Which Axle Should Electric Brakes be Installed on with Tandem Axle Trailer

Question:

I have just acquired an older trailer and I want to put brakes on one of the axles. First: which axle front or rear should I put the trailer brakes on? Second: how do I determine which size trailer brakes to get to include drums. My lug pattern seems to be 5 on 4.75 Thanks.

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Helpful Expert Reply:

When installing electric brake assemblies on just one axle of a tandem axle trailer, you will essentially want to choose the axle that is going to be seeing more weight. Typically on utility trailers, most of the weight will be in front of the axles so the brake assemblies will be installed on the front axle. For boat trailers, where the motors are at the rear, you will usually see brakes on the rear axle.

I have attached a great article that details everything you will need to install electric brakes on your trailer, along with helpful installation tips. In order to determine exactly what parts you need, you will want to find the weight capacity for your axles, your mounting flange bolt pattern (if present) and the depth/diameter of your drums if you already have hub and drum assemblies.

If you just have idler hubs (and no drums), you will want to find the inner and outer bearing numbers on the hub. You can find these by pulling the hub and checking for the numbers that should be stamped onto the bearings themselves. If you cannot locate this information, you can also take a few measurements along the spindle where the bearings sit. I have attached an image that shows where these measurements will be taken. I recommend using a digital caliper like # PTW80157.

If you are able to tell me this information, I will be happy to make some recommendations for your trailer.

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Christopher R

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Question:

This is for Chris R. Chris, this is Brad. I could not read the numbers off the bearings but I took the measurements based off the illustration you had. It is as follows: Measurement A: 1.7735 inches. B: 1.721 inches. C: 1.378 inches. D: 1.059 inches. I measured the mounting holes and adjacent holes are 3.2885 inches outside to outside. I would guess 3.25 center to center. My lug spacing is 5 on 4.75 Please let me know what I need to get me some breaks.

asked by: Brad

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Helpful Expert Reply:

If your trailer currently has idler hubs installed, without integrated drums, you will need to first replace them with hub and drum assemblies. Based on the information you provided (thank you!), the correct hub and drum assembly should be the etrailer.com # AKHD-5475-35-EZ-K. This hub is designed for 3,500 pound axles and uses the # L68149 inner bearing and # L44649 outer bearing, which match up to the spindle measurements you took. You will just want to verify that your trailer does feature 3,500 pound axles.

Then, for compatible electric brake assemblies, I recommend the etrailer.com # AKEBRK-35R-SA for the Right Hand and # AKEBRK-35L-SA for the Left Hand. These are really nice, self-adjusting brakes that will not require periodic manual adjustments like standard brakes. They feature a 4 bolt mounting flange pattern. You will need to verify that this matches the brake mounting flange on your axle. If there is not a flange already present, one will need to be added.

Once you have the brakes installed, you will just need to wire up the trailer. You will need to run wiring, such as the 10 gauge # 10-1-1 (sold by the foot), from the front of your trailer to your trailer brakes in order to carry electric power to them. You will also need to convert the trailer side connector to a 7-Way like # H20046 if not already present.

Each brake assembly should have 2 wires coming out of the back. Attach one of the wires to a clean, bare metal surface of the trailer for ground. The other wire will receive the power. It does not matter which wire you use for which purpose. Run the 10-gauge wire from the front of the trailer to one of the brake assemblies. Connect the power wire to the non-grounded wire on the brakes, and then run another wire from the power wire on this brake to the brake on the other side of the axle. You can also refer to the attached article on adding electric brakes for a more detailed explanation.

Finally, you will need to equip your tow vehicle to connect with and control the brakes on the trailer if it is not already. If you can let me know the year/make/model of your vehicle, along with what it is equipped with, I will be happy to make the necessary recommendations.

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helpful expert reply by: Chris R
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Christopher R

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Question:

If I order item number AKHD-5475-35-K will the bearings I get with the hub be the correct size or will I need to order the bearings, you mentioned, separately?

asked by: Brad

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Helpful Expert Reply:

The etrailer.com Trailer Hub and Drum Assembly # AKHD-5475-35-EZ-K includes the needed bearings, races and grease seal. These will not need to be obtained separately.

I have attached a short video demonstration on this product that you can also take a look at.

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helpful expert reply by: Chris R
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Christopher R

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