What is the Modern Tire Equivalent of a B78 x 15C Tire and How to Add Electric Brakes to Trailer

Question:

I have a 1986 Wells Cargo enclosed trailer, single axle, that has two different size tires on it, and I have been unable to locate the modern equivalent to the tire designation on the trailers tag, which is B78 x 15C. Do you know what the modern equivalent would be? Also, this trailer doesnt have brakes. Whats the simplest, least expensive option to add brakes to the trailer?

asked by: David B

Expert Reply:

A B78x15C tire is an obsolete tire size with an approximate diameter of 25" and the closest available size we have to that is the Kenda Karrier 205/70/R15 # AM10245, which will be approximately 27.1" in diameter. These tires have a 2150-lb capacity (per tire), so as long as your trailer's GVWR is less than 4300-lbs these would work well.

When it comes to adding brakes, you'll first need to verify that your trailer has brake mounting flanges on the axles; it would also be helpful to know the axle capacity, which should be stamped on a plate on the axle. If I had to guess you most likely have a 3500-lbs or 4400-lbs axle, but it could also be a 5000-lbs axle. A 3500-lbs/4400-lbs axle would have a 10" hub/drum on it and use 10" brake assemblies, but a 5k axle would use 12" assemblies.

The most economical solution for 3500-lbs axles would be the etrailer Electric Trailer Brakes # AKEBRK-35, which are a brake assembly that require manual adjustments; you could also use the # AKEBRK-35-SA for self adjusting brakes. You will need brake mounting hardware # BRKH10B to install the brakes and if you go with the manually adjusted brakes I recommend using a brake adjustment spoon like the # W80630. To complete the wiring you'll need to use a 2 wire, jacketed wire like the Deka # 12-2-1 (sold by the foot).

Once you've got the brakes installed, if you don't already have a 7 way connector on your trailer you will need to install one. The best solution for this is using a 7 way with integrated junction box like the # HS381-9000, which will make wiring everything in much easier and cleaner.

If you don't already have a 7 way on your vehicle and a brake controller installed, you will also need these parts to make your trailer brakes function. If you can tell me what your tow vehicle is, I'm happy to help you find the parts you need for that. I've also linked some helpful installation and review videos, as well as one of our help articles on adding electric trailer brakes to a trailer that I do recommend having a look at as well.