Upgrading Big Tex #35SA Trailer With Brakes

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Question:

I would like a recommendation for trailer brakes. I have a Big Tex 12ft, single axle trailer model # 35SA-12BK4RG. 3000lb, 15 rims.

asked by: Charlie C

Expert Reply:

It sounds like your Big Tex trailer did not come with brakes. Based on this, to convert your trailer with no brakes, to adding electric brakes, on your Big Tex 35SA trailer, the first thing you need is a left and right brake kit. You could use the Dexter 23-26-27 kit (includes left and right) which matches your Dexter axle 4” X 4” brake flange. However, for a little more I would recommend Dexter # 23-468-469 Nev-R-Ajust self adjusting brake kit. Most people do not want to have to periodically get under the trailer and behind the brakes to adjust them.

Next you will need 10” x 2-1/4” brake drum hubs rated for 3500 pounds, with a 5 on 5 lug pattern, and EZ lube spindles. I recommend the etrailer # AKHD-550-35-EZ-K drums which come with Inner bearing (L68149) and race, outer bearing (L44649) and race, grease seal, grease cap, and lug nuts. These bearings match nearly all 3500 pound axles. (Buy 2) The exact measurements are as follows.

Bearings:
Inner bearing: L68149 (1.378" inner diameter)
Outer bearing: L44649 (1.063" inner diameter)
Races (included)
Inner race: L68111
Outer race: L44610
Grease seal (included): 58846
Inner diameter: 1.719"
Outer diameter: 2.565"

If yours are different just email me back the measurements for a corrected recommendation. I have attached a picture showing where to measure.

Next you will need to run wires to the brakes and upgrade your flat 4-pole electrical connector to a standard 7-pin connector. For brake wires use Deka # 10-1-1 blue 10 gauge wire, sold by the foot. The two wires that service the brakes are not polarized. You can connect your blue 12-volt wire to either wire, and the other wire will ground to a grounded metal part of the trailer frame. You will want heat shrinking butt connectors for 12-volt and a ring terminal and self tapping screw for the ground wire. Hook up both sides and run your 12 volt wire up to the coupler for now. Use Deka # DW05705-1 ring terminals (buy 10) and # FA1131822 self tapping screws (buy 4), and Deka # DW05745-5 heat shrinking butt connectors. If you don't already have an excellent crimper I recommend that you add the Performance Tools # PTW30764 Crimping Pliers to your shopping cart. They make a tight connection every time.

You will already have four wires running to the front of the trailer for lighting. Now you have two more wires for brakes. Remove the 4-pole connector and crimp ring terminals on those 4 plus the two brake wires.

At the front of the trailer, on the frame, attach the # HS381-9000 junction box with 7-way cable. The wires running to the front of the trailer attach on the same lugs as the wires from the 7-way cable.

If you need to upgrade your tow vehicle to a 7-pin connector just email me for additional recommendations.

expert reply by: Les D

click to enlarge

Jules

11/26/2024

Hello Les D, I also have a big tex 12ft 35SA single axle 3k lb trailer and would like to replace the trailer harness and all lights. Can you help my put a list together, so I may place an order?

Kate F.

11/27/2024

@Jules Hello Jules. To change out your wiring you are going to want the 4-Flat Connector Wishbone Style - Trailer End # W002230, this wiring is 30' long so it will definitely get the job done on your Big Tex. I don't have the schematics on the Big Tex so you will need to double check the measurements on the lights. It looks like they have a grommet mount light so you can either get the Optronics Fleet LED Trailer Tail Lights # TLL12RK which will give you new wire harnesses, grommets, and the lights. If you just need to swap out the light portion you want the # STL72RB, these are sold individually so you will need 2 of them. The dimensions of the lights are 6-7/16" long x 2-1/8" tall x 1-3/4" thick (thickest portion). For new wire pigtails you want # A45PB, or for a right angle you want # A47PB. From my search I see that you have quite a few round red/amber clearance lights, for the red you want Optronics LED Trailer Clearance or Side Marker Light # MCL55RB and for Amber # MCL57AB, these are 2" round. If you need new grommets # A54GB, and new pigtails # A86PB. If you have added brakes on the trailer and need additional parts, please let me know. I have also included a help article about wiring a trailer for you to reference if needed.

Helpful Links

faq-wiring-4-way.aspx

tv-install-wesbar-trailer-wiring-w002230.aspx