When it comes to rear-ends and ordering custom axles, there are a lot of different measurements to be aware of, even within the same type of housing family. One of the critical measurements is known as “axle hangout” which, as the name implies, is the amount the axle protrudes from the face of that axle flange. “Each style of housing end has its own unique hangout,” explains Jeff Geesaman of Moser Engineering. “The amount of axle hangout will determine your brake gap.”

The first step to find the proper axle hangout is to determine exactly which style of housing end you have. That in and of itself can be a tall task, thanks to the sheer number of options in the wild.

“The easiest way to determine your flange type is to measure either the vertical or horizontal, center-to-center distance between bolt holes on your axle flange,” explains Geesaman. “You can do that with a tape measure, or more to be more accurate, you can use a set of dial calipers.”

Although similar, axle hangout and the “B-dimension” needed on a custom axle order sheet are critically different.

In some cases, proper axle hangout cannot be determined by flange style alone. In that case, a second dimension referred to as the “B-Dimension” is required to get the proper axles.

“The B-dimension is not the actual axle hangout, but rather the distance from the outside of the axle flange to the bearing stop,” Geesaman said. “The axle hangout is actually the distance from the axle flange to the housing end. The bearing stop on the axle itself [and thus, the “B-dimension”] actually protrudes slightly from the housing end.”

During the order process, this can cause a bit of confusion. To ease this, Moser has taken the time to create a video detailing the difference between axle hangout and the “B-Dimension” on the order form with very well illustrated examples and explanations.

Watch the video above, you never know when the knowledge may come in handy.