Question about disc brake reverse solenoid

[Tedd]

I bought a disc brake conversion kit for my trailer from Blue Water Yachts. Installation of the rotors and calipers was a piece of cake and it was starting to look like installing the new master cylinder would be, too, but then I ran into a snag. To go with the kit, I bought a solenoid valve that locks out the master cylinder when you're reversing (necessary for disc brakes). It appears to be a Dexter 059-Z00-87. I can't identify the fitting on the downstream side of this solenoid (see photo).
Near as I can tell the thread matches a standard SAE "inverted flare" brake line fitting. But the sealing face at the bottom (if that's what it is) is completely wrong. It should be larger and more cone shaped. Is this just some alternate kind of SAE fitting I've never seen before, or is it something else?
Tomorrow I'll call Dexter if I can't figure it out, but I was really hoping to finish the job today.

 

[Project_Mayhem]

I'm guessing that's a double flare fitting. This site seems to have similar fittings listed as such
https://www.affordablestreetrods.com/3-8-npt-male-to-5-16-inverted-flare-female-adapter.html


Out of curiosity, why is having brakes when reversing a bad thing?

 

[Tedd]

Thanks, PR!

That actually makes perfect sense because I had noticed that the hex fit a 12 mm wrench better than a 1/2 inch wrench, and double-flare is more commonly a metric format. Perhaps I inadvertently ordered the metric version of the solenoid valve.

The solenoid valve is necessary because of the way surge brakes work. The master cylinder is actuated by the inertia of the trailer itself, via a telescoping mechanism in the tongue. Because disc brakes have far less "lash" than drum brakes, even a small amount of interia will activate them, meaning that it can become impossible to back up at all unless the brakes are disabled. Normally, this is done by putting a solenoid valve between the master cylinder and the calipers, connected to the reverse lights on the tow vehicle.

 

[Project_Mayhem]

Ahh yes, I forgot about that. I only have experience with electric brakes on trailers.

If you have to flare your own lines I highly suggest you get some extra line to practice with. I did it once in high school autos class with a cheap flare kit. The lines weren't pretty but they did work.

 

[Tedd]

A follow up:

It appears that Project Mayhem was right. I've never seen SAE inverted flare fittings that look quite like this one before, but I flared the line for that and it seals just fine.

The disc brakes feel great, although I only have a short jaunt to judge them by up to now. Tomorrow we head out on a small trip so I'll know more in a few days.

Tedd