Brake hardlines vs. rubber....

[YNOTBOB2007]

I'm going to replace the hardlines from my master cylider to the proportioning valve...the rubber is cracking where it meets the metal crimp of the hardline. Drum brakes. I see there are rubber replacement and hardline replacements from the vendors. Does anyone have a preferance? The existing hardlines going into the MC have adaptor fittings on them to fit. Thanks

 

[bronkenn]

You can make your own with the NiCop brake line. It is very easy to work with and you can get the correct fittings at the auto parts store, so you don't need any adapters.

 

[Apogee]

The less flexible hose, the better IMO. Rubber hoses will be the largest source of compliance in any brake system, so the less you have, the lower the compliance and the more efficiently your brake system should function. Additionally, I would minimize the number of connections, so if you can eliminate the adapter fittings, that would be ideal.

 

[YNOTBOB2007]

You can make your own with the NiCop brake line. It is very easy to work with and you can get the correct fittings at the auto parts store, so you don't need any adapters.

It looks promising....so there is no rubber? I would order a roll/length with the correct fittings already attached and bend it myself with a tubing bender? Thanks

 

[Johnnyb]

Don't forget these lines run right by the headers are exhaust manifolds and so are exposed to a fair amount of heat. I'm going to use the wild horses ones with braided stainless on the outside. We'll see how it goes

 

[DirtDonk]

My originals lasted about 10 years before they looked fairly old and tired. The stock replacements I bought from the dealer in the early eighties on the other hand still look almost new today.
I removed them just recently to replace the eighties vintage master cylinder. Although they looked great I couldn’t take a chance. Figured new it was.
I like our rubber replacements, but I think I’m going to go all metal this time.

 

[bronkenn]

It looks promising....so there is no rubber? I would order a roll/length with the correct fittings already attached and bend it myself with a tubing bender? Thanks

No there is no rubber lines. You can buy the line/tubing by the foot or a small roll. You will need to know the size of your fittings on the Master cylinder and get them at your parts store. You will also need a flaring tool. shouldn't take more than a couple hours. By the way I have since replaced that Master for a Wilwood. That one was from CJ's and I could not get it to stop leaking around the top.

 

[jonesallu]

I just recently replaced my stock MC rubber lines when I converted to power drum brakes. Here's how it turned out. There's a company that sells the hard lines prebent with correct tube nuts (no adapters needed) and then I used the shortest flexible in between I could find. Note I used the stock tube bracket happily purchased from a member. The first two photos show without the rear connected yet, the last two show the hard lines down at the differential valve. IMO the spiral hard lines replaced the rubber lines because they were less expensive to manufacture. Note that you can purchase the correct tube nuts to avoid using adapters, if you want two less connections.



Good luck,
Al Jones
'71 U

 

[nvrstuk]

Don't forget these lines run right by the headers are exhaust manifolds and so are exposed to a fair amount of heat. I'm going to use the wild horses ones with braided stainless on the outside. We'll see how it goes

Braided hoses, even the teflon lined ones are only to be used when flexibility is needed and use the shortest amount needed. Use hard line for everything else. This is from several brake companies and their tech dept when I was debating using more braided in spots and asking them if braided line expanded.

You don't want a spongy pedal and rubber and braided lines are the culprits.

 

[jonesallu]

You don't want a spongy pedal and rubber and braided lines are the culprits.

Here's how I look at it. OE-type rubber brake hose expands by 0.14 cc/ft at 1,000 psi and the teflon braided ones expand at 0.00029 cc/ft at 4,000 psi. A visual: if the volume of a drop of brake fluid is 0.05 cc, braided PTFE is essentially rigid in terms of expansion. Meaning at 4000 psi, that's less an an extra drop of brake fluid needed to overcome the expansion of a foot of PTFE line. In reality, its less than 1/10th of a fluid drop per foot of line. You decide if that qualifies as "sponginess". In terms of OE-type, that's less than 3 drops of fluid of expansion per foot. Six drops at 2000 psi. If the master cylinder piston diameter is..., you can quickly calculate the added brake travel to overcome the hose expansion. It's substantially less than a small amount of air in the system.

Al Jones
'71 U

 

[Johnnyb]

I've had hard lines from the master cylinder to the distribution block for years. Biggest problem I've had is that they get messed up when you need to do things like change your master cylinder, add vacuum boost, or get to the headers for any reason. The steel lines aren't as forgiving as the flexible ones. I like the numbers provided in the last post, makes it seem like proper bleeding could yield as firm a pedal as the steel lines that I'm running right now.
Of course I'm going to be sure to do a full bench bleed of the master cylinder as well.

 

[nvrstuk]

Here's how I look at it. OE-type rubber brake hose expands by 0.14 cc/ft at 1,000 psi and the teflon braided ones expand at 0.00029 cc/ft at 4,000 psi. A visual: if the volume of a drop of brake fluid is 0.05 cc, braided PTFE is essentially rigid in terms of expansion. Meaning at 4000 psi, that's less an an extra drop of brake fluid needed to overcome the expansion of a foot of PTFE line. In reality, its less than 1/10th of a fluid drop per foot of line. You decide if that qualifies as "sponginess". In terms of OE-type, that's less than 3 drops of fluid of expansion per foot. Six drops at 2000 psi. If the master cylinder piston diameter is..., you can quickly calculate the added brake travel to overcome the hose expansion. It's substantially less than a small amount of air in the system.

Al Jones
'71 U

Yup, and that's all well and good when they are brand spanking new. When flexible lines age they will be the part of the brake system that expands giving you a spongy pedal and then eventually fail.

Your choice- run the entire chassis with rubber brake lines since according to your "3 drops per foot" theory you should be good forever.

I, like Ford and every vehicle manufacturer- including exotics, choose to eliminate failure possibilities so I'm sticking with my post and following every aftermarket brake companies recommendations to use as little flexible hose as possible to help eliminate any potential "sponginess" and eventual failure.

I think everyone would agree that hard lines always outlast flexible lines. When you've seen rubber lines expand to 3x their normal size because they eventually get soft - - my experience says minimize the risk! How many times on this site alone have posters said they were dealing with a spongy pedal or couldn't bleed the brakes properly because the rubber lines were bulging. I wrenched at a GM dealership decades ago and it's more common than most want to believe.

Gotta be a reason that nobody in the industry uses flex hose when they don't need to. I don't have to decide if your calculations qualify for sponginess or not. It's not accepted in the industry for a reason, math or no math. Easy decision.

 

[jonesallu]

The original discussion was not about durability but "sponginess". I wasn't making the case to NOT use metal lines, I was just adding some facts that non-metal brake lines are not as bad as they were made to be in the tread. Now, the thread is talking about how long lines last - durability. Not the same, but could be related. If anyone is interested in a rational approach to brake lines (expansion of non-metal brake lines), I encourage you to look up the work Goodridge has performed on brake hoses. Also, if you want to "play" with the numbers, all the minimums are defined in SAE J1401. It can be thick reading, but interesting.

Thank you,
Al Jones
'71 U

 

[nvrstuk]

The original discussion was replacing hardlines with flex lines and my concern was from being on this list for 20+ yrs was the number of people who have asked in the past about replacing metal lines with flexible ones and others who have had brake pedal "issues" from flex lines-some not very old.

See the quote below- the original OP's post.

"I'm going to replace the hardlines from my master cylider to the proportioning valve...the rubber is cracking where it meets the metal crimp of the hardline. Drum brakes. I see there are rubber replacement and hardline replacements from the vendors. Does anyone have a preferance? The existing hardlines going into the MC have adaptor fittings on them to fit. Thanks"

So being concerned about novice "home repairs" and replacing OE metal lines with flex lines I wanted to emphasize the safety & potential issues of replacing metal lines with flex.
Was he going to replace the entire brake system with flex line? No. Have I seen others do it? Yes. Have even more asked if it was OK to do? Yes.

How are we to assume that possibly the OP and/or others wouldn't just move in this direction? We can't.

In a perfect world with new hoses (preferably not made in China) the numbers might hold up. Your reference has good info-not doubting it.

I however doubt the ability of people who aren't mechanics to understand why things should or shouldn't be done. No fault, just don't understand.

Have a good day.