How to Measure Trailer Spindles and Hub to Select Correct Grease Seal

Question:

i have a 1-5/16 shaft where the seal goes. do i get a 1-5/16 seal or do i get one a little smaller? like a 1- 9/64?

asked by: Jon

Expert Reply:

Grease seals are generally best measured to the nearest thousandth of an inch, such as 1.234-inches, using a precision caliper. This is because no ruler or measuring tape (and few human eyes) can be this precise. The actual dimensions of a trailer spindle and the correct grease seal for it usually differ only by a few thousandths of an inch.

A grease seal for a trailer hub has two dimensions that matter, the inner diameter (I.D.) that needs to fit the spindle's diameter; and an outer diameter (O.D.) that needs to match the diameter of the hub's rear bore. We sort all of our seals by these dimensions and you can see all items on the linked page.

In general it is desirable for a seal's inner diameter to be a few thousandths smaller than the spindle diameter to ensure good retention of the bearing grease.

expert reply by: Adam R