Need on-site help bleeding disc brakes

[Titanguy]

Ask Gary what size main line they use on triple axle disc conversions. I think you will find they use 1/4". The cross overs and T fittings are still 3/16.

 

[porthole]

Surprised I missed this thread, then remembered, it started during my frustrating lack of net access I had with all my new wiz bang net gear.

about the brake lag that he had. I asked, and was told that he bought a kit with all the lines included. All were 3/16. I suggested that he run 1/4 in.
He contacted me once again and reported that after replacing the 3/16 with 1/4 in. line his braking lag time was no longer an issue.

I'd be willing to bet he noticed a change because he ended up having his brakes bled in the line change.

I don't think that going from 3/16" to 1/4" is going to change the lag time. The lag time is a result of the pump spinning up from 0 PSI to the 250 mentioned by Titanguy.

If you have 20' of 3/16" or 1/4", and there is no air in the system, actuating the pump should have a negligible difference in time, at least using the the "butt" as the measuring instrument.

The way I look at it, the larger line will take longer to build pressure as there is an increase in volume.

I know it it is not the same, but using fire engines and hoses as an example. With fire hoses you can actually see the difference in time it takes to fill 200' of 1 3/4" and 2" lines at 100 psi. I takes longer to fill the larger volume hose, not much, but something you can see.

But once filled to 100 psi and bumping the pressure to 150, the hoses "appear" to increase at the same rate. You have to see how the hoses react to understand what I mean.

Brake lines having such a small difference in diameter still have a sizable difference in capacity. Going from 3/16" to 1/4" almost doubles the volume in the lines, so in theory, it should take the pump longer to move that doubled volume.

I'm sticking with any noticeable brake lag is a result of the the time it takes the pump to spin up. And that time may be different between the Super Duty's and all the other actuators. With standard electric brake controllers the pump could start spinning up as soon as you apply enough pressure on the pedal to activate the brake light circuit. With Ford's hydraulic activated TBC you could have your brakes activated, but still have little to any pressure in the system. thus not activating the hydraulic pump.

That all said, I'll take 3/16" lines and hydraulically activated TBC's any day over drum brakes.

Now if my pump ever goes bad, the Titan pump looks like a viable upgrade.

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but I have difficulty seeing how it would make an improvement when the hydraulic outlet on the actuator is 3/16 inch. Maybe that isn't a real factor. I need to talk with my son, the aerospace engineer.

Back to fire hoses. Years ago all standard attack hand lines were 1 1/2".
Sometime back in the 80's someone figured out we could move a lot more water with less friction loss by moving up 1 3/4" hose lines. So the increase in diameter gave us higher volume, effective fire streams at manageable pressures.

The reason I mention this is that hose diameters changed but all the couplings and fittings remained at 1 1/2".

So if you were to use an adapter to go from 3/16" to 1/4" should you decide to change your brake lines, I don't see it effecting your brake performance. But, as long as you are changing, why not replace the fitting with the proper fitting.

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I also noted that the disk brake calipers have 2 bleeder screws on each piston (4 per wheel). Do I crack them both together, or seperately?

You have 4 bleeder on each caliper?

2 bleeders are common on universal type calipers, top and bottom. That is because they are universal in side to side, what is the top bleeder on the right becomes the bottom when switched to the left.

The highest bleeder is the fitting you use to bleed the system.

 

[cookie]

I know it it is not the same, but using fire engines and hoses as an example. With fire hoses you can actually see the difference in time it takes to fill 200' of 1 3/4" and 2" lines at 100 psi. I takes longer to fill the larger volume hose, not much, but something you can see.

I guess I would question that statement as a comparison to the size of brake lines.
You are talking about filling a line (hose) verses using a line that is already filled.
I really can't say if one size is better than the other, I only know what I have heard and how mine works, actually how well it works.

Peace
Dave

 

[porthole]

I guess I would question that statement as a comparison to the size of brake lines.
You are talking about filling a line (hose) verses using a line that is already filled.
I really can't say if one size is better than the other, I only know what I have heard and how mine works, actually how well it works.

Peace
Dave

I only brought fire hoses into the discussion because the average person may not know that just going form 3/16 to 1/4 almost doubles the volume.

You left out this part.

"But once filled to 100 psi and bumping the pressure to 150, the hoses "appear" to increase at the same rate. You have to see how the hoses react to understand what I mean."

I only know what I have heard regarding trailer disc brakes setups, and for the most part it is all "net talk".
Having a larger volume line is not always the answer in hydraulics, you still have to move the fluid. Sizing he line to the application is the important part.

I think the key point is; if you have a factory or MOR/ryde installed system with 3/16" lines, there is no reason to change that. If you are installing from drum like you and Jon did, yeah, maybe making the home run at 1/4" is a viable idea.