The Stovebolt Site Forums The Shop Area The HiPo Shop What size brake lines?

I'm redoing the brake lines on my truck, and I'm wondering what size I should use. The standard size seems to be 3/16, but whomever did the lines on my truck last used 1/4. Now, my truck is not stock. It has power brakes, front disc and rear drum, and the MC/booster, calipers and rear wheels cylinders are all from a 70'Chevelle. So the previous owner used a combination of 3/16 and 1/4 brake lines, with a lot of adapter fittings. The rear brake hose used, which I'm guessing is 70' Chevelle also, has a 1/4 female ports.

So my question is, is there any legit reason why the PO would have done it this way? I want to redo the whole system using 3/16 lines to keep everything standard and use no adapters. I figure the fewer joints the better- less chances of leaks.

So given the setup, is there a reason it may have been done this way, or do you think the previous owner just used whatever he had laying around and that's why it's that way?

I am working on a 52 Chevy Styleline, at least untill my knee replacement, and my brake lines were like yours, a combination of 3/16 and 1/4 lines. I have no idea why!!!! I used only 3/16 to plumb it now. Haven't done any bleeding on it yet though, too much else to do first. My 53 ad pickup had all 3/16 lines, but it was not on an original frame when I bought it. Hope that helps!
Coach Frank

Find a 70 Chevelle that has the same options as your donor. Use the size lines and fittings that were on that car so everything will work like it was designed. Factory engineers don't just make this stuff up. My donor was a Monte carlo and it had 3/16 to the front discs and 1/4 to the rear drums. That is what I used in the truck.

the reasoning on the diffrent size lines front to rear is that disc brakes have more fluid demand than drum brakes. same as the master resevoir if you look the front has double the capacity of the rear. it takes more fluid pressure with the disc brakes to apply than the drum brakes in the back. in all actuality the engineers probably had 3/16 in the plans for the whole car but you have to remember that manufactures have a tendacy to use what they got. 1/4 line is cheaper than 3/16 so they would substitute to save a buck.

I often wondered that too. I've been pulling some calipers off of an 07 Van and the OE line seems to 3/16 on the whole thing. The van has huge dual piston calipers, seems like 1/4" would be the better way to go being it's larger. I wonder if it has anything to do with the anti-lock systems on modern vehicles.

It comes down to fluid flow.


Drum brakes take more fluid to operate, the piston in the wheel cylinder has to move further because the shoes are retracted from the drum after each use.
Drum brakes of any normal size use 1/4" line or larger yet on big trucks. It'll be a small drum brake that uses 3/16", cars and light trucks.

Disc brakes don't have return springs, the pads are always skimming the rotors and very little fluid volume is necessary to apply the brake. That's why many of them use 3/16" line. Still there are exceptions, I've used huge dual piston calipers on medium duty trucks that have (came with) 1/4" brake lines.

Then there are situations like a rear axle with disc brakes could be fed with a single 1/4" line and branch out into a different 3/16" line for each side.

Some folks tell you as a rule of thumb that 3/16" is for disc and 1/4" is for drums... That's misleading at best.
Much more accurate as a rule of thumb to use what the original vehicle used (the vehicle that the brakes you're using came from).

Grigg

Fewer adapters/joints is better. I don't think the flow is high enough to notice a difference, and 3/16 is less expensive. I used 3/16 on my '65 with stock drums all around...works good.

cm

My 53 3100 had 1/4 to the fronts and a single 3/16 tot the rear that split at the rear axle before going to the brake cylinders. Now I'm installing my disk conversion kit and the proportioning valve is set up to replubm exactly that way.

The 1/4 line is going to give you better brake feel and modulation as it will allow the pedalmto move farther through it's stroke as the caliper demands mor fluid as you increase pressure. A larger diameter line moves allows more fluid to flow with less pedal travel. This could cause the pedalnto feel like it is hardly moving through its stroke before maximum braking occurs.

I'm not following what you're saying?

Remember a fluid doesn't compress and that the lines are already full. I don't see how line size relates to pedal travel. With the exception of a larger line under pressure will expand/stretch a tiny bit more than a smaller line at the same pressure... so you can get more fluid in it only because the line it's self swells up, and that's inconsequential in a hard line in these sizes..

Pedal travel has everything to do with MC bore size, wheel cylinder or caliper bore, and brake adjustment.

Decided to go with 3/16" line throughout. Seems to make the most sense to stay consistant.