Brake line questions

[Ramiro0727]

I have a 69 C10 and swapped in a front crossmember off a 72. Which brake lines do I get? I know the 72’s are a little different. Do I get the brake lines for a 72 for just the front then get the long line to the axle and the axles lines for a 67-70 am I able to swap lines?

[MikeB]

Well, the 72 has front disc brakes, right? So the caliper-to-frame hoses you'll need are for a 71-72. Frame-to-master cylinder hard lines depend on whether the M/C is power or manual. (Power M/C sticks out further from the firewall.). Same is true for the rear line.

If you are handy with a tubing bender and flaring tool, you can simply modify the existing hard lines if necessary. I did exactly that many years ago when I converted my 69 front drum brakes to 86 C10 discs.

[Ramiro0727]

Originally Posted by MikeB

Well, the 72 has front disc brakes, right? So the caliper-to-frame hoses you'll need are for a 71-72. Frame-to-master cylinder hard lines depend on whether the M/C is power or manual. (Power M/C sticks out further from the firewall.). Same is true for the rear line.

If you are handy with a tubing bender and flaring tool, you can simply modify the existing hard lines if necessary. I did exactly that many years ago when I converted my 69 front drum brakes to 86 C10 discs.

So I can keep the 67-70 lines for the rear?
Posted via Mobile Device
Posted via Mobile Device

[MikeB]

Yes, if you keep your master cylinder.

[Ramiro0727]

Originally Posted by MikeB

Yes, if you keep your master cylinder.

MikeB we will be replacing the master cylinder also. Since this build is from the ground up.

[jocko]

If you're replacing all the lines - yes, get a full set, front and rear, for a 72. You can re-use the existing lines of the rear circuit if you want - master cyl all the way back (But I'd replace them all too since you mentioned you're doing a ground up). If you don't want to replace the rear lines, just buy a 72 disk front line set, master to calipers.
Keep in mind the front disk system uses 3/16" lines (which is what you should get if you order a 72 front line system). All your current lines, front and rear, are 1/4" - and the 72 system uses 1/4" in the rear also. Good idea to use a new master cylinder, get one for a 72 as it is designed for disk brakes.

[Ramiro0727]

Originally Posted by jocko

If you're replacing all the lines - yes, get a full set, front and rear, for a 72. You can re-use the existing lines of the rear circuit if you want - master cyl all the way back (But I'd replace them all too since you mentioned you're doing a ground up). If you don't want to replace the rear lines, just buy a 72 disk front line set, master to calipers.
Keep in mind the front disk system uses 3/16" lines (which is what you should get if you order a 72 front line system). All your current lines, front and rear, are 1/4" - and the 72 system uses 1/4" in the rear also. Good idea to use a new master cylinder, get one for a 72 as it is designed for disk brakes.

Jocko, so say if I were to keep the rear lines for the 69. Since it is smaller am I able to mismatch the brakes lines since they are smaller than the 71-72? Is it safe and are they're adapters or unions that'll make that work if I did that?

[leddzepp]

Here is the info you need:

http://67-72chevytrucks.com/vboard/s...d.php?t=762513

[jocko]

Originally Posted by Ramiro0727

Jocko, so say if I were to keep the rear lines for the 69. Since it is smaller am I able to mismatch the brakes lines since they are smaller than the 71-72? Is it safe and are they're adapters or unions that'll make that work if I did that?

I'm not really understanding your question. The front lines on your 69 are bigger than the front lines on a 71/72 with disks - the 71/72 are supposed to be smaller diameter (your question implies that something from your 69 is smaller than something on a 71/72, and that is not the case). The front lines for a factory 71/72 front disk setup are 3/16" rather than the 1/4" your truck currently has in the front - that is why we're saying it's ok to leave the rear lines in place - 1/4" is correct for all the drum rears. 3/16" is smaller diameter than the pre-71 1/4" lines - for higher pressure at the caliper. It can be done without changing ANY lines - but it's not factory correct, the fronts should technically be 3/16" for a disk setup to have the correct pressure in the front system. The link ledzepp posted has good info about the fittings you'll need. Or you can just take your master cylinder and combo valve and the first few lines to the parts store and sort out what fittings you need as well. It is safe, and it is factory correct to have 1/4" lines to rear drums and 3/16" lines to front disks. The systems never cross/mix, front and rear are separated at the master. Front system should be a 3/16" line from the master to the combo valve and then 3/16" all the way to the calipers (or, more correctly stated, to the front rubber lines - and those should be replaced also). Hope that helps!

[Ramiro0727]

Originally Posted by jocko

I'm not really understanding your question. The front lines on your 69 are bigger than the front lines on a 71/72 with disks - the 71/72 are supposed to be smaller diameter (your question implies that something from your 69 is smaller than something on a 71/72, and that is not the case). The front lines for a factory 71/72 front disk setup are 3/16" rather than the 1/4" your truck currently has in the front - that is why we're saying it's ok to leave the rear lines in place - 1/4" is correct for all the drum rears. 3/16" is smaller diameter than the pre-71 1/4" lines - for higher pressure at the caliper. It can be done without changing ANY lines - but it's not factory correct, the fronts should technically be 3/16" for a disk setup to have the correct pressure in the front system. The link ledzepp posted has good info about the fittings you'll need. Or you can just take your master cylinder and combo valve and the first few lines to the parts store and sort out what fittings you need as well. It is safe, and it is factory correct to have 1/4" lines to rear drums and 3/16" lines to front disks. The systems never cross/mix, front and rear are separated at the master. Front system should be a 3/16" line from the master to the combo valve and then 3/16" all the way to the calipers (or, more correctly stated, to the front rubber lines - and those should be replaced also). Hope that helps!

Thanks Jocko. I think I understand it now.

[davepl]

Just FWIW, the diameter of the line has NOTHING to do with the pressure. Basic laws of hydraulics tell you the pressure is the same throughout the system at all points.

There could be flow issues, and it could be that rear discs (as a made up example) could need a larger line just for fluid flow, but the pressure is what the pressure is.

Put more simply, line size affects only flow rate, not pressure.

[bubbasimms]

I have a 69 step side that was of course 4 wheel non power drums. I swapped in the front cross member from a 71 for the 5 lugs and the power disc and power steering. I retained the narrow 69 12 bolt and used the conversion axles in the rear. I ordered inline tubes complete stainless brake line kit for a 71 short bed as well as their 3 piece hose line set. All the lines fit great with only minor tweaking. The only thing I had to do was get a couple fittings and I had to re locate the bracket that holds the "T" fitting where the flexible line joins the two hard lines on the rear axle. The bracket needs to be place on the passenger side of the rear axle tube, on the front of the axle tube near the diff.

[jocko]

Yes, incorrect term - flow rate difference rather than pressure. The point is fronts are 3/16 and rears are 1/4 for a reason.

[rockyrivermark]

I just went through this and here is a simple way to go.
I have a 1970 with 1971 front disc and 5 lug
Call inlinetube.com
They have a lines specifically for this conversion and I got all stainless for $180. All the lines fit perfect.
Also buy the proportioning valve from them.
Then just purchase a disc/drum master cylinder for a '71 at local auto parts store.

I just last week added rear disc conversion from little shop mfg.
old lines worked and was $440 with shipping. Just a thought if you're interested.

[Ramiro0727]

Thanks everyone for chiming in on my brake line question. All the information is valuable to me and my son what we need do on his truck.

Thanks,
Ramiro