Like a dufus I ordered these brake lines without understanding what kind of fitting they came with. The company says they are dual seat fittings, they say "all our fittings have what we call a 'dual' seat, that's designed to accommodate concave, convex, or even flat opposing seats". They say it's 90 degrees, so I think that means it's good for metric SAE.

But, you can see in the third picture below that it seems to be too wide for a metric SAE flare to mate up to. Does anybody have experience with this sort of fitting and know what sort of adapter I should be looking for? Or maybe these two ends are supposed to mate up to each other in some magical way that I can't perceive. Feels like I'm missing something fundamental, like maybe 1/4" vs. 3/16"?

 

I'm not familiar with dual seat fittings. Not sure if there are adaptors available to mate up with the OEM components or not. I believe the flares used on standard lines are "double flares" which is maybe where the confusion started.

 

I think you may be right. I found this image comparing single and double flare. The single is huge and probably would fit. So I think I probably need a single flare to double flare adapter.

 

But then you're not supposed to use single flare on brakes, so. Hmmm.

 

Both, Flare and Dual Seat are "types" of connections. Different way to achieve a tight, secure connection. They don't make adaptors that mate different styles of connections together. Regardless of which type you have, what ever is on the line must also be on the other half of the fitting that screws into your cars brake components.

Did the brake lines come with the other half of the fittings to screw into your calipers and master cylinder? If not, you may need to find out what size of threads are in your brake parts and see if whoever supplied you with the lines, can also supply you with the fitting that have the correct threads that fit your car.

Or, if you know what size threads are on the other half of the Dual Seat fittings, you might find a threaded adaptor that will mate those fittings to your cars brake components.

 

The other end of the line is a banjo, no they didn't supply a fitting to mate to the dual seat end so I'm not sure what exactly these things are supposed to mate into. I can't find anything on the internet with a search for "dual seat" other than this very thread. I think they work like AN except that they're 45 degrees. They say, "All our fittings use a dual seat and can be fitted to both concave and convex applications" (the fitting itself is 10x1.0, it's just the seat that is a mystery).

Meanwhile, 339 reviewers seem to know what they've bought, so I'm feeling mighty stupid, and my communications with the company have not helped, but I'm persevering, waiting for the lightbulb to go on.
https://auto.helperformance.com/cust...ed-brake-lines

 

Okay, I think I see. "10x1.0 concave" and "10x1.0 convex" are types of connections - they're called "metric" connections, as opposed to AN connections or SAE connections.

Pegasus has metric to AN adapters, and they have AN to SAE adapters, but not metric to SAE So now at least I know what to hunt for!

 

Might be easier to just buy the correct line. You can get SA and FB lines in either rubber or stainless.

 

Yeah, this is actually from MC to hard lines, trying to eliminate all those fiddly leaking connections on my FD.

Yup, at this point I'll either try again from somewhere else with the right connector or replicate the small hard lines with nicopp.