.

The correct application of the bias ply tire will provide the best possibility for the maximum performance of the tire, the rim and other machine components. However, the radial tire is still the preferred tire for use on the off-highway trucks.