Quick update -- I finally got back out and played with the brakes again. Things appear to be improving. I just need my "helper" for an hour or so and I think that I can get it back to where it was. It is just too hard, and takes too long, to bleed the cylinders by myself.
Pump the brakes, use a block of wood to block the pedal at half stroke, open the bleeder, push the pedal full stroke and block again, being careful not to "release" the pedal, then going to close the bleed screw. Then doing it all over again..
Quote:
I can't even BEGIN to count all the problems in this thread, but I'm going to address a few...
1. *IF*... You want MORE braking pressure at the wheel cylinders/calipers, you use a SMALLER BORE master cylinder, not a larger one.
Larger bore Master Cylinder will REDUCE your brake line pressure at the wheel pistons.
If you want more VOLUME, which you DO NOT NEED with 4 wheel discs, you use a LONGER STROKE, now a larger bore....
This is basic hydraulics.
Thanks for the response, while I agree with most of what you typed, this has me very confused. I would have thought that a smaller bore master cylinder would require more pedal pressure than a larger bore cylinder to achieve the same end of line pressure, assuming that the only difference in the system is the master cylinder bore size. I thought that the ratio of areas was inversely proportional to the ratio of pressures.
I'm not very worried about peddle pressure right now. I am more worried about stoke since I have "upgraded" both the front and rear stock CJ brakes to 3/4 ton brakes. I have not researched the hydraulic capacity of the new calipers vs the old calipers/drums, but I guess that I need to calculate whether or not I should increase the master bore size.
My "seat of the pants" testing, prior to my recent problem, indicated that I had more pedal travel with the 3/4 ton calipers than I did with the stock calipers/drums. This would indicate to me that I would need more area in the master cylinder bore to increase my pedal height back to where it was.
It is not a good day if I don't learn something new. Can you help me understand what I am missing with regards to the hydraulics?
My comment about replacing my stock combo valve with a Jegs adjustable is that I can retain the brake indicator light circuit, which is important to me, and so that I can balance my front to rear, if needed. It may not be needed. You are correct, since the Jeep primarily sees low speed conditions, the balance is not critical.
However, when I run it on the street, I don't want to lock up one end sooner than the other, if I can help it. I thought that brake lockup would be a fairly complex function of speed, weight distribution front to back both static and dynamic (standing still and while braking), the ratio of caliper size and ratio of pad area front to back, and disk diameter ratios.
Basically, if I am going to go through the trouble of replacing my brake lines, I want to make sure that I can adjust the system to account variables beyond my control without tearing the entire system apart again.
Thanks for all of the constructive help.
-- Mike