00-008-VEH: Desgaste del tambor de freno por encima del diámetro máximo

Fecha de registro	6 de abril de 2000
Número de asunto	00-008-VEH
Nombre	Ken Tozi
Agencia	California Highway Patrol
Dirección	CaliforniaUnited StatesVer en el mapa (se abre en una pestaña nueva)
Comité	Comité de Vehículos
Estado	Cerrado
Resumen del asunto	Que el desgaste del tambor de freno por encima del diámetro máximo se añada al OOSC.
Justificación o necesidad	Se debería considerar el uso de bidones de gran tamaño.
Solicitud de acción	Determinar si esta condición se puede medir al borde de la carretera y, de ser así, proporcionar un OOSC que refleje los estándares mínimos.
Medidas adoptadas por el comité	The Vehicle Committee took the inspection question to the brake drum manufacturers. No manufacturer came forth with a reliable means to measure a drums inside diameter when it is on the vehicle. While instruments using a dial indicator to measure the brake surface diameter of a drum on a vehicle were mentioned, it was noted that the lack of repeatability in their readings makes the results from using them unreliable. The following summarizes the manufacturers comments. 1. It would be difficult to measure the diameter accurately while the drum is already on the vehicle. This difficulty is compounded when the brakes are equipped with dust shields. 2. Drums in service for extended periods suffer permanent distortion from trying to conform to the brake shoes. This condition may lead to a false drum oversize reading. 4. The bus industry uses oversized linings and drums. A drum dimension criterion for them will have to be set differently than for trucks, complicating the inspection task. There was agreement among brake drum manufacturers that the only reliable method of determining the brake surface diameter is with the drum off of the axle where it can be measured with an inside micrometer. And even with this method a calibrated micrometer and a trained technician are required to produce reliable data. Out-of-round drums are particularly difficult to measure accurately and they will even thwart untrained persons using a go-no-go gauge. The definition of too much wear is another issue. While an increase in inside diameter of .120 inch (a little under 1/8 inch or 3mm) is usually taken as the worn-out value for a 16.5 inch (42cm) brake drum, this is not addressed in federal law and has not been universally adopted in the United States. Those doing accident reconstruction need a library of material to ensure that they use the proper wear limits for each size and type of brake drum. There was a brief discussion of in-depth, accident reconstruction, vehicle inspections. Based on the discussions and the advice of those that design and manufacture the drums, there was general agreement that brake drums are not amenable to wear measurements during roadside inspections. The Committee decided that brake drum measurements should not be added to the North American Uniform Out of Service Criteria.

Fecha de registro

6 de abril de 2000

Número de asunto

00-008-VEH

Nombre

Ken Tozi

Agencia

California Highway Patrol

Dirección

CaliforniaUnited StatesVer en el mapa

Comité

Comité de Vehículos

Estado

Cerrado

Resumen del asunto

Que el desgaste del tambor de freno por encima del diámetro máximo se añada al OOSC.

Justificación o necesidad

Se debería considerar el uso de bidones de gran tamaño.

Solicitud de acción

Determinar si esta condición se puede medir al borde de la carretera y, de ser así, proporcionar un OOSC que refleje los estándares mínimos.

Medidas adoptadas por el comité

The Vehicle Committee took the inspection question to the brake drum manufacturers. No manufacturer came forth with a reliable means to measure a drums inside diameter when it is on the vehicle. While instruments using a dial indicator to measure the brake surface diameter of a drum on a vehicle were mentioned, it was noted that the lack of repeatability in their readings makes the results from using them unreliable. The following summarizes the manufacturers comments.

1. It would be difficult to measure the diameter accurately while the drum is already on the vehicle. This difficulty is compounded when the brakes are equipped with dust shields.

2. Drums in service for extended periods suffer permanent distortion from trying to conform to the brake shoes. This condition may lead to a false drum oversize reading.

4. The bus industry uses oversized linings and drums. A drum dimension criterion for them will have to be set differently than for trucks, complicating the inspection task.

There was agreement among brake drum manufacturers that the only reliable method of determining the brake surface diameter is with the drum off of the axle where it can be measured with an inside micrometer. And even with this method a calibrated micrometer and a trained technician are required to produce reliable data. Out-of-round drums are particularly difficult to measure accurately and they will even thwart untrained persons using a go-no-go gauge. The definition of too much wear is another issue. While an increase in inside diameter of .120 inch (a little under 1/8 inch or 3mm) is usually taken as the worn-out value for a 16.5 inch (42cm) brake drum, this is not addressed in federal law and has not been universally adopted in the United States. Those doing accident reconstruction need a library of material to ensure that they use the proper wear limits for each size and type of brake drum. There was a brief discussion of in-depth, accident reconstruction, vehicle inspections. Based on the discussions and the advice of those that design and manufacture the drums, there was general agreement that brake drums are not amenable to wear measurements during roadside inspections. The Committee decided that brake drum measurements should not be added to the North American Uniform Out of Service Criteria.