Amtrak has removed all 20 of its Acela Express trainsets from service on the Boston-New York-Washington Northeast Corridor after cracks were found in the braking system on many of the trainsets’ coaches during routine inspections. Cancelled are 15 New York-Washington trains and 11 New York-Boston trains, which will remain out of service until the problem is resolved.

That could take a considerable amount of time. The cracks have been found in the spokes of the axle-mounted hubs that support the coaches’ inboard disc brake rotors. There are three inboard rotors per axle, four axles per coach. Multiplying that by six coaches yields 72 hubs and rotors per trainset. That’s 1,440 integral hub/rotor assemblies in the fleet of 20 trainsets. The only way to replace the hubs is to drop every wheelset, remove every wheel, and remove every hub/rotor assembly.

Much is unclear at this point: Whether the hubs can be replaced without modifications or if a redesign is needed, and how long that will take. Whether there are enough spare hubs in inventory (probably not). Whether Amtrak will be able to substitute Amfleet-equipped trains to protect NEC service. In any case the spoke-cracking problem most likely means the Acela Express will not be in service for a while. That service accounts for 53,000 NEC seats—over $6 million in revenue—weekly.