How to Measure a Trailer Hub for the Correct Size Grease Cap

Updated 05/14/2025 | Published 08/19/2014

Question:

looking for dust caps rubber plugs and covers for 11\16 shaft 1995 model boat trailer I think its ez lube help

asked by: D

Expert Reply:

You would need to measure the inside diameter of the hub opening to determine which cap size is needed. You would want to choose a cap whose outside diameter matches the inside diameter of the hub.

Some of the most common sizes are 1.980 inch, 1.986 inch, 2.441 inch and 2.717 inch. As you can see the sizes can differ by very small amounts. To measure accurately you may want to get a dial caliper so that you can be confident you are getting the correct size for your hub. I have included a link to our grease cap main page for you.

expert reply by: Chris O

Mike

5/7/2025

Sizes bigger than 1.980 grease cap. It's just a small fraction to small??

Andrew N.

5/14/2025

@Mike Hey Mike, the grease caps and hubs are machined to be a very tight fit to keep the cap tight and keep all of the grease in place. If 1.980" cap like # DE69YR is not fitting snug for you, you may need the slightly larger Grease Cap, 1.99" # RG04-040. While these are typically interchangeable, the slight .01" difference may be what you need. I would take a micrometer and measure the inside diameter of your hub's bore to make sure it matches up correctly. Do you have a 3,500lb axle? If so, one of these caps is typically the solution. The next jump up is nearly half an inch larger at 2.44" and I doubt you need that.