Son has ranger dual axal trailer and I have noticed in the center of the hub, there is a black plastic cap. This is a regular ranger trailer. On one wheel, the black plastic hub is sticking out and on the other wheel, it is sticking in. Is there any significance to the position of these black plastic hubs? Thanks in advance as this trailer is new to us. The trailer is a model year 2002. Thanks again.

Thats normal, without walking out to the garage I believe on the brake axle the hubs are further in than the front hub or vice-versa. If that it is what you are referring too.