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  #1  
Old 02-17-2023, 12:29 PM
bshawco bshawco is offline
 
Join Date: May 2021
Location: Near Durango, CO
Posts: 45
Default Brake Line Fittings

From KAI Section 5.22:

"Install compression fittings to plastic tubing using the following steps:

Step 1: Drill #29 the inside of the tube."

I followed this directive and found the brass inserts fairly easy to insert to the plastic tube.

Step 4 implies that the insert should be difficult to install and probably requires putting the end of the plastic tube in boiling water to get the brass insert fully installed.

Am I making a mistake in drilling out the ends of the plastic tubing that will result in leaking brake fittings?
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  #2  
Old 02-17-2023, 01:16 PM
Scott Hersha Scott Hersha is offline
 
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 2,567
Default

Brad,
I think if youíve followed the company installation directives youíll be OK. When I did mine, I didnít have that specific instruction, and it was difficult to get the insert in the tubing even after heating it up. Iím guessing the wall thickness on my stretched tube ended up being similar to your reamed tube. The ferrule on the compression fitting doesnít care what the diameter is as long as it fits, because of its tapered design. It just needs to squeeze down on the plastic tube strongly enough to seal it under system pressure. I hear what you are saying about possibly weakened wall because youíve removed material, but the the end result is the same with one that is stretched under heat and pressure. The only difference I see is that the way you did it is easier. Just donít ream the ID past where the insert will rest.
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  #3  
Old 02-17-2023, 01:30 PM
pazmanyflyer's Avatar
pazmanyflyer pazmanyflyer is offline
 
Join Date: Jul 2007
Location: Litchfield Park, AZ
Posts: 1,260
Default

Quote:
Originally Posted by bshawco View Post
From KAI Section 5.22:

"Install compression fittings to plastic tubing using the following steps:

Step 1: Drill #29 the inside of the tube."

I followed this directive and found the brass inserts fairly easy to insert to the plastic tube.

Step 4 implies that the insert should be difficult to install and probably requires putting the end of the plastic tube in boiling water to get the brass insert fully installed.

Am I making a mistake in drilling out the ends of the plastic tubing that will result in leaking brake fittings?
No your not. It's a mix of old and new instructions. The old way was to soften the plastic in water so that the insert will go in. The newer way is removing a touch of material for the insert to go into place. The compression fitting will take care of the seal.
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  #4  
Old 02-18-2023, 07:42 AM
TS Flightlines TS Flightlines is offline
 
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 3,205
Default

But the idea is to get the ferulle to compress the tube against the insert to form the pressure sealing. Having a larger ID, or thinner wall provides some 'clearance' or a slight 'void' space between the liner wall and the insert. All things being equal, the ferulle will compress to a known dimension, so the ID of the ferulle will compress similarly. If the ID of the tube has been changed by drilling, so does the the amount the ID will compress against the insert.
It may still be enough to hold pressure for the brakes to work, but after continued pressure cycles it will eventually start to leak.

Be carefull. Mixing and making OR changing the specs will change the way things work.

Tom
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  #5  
Old 02-18-2023, 10:01 AM
KEG KEG is offline
 
Join Date: Aug 2020
Location: Tuscumbia, Alabama
Posts: 46
Default Second tightening

Van's instructions are clear regarding the initial tightening of these type fittings (one turn past finger tight I believe). Is there a spec for retightening if you have to disconnect the tubing?
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