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Old 01-08-2018, 07:23 PM
Russ Thurber Russ Thurber is offline
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Default Treadle Vac Issue

Originally Posted by simplyconnected View Post
Russ, is the new M/C piston depth that much different from your original M/C? I would think you can simply adjust with the brake pedal bolt (which IS the eccentric). Simply loosen it and turn. You will see the rod change lengths.

I asked if you bench bled. It takes me about 20 pumps to get all the air out of a dry M/C. Doing this on a level bench is much easier. I use plastic tubes to return the fluid to the reservoirs. That way I don't waste brake fluid, I can see the air and I know when it's running clear. With some 'dry' M/Cs, I shade the output with my finger just to get things going while I pump the piston. YouTube has many videos regarding, 'bench bleeding'.

What brake fluid are you using?

If you get all the air out and properly adjust your wheel cylinders and your brake pedal rod, a one-inch bore M/C will work nicely. I am not a big fan of Treadle Vac boosters because they don't offer much assistance (even when new) and they are expensive to rebuild. I don't think there is much 'bang for your buck' after all is working again.

Part of the reason is, I believe every Squarebird that drives on our highways is in competition with modern cars that have disk brakes. Squarebirds do very well with power front disk brakes. It's one of the very best moves I made on our '59 Galaxie. Many of our Squarebird members have retrofit their cars. I haven't heard one complaint yet nor has anyone gone back to drum brakes (that I'm aware of). We use a two-stage 8" booster with a 1" dual-piston M/C. The difference in stopping is amazing. - Dave
Hi Dave
To adjust the M/C rod length, I would have to remove the dash panel to get at the rod eccentric bolt & nut which is way above the booster. Now the eccentric for the booster valve IS accessible right in front of the booster but I don't think that adjustment can effect the pedal travel. Can a shim "button" inserted in the M/C bore in front of the piston be a possible solution to get the rod length I need? M/C has been bled, wheel cylinders bled, shoes are well adjusted. Everything is new except for the booster.
Thanks for your help. I need to do something soon !!
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Old 01-08-2018, 07:28 PM
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Frango100 Frango100 is offline
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No, the eccentric on the booster doesn´t change the pedal rod length. With that eccentric you can adjust the point the booster starts to work. If its not set well, you will feel a vibration in the pedal while braking.
I don´t have the adjustable rod on my bird anymore and used a shim inside the MC piston hole, but I think if you have the adjustable rod, that you better use that adjustment, even if it would give more work now.
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Old 01-08-2018, 09:38 PM
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simplyconnected simplyconnected is offline
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Originally Posted by Russ Thurber View Post
Hi Dave
To adjust the M/C rod length, I would have to remove the dash panel to get at the rod eccentric bolt & nut which is way above the booster...
You may need to remove just a bottom panel, not the dash. The eccentric shoulder bolt is #2462:

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Old 01-09-2018, 10:47 AM
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partsetal partsetal is offline
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Some facts-The Bendix Treadle-Vac was never used on the Squarebird. What was used is the Kelsey-Hayes bellows type under the dash unit and the Bendix Master-Vac under the hood. The Kelsey Hayes units were found exclusively on the 58, some early '59's and all Air Conditioned cars. The Master-Vac was installed in late 59 and 60 non-Air Conditioned cars. All power brake equipped Squarebirds left the factory with the 1-1/8" Master cylinder, the 1" for non-power. The 1-1/8" provides a harder pedal but a shorter stroke. This M/C is no longer produced and many catalogs of today and many counter people affirm that the 1" is correct since it is still available.
The rod on the Kelsey Hayes unit is adjustable using the push rod adjusting eccentric lever. It is hard to reach with the lower dash installed. My method is to use a 9/16" open end wrench and loosen the nut at the eccentric just a bit and rotate the eccentric upward to shorten the rod and downward to lengthen the rod. You should be able to feel resistance when lengthening the rod, this means the pushrod is seated in the M/C bore. You should be able to go a little more but then check to see that you have not blocked the compensator port in the M/C. Another key to getting better pedal is to adjust the brakes after they have been run a little. This gives the lining a better chance to seat in and may allow you to shorten pedal travel. My method is to tighten the adjuster while rotating the wheel, stop when you just hear a whisper of contact. What has worked for me with the Kelsey Hayes setup is: Use the 1 1/8" master cylinder; re-bleed the system; adjust the pushrod length; re-adjust the brakes after a short drive.
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