brake rant

well, I got it welded up and made a push rod out of 3/4 stock. the end is reduced to .45something goes into the master in the piston and the other end has 7/16-20 threads for the heim joint I found attached to some junk. The brake arms pivot bolt is now on the wrong side so I drilled and tapped 5/16 threads and installed a good grade american cap screw through the ball of the heim joint. Probably finish it tomorrow.

 

I approve! fb

 

I like it.

If I had similar tools, I see a re-use for my worn t-98 intermediate shaft and the pedals of my jeep which are sort of wallowed oblong and are thinner on the edges than the center... Thoughts about having them bored then sleeved with bronze bushings ... Or just cut and put new ends on them.

 

I thought about boring and rebushing my brake pedal arm. Its just not worth it. for under 50 bucks I can have a new one. The tube was worn out pretty bad too. Those are cheap. Since I am using a giant master and need a custom bracket and the mount for the tube is wore out also, I just went this route. I also happened to have a prefect piece of hard chromed hydraulic ram. I don't often walk past a piece of steel and not take it home. I am thinking that once I bolt the bracket to the frame the shaft that the brake arm and clutch arm/pedal ride on will not be able to move at all. Should tighten things up a lot and remove this particular variable from my brake issues.

 

You say in the beginning you replaced the residual valves, do you mean got rid of or got new ones? Later you say they are mostly garbage. You shouldnt have residual valves with 4 wheel disc.
Jon

 

GM disks front and rear generally require 2LB residual valves so I have read. I took one out, looked at it and saw that the cup with the spring was in sideways after use. It was installed and used as designed and failed in short order. Thats garbage. I removed and replaced the valves. So, why is it that all the information online points to using a 2LB residual valve to keep slight pressure in the calipers? Apparently they don't always work anyway.

 

Got it all back together today. The new shaft for the brake and clutch arm to ride in with the new support that connects tot he master cylinder mount works really great. There is no more side to side movement on the clutch arm and just a little bit on the brake arm. The brake arm bottom hole is egged out, so its to be expected. This fabrication was worth the effort to get the play out and to make sure the push arm for the master cylinder was at 90* to the piston.

I used all NiCopp for the new brake lines I made. I will never use steel again. It flares much easier, bends easier and seals correctly with minimal effort. The steel line is garbage in comparison and rusts.

The brakes are better for sure, but I am still just not going to lock them up period. The big 35s and the 4" lift just have too much leverage on the disk/caliper/ organic pads. I also don't think the rear brakes do almost anything. I know they work and apply pressure though. This corvette master does not apply pressure right away to the fronts and the first bit of pedal travel goes only to the rears, doing almost nothing. It might be a function of using front calipers on the rear, but i don't know how this would cause issue.

Maybe I am asking too much for a manual system. At slow speeds these brakes are great. For trail riding they will be more than adequate. Let me be clear, they are NOT unsafe. Maybe I am too spoiled with the hydroboost system on my Chevy 2500.

 

Residual valves..........be them manually installed in line.........or part of a correct Master Cylinder or correct Proportioning valve are there to keep the Caliper Pistons & friction surface near the rotors at all times........1) to help eliminate pedal travel............2) In applications whereby the Master Cylinder is mounted below the horizontal plane of the calipers where fluid drain back can occur.

Looking at the picture of the Master & Linkage on the Bench.........it looks as though the ratio may be OK but the starting point at which the leverage is being applied to the current push rod length (if that is the way it will be installed) seems like it is already over center and too steep. Which may mean a longer push rod may be needed...................just a thought!

Did you check your Pedal Ratio?

 

When you fabricated your new master cylinder mounting bracket, which is a nice piece of workmanship, did you maintain the same bracket dimensions as the one you replaced? I understand Tarry99's suggestion that a longer push rod may be needed to aid in the leverage of the brake arm to master cylinder. I wonder if that is possible with this bracket. The reason I ask is this. When I look at post #39 top picture, it appears the new brackets dimensions are different than the old one you replaced although this could be an optical illusion. In the picture it looks as though the distance between the master cylinder mounting surface and brake pedal mounting pin is now longer. It also looks like dimension between the plain of the master cylinder bore to brake pedal mount pin is less. What all this means to me is the geometry between the brake pedal and master cylinder has changed reducing the brake pedal leverage to master cylinder i.e. the reason Tarry99 recommends a longer push rod.

 

Terry, I don't know how the heck you noticed that the pivot point on the brake arm to rod was too high, but it was. I installed it and immediately noticed it was incorrect, pulled it, drilled the brake arm again and tapped it for 5/16 bolt about 3/16 lower.

I didn't check the lever/fulcrum ratio because there is only so much wiggle room I have if i want to stay anything like the stock position. My idea is that if i couldn't get satisfactory results from this mod with 30 bucks invested and a bunch of junk and my time, I was going to go swinging and power assist. That may happen in the future for sure, but not today.

My master cylinder is above the level of the calipers because of the 4" lift. I really think the rear 2# residual valve is faulty. Too much pedal travel for no other plausible reason, that and I have removed 1 that was faulty after 20 miles. Could be something else for sure, but I have no similar problem with the front brakes.

I just drove about 10 miles in city/suburb traffic with this setup. The clutch feel is vastly superior. The brakes will stop me and if I really put my foot into them, will stop me better. That was the problem with the old setup. It would stop me, but under duress , it didn't do much better.

I had to figure out how to make a brake light switch too, as there is no threaded section in this Vette master to screw into like the CJ5 one. I feel this is better because this eliminates another area where air can be trapped in the master cylinder piston. I just plumbed it inline with some brake fittings. works fine...

Speed bleeders all 4 corners. if you have brake trouble its worth the 14 bucks an axle. don't need help.

 

Ed, its all different. The push rod is a complete new fabrication made of 3/4 stock machined down to .455 or so to fit in the piston. The push rod now also mounts on the opposite side of the brake arm. The mount is wider to accommodate the larger physical size of the reservoir. I also made it longer to more easily clear some body fabrication i made and just ease of working on it. I also made it all out of 3/8 plate with 3/16 gussets. It uses 3/8 cap screws tapped into the plate. My pushrod was initially too short and too high on the brake arm. I re drilled it and moved the pivot point forward and down. Fixed my issue. There is NO flex with my mount. The mount is probably overkill, but its what i had laying around. The plate is a real joy to TIG weld and you can really crank up the heat and amps without burning a hole or distorting it too easily.

 

Chris,

What I really was keyed up on is that starting point of your pedal ( in the photo on the bench) in relationship to the arch and where that should start in order to get the most benefit from the mechanical advantage in the pedal ratio..............That should in a perfect World always start just before the center of the fulcrum and then travel over the top of the arch to a point that is near full push just on the other side. What I see in that photo...........is you are near out of mechanical advantage when you first start and at that point pushing near a 1:1 ratio........as that pedal starts to flatten out.