are you tring to replace existing hubs or are you tring to size rims?? most trailors use a common hub are are ez to replace McClaine trailors in Houston or Sportsman trailors in Santa Fe. hope this helps.
When I replaced the hubs on my McClain trailer, I went to a trailer store on the 610 loop just past Gulfgate Mall. I can't recall the name of the place, but they had everything you would possibly need to rebuild your trailer. The guy said my hubs were common everyday Ford car (front hubs) w/ 4 1/2 inch bolt circle.
The entire assy including hub, studs, bearings, lug nuts and grease cap was $26. That was about three years ago.
Good luck with your project.
I may be able to help coming from a trailer mfg. background.
To measure a bolt pattern on a hub you must measure between the studs. On a 4-bolt pattern it's from 1 stud to the next. On a 5-Bolt pattern you measure from stud #1 to stud #3. ie you skip a stud. Sometimes it a little tricky because the bearing housing is in the way.
The BEST way to get a correct match is to take the hub off and take it in.
There is more than a stud match, there must be ALSO a bearing /race match.
Buy a complete hub/bearing/seal kit, spray it with WD40, put in a HD plastic bag
and burry it somewhere in your boat.