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3/16" vs 1/4" brake line

Discussion in 'The Garage' started by boz42, Dec 27, 2006.

  1. boz42

    boz42 1/2 ton status GMOTM Winner

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    i am completely replumbing the brakes on my k5 it is 1 ton & has rear disc & a large bore mc. could i run 3/16" line frt & rear or should i leave the rear 1/4"?

    i think 3/16 would be fine since the rear is disc now. any debate?
     
  2. Tominator II

    Tominator II 1/2 ton status

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    You should not have any problems. I put an Eaton 1 ton rear in my 77 Jimmy and used 3/16 brakeline from a 77 14 b instead of the 1/4 inch the Eaton had and still am running Drum brakes and have not had problems with the brakes for over 7 years.
     
  3. 1977k5

    1977k5 3/4 ton status Vendor

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    Leave the rear @ 1/4", it will push less pressure at the rear brakes (which you want).
     
  4. AuH2O

    AuH2O 1/2 ton status

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    If I may borrow this thread for a question somewhat pertaining to the subject... Is is wrong to have copper brake lines, and if so, why? I've seen that some shop manuals, Haynes among them, more or less strongly advice against copper for brake lines. But they don't explain why! The reason I'm asking is that the brake system was recently renovated and redone on my K5 before I bought it, with - yep, you guessed it - copper lines.
     
  5. boz42

    boz42 1/2 ton status GMOTM Winner

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    why would u wany less pressure, i will be running an adjustable rear prop valve, so that is no biggee


    copper is not rated for pressure as high as brake lines get.
     
  6. diesel4me

    diesel4me 1 ton status Premium Member

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    aint strong enough..

    I discussed using copper brake lines a few days ago here..it isn't legal here,copper lacks the strength needed to prevent the line from balloning and eventually popping...they do make "air brake tubing" of copper with thicker walls than regular copper tubing used on refrigeration or LP gas lines,but it still does not meet D.O.T. standards...copper also "work hardens" and cracks from vibration eventually..I have used it for gas lines on carbed trucks with good results however..

    I had one truck that was plumbed with copper lines,the guy I got it from had used it only to plow his driveway and around his farm,so he used copper ,to prevent from having to replace them every year or two..never had any brake troubles with the lines,but I never stomped hard on the brake pedal either!..

    I used the truck only on local roads and almost never on long trips or on the expressway..I will say I'd trust a copper line more than 99% of the rotted steel lines on many vehicles I see here!..they certainly cant be any weaker than they are!..:eek1:

    Many cranberry growers here use copper brake and fuel lines on the "bog buggies",to avoid having to replace them so often-(and to prevent brake fluid from getting in the cranberry bogs!--they must use "food grade" gear oil and as many other non-toxic fliuds in them also!)...

    I've been tempted to try copper on tranny cooler lines,I think it will work,has ample pressure capability,but might crack from vibration after awhile--bet it would help cool the fluid too..so far I just used the cheesy 5/16" steel lines,that seem to start to dissolve the moment you put them on...don't want to find out the hard way copper wont hold up on a long ride or under heavy use like plowing..might be OK to use copper on a buggy or a truck that sees no "on road" use..:crazy:
     
  7. loafer

    loafer 1/2 ton status

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    The pressure will be the same regardless of what size line you use.

     
  8. AuH2O

    AuH2O 1/2 ton status

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    Thanks for the detailed reply! I'll let mine be for the time being, but I'll keep a close eye on 'em.
     
  9. divorced

    divorced 3/4 ton status

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    How do ya got this figured?






    The 3/16" will work fine. Both sizes would have the same pressure.







    .
     
  10. 1977k5

    1977k5 3/4 ton status Vendor

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    Yeah, didn't really think about it before I posted I guess :doah:

    I overlooked the fact that the brake lines run into calipers/wheel cylinders and that the line size only governs the amount of fluid flow necessary for the caliper piston/wheel cylinder throw.
     
  11. roadnotca

    roadnotca 3/4 ton status

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    Yeah, brakes are a pressure system, not flow. Check-out the ID of your flex lines.
    As for Copper, they're not street legal because they do eventually break; brake lines = crash, gas lines = fire.
    I know it would be a pain but less work, I would think, to paint the steel lines (Rustoleum). Or nowadays, you can get SS lines for any of the GM fullsize (LMC). :D
     

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