Brake hard lines

[PrairieDrifter]

80's k10. From my research all the lines after the proportioning valve should be 3/16 correct? Are all fittings to the wheels and brake hoses 3/8-24? As well as into the proportioning valve? All are 45 degree double inverted flare?

Just for future info one of the lines to the factory prop from the master is 1/4 inch correct? And some weird flare nut size?

Just looking for a for sure answer, I'm swapping to an aftermarket master and prop valve, so I'm redoing all my hard lines. Couldn't find a definitive to all my questions, haven't done a full hardline replacement. Just need a spec sheet for all of the hardlines.

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[Blue Ox]

I'm fairly certain the line to the rears is 1/4" until it splits at the hose/axle, then 3/16" from there.

 

[PrairieDrifter]

I'm fairly certain the line to the rears is 1/4" until it splits at the hose/axle, then 3/16" from there.

I was thinking it was larger, I haven't looked at it too hard. I'm swapping to discs so I won't need to run bigger line than the fronts to the rear.

But I appreciate the info, I would very much like to have this info on hand.

 

[Blue Ox]

It's bigger because you're supplying two brakes with a single line. If you're running two lines from the prop valve then it doesn't apply.

 

[PrairieDrifter]

It's bigger because you're supplying two brakes with a single line. If you're running two lines from the prop valve then it doesn't apply.

Makes sense. I assumed it was for the drums. I know one line is bigger than the other going from the master to the prop valve. Did you know the flare nut size? Still 3/8-24?

 

[Grit dog]

Objectively I’d say it’s not that critical as the amount of fluid needing to move through the lines when braking is minuscule in either disc brakes or properly adjusted drum brakes.

 

[Blue Ox]

Makes sense. I assumed it was for the drums. I know one line is bigger than the other going from the master to the prop valve. Did you know the flare nut size? Still 3/8-24?

Don't quote me, but I'm fairly certain the lines from the master (on my truck, YMMV) are the same diameter, but they use different size threads to prevent them being mixed up. The fronts split down to 3/16" at the prop valve. The rears split to the smaller size on the axle.

Sorry, no idea on the thread size for your truck.

 

[PrairieDrifter]

Don't quote me, but I'm fairly certain the lines from the master (on my truck, YMMV) are the same diameter, but they use different size threads to prevent them being mixed up. The fronts split down to 3/16" at the prop valve. The rears split to the smaller size on the axle.

Sorry, no idea on the thread size for your truck.

Mine are different sizes for sure. One looks to be 1/4 and one is 3/16. I know the flare nuts are different size as well.

 

[PrairieDrifter]

Alright with some more digging, I believe I've got it.

3/16 line for fronts from master to prop valve, 3/16 from prop to both front hoses with 3/8-24 fittings at the hoses.

Then 1/4 line from master to prop valve for the rear, and 1/4 from prop valve to rear hose, to 7/16-24 at the rear hose.

Then of course the axle hard lines are 3/16 with 3/8-24 fittings at the hose. But I couldnt find if the wheel cylinders were 3/8-24 or 7/16-24?

 

[bucket]

All lines are 3/16" except for the line to the rear brake hose that is 1/4". All fittings are the standard size for that size line (3/8" and 7/16" respectively).

However! The lines from the master cylinder are always oddball and fitting thread sizes vary with year and application.

 

[PrairieDrifter]

All lines are 3/16" except for the line to the rear brake hose that is 1/4". All fittings are the standard size for that size line (3/8" and 7/16" respectively).

However! The lines from the master cylinder are always oddball and fitting thread sizes vary with year and application.

Thanks for the confirmation. I can verify that my 84 is 1/4 inch and 3/16 from the master to the prop valve.

Would you guys waste your time putting a union in halfway for the rear line like factory? Im sure if I don't do it I'll regret it someday. As well as it would be easier to install than an entire 18ft line. But it's also just another leak point.

 

[bucket]

Thanks for the confirmation. I can verify that my 84 is 1/4 inch and 3/16 from the master to the prop valve.

Would you guys waste your time putting a union in halfway for the rear line like factory? Im sure if I don't do it I'll regret it someday. As well as it would be easier to install than an entire 18ft line. But it's also just another leak point.

I always install unions. Not just for ease of partial line replacement, but because I hate rolled line with a passion. I like arrow straight lines with nice tight bends. Working with rolled line is clumsy and annoying, imho.

 

[QBuff02]

inlinetube.com makes complete factory replacement/drop in brake line kits for these trucks and for the price of them, you can't mess with fabricating your own, or piecemealing it together. have installed a couple of kits and they are very nice.

 

[PrairieDrifter]

inlinetube.com makes complete factory replacement/drop in brake line kits for these trucks and for the price of them, you can't mess with fabricating your own, or piecemealing it together. have installed a couple of kits and they are very nice.

I didn't see a rear disc conversion kit. I have an aftermarket master and prop valve going on so I can't use the factory routing. I definitely checked their stuff out. They didn't have the bulk line I needed either.

 

[Number 6]

Dumb question, but who sells the rear disk kits? Or are they from a newer "donor" Truck?