Hi,
I have to replace brake line from prop vale to rear axle. Original line appears to be 6mm steel. However 6mm steel line is not available in local auto supply stores.
Can I use 4.75mm coper pipe instead of 6mm steel to hookup brake line?

 

Hell no!!! never use copper for brake lines, its much softer and will burst.

1/4" od steel tubing is just a hair larger and will work just fine. If you can salvage the nuts on the line, they will work on the 1/4" line, but you may have to drill them out to 1/4". Not a big deal, put them in a vise and slowly drill them out, its not going to remove a lot of material.


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just noticed you are in europe, not sure if you can get 1/4" line there. You will need to find 6mm or 1/4" somewhere.

 

OK, finally I found 6mm tube in hydraulic joint shop.
they are available coper and zinc coated steel.
Seems like I will go steel tube.
I wounder why so many people not suggest to use coper brake lines and the same time only coper tubes are available as replacement for rusted stock in local part supply stores.

When I rebuilded rear suspension in my VW Golf daily driver I used coper 4.75mm tubes. I have installed 'em 2 years ago and still have not seen any problems.

I also noticed 6mm OD coper tube have smaller inner diameter compared to steel. seems like compensate for coper weakness.
The only advantage coper over steel is rust resistance.

 

Use Kunifer (cupronickel). It is an alloy of copper and nickel. Strong, highly corrosion resistant and much easier to bend and flare than steel. Loads on Ebay.

Theres no way you'd even burst copper, most copper brake line is rated to 8000psi, If you jumped on the brakes, you would be lucky to exceed 2000psi.

 

let me rephrase my comment.

If the copper line is brake line, rated for pressure, then its fine to use. I was referring to regular soft copper line, similar to plumbing line. Its thinner wall and not strong enough.

In a perfect world, i would do it all in stainless. That way it will never rust or rot or corrode again.

 

USE LINE MADE FOR BRAKE LINE USE!!!!! Copper line will crack over time...i dunno about bursting, but the reason you don't see copper line in automotive use is that it will work harden with use from moving, expansion and contraction and vibration and will crack.

You are working on brakes here...do not take any chances. Use line either from a brake parts supplier or the 6mm or 1/4" stuff you can get at the parts store. Use proper fitttings and tools. Make the correct flares, and use the correct connection hardware.

This post isn't meant to **** on anyone's parade, but i cannot say it enough...when working on brakes, if you don't know how, can't afford to do it right, or don't care if you're doingit right, DON'T TOUCH IT!

You obviously wanna do it right,'cause you're here asking questions

 

i seen 6mm brake lines today at AZ and O'reliys

 

Thanks, but I already got 6mm stainless steel.
i will make a little writeup later...