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Air brake hose size question.


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I am getting ready to replace my front brake chambers on my 1985 Superliner. My question is the rubber hose size. Not sure if mine are 1/2" or 3/8" hose, but are about 18" long. 

What doesn't make sense to me is, why do they both go through a 3/8 fitting. What is the advantage of 3/8" fitting to 1/2" hose to 3/8" fitting over a 3/8" fitting 3/8" hose 3/8" fitting. No matter what size hose you use, it still narrows down to 3/8"

I want to make sure I put the correct ones on. All my drop-down hose are so old, that all the markings and sizes on them are long gone.

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It has to do with the volume of air entering the brake chamber. The smaller the diameter hose the less amount of air entering the brake chamber within a given amount of time. This will affect brake timing. Going down in hose I.D will dramatically change brake timing. 

V

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The I.D. of those hoses is 3/8"..  that is plenty... There are D.O.T. grade fittings that you build in your hand, they even come with the 5/16" allen wrench to build them. you buy a length of D.O.T. hose and cut it to what you need, screw these fittings in the end and your done... I will look for the name of them.. I have used dozens of these but cant remember the name... Crazy...

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All you need is a tape measure and a box cutter, a roll of hose, and these fittings, and you can make lines for days.... :) Jojo

20TRA31402.jpg

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On 4/3/2021 at 12:20 PM, jackdk said:

I am getting ready to replace my front brake chambers on my 1985 Superliner. My question is the rubber hose size. Not sure if mine are 1/2" or 3/8" hose, but are about 18" long. 

What doesn't make sense to me is, why do they both go through a 3/8 fitting. What is the advantage of 3/8" fitting to 1/2" hose to 3/8" fitting over a 3/8" fitting 3/8" hose 3/8" fitting. No matter what size hose you use, it still narrows down to 3/8"

I want to make sure I put the correct ones on. All my drop-down hose are so old, that all the markings and sizes on them are long gone.

There are federal regulations on brake timing. (Time that brakes apply and another regulation for when they release)

Timing is done when there are changes made at the factory to make sure that the brakes apply and release within a certain amount of time.  If you make any changes to the air system, from how it was built at the factory you could change the timing.

Little changes from changing from a straight or 45⁰ fitting to a 90⁰ fitting could even change your timing.  So putting a smaller house on that was originally on there can possibly affect your timing.

I work in Macungie and have worked a bit on the air system.

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14 hours ago, MackTech said:

There are federal regulations on brake timing. (Time that brakes apply and another regulation for when they release)

Timing is done when there are changes made at the factory to make sure that the brakes apply and release within a certain amount of time.  If you make any changes to the air system, from how it was built at the factory you could change the timing.

Little changes from changing from a straight or 45⁰ fitting to a 90⁰ fitting could even change your timing.  So putting a smaller house on that was originally on there can possibly affect your timing.

I work in Macungie and have worked a bit on the air system.

Thanks MackTech. I guess the best thing to do is when I remove the hoses, cut it, and measure the inside diameter to see if its 3/8 or 1/2. Not sure what has been done to this truck before I purchased it, and what mods its been through. I know a lot has been done. Started as a tractor, then stretched and made into a tri-axle dump, air to the rear for pintle hitch trailers. Thanks again. 

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On 4/3/2021 at 2:49 PM, Vmac3 said:

It has to do with the volume of air entering the brake chamber. The smaller the diameter hose the less amount of air entering the brake chamber within a given amount of time. This will affect brake timing. Going down in hose I.D will dramatically change brake timing. 

V

Thanks Vmac

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On 4/3/2021 at 5:13 PM, Joey Mack said:

The I.D. of those hoses is 3/8"..  that is plenty... There are D.O.T. grade fittings that you build in your hand, they even come with the 5/16" allen wrench to build them. you buy a length of D.O.T. hose and cut it to what you need, screw these fittings in the end and your done... I will look for the name of them.. I have used dozens of these but cant remember the name... Crazy...

Sounds good Joey Mack. Might be good to stock up on that stuff. Thanks. 

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