This condition occurs when heavy or prolonged braking generates excessive heat, causing the steel on the wheel tread to develop a web of hairline thermal cracks. If left in service, a comby wheel can spall or shatter under load. Car inspectors look for these heat checks during routine yard inspections to bad-order the car before a catastrophic failure.
Heard on the job
Bad order that gon on track four, the lead axle has a comby wheel on the engineer side.
Insider tip
A comby wheel usually points to a dragging brake shoe or a handbrake left tied on during a move.
Also heard as
- thermal cracking
- heat checked