brake tubing + steel compression union = ??: Off-topic discussion forum: Grassroots Motorsports Magazine

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Jan. 14, 2012 8:06 p.m. fasted58 SuperDork

Continuation from my '02 Silverado brake line rot/ run it till warmer weather til I can DIY vs $hop replacement thread.

All hard lines were replaced, picked up tonight to the tune of $800 plus. OK, I'm supreme berkeleying happy it's done, I'm working 7 days/ wk and the temps are too frigid to work on it here, no problemo.

Thought I'd check out the work tonight, C+ on routing and bending... it's tight quarters so OK there... but, popped the hood to inspect and found two steel compression fittings on the two original hard lines from the MC to new tubing... WTF?? There's prolly another 20" of tubing to make it from the new lines to the MC, why stop short... or why not just use brake tubing couplers.

I'd never use compression fittings (these are Swagelock steel type) on brake tube although I've used many steel compression fittings on hydraulics way above brake line pressure over the years.

Is this even legal for vehicle inspection? State of PA... and confusion.

I found nuttin' on this in da googles.
Jan. 14, 2012 8:25 p.m. Ranger50 Dork

I have a brass one on my rear line from rot and letting a buddies shop repair it. But what do I expect for $35?

Here is the deal though, I believe since the brakes are an essential part of accident avoidance and saving your ass from death, is why they aren't allowed. The fittings like a smooth rise in pressure, not a huge spike like a brake system can make.
Jan. 14, 2012 9:25 p.m. fasted58 SuperDork

any PA state inspection mechanics here to weigh in on whether steel compression fittings are legal?
Jan. 14, 2012 9:30 p.m. hotrodlarry Reader

As far as I know... NH does not allow compression unions as a legal brake repair. I could be wrong though.

compression unions are not rated to handle the pressure of a brake system. yes they work, but....a proper fix is better.
Jan. 15, 2012 12:06 a.m. Streetwiseguy SuperDork

If its a ferule type compression fitting, its not legal. Must be double flares.
Jan. 15, 2012 2:00 a.m. curtis73 SuperDork

fasted58 wrote:

any PA state inspection mechanics here to weigh in on whether steel compression fittings are legal?

Not an inspector, but I know they absolutely do not pass inspection. Aside from not passing inspection, they'll work fine for normal braking, but that first time when you NEED fast braking is when they'll pop.

The best compression fitting I ever saw was rated at 500 working psi and 800 burst psi. Under full heavy braking you can pretty easily see 2000 psi or more. Add the vibes from ABS and that braking pressure will laugh in the face of its rated psi.

Get rid of them NOW.

You guys know me as one who stretches engineering. Usually you guys laugh at me for some of my ideas . This is one not up for question. Even a single flare would be sufficient.

What bothers me is that doing a single flare is not really much more work than installing a compression fitting. I can understand duct-taping a repair if it provides 90% of the reliability with half the work, but this is still most of the work with massive liability.
Jan. 15, 2012 5:55 a.m. Curmudgeon SuperDork

Dunno about passing inspection etc but on single flare: I watched a single flared brake line blow out of the tube nut on a forklift. Uh uh, no way. Do it right or don't do it at all.
Jan. 15, 2012 6:30 a.m. Zomby woof SuperDork

If it's really a swagelok, it's not really compression, and in 1/8" size is good for about 10,000 psi.
Jan. 16, 2012 9:13 a.m. Gearheadotaku SuperDork

I'd like to hear more about these swagelok's. Their web site looks interesting, but didn't address this application directly.