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Instructions To Add Electric Brakes To Trailer Without Brakes


I have a single axle boat trailer, mfg in 1997. It has a 2x3 down axle with no brake flange. 3500 lb rating with tapered spindle. I bought two 4 hole brake flanges to fit the axle. I am interested in adding electric brakes, but am concerned about the clearance from hub face to future brake flange location. The local trailer shops wont replace spindles .... its either a liability issue or they dont want the work. They say best to replace the axle. Which measurements should I take ? and how much should I expect to pay for a replacement axle with brake flanges if it comes to that? Regards,


Expert Reply:

The shop that told you that was correct, since your trailer axle didn't have brake flanges welded already it is much easier to just replace the entire axle.

Reason being is, to add brake flanges would require them to be welded square and concentric. This usually requires a jig to hold both parts in position. Ordering a new axle complete with electric brake assemblies and drums may actually cost less than buying separate parts.

For the measurements, you will want to measure the spindles at the inner (C in diagram) and outer (D in diagram) bearing surfaces, as well as the seal contact surfaces (B in diagram).

Since you mentioned that you are wanting to add electric brakes you will need to run wiring from the front of your trailer to your trailer brakes to power to them and you'll also have to convert your trailer connector to a 7-way that includes a circuit for electric brakes.

Finally, you're going to need to add a brake controller like # 90885 so you can use the newly added brakes.

I have included an FAQ that dives deeper into this process for you to check out.

Spindle Measurements
Spindle Measurements
(click to enlarge)
expert reply by:
Bryce D

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