00-008-VEH: Usure du tambour de frein au-delà du diamètre maximal

Date d’inscription	6 avril 2000
Numéro de l’enjeu	00-008-VEH
Nom	Ken Tozi
Organisme	California Highway Patrol
Adresse	CaliforniaUnited StatesVoir sur la carte (s’ouvre dans un nouvel onglet)
Comité	Comité des véhicules
État	Fermé
Résumé de l’enjeu	L'usure du tambour de frein au-delà du diamètre maximal doit être ajoutée à l'OOSC.
Justification ou besoin	Il vaut la peine d'envisager l'utilisation de fûts surdimensionnés.
Demande d’action	Déterminer si cette condition peut être mesurée en bordure de route et, le cas échéant, fournir une OOSC reflétant les normes minimales.
Mesures prises par le 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.

Date d’inscription

6 avril 2000

Numéro de l’enjeu

00-008-VEH

Nom

Ken Tozi

Organisme

California Highway Patrol

Adresse

CaliforniaUnited StatesVoir sur la carte

Comité

Comité des véhicules

État

Fermé

Résumé de l’enjeu

L'usure du tambour de frein au-delà du diamètre maximal doit être ajoutée à l'OOSC.

Justification ou besoin

Il vaut la peine d'envisager l'utilisation de fûts surdimensionnés.

Demande d’action

Déterminer si cette condition peut être mesurée en bordure de route et, le cas échéant, fournir une OOSC reflétant les normes minimales.

Mesures prises par le 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.