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What Does BTR and BT8 Mean when Picking Out Replacement Trailer Hub  


Im looking at a couple of the 1inch axle 4 on 4 trailer hubs and I would like to know what BTR and BT8 means and what the difference is.


Helpful Expert Reply:

BTR and BT8 are the reference numbers for a standard trailer spindle size. When picking out a hub for a trailer you have to make sure that the hub is designed to fit the spindle. What you will need to do is measure spindles on your trailer where the bearings ride and with the info we will be able to tell what hubs will fit.

If the spindles are .99 inch and .99 inch where the bearings ride you have a BT8 spindle and would need # AKIHUB-440-2-1K.

If the spindles are 1.06 and 1.06 inch where the bearings ride you have a BTR and would need # AKIHUB-440-2-2K.

expert reply by:
Jameson C



Hi there, I'm looking to find a hub for a 1" spindle, but the length of the spindle where the bearings ride is only 3". Can you help? The trailer is about 50-60 years old.

Etrailer Expert

Chris R.


This sounds like a short spindle that is sometimes used on boat trailers that require their own, unique hub assemblies. Are there any numbers stamped inside the existing bearings? Is the trailer manufacturer still around?



@ChrisR Thanks for the response Chris. Yes it’s an old trailer originally sold with a 12’ sea king “ alum boat ( my grandfathers) I believe these were marketed by Montgomery ward at the time. Original hubs and bearings unfortunately are long gone. I’ve got new 30 year old spindles hubs and bearings, but was trying to avoid the welding to install the spindles. If I could find replacement hubs I could use the bearings, races that I’ve got and existing axle.



@ChrisR After a little more digging, I'm pretty sure this is a 1958 or 1959 Mastercraft "Modernline" trailer. There were 3 different models, this one I suspect is a MOD 300, the smallest of the lot.
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