Brake plumbing: 3/16 or 1/4 hard line?

[parsonsj]

I think this is an easy question. I'm gonna be plumbing my brakes soon, and I'm wondering what diameter hard line to get. I thought the answer was an easy 3/16", but I've noticed plumbing retailers offering fittings and line in 1/4".

Anybody know 'bout this?

Oh, if it matters: Wilwood dual masters (3/4, 3/4) on a balance bar, Wilwood 6 piston, 14" rotor up front, and Wilwood 4 piston, 12" rotor in back.

thanks!
jp

[MrQuick]

Hi John.... 1/4 from master to distribution block. 3/16" distribution to front brakes. 1/4" distribution to rear tee, then 3/16" from tee to calipers....I have know idea what brake system you are using due to goverment type secrecy :doh: but that would be a guide line.

[ProdigyCustoms]

John, just had this very conversation with Willwood Friday. They said 3/16 all over with keep pressure up. Said their calipers do not need much volume. I thought it would be exactly oppisite

[chicane67]

It depends on caliper volume really.

For what most of us know, 3/16 front and 1/4 rear has been the norm. But, most of what were talking about is on 30+ year old chassis. The 1/4 was because of a volume issue with drum brakes. All of the newer 4x disc systems are 3/16 standard, front and rear.

If you were to run the newer master like on the C5/6, 3/16 will do just fine, as it is set up for the volumes typically used in newer ABS systems that deal with known caliper volumes.

This is the master I am refering to:
https://static1.pt-content.com/images/noimg.gif

If you are using something other than that, knowing the caliper volumes will be a big help on figuring out what is really necessary. Another couple of things I remember:
· It is recommended that rigid lines with an ID of 3/16" be used throughout the chassis because of their resistance to flex.
· AN-3 stainless steel braid Teflon should be used from the chassis out to the calipers and rear axle.
· Flex lines in AN-2 will restrict fluid flow and lines in AN-4 will increase displacement with the possibility of a spongy pedal feel. AN-4 is good for the clutch line.
·Route all lines down hill from the master cylinders and avoid loops that go up in the SS braided lines.

Here is an interesting read on a related subject:
Stop Tech (http://www.stoptech.com/whitepapers/proportioning_valves.htm)

And these are somethings to consider aas well:
Stewart Development (http://www.stewartdevelopment.com/products.html)

[parsonsj]

You guys rock!

I'm using two standard Wilwood masters in 3/4" diameter. Sounds like 3/16 and AN3 all around, though the 6 piston SuperLites might consume a bit more volume. That would be counter-balanced by having a dedicated master for it though. I'll check out the links as well.

thanks!
jp

[cantstopit]

I always thought you used 1/4" going to the rear lines because you are using 1 line to supply fluid to 2 brakes, and then tee it off to 3/16 on the rear end??

[MrQuick]

Thats what i've always thought too, but I think John is running 4 masters..lol ...hows the weather in Salt Lake? Anywhere near Greenvalley?

[parsonsj]

I always thought you used 1/4" going to the rear lines because you are using 1 line to supply fluid to 2 brakesActually, I'm doing that for both the front and back. I was gonna do it like this (hey, that's a great song lyric) for both front and back brakes: master to t-junction and then each leg goes to a brake.

Other than length of the line from the master cylinder to the t-junction (which doesn't matter since the fluid is not compressible), the only difference is the placement of the flex line. There are two flex lines in the front from the frame to the caliper, and one on the back feeding the t-junction on the top of the rear housing.

I'm thinking Tom (chicane67) is right: the 1/4" supply line is needed for drum brakes. So 3/16 all around sounds right to me, which Wilwood confirmed to Frank.

Good discussion!


but I think John is running 4 mastersVince, you kill me! :cheers: Nah, just two: one for da front, one for da back.

jp

[MuscleRodz]

I agree with the posts above, 3/16 front, and 1/4 for the rear to the tee. Pressure is pressure though, the only thing you might notice if you ran 1/4 instead of 3/16 is a longer pedal travel to reach your required operating pressure. I don't think it would be as much of an issue with power brakes, but it might be more noticeable with manual. Isn't many of Wilwoods systems designed to run manual setups? If so that may be the reason they are recommending 3/16 all the way around. Would it also stand to reason that by running a larger rear brake line you would be slightly delaying maximum brake pressure thus creating a bias to the front? If you running an adjustable bias valve this would negate line sizes. Same theory applies to master cylinders. Oh the decisions. :crying:


Mike

[parsonsj]

I'm using a balance bar between the masters which will allow me to adjust for front/rear bias. I would say not to use line size as an adjustment parameter, but use what will provide the best performance for each individual brake and then adjust bias with a bias valve or balance bar. It ain't easy swapping brake hard line!

jp

[paul67]

I would go with what willwood recomend as they have designed the system+ plus with the 1/4 pipe you will need a larger volume master cylinder for the rear brakes , any maths people here to see what the extra volume of oil would be needed to move the rear calipers if using 1/4" instead of 3/16 pipe .
paul67. just a thought

[MuscleRodz]

I'm using a balance bar between the masters which will allow me to adjust for front/rear bias. I would say not to use line size as an adjustment parameter, but use what will provide the best performance for each individual brake and then adjust bias with a bias valve or balance bar. It ain't easy swapping brake hard line!

jp
I would never try and use line size as a bias mechanism, but it does work in theory. Bias bar or proportioning valve is the only way to go. We really need an engineer to build these cars with all the complicated mathmatical computations! Man that is alot of big words. :hmm:

Mike

[zman1969]

just want to chime in here, the size of the line wont affect pressure - it is equal over the entire system the bigger line to rear adds more volume .pressure wont be affected by this :naughty:

[fuzzyonion]

A completely rigid hard line's diameter will not effect pressure in a sealed hydraulic system AT ALL (see Pascal's law), even if you were to use 4" sewer pipe.

Flex line can effect pedal travel because it tries to straighten out as pressure is applied. The less flex, the less pedal travel. Larger diameter hose will flex more than smaller. Longer hose will flex more than shorter, and rubber encased hose will flex more than SSbraided.

The small amount of fluid flow in a brake system is negligable when considering the difference between 1/4 and 3/16 line, especially considering it is then restricted back to 3/16 or less by the line's seat anyway.
There were and are plenty of cars using 3/16 hard line throughout the system to large volume wheel cylinders and calipers.
GM changed to 1/4 line to the rear axle when they added the tandem master in 1967. Why they did this is anyone's guess, but it is probably for fluid weight, since many of the cars after that used no residual valve at all to the drums.

Dont confuse a closed hydraulic system with an open one, such as once used in rock quarries. They have somewhat opposite properties.

[BRIAN]

Also be careful with the type of line you purchase. I use 2 different suppliers and one bends a lot easier than the other. Problem is it is also more eaisly damaged if hit by something. If you haven't routed your lines yet try some clamps by Kugel, low cost and neat appearance.
Also I think Inline Tube will bend anything on their machines if you supply a template. They can even cover with the armor. Good luck

[parsonsj]

Damn. From Inline Tube:
Please remember we can only duplicate lines for factory original cars with factory original parts. Inline Tube does NOT make lines for modified cars with aftermarket parts retrofitted to the factory cars.

Good thought though.

jp

[MuscleRodz]

Yes Inline tube SUCKS! They won't modify stock lines, or build custom ones either. not to mention the salesman I talked to late last week was unpleasant to talk too.

The good news. I called Classic Tube and got a much better response along with talking to someone who wanted to help me. And they can do custom work!

Mike

[parsonsj]

Classic tube, eh? I'll check 'em out.

Here's another question: it seems to me that doing the whole system in AN is far easier than 45 degree and the double flaired ends that go with it.

Thoughts?

jp

[MuscleRodz]

AN no problem for them. Background: Call them last week about stainless fuel and brake lines for the Blazer. Told them what I was doing. Stock brake likes except at the booster since I am planning a Hydroboost setup, and stainless flex brake lines which they have DOT as well. Brakes done. Next I asked about modifying the stock fuel line setup since I am putting my LT-1 in it and need an intake pump which is at a different pickup location. No problem. They would swedge an AN end where I wanted and attach a stainless flex line to the pump. They would also install an inline frame rail fuel filter as well. I was very happy with my phone call to them. Price wasn't anymore expensive than buying finished lines.

Mike

[tripower]

Yes Inline tube SUCKS! They won't modify stock lines, or build custom ones either. not to mention the salesman I talked to late last week was unpleasant to talk too.

The good news. I called Classic Tube and got a much better response along with talking to someone who wanted to help me. And they can do custom work!

Mike

Was it Colin or Mark? I spoke to both of them and they both seemed rather condescending and acted like you don't know what your talking about when asking questions. (What ever happened to good customer service?) I asked them some questions regarding a couple of their products to clarify it's would work for my application. they said yes and of course it was screwed up when I got it. I liked the "master cylinders fitting sizes are all the same" answer I got when I asked them about their MC to distribution conversion line set which I bought. Of course I had to spend 2 hours flipping the lines around to make it right for my MC.

[MuscleRodz]

Was it Colin or Mark? I spoke to both of them and they both seemed rather condescending and acted like you don't know what your talking about when asking questions. (What ever happened to good customer service?) I asked them some questions regarding a couple of their products to clarify it's would work for my application. they said yes and of course it was screwed up when I got it. I liked the "master cylinders fitting sizes are all the same" answer I got when I asked them about their MC to distribution conversion line set which I bought. Of course I had to spend 2 hours flipping the lines around to make it right for my MC.
Don't remember who it was. it wasn't worth the brain space because I won't be calling them back.

Mike

[parsonsj]

Let me re-phrase (sometimes I can be a little obscure):

Is there any reason not to use AN fittings on brake lines?

jp

[MuscleRodz]

I don't see why you couldn't use them as they can take lots of pressure. I think you would have a harder time using them just trying to adapt them to the components.

Mike

[tripower]

Don't remember who it was. it wasn't worth the brain space because I won't be calling them back.

Mike

I only remember their names because I cursed both their names while rebending stainless tube that should have been right for my app if they paid attention to my questions!!! :)

[parsonsj]

I want to use AN 'cuz I already gots a AN tubing flare tool. The double flare 45 tools are scary expensive.

I just use AN adapters in the masters and calipers and vyola: everything else goes to AN.

jp

[MuscleRodz]

I say go for it. Just one more little thing to draw the eye to. My only thought was for some reason I didn't think the OE brake fittings are pipe threads, they were straight. And finding an AN adapter fitting would be hard. But I may or am wrong about it.

The flaring tool may be cheap, but wait till you start pricing all the cool AN stuff. Adds up in a hurry. Scary when a single handful of fittings can run over $100. Yeah I know the double flair tool is not chump change either.

Mike

[parsonsj]

I just read the documentation that came with my master cylinders, and found that they ship with AN3 fittings as well as the 3/8-24 double flare fittings.

I'm guessing I should use steel fittings and not aluminum, right?

jp

[MuscleRodz]

yes, I would. There is a yield point for using aluminum fittings due to pressure requirements of a given system but don't remember what is. Make sure all your other fittings are steel as well. Stainless can also be used but is a little harder to find certain sizes.

Mike

[CarlC]

For a really good practical manual for hose and tubing pick up Carroll Smith's Nuts, Bolts, Fasteners, and Plumbing. It's an excellent referance manual.

After a huge leaning curve and spending way to much time and money I've switched to using only AN fittings. After dealing with inverted flare and all of the different and wierd fitting sizes that the OEM's put on the cars, simple AN is a blessing to deal with.

One thing to consider is using stainless for all of your hardlines. In 3/8" diameter and smaller there is no requirement for double flares. Single flaring stainless is easy using a good 37* flaring tool as long as the tube is properly prepared and the threads on the tool are well lubricated. I can dig out the tool part number if you are interested.

Aircraft Spruce sells fittings and tube for reasonable prices. You may want to check with your local hydraulics dealer (Parker), especially for tubing. You don't want to fold up a nice new stainless tube for shipping if you can find one locally. Stainless nuts, ferrules, and junctions (T, L, etc) are also available in stainless.

Use bulkhead connectors to brace a hard-to-soft line connection (brake line).

For disk-disk systems 3/16" / -3 is sufficient.

[gmachinz]

I'm a little late here but, the statement about the pressure being the same in a sealed hydraulic system regardless of diameter doesn't make sense to me. One basic rule of hydraulics is when diameter goes up, pressure comes down and vice versa all else being equal with the same amount of pressure applied every time. It makes me imagine what the heck your brakes think is going on when the master is forcing fluid through a 1/4" line then it suddenly splits to two 3/16 lines. Yes, it's a sealed system but when you have more fluid volume then it shrinks to two smaller lines, it must make for a touchy pedal-sometimes short pedal travel, other times long-at least as far as rear disc brakes are concerned. I dunno-maybe I'm wrong. It's just too damn early for me right now! LOL -Jabin

[parsonsj]

Carl: Good information, thanks. That seals the deal.

I was going to use stainless hard line. I have a local supplier that sells it in whatever length I want (up to 22 ft, I think). I have an Aircraft Spruce catalog at home (I'm on the road this weekend), so I'll check it out. Doing all the plumbing in AN with all stainless fittings sounds good to me. I think Speedway Motors makes SS kits for this sort of thing too.

Oh, and do post the tool pn, please. I have an AN flaring tool, but would like to compare what I have with what you know works.

jp

[CarlC]

Imperial 437-FB. Lube the thread with ARP thread lubricant or a moly-based grease to ease the process.

Don't be afraid to use the flare seat seals. They work very well if you have a small leak.

[parsonsj]

Muchas gracias, mi amigos.

jp

[fuzzyonion]

I'm a little late here but, the statement about the pressure being the same in a sealed hydraulic system regardless of diameter doesn't make sense to me.
It might not make sense, but it's the law.
http://www.lerc.nasa.gov/WWW/K-12/WindTunnel/Activities/Pascals_principle.html
The inlet to the slaves is smaller than 3/16" anyway.
In a non contained system, such as for cutting rock, compared to a brake system, the outside world is a large slave cylinder, the pipe is the master, and the resivoir is your foot. ;)
With respect to flow in a contained system, a severe restriction, such as in a proportioning valve, will actually decrease pressure, not increase it.