Parts Needed To Add Electric Brakes To A BigTex 30SA Trailer  

Question:

Expert Reply:

Hi Eric!

I can definitely help you out with adding brakes to your BigTex 30SA. From the info I found, you have a 3,500 pound axle, so that makes it pretty easy to find the correct parts. However, there are two thing you will need to check to make sure these parts will indeed fit.

First, make sure you have a flange on your axle that has 4 bolt holes in it (see attached image). You will also want to make sure that flange has the measurements included in the image. If you don't have that flange, you will need to have the Brake Mounting Flange for 2-3/8" Round Axle # 4-35 welded onto each side.

Second, make sure you have a 5 on 4.5 bolt pattern. I found things saying you have a 5 bolt pattern, but not which one specifically (there are technically 4 different sizes that are 5 bolt). I have a second image attached that will show the easiest way to measure. If you find it to not be a 5 on 4.5 bolt pattern, let me know and I can find the proper hub/drum for you.

If all this checks out, you will want the following parts:

etrailer Easy Grease Trailer Hub and Drum Assembly for 3.5K Axles - 10" - 5 on 4-1/2 - Pre-Greased # AKHD-545-35-EZ-K
etrailer Electric Trailer Brakes - Self-Adjusting - 10" - Left/Right Hand Assemblies - 3.5K # AKEBRK-35-SA

Keep in mind the brakes are sold as a pair (left and right), but the drum is an individual part and you will need two of them to do an axle. Also, these brakes are self adjusting as I think they are way easier to live with, but we do have the manual adjusting ones with # AKEBRK-35. This is the same capacity and also comes as a pair, but you have to adjust them every so often to make sure you are getting good braking.

The last part you will need is a 7-way plug so you get power to everything. For that, I think the etrailer Trailer Wiring 7-Way Upgrade Kit w/ Junction Box and RV Style Connector # e99011 is the best way to go. The posts are color coded and having those to connect to makes the whole wiring experience a lot easier. You will also want some ring terminals like # 44-5310A and 10 Gauge Wire # 10-1-1 running to the brakes, but you will need to measure for how much you need (it's sold by the foot).

Do you have a brake controller in the towing vehicle already? And out of curiosity, what is the towing vehicle?

expert reply by: Lazer S

0

3,500 Axle Brake Flange Measurements
(click to enlarge)

Measuring 5 Bolt Pattern
(click to enlarge)

Lazer S.

1/27/2026

Hey Eric, how did things go with adding brakes to your BigTex 30SA trailer? Were the self-adjusting brake assemblies and hub/drum setup a good fit for your axle? Your update could make it easier for others working on the same trailer.