1965 C10 LWB Project Build Thread

[SCOTI]

Originally Posted by JohnIL

I want to start this installment by thanking Scoti for his advice on an alternate procedure for manually bleeding brakes. His process is much more controlled and methodical than the way I've always done it. After three rounds of bleeding Scoti's way, I don't think I'm chasing air bubbles anymore. In fact, I didn't see any air bubbles at all. Now, I'm pretty sure I have a different challenge.

After bleeding again, the pedal was still soft. The brakes stop the truck, but the pedal feel was awful. I've felt air in the lines before (on other vehicles) and this felt different. It felt like maybe I wasn't getting enough brake pedal travel, like the pedal was hitting the floor before the master cylinder was maxed out. After thinking about the geometry of the booster and master cylinder, I lengthened the brake rod by adjusting it out one full turn. This improved the pedal feel. It's still softer than I would expect, but I finally got resistance at the end of the pedal stroke. So, I adjusted the rod out two more full turns and the pedal is starting to feel normal-ish.

All of this begs the question, how do you properly adjust the brake rod length?

With the old manual drum setup, I just took all the slack out of the pedal and adjusted the rod so there was 1/8" of free play before the brakes started to engage. I tried to do the same thing with the new power setup, but that appears to be way to loose. With the cushioned resistance of the brake booster, it's very difficult to tell when the brakes begin to engage. Is there a magic formula or should I just keep lengthening the rod until the brakes drag?

As always, I appreciate any wisdom you guys can share.

Manual & power brakes use different leverage on most vehicles. When I swapped to vacuum/power assisted brakes from Hydraboost on my Squarebody dually, it required a different ratio.

When I swapped to disc brakes on my drum brake trucks, I kept them manual so it was just as you did (remove the slack @ the pedal).

[JohnIL]

Originally Posted by SCOTI

Manual & power brakes use different leverage on most vehicles. When I swapped to vacuum/power assisted brakes from Hydraboost on my Squarebody dually, it required a different ratio.

When I swapped to disc brakes on my drum brake trucks, I kept them manual so it was just as you did (remove the slack @ the pedal).

I actually had that same thought. If I can't figure out how to firm up the pedal, I would almost rather go back to manual brakes. The pedal actually feels pretty good without the engine running (no vacuum assist). I've worked with factory power disc/drum setups on lots of other cars and I've never felt a brake pedal this spongy before. I've also never done a manual to power conversion before, so this all new territory for me.

I did some extracurricular reading last night. My booster and master were part of a CPP kit. According to CPP's online documentation, they should already be "mated" to each other. But, there's always a chance that the booster actuator rod needs to be adjusted. That would explain the soft pedal. I have a booster rod measuring tool ordered from the Amazonians. When it arrives next week, I'll verify that the booster and master are playing nice with each other. Then, theoretically, I should be able to adjust the brake pedal rod, more or less like a manual setup. Take out the slack and adjust to 1/8" -1/4" headspace.

Keep the advice coming. I'll take all the help I can get!

Thanks.
John